Man under vibration, suffering and protection, Volume 13: Proceedings of the International CISM-IFToMM-WHO Symposium, Udine, Italy, April 3-6, 1979 (Studies in Environmental Science)

MAN UNDER VIBRATION SUFFERING AND PROTECTION

Studies in Environmental Science Volume 1

Atmospheric Pollution 1978 Proceedings of the 13th InternationalColloquium, held in Paris, April 25 -28,1978 edited by M. M. Benarie

Volume 2

Air Pollution Reference Measurement Methodsand Systems Proceedings of the InternationalWorkshop, held in Bilthoven, December 12-1 6,1977 edited by T. Schneider, H. W. de Koning and L. J. Brasser

Volume 3

Biogeochemical Cycling of Mineral-Forming Elements edited by P. A. Trudinger and D. J. Swaine

Volume 4

PotentialIndustrial Carcinogens and Mutagens by L. Fishbein

Volume 5

Industrial Waste Water Management by S. E. Jsrgensen

Volume 6

Trade and Environment: A Theoretical Enquiry by H. Siebert, J. Eichberger, R. Gronych and R. Pethig

Volume 7

Field Worker Exposure during Pesticide Application Proceedings of the Fifth InternationalWorkshop of the Scientific Committeeon Pesticides of the InternationalAssociation on Occupational Health, held in The Hague, October 9-1 1, 1979 edited by W. F. Tordoir and E. A. H. van Heemstra-Lequin

Volume 8

Atmospheric Pollution 1980 Proceedings of the 14th InternationalColloquium, held in Paris, May 5 -8,1980 edited by M. M. Benarie

Volume 9

Energetics and Technology of Biological Elimination of Wastes Proceedings of the International Colloquium, held in Rome, October 17 -1 9, 1979 edited by G. Milazzo

Volume 10 Bioengineering, Thermal Physiologyand Comfort edited by K. Cena and J. A. Clark Volume 11 Atmospheric Chemistry. FundamentalAspects by E. MBszbros Volume 12 Water Supply and Health Proceedings of an InternationalSymposium held at Noordwijkerhout, 27 -29 August 1980 edited by H. van Lelyveld and B. C. J. Zoetman

Studies in Environmental Science 13

MAN UNDER VIBRATION SUFFERING AND PROTECTION

Proceedingsof the International CISM- IFToMM-WHO Symposium, Udine, Italy, April 3-8.1979

edited by

Gm Bianchi

Technical University of Milano Department of Mechanics, Milano

K. V. Frolov

Institute for the Study of Machines Academy of Sciences of the U.S.S.R., Moscow

Am OledZki

Warsaw Technical University lnstitute of Applied Mechanics, Warsaw

ELSEVIER SCIENTIFICPUBLISHINO COMPANY AMSTERDAM-OXFORD-NEW YORK

-

PWN POLISH SCIENTIFIC PUBLISHERS WARSZAWA 1981

Distribution of this book is being handled by the following publishers for the U.S.A. and Canada ELSEVIER/NORTH-HOLLAND, INC. 52 Vanderbilt Avenue, New York, N.Y. 10017 for Albania, Bulgaria, Chinese People’s Republic, Cuba, Czechoslovakia, German Democratic Republic, Hungary, Korean People‘s Democratic Republic, Mongolia, Poland, Romania, the U.S.S.R., Vietnam and Yugoslavia ARS POLONA Krakowskie PrzedmieScie 7, 00-068 Warszawa, Poland for all remaining areas ELSEVIER SCIENTIFIC PUBLISHING COMPANY 335 Jan van Galenstraat, P.O. Box 21 1 1000 AE Amsterdam, The Netherlands

Library of Congress Cataloging in Publication Data International CISM-IFToMMSymposiurn, Udine, Italy, 1979. Man under vibration, suffering and protection. (Studies in environmental science; 13) Bibliography: p. 1.Vibration-Physiological effect-congresses. 1. Bianchi, 2. Vibration syndrome-Congresses. Giovanni, 1924- 11. Frolov, K.V. 111. Oledzki, Andrzej. IV. Title. V. Series. QP82.2.V5157 1979 61 2’.01445 ISBN 0444-99743-1 (Vol. 13) 044441 696-X (Series)

Copyright

81 -262 AAC R1

0 by PWN - Polish Scientific Publishers - Warszawa 1981

All rights reserved.

No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form.or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in Poland

LIST OF CO-

Ix

ORGANIZINGCONMITTEE

XI1

FOREWORD.

OPENING SESSION

...................

Allocution

. .

K. V. Prolov

MODERN PROBLEMS OF VIBRATIONS I N THE SYSlpEMs '~MAN-MACHINE-ENVIRONME"P1

Session I

- VIBRATIONAL ET!'FECTS

XIV 1

ON BIOMEHANICBL CHARAC-

TERISTICS

1.

2.

3.

G. C. Agarwal, G. L. G o t t l i e b

EFFECTS OF MUSCLE VIBRATION AND JOINT OSCILLATION ON RUMAN MOTOR MECWISMS

42

A. Seireg, R. Arvikar EFFECT OF BASE OSCILLBTIONS ON THE HUMAN SKEIXTAL MUSCLE AND J O I N T FORCES IN ASTANDINGPOSTUFtE.

55

..................

A. S . Mirkin, S. V. Petukhov NECHANORECEP!POR SYSTEMS OF THE ORGANISM FROM THE VIEWPOINT OF VIBRA-

TIONAL BIO"ICS

4.

5.

€I Dupuie, .

65

G. Jansen

IMMEDIA!l!E EFFECTS OF VIBFUTION TRANSMITmD TO T!HE H4ND

76

A, A. Menshov BASIC PRINCIPLES FOR HYGIENIC RBTING OF INDUSrpRIAL WHOLE-BODY VIBRATION IN TIE U.S.S.R.

87

V

6.

7.

R. G i l i o l i , M. Tomasini, C. Bulgheroni, A. Grieco, F. Gra5ia EFFEXIPS OF VIBRATING TOOIS ON THE PERIPHERAL YESSELS AND THE PERIPHERAL NERVOUS SYSTEM IN WORlcERs OF AN IRON FOUNDRY. P E U " T p IVX SUGGESTIONS

P o K. Bhwat, V.

N o GLlpta, D . F a McCoy COMPhRIIUALYSIS or' HUMBN AND s u m OPERBWR PERFORMANCE I N A CONTROL fro02

r m

0.

a.

9.

97

H. Schnauber DIFFICULTIES OP THE EVALUATION OF STRIBS DUE TO MECHANICAL VIBRATION SUFFERED BY MANKIND....................

M. Bovenzi, L. Petronio, F. Di Marino

141

MD-ARM

VIBRATION I N SHIPYARD CAULKERS

Session I1

130

151

- BIOMECHANICAL MODEIS 03 THE HUMAN BODY UNDER VIBRATION

1.

2.

3.

V.

A. S. Bruin, L. M. Raisin, G. J. Panovko THE DETEFWINATION OF THE EQUIVALENT BIOMECHANICAL CHARACTERISTICS OF THE ANKLE J O I N T MUSCLES BY VIBRATION TESTS

M. Zatsiorsky,

Do P o G m g DYNAMIC MODELING AND VIBRATORY RESPONSE OF lIUMAN SUBJECTS I N HEAVE MODE

5. 6.

7.

VI

176

B. M. Nigg, J. DenOth, P. 8 . Neukonun "HE LOAD ON THE LOWER EXTRXMITIES I N S I U C T E D SPORTS AC!CIVIT ~ . . . . . o . . . . . . o o o o o o o o o

4.

166

11. KaiqBek SOME PROBLEMS OF IDENTIFICATION AND MODELLING OF THE IiQfAN BODY

................. .........

190

200

A VIBRATION MODEL'FOR T B HUMAN HANDBRM-SYSrn.

210

THE ANTHROPOMETRIC I4ODEL OF A HUMBN HAND....r.......

222

G. Meltzier

I. V - ~ i l i e v

B. A. Potemkin, K. V. Frolov NON-LINEBR EFFETS C0"M:TED WITH THE S9ATIA.L VrRRalIOMS 02 B30mHBIO1cusm.TEMs

...............

228

8.

. . . . ... . .

0. S o N m a i k i n , Go J. Panovko VIBilATION DEFENCE OF MAN: QUZSTIONS OP MODELING

Seesion I11 10

235

- EXPERIMENTAL METHODS AND TECHNIQUES

V. V. Kljuev,. V. A. Klochko, V. G. G r a d e t s k i j , D. A. G r e c h i n s k i j , V. G. Rygalin, Yu. V. Ivanov AUTOMATIC SXS'PEM FOR STUDY AND MEASUREMENT OF VIBRATION PBRAMETEFG AE'FECTING HUMAN BODY 247 0

2.

P. Xrauae, A. O r b a n , K. J. Panzke, I(. Popov CRITI C A L ASSESSMENT OF COMMON METHODS TO DE!TERMINE VIBRATIONAL STFUSS 03' HAND-ARM SYSTEM 0

0

ON THE NEASURING OF COU'l!ACT P O R C S HUMAN BODY AND $QUIPIVIENT

3.

A. Olqdzkl

4.

A. Mueeyllska

5.

R. I. F u r w h i e v , A. G. I s m l l o v OPTIEIIZATION OP SIM)CIIBSTIC MAN4IACHINE SYSICEMS. 0

"!EH

275

A SURVEY OF VIBRATION CONTROL METHODS 287

315

0

6.

70

261

P. Tirinda, R. C h m u r n y

EXPIWMENTU METHOD FOR THE IDl$"PDICANON 03' DYNAMIC PROP-, OF A V I B R O - I S O U B I V E SYS2m WITH A RUBBER W R I N G

330

E. So A v e t i a o v , A. M. Kotliarsky, V. A. M o c h e n o v , I. L. Smolyaninova, I(. V. Prolov, K; K. G l u k h rev, M. A. Belsky BIFIXATION AS A. DYNAMIC SEIIF-REGULATING S Y S m

Session I V

0 . 0

- SYS2EMS FOR PROTECTION OP

0

341

MAN FROM VIBRA-

TION

1. 2.

. .......

E. I. Shemyakin, N. P. Benevolenskaya, A. Ya. T i a h kOV VIBRATION MAC= AND MAN K. V. Frolov, A. V. Sinjov, V. S. Soloujov, J. 0. Safronov KINIDIATIC TYPE ACTIVE VIBRO-ISOLATIONDEVICES 0

3.

348

0

0

0

353

M. K. P a t l l , M. S o Palanichamg, D. N. G h i s t a M I N I ' TUUMATIC V I E W MIZATION OF TRACIK)R-OCCUPBN!I? S

VII

TIONAL RESPONSE 13y MEBNS OF THE " P A T I L - P U I C W - G H I S I P B " (PPG) TRACTOR SEAT SUSPENSION

A. K. D a l e B,

THE N I B E SUSPENDED CAB TUCTOR

....

VIBRO-ISOLATION IN POR'PABLE CONCEPTS AND METHOD, DEVELOPMENT OF CONCEPTUALLY N E W VIBRIL'J!IOI-SBFE M O I S , FURTHER IMpROVEMEN'l!S) No P. Benevolenskaya, 2. B. Basova, L. L. Lysenko MAN-MACHINE-OBJECT BEING W0RB;ED-ENVIRONMENT SYS'PEMANDVIBRATION 0 0

364

372

Go Goldshtein

N O I S (SCIENTPIFIC

.

.

PROPERTIES OF NON-LINEAR VIWITH DIFFERENT DISBRATION-PROTECTION SYSSIPATIVE CHARACTERISBICS 0 a 0 0 0 0

387

395

2. C h e r n e v a - P o p o v a

DISCUSSIONS

LIST OF PARTICIPANTS

VIII

0

0

0

o

0

0

0

0

0

409 419

435

ORGANIZING COMMFITEE

Chairman I Prof. K. FROLOV Corresponding-member of t h e USSR Academy of Sciences Mech. Eng. Research I n s t . Griboedov S t r e e t 4, Moscow-Centre, 101000 (USSR) Vice-chairmen

I

Ph. D. Donald W. BADGER National I n s t i t u t e f o r Occupational S a f e t y and Health 4676 Columbia Parkway, C i n c i n n a t i , Ohio 45226 (USA) Prof. G. BIANCHI S e c r e t a r y General of CISM Pfazza G a r i b a l d i 18, Udine ( I t a l y ) Members t Academician G. BRANKOV 1, Noemvri S t r e e t , Academy of Sciences, 1000 S o f i a (Bulgaria ) Dr. &A. EL BATAWI , Chief Medical Officer, WHO, 1211 Geneva 27 (Switzerland) Prof. D.P.

GARG

Dept. of Mech. Eng. and Material Science, Duke University, Durham, N.C.

27706 ( U S A )

Ix

Prof. Dh. N. GHISTA AMES Research Center Moffett Field, California 94035 (USA) Prof. H.E. von GIERKE Aerospace Medical Research Laboratory Wright-Patterson Air Force Base, Ohio 45433 (USA) Dr. M.J. GRIFFIN Institute of Sound and Vibration, University of Southampton Southampton SO9 5NH (UK) Prof. 0. JANSEN Institut ftlr Arbeits-und Sozialmedizin Obere Zahlbacher Strasse 67, 6500 Mains (BRD) Dr. G. MELTZER Zentralinstitut ftlr Arbeitsschutz, Gerhart-Hauptmann Strasse 1 , 8020 Dresden (DDR) Prof. A. MORECKI Secretary General of IFToMM Al. Niepodlegkodci 222, r. 206, 00-663 Warszawa (Poland) Dr.

Ing. St. NEUSCHL Department of Computers EF-SVST Vazovova 5, 8801 9 Brat islava (Czechoslovakia )

Dr. B.M.

NIGG Swiss Federal Institute of Technology Weinbergstrasse 98, CH-8006 Ztlrich (Switzerland)

Prof. A. STAN Academy of Sciences, Commission for Acoustics Calea Victoriei 125, Bucharest (Rumania) Scientific Secretary: Prof. A. PEDOTTI Istituto Elettrotecnica, Politecnico d i Milano P. L. da Vinci 32, 20133 Milano (Italy)

X

Secretary t

Dr. A. BERTOZZI CISM

Piazza Garibaldi 18, 33100 Udine ( I t a l y 1

XI

FOREWORD

The idea of this symposium originated with Professor Konstantin Frolov, corresponding member of the Academy of Science of the U, S. S. R.,

within the framework of a long tradition of cooperation

between the International Federation for the Theory of Machines and Mechanisms IFToMM, and the International Centre for Mechanical Sciences CISM. This cooperation had already produced several seminars

and 'advanced courses in various fields of mechanics and bio-

engineering and a s e r i e s of, I believe, well-known sympasia on the "Theory and Practice of Robots and Manipulators". The study of "Man under Vibration requires several lines of attack.

- Suffering and Protection"

The analysis of the propagation of

vibration in the skeletal and muscular structure of the human body

is a typical, and advanced, problem of mechanics. The mathematical model of body behaviour can be determined by methods of system theory and identification.

The evaluation of the influenae of vibration

on the body organs and structure is a medical problem.

The defini-

tion. of the threshold of allowable vibration must translate clinical results into mechanical terms. Finally, the design of protective devices relies on the skills of the mechanical engineer and also acquires

XI1

an obvious social significance.

One of the aims of our Centre is to encourage the meeting and cooperation of persons workrng in different branches of mechanical and related sciences at both basic and applied levels.

The proposal

for the symposium w a s therefore received at CISM with the greatest interest, and was immediately accepted, Working with the m e m b e r s of the organizing committee has been a rewarding experiede. In particular, I have appreciated the opportu-

nity of becoming better acquainted with the impressive work 'done in this field in the Mechanical Engineering Research Institute of the Academy of Sciences of the U.S.S.R.

under the direction of Professor

Frolov. I am very thankful to Professor Adam Morecki, Secretary General of IFToMM, for his most valuable contribution to the success of the symposium through the support of his Federation and f o r making it possible to have the Proceedings published by the most cooperative and efficient Polish Scientific Publishers (PWN).

I should also like to

extend hearty thanks to Profeesor Andrzej Oledzki of the Warsaw Technical University, who as Polish editor of the Proceedings has dedicated much enthusiasm, competence and time to the publication of this volume.

Giovanni Bianchi Secretary General of CISM

XI11

Dear c o l l e a g u e s , l a d i e s and gentlemen, F i r s t of a l l I would l i k e t o c o n g r a t u l a t e you on t h e opening t h e F i r s t I n t e r n a t i o n a l CISM/IFToMM Symposium on "Man under V i b r a t i o n " , devoted t o a great s o c i a l problem o f i n t e r n a t i o n a l s c a l e : t h e p r o t e c t i o n o f man from v i b r a t i o n s and n o i s e , a t y p i c a l problem o f environmental p r o t e c t i o n . It i s v e r y important t h a t t h i s f i r s t Symposium was o r ganized i n c l o s e d c o o p e r a t i o n by t h r e e i n t e r n a t i o n a l o r g a n i z a t i o n s : CISM, IFToMM and WHO. The p u r p o s e f u l work and e f f o r t s of t h e s e o r g a n i z a t i o n s ensured t h e s u c c e s s of t h e Symposium. The s c i e n t i f i c programme and t h e c a r e f u l s e l e c t i o n of papers was t h e r e s p o n s i b i l i t y of t h e members o f t h e Organ i z i n g Committee. TaKing t h i s o p p o r t u n i t y , I, as a Chairman of t h e Organizing Committee., would l i k e t o e x p r e s s my g r a t i t u d e t o a l l t h e members f o r t h e i r great and f r u i t f u l work. We, s c i e n t i s t s and e n g i n e e r s of many c o u n t r i e s , have g a t h e r e d h e r e i n h o s p i t a b l e I t a l y , i n t h e Head-quarters of t h e I n t e r n a t i o n a l Centre f o r Mechanical S c i e n c e s . A s p i r i t of understanding and c o o p e r a t i o n , d e v o t i o n t o o u r new, but speedly developing, maybe t h e most humane s c i e n p r o t e c t i o n of man from v i b r a t i o n s u n i t e a l l od u s . ce I wish I could e x p r e s s confidence i n t h e hope t h a t t h e r e s u l t s of our j o i n t work, panel and s c i e n t i f i c round table d i s c u s s i o n s , w i l l n o t o n l y f u r t h e r s c i e n t i f i c - t e c h n i c a l progress b u t the cause of peace i n our p l a n e t as w e l l . L e t me wish a l l t h e p a r t i c i p a n t s of t h e F i r s t I n t e r n a t i o n a l Symposium great s u c c e s s i n t h e i r work and e x p r e s s t o a l l t h o s e who have p r e s e n t e d s c i e n t i f i c p a p e r s , s i n c e r e gratitude. I would l i k e t o thank o u r I t a l i a n c o l l e a g u e s a t t h e D i r e c t i o n o f CISM, i n p a r t i c u l a r , Prof.G.Bianchi, Dr.V.Turello, Dr.A.Bertozzi and Prof.A.Pedotti f o r t h e i r e f f o r t s which provided t h e c o n d i t i a n s f o r o u r f r u i t f u l work.

-

-

-

K .V . F r o l o v

MODERN PROBLEMSOF VIBRATIONS IN THE SYSTEMS

MAN-MACHINE-ENVIRONMENT"

"

K.V. Frolov Mechanieol Engineering Reseorch Institute, Moscow, U.S.S.R.

SUMMARY

The characteristics of vibrations acting on man under various production conditions a r e described. The physiological and mechanical reactions of the human body to vibration a r e analysed. Results, a r e presented from experimental studies of the dynamic characteristics of the hu,tnan body and the a r m s of an operator. A significant change is demonstrated in the parameters of dynamic models of biomechanical systems, associated with a change in position o r degree of muscular tension. The instability of the dynamic characteristics of the human body under the long-term influence of vibrations is analysed, and mathematical modelling of the active changes in the mechanical parameters of the body by man is discussed.

I. VIBRATION AS AN ENVIRONMENTAL FACTOR ARTIFICIALLY CREATED BY MAN

A. Introduction.

During the process of evolution, man conscio-

usly o r unconsciously changes his environment. As a result of technical and industrial progress, resulting from the desire to increase the speed and power of modern machines and technological equipment, man harr artificially created new external conditions. The significance of certain individual environmental factors, previously insignificant

1

for human life, has significantly increased as a result.

-

This tendency is doubtless clearly seen if we consider vibration mechanical oscillations of elastic bodies of various shapes

-

which

man encounters every day at the present time. Man’s desire to mechanize heavy manual labor, a s well a s the desire to travel rapidly over long distances, has resulted in the creation of effective machines .and high speed transportation equipment; however, a s technology has developed, the problem of protecting man from the harmful influence of vibration loads generated by various machines, mechanisms and automatic production lines as they function has become acute.

The problem of the interaction of man with his environment has become the theme of the century. The study of the influence of vibration on man in o r d e r to create effective means of vibration protection is a part of the overall struggle f o r quality of the environment of o u r planet, f o r improvement of the life of man on Earth, f o r protection of the natural riches around us. This modern problem has both social and economic aspects. B. Classification of Vibrations.

There is no one single type of

vibration in nature. The concept of vibration actually covers a great variety of physical phenomena and processes. It is not surprising therefore that a universal means f o r protecting man from vibration and the noise which it generates has never been created.

.

The great variety of oscillating processes which man encounters in his daily life is divided first of all into two classes. The first class includes vibrations, the behavior of which can be predicted in advance, given certain a priori information.

These oscillating pro-

cesses are called deterministic vibrations. A deterministic physical process can be mathematically assigned as a certain definite function of time. A classical example is found in stable harmonic vibrations, described by the function: u ( t >= u

2

0

c o s a t,

where u

0

is the amplitude of the vibrations,

u) is

the angular frequen-

cy, t is time. The amplitude and frequency of such vibrations remain constant as time passes. Although this classical form of vibration is actually

only an idealization of more complex oscillating processes in actual machines, it is sometimes used in laboratory tests, and also in calculating the simplest forms of oscillations. W e must frequently deal with vibrations, which a r e usually represented as the sum of a finite o r infinite number of harmoric components:

where (Pi

-

is the phase shift between harmonics.

They can be

periodic o r apefiodic, the case depending on the ratios between all the frequencies ui. Generally speaking, aperiodic vibrations vary much more widely than do periodic vibrations. Important in this group a r e the so-called "attenuating harmonic" and quasiharmonic unstable vibrations with continually changing frequency. Such vibrations arise, f o r example, during acceleration and braking of mechanisms with rotating elements. Oscillations following an "attenuating sine wave'' can be mathematicall y represented by the expression: u ( t ) = uo e where uo,

8, G), 'p

- &t . s i n ( w t +@,

a r e constant quantities characterizing the initial

amplitude, attenuation, frequency and phase shift of the oscillations. Quasiharmonic vibrations, with continually ihcreasing frequency, can be described by the expression: u ( t ) = uo s i n ( a t where A

+

At

2

+ v),

is the rate of change of the frequency.

Periodically repeating impact pulses, which arise when compara-

3

tively great forces a r e applied briefly, are also frequently considered vibration loads. Impact effects can quite arbitrarily be divided into impulse-type and limitation-type effects. The f o r m of impulse effects

is rather arbitrary, but in all cases the following expressions are correct: u (t)

#

u(t) =

0, where t

&C ,

0, where t > 2

.

Limitation motions a r e characterized by the fact that as time passes, they approach a certain constant limiting value. This can be represented mathematically, for example, as follows:

p

p

.

a r e real numbers and > oc 1' u2, oc, Examples of these idealized forms of vibration a r e shown in

where u

Figure 1. Strictly speaking, in nature there a r e not and cannot be any "purely" deterministic processes. Therefore, actual vibrations can be considered deterministic only approximately.

Consequently, the second

class consists of random vibrations, the behavior of which cannot be described as a regular function of time. At each fixed moment, the parameters of this type of vibration may take on some quantitative value from the area of possible values. Mathematical description of random vibrations utilizes statistical characteristics, the sense of the use of which lies in the resultant transition from random functions to deterministic functions defining the mean estimates of the random vibrations, In practice, we encounter quite frequently random vibrations for which the statistical characteristics do not change over the time interval analyzed as time is shifted, i.e.,

as t is replaced by t

+

a, whe-

re a is an arbitrary quantity. These can be thought of as random oscillations about a certain mean value, and the source of oscillations has a nature which does not change with time.

These random vibrations

a r e called stationary, in contrast to unstationary vibrations, which

4

include all other vibrations, not satisfying the above condition. Depending on the range ( o r band) of frequencies contained in the random vibrations, they a r e arbitrarily divided into narrow band and wide band vibrations. In the theory of random vibrations, an important role is played by so-called Gaussian random processes, which a r e a particular class of random processes and are distinguished from non-Gaussian processes in that they a r e fully defined by a single statistical characteristic

- the correlation function.

C. Parameters of a Vibration Stimulus and Units of Measurement.

When we study three-dimensional vibrations of the human body, we generally distinguish the primary axes of motion. The orientation of the axes of the system of coordinates thus introduced and its connection to the human body f o r 6-dimensional vibration is shown in Figure 2. In accordance with these symbols, vibrations differentiated arbitrarily into vertical z, longitudinal x, transverse y and angles

(a,p , $)

vibrations.

To provide a quantitative description of a vibration motion along one of the axes x, y o r z, we most frequently use three main parameters: motion u, velovity 6 and acceleration

u . We

should note

t

that estimates of these parameters can be developed by several methods. The instantaneous value of a parameter being studied corresponds to the value of the parameter as a fixed instant in time. D. Sources of Vibration in Industry and Domestic Life. Vibra-

tions refer primarily to perturbing forces which vary in their nature and mode of action. Vibration sources might be irregularities of roads o r fields, gusts of wind, pressure pulsations in turbulent layers

of the atmosphere o r a body of water, unevenness, o r imbalance of the rotation of machine and engine parts, friction and microscopic impacts between the working organs of machine tools, gaps in bearings and gears, oscillations of the rotors of electric machines

5

under the influence of magnetic fields, acoustical loads resulting from the exhaust streams of jet engines and airplane propellers and pulsations of pressure in pneumatic and hydraulic machines. We should distinguish a special type of machine, the working process of which is based on the use of the vibrating principle of action. In many cases, these machines a r e the only economically expedient means of mechanization of labor-consuming processes. Since vibrations cannot by definition be excluded in this type of machine, the problem of vibration protection of a human being controlling such a machine is a most difficult and important one. The many sources of vibration .generate a wide variety of forms of vibration stimulus acting on man at work and at home. In this chapter, we will present examples illustrating the spectral and amplitude characteristics of actual sources of vibration, experienced by man, as he travels in surface, air o r water vehicles. The random vibrations of the wheel rolling over a r o a d with an uneven surface a r e to a great extent transmitted through to the floor of the.cabin and the seats in the vehicle. In addition to the vertical oscillations, a passenger sitting in a motor vehicle also experiences longitudinal and transverse oscillations. Tests have shown, however, that the horizontal accelerations in the body of a motor vehicle are less than the vertical acclerations. Production workers in many branches of industry a r e constantly exposed to vibration with various spectra and levels. In factories and working locations in the machine building, textile, construction and other industries, human operators generally work standing up. Vibrations a r e transmitted to the body through the floor. When working with mechanized hand tools, vibration and impulse effects a r e transmitted to the body primarily through the arms. Vibrations have also begun to reach into people's homes. Housework in the modern home is largely mechanized and frequently quite reminiscent of production processes, The well known architect L e Corbusier is justified when he calls the modern apartment a "living

6

machine".

In the modern apartment, we find an ever increasing num-

ber of domestic machines, instruments and mechanisms generating intensive vibrations and noise. Furthermore, the tendency in construction is to increase the height and decrease the weight of structures; as a result, the tall, flexible buildings of today oscillate significantly in the wind. In the lat e 1960'8, the problem of decreasing the deflections of tall buildings became more pressing for the construction industry than the reduction of s t r e s s e s in structures

(21. Low-frequency oscillations of buildings

resulting from lateral wind pressure have a significant influence on the comfort of the inhabitants of the upper stories. Analysis of the

oscillations of a 55-story building in New York

[31

showed that

during strong northeast winds, the inhabitants of the upper floors could not write, so that workers employed in firms on the upper floors w e r e regularly given time off on days with such winds. E. Influence of Vibrations on t h e Human Body and i t s Efficiency.

The role of man as the operator of technical systems is ever increasing. It is therefore quite important to study the influence of various factors on the efficiency of an operator, as a link in the-machine sy-

stem. The vibrations of machines, acting on man, can reduce thq productivity of labor and its quality significantly. The results of many studies [4]

-

[SJ

indicate the unfavorable influence of vibrations on

the functions of t h e visual analyzer of a human operator, the inaccura-

cy of performance of tracking tasks, etc. In reference

[7]

it is

noted that the Gemini astronauts, when subjected to vibration at a f r e quency of 50 Hz. could not read the indications of their instruments, since the eyeballs vibrate at this frequency and the eyes a r e literally covered by a film. W e have performed special investigations designed to evaluate the

influence of vertical low-frequency vibrations over periods from two to four hours on the efficiency of human subjects. Analysis of the results of our studies has shown that by the beginning of the second hour of

7

exposure to the vibrations the mean square e r r o r of operators performing compensatory tracking of a random signal had increased by 1.5 times in comparison to the initial level of error. Furthermore,

periodic changes in the quality of tracking appeared with the passage of time. The slowing of the motor reaction of o u r human subjects was particularly clearly seen in the resonant mode 4.75 Hz )

, three hours

(

vibration frequency

after the beginning of a session.

When exposed to harmonic vibrations with frequencies of 3-8 Hz, 2 with a mean square level of acceleration of 1.5 m/sec , the visual acuity of operators remained practically unchanged over a two-hour session: however, when the vibration level was increased to 4.5 m/sec2 at a frequency of 4.5 Hz, 9 Hz, visual acuity dropped by 17%. This deterioration was observed throughout the entire session, 'which lasted two hours. Figure 3 shows curves of equal resolving capacity of the eyes under the influence of vibrations.

The curve corresponding to unity

shows the resolving capacity of the eye at rest; the other curves illustrate the deterioration in resolving capacity of the eye under the influence of vibrations. On Figure 3, we can see three zones of increased sensitivity of the eyes to vibration: around 5 Hz, 14-30 Hz (except for the 22-26 Hz a r e a ) , and 60-70 Hz (higher frequencies

. At frequencies 4-14 Hz, 22-26

Hz and over 30Hz, increased "interference stability" of vision was observed. W e can assume that f o r the 22-26 Hz zone this phenomenon is a result of adap-

were not studied)

tation of the organs of vision to vertical vibrations at the natural oscillating frequency of the head (20-30 Hz). At the end of a vibration session, the functional condition of the operator was rapidly restored ( i n no less than 5 minutes) to its initial level. Vibrations in the resonant mode (4-5 Hz) have a greater influence on the functional state of a human subject than vibrations i n other modes, manifested both as a significant reduction in the speed and accuracy of actions and in a significant deterioration of the functional status after the vibrations are turned off,

8

The effects of vibration on the human body a r e presently being widely studied. Vibrations cause a sensation of discomfort, irritation, nausea and other unpleasant phenomena; when applied briefly, the subjects complain of dysphoria, pain in the stomach and back, headache, general fatigue, difficulty in breathing, itching, deafness, etc. Under the influence of vibration, the mechanical reaction of the human body, manifested a s displacement of mobile structures, deformation and bending of parts of the.body, effects!

can cause t h e following

1) changes and possible disruption of the normal course of

processes both in individual organs of the body and in molecular o r cellular structures; 2 ) pinching of the tissues, blood and lymph vessels; 3) resonance and standing waves in the blood vessels; 4) extension and compression of nerve tissue; 5 ) heating resulting from friction. Vibrations also cause: 1) dynamic loads on the skeleton; 2) possible damage to the tissues a s a result of counteracting forces from supports; 3) changes in the compliance and pressure of the perivascular tissue and structures in the thorax, particularly those adjacent

to a support and a body fixation system ("passive pump'' of peripheral blood vessels and lungs). These phenomena may be accompanied by the following main physiological reactions by the body: l! stimulation of vascular and muscular mechanoreceptors; 2) phase shifts in the central and peripheral intravascular pressure, capable of changing the filling of the heart and its output, as well as the peripheral blood flow; 3) phase influences on the resistance of the vessels due to periodic fluctuations in pressure in

the arterioles and veinules,

resulting in instantaneoue reactions (the BeFlis effect 1 and a change in capillary pressure; 4) possible intermittent vascular spasms with subsequent ischemia o r stasis. Vibrations also influence anaphase, i.e.,

the stage of cell divi-

sion during which the chromosomes begin to split, Thus, in experiments with mice subjected to vibrations characteristic of a rocket engine, after one day the percentage of anaphase formations in the spinal column reached 9.79,

whereas in .a control group of animals

9

it was only 2.6 1%.

Vibrations cause the earliest and most significant changes in the cardiovascular and nerGous-muscular systems. Vibrations acting on the peripheral nerve endings cause changes of various types in their sensitivity.

The reactions of the central nervous system are manife-

sted as loss of equilibrium of nervous processes,

It has been esta-

blished that the cortical a r e a s of the brain are quite sensitive to vibration stimulus. According to data in

[9J, vibrations cause depree-

sion of the alpha rhythm on the electroencephalogram, followed by exhaltation of this rhythm with longer exposure to vibration. It has been shown in a number of works

[lo] ,

[lu

that vibra-

tion at frequencies of 10 to 70 Hz causes disruption of the static and dynamic coordination of motion and has an unfavorableinfluence on the nervous:muscular

system.

Many investigators [12J

have observed changes in the pulse fre-

quency and arterial pressure under the influence of vibration, A dependence of the change in the respiratory function on the amplitude of motion o r acceleration of vibrations at frequencies of 4-5 Hz has been noted. We have performed experimental investigations

[ 133 of the simul-

taneous influence of vibrations and static load on the muscles. In the experiments, we reassured: excitation in the nervous-muscular system by means of EMG, muscular tonus, vibrasensitivity, pulse f r e quency, ECG and arterial pressure.

The results show that under the

simultaneous influence of vibration and measured physical loads, changes occur in all the systems studied. The depth of the changes observed under our experimental conditions did not go beyond the limits of the physiological norms. However, definite trends were noted. F o r example, the greatest changes were observed in the condition of the cardiovascular system. A stable, reliable increase in the frequency of heart contractions w a s noted under the influence of random vibrations following 20 minutes of the experiment, while sinusoidal vibrations with a frequency of 5 Hz caused a change i n pulse frequency

after 30 minutes.

During the period of the tests, we also observed

a change in the arterial pressures. The maximum systolic pressure generally dropped, the minimal pressure increased. Vibrations and measured physical load also caused a significant change in the nervous-muscular apparatus.

The tone of the muscles of the back and

neck increased significantly.

The greatest changes, as i n the fun-

ctions of the cardiovascular system, were observed under the influence of random vibrations. Analysis of the peculiarities of the changes of all the functions we have studied rather clearly shows the difference in the nature of the influence of sinusoidal and random vibrations.

Sinusoidal vibra-

tions caused changes in peripheral circulation and the nervous-muscular apparatus, which were restored in 20 minutes. After random vibrations, we noted an increase in the tone of the peripheral vessels, combined with change6 in the nervous-muscular apparatus of inhibitor y type. The increase in electric activity of the muscles, along with a reduction of skin sensitivity, muscular endurance and productivity (elongation of ch0rn-j

indicates complex interactions in the central

nervous system in response to the influence of random vibration. Vibrations cause a change in the morphological composition of the blood, characterized by a reduction in the number of erythrocytes and the percentage of hemoglobin [14]

,

[15]

. Many investigators

relate these changes i n the composition of the blood to changes in the central nervous system. The changes detected under the influence of vibration in the condition of the endocrine system

[lS] indicate significant irritation of

various elements of the endocrine system by vibration.

The long-term

influence of vibration can cause stable, irreversible changes i n metabolic processes in the human body. It should be noted that the general clinical indicators (ECG, EEG, frequency of respiration, pulse, blood pressure, etc.) rapidly return to the normal level following interruption of the vibration. However, with a test subject in good general health with no visible deviations, latent disruptions in the internal

11

medium of the organism may arise, particularly in the metabolism of biologically active substances serotonin, etc.).

acetylcholin, catecholamines histamine,

Those functions of the organism which depend sig-

nificantly on the humoral mechanism of regulation,

particularly those

whose regulation involves the autonomic innervation, a r e comparatively resistant to vibration. However, i f changes do occur, they a r e relatively stable, i. e.

, the

Studies performed

aftereffect period is long. [17] indicate changes, under the influence of

vibration, in the activity of the enzyme diaminoxidase (DO’, as well as changes in the histamine-serotonin ratio.

Histamine has extremely

high activity and a broad spectrum of action; it participates in a number of important physiological processes: it increases the permeability of blood vessel walls, causes contraction of smooth muscle f i bers, participates in the regulation of t h e microcirculation of the blood and stimulates the secretion of gastric juice. In various functional states of the organism resulting from extreme stimuli, the changes in the content of histamine a r e accompanied by changes in the activity of enzymes participating in its formation and breakdown. An excess content of histamine in the organism results in vegetative disorders in the functioning of its systems and in the development of d l e r g i c states. Serotonin is widespread in human and animal tissues. Serotonin is synthesized primarily in the chromation cells of the gastrointestinal t r a c t It is formed in nerve tissue from the initial product B-hydroxytryptophan. Serotonin has high biological activity and influences the activity of the nervous, cardiovascular, respiratory, secretory and other systems. It is closely related to histamine and noradrenalin, indicating the functional relationship between serotonin and the hypotha-

lamus-hypophysie-adrenal regulatory system. The results of investigations have shown that when vibrations at frequencies of 2-10 Hz with amplitudes of 0.2-018 mm act on the body, the dynamics of the histamine [.Do and histamine) serotonin ratios reflect a long-term

12

aftereffect, while the changes in general

clinical indicators a r e quite transient. F o r clarity, Figure 4 shows the correlation relationships between the level of histamine and the DO activity. Here, the enzyme has shown i t s significance as a "balan-

c e r " reflecting the capability of the regulatory systems of the body for adaptive behavior. At the present time, researchers have described various forms

of vibration sickness, which developed under the systematic influence of the vibration stimulus over a period of years. In spite of the tremendous number of works dedicated to the study of the influence of vibration on the human body, the pathogenesis and mechanism of development of vibration disease remain insufficiently clear. Complex clinical and hygienic investigations have allowed us to reveal two main forms of vibration pathology: 1) peripheral

- from the influence of

local vibrations on the a r m s of the workers; 2)

- from the

cerebral-peripheral

equal influence of both general and local vibrations.

The clinical symptomatic8 of peripheral pathology vary significantly depending on the structure, power and frequency characteristics of the vibrating tool. The primary indicators of the disease are: attacks of pale, cold fingers, paresthesia and pain in the distal segments of the arms at r e s t and at night. Trophic and sensory disorders of

distal type, hypertrophy of the skeletal muscles and less frequently of the shoulder girdle a r e noted. The cerebral form of vibration disease is characterized in its initial stages by general cerebral vascular and cortical-subcortical,

meso-disencephalic neurodynamic disorders; in later stages organic brain damage develops. With this form of the disease, peripheral vegetovascular and sensory disorders are also observed, but they a r e of secondary significance. We should also note the fact that vibrations can have a useful influence on the human body. General vertical vibrations have been successufully used for the removal of stones of the ureter -since 1965. Horizontal vibrations facilitate the passage of stones from the kidneys. In [18] results a r e reported of the use of vibration therapy a s an

13

effective method of dropping stones in the ureter and in the diagnosis of certain forms of urolithiasis. Studies of the respiration, pulse, arterial pressure and bipotentials of the ureter have allowed parameters of vibration to be found which combine absence of any harmful influence on the body with the maximum therapeutic effect. Analysis of the resonant frequencies of the organs in the lower abdomen, as well as concrements of the ureter, have allowed the most effective parameters of sine wave vibrations to be found: frequency 10-15 Hz, amplitude 2 m m A vibration stimulus, strictly measured as to frequency and expo-

sure, has been successfully used to treat the peripheral nervous system, sceletomotor apparatus, nonspecific diseases of the lungs, the gastrointestinal tract, gynecological and other diseases. The therapeutic nature of moderate doses of audio frequency mechanical oscillations results from the fact that they act as stimulators to the protective mechanisms developed by the body itself i n the process of evolution. As a result of the influence of vibration of low

intensity and brief duration, a complex of protective and adaptive mechanisms comes into play in the body; however, more intensive, longer-acting vibration suppresses the protective reaction of the body. One well-known basis f o r an explanation of the mechanism of action of vibration

a8

a function of the initial condition of the organism is

the study of N.Ye.Vvedenskiy,

who found that the intensity of para-

biosis can be decreased by weak stimuli used in small, gradually increasing doses. Finally, w e can draw the following conclusions: 1. Vibration can be looked upon as a stimulus acting on the human

body from the environment during daily life both at work and at home. 2.

The vibrations are quite complex in nature and varied as to

form of stimulus, which must be described using several parameters o r groups of parameters. 3. The selection of any given group of parametera to describe

vibrations is rather arbitrary, which complicates the investigation of

14

the influence of vibrations on the human body, and also leads to dif-

ficulties of comparing the results of different investigations. 4. A tremendous amount of factual material has been accumulated

concerning the harmful and useful influence of vibration on human health and man’s working capacity.

However, no single theory has yet

been developed to form a foundation for objective criteria f o r evaluating the influence of vibration on the human body. 11. BIODYNAMIC CHARACTERISTICS OF THE TISSUES OF THE HUMAN BODY A. An Amplified Approach to the Evaluation of the Dynamic

Characteristics of the Components of the Body Subject to Vibration. The reactions of the body to vibrations u (x,y,z,t)

generated by sour-

ces of oscillation distributed in some manner in space can be arbitrarily represented by a simplified block diagram, as shown i n Figure 5. This diagram includes three elements: the mechanical system, including man’s skeletomotor apparatus and internal organs; a group of receptors converting mechanical oscillations to electrical impulses; and the central nervous system, regulating the processes in the body. The skeletomotor apparatus consists of two parts: passive and active. The passive part consists of the skeleton which, serving as the support for the entire body, also represents a system of levers articulated to each ocher. The active part of the motor system consists of organs called musles which, being located between the hard parts of the skeleton can, due to their capability f o r active contraction, move the levers of the passive s y s t e m In the mechanical system we also include all s o r t s of connective tissues and fluid components in the human body. The oscillations of the elements of the mechanical system a r e further received by receptors which can react to various stimuli. The receptors a r e quite varied structurally. They include comparatively simply constructed nerve endings, highly differentiated special forma-

15

tions (sensors) and individual elements of the complex sense organs. Usually, in response to a stimulus, a receptor, by means of highly complex electrical and chemical processes, generates a sequence of electrical impulses (afferent signals) which, when they reach a certain intensity, pass along the nerve fibers to the cerebral cortex. It has been established that the number of afferent impulses, within certain limits, is directly proportional to the logarithm of the intensity of the stimulus. The receptors a r e divided into exteroceptors, proprioceptors and interoceptors. The exterdceptors a r e located on the outer surface of the body and receix-e stimuli from the environment, The proprioceptors a r e located i n the muscles and joints and perceive the contractions and extensions of the musculature and the positions of the points, i. e.,

signal the position and movements of

the body. The interceptors a r e located in the internal organs and

perceive changes in the internal environment and the condition of the visceral sphere of the organs. Each receptor has its own threshold of stimulation,

i.e.,

the minlmum intensity of the stimulus

sufficient to cause excitation. Each type of receptor is adapted to

its own qualitatively specific stimulus. F o r example, f o r the eye the significant stimulus consists of light waves, for the e a r , sound waves, etc. The specific stimulus f o r a given receptor, to which it has become adapted in the process of evolution, is called i t s adequate stimulus. We should note that mechanical oscillations a r e a particular type of stimulus, since they cause activity even in receptors for which they are not adequate. F b r example, mechanical stimulus of the retina causes the sensation of flashes of light. In studying the effects of vibration on man, we can distinguish the following basic levels of analysis of phenomena occurring in the human body: 1. The subcellular level. 2.

The cellular level.

3. The tissue level.

4.

The level of organs and systems.

5. The level of the entire organism. However, in selecting any one of these levels we must always first determine the mechanical characteristics of the biological com-

ponents which participate in the oscillating process. B. Mechanical Characteristics of Biological Tissues Making

up the Skeleton.

The spine o r spinal column consists of segments

called vertebrae. Although they share a common type of s t r u c k r e , the vertebrae differ significantly from each other in shape

i n the various

areas of the spine. The combination of the solid bone vertebrae connected by elastic discs and bound by a system of fibrous ligaments, forms a strong and flexible column, allowing significant movement due to the intervertebral joints. The spinal column is not straight. With the body in the upright psition. if forms several bends in a plane. Due to these bends, the resistance of the spine to vertical mechanical loads is elastic in nature. The results of experimental studies

[ld

performed on cadavers

in order to determine the dynamic characteristics of the spinal column are shown in Figure 6. In these experiments, strain sensors were attached to certain vertebrae with the body in a seated position. Mechanical loads were applied f i r s t to the head (curve I), then to the shoulder (curve 11); these respective curves illustrate the nonlinear behavior of the spine under heavy loads. Works a r e known [20J

in which the mechanical characteristics

of individual vertebrae and intervertebral discs have been studied.

Figure 7 shows a graph f o r the first lumbar intervertebral disc together with the body of the 12th thoracic and first lumbar vertebrae. This section of the spine was placed in a press. A s the load was increased, a strip-chart recorder was used to record the compression curve. The load wa8 gradually increased from 4000 to 6000 N, then compression w a s continued without increasing the load; on the graph,

17

this moment corresponds to the flat section AB. After this, the load

was once more increased to 15000-20000 N. In experiments involving extension, it has been found that a load of 1980 to 2480 N is sufficient to burst a disc. The ruptures were generally found to take place at the point of connection of a disc with a vertebra.

C, Models of the Human Body Under the Influence of General

Vibrations.

A model can be defined a s a system which does not dif-

fer from the object being modeled as concerns certain properties which a r e considered "essential",

but may differ from it i n relation-

ship to other properties, called "nonessential".

In the group of pro-

blems of biomechanics related to the influence of vibrations on man, the essential properties, as we have stated, can be considered the

dynamic characteristics of the human body aa an elastically damped oscillating system. A model of the human body adequate with respect to dynamic characteristics can naturally be thought of as an approximation of a f u l l biomechanical model; Such a model allows u s to predict the mechanical reaction of the human body to vibrations of various types. Furthermore, such a model allowe the engineer to design

an effective vibration protective system for man. The parameters used to evaluate the similarity between the model and the object depend on the purposes of modeling. F o r example, in problems of vibration protection, we frequently limit ourselves to an

estimate of the input mechanical impedance of the object being protected. In analyzing the propagation of vibrations through the human body, we also study the transfer functions of the systems. One essential problemin the construction of a model of an object

is the selection o r determination of its structure. The structure of a calculation model in problems of vibration protection is determined to a great extent by the spectrum of frequencies of the vibrations applied. If these frequencies a r e significantly lower than the natural frequencies of the

elastic body, we can consider the body absolutely

hard. The higher the frequencies of the vibration applied, the more complex the structure of the model must be. In studying biomechanical systems, w e encounter difficulties which cannot be solved by theoretical methods of analysis, which are effective i n the investigation of various physical systems. Without reliable experimental data, w e cannot go over to construction of sufficiently well-founded mathematical and mechanical models of the system being studied. During the past 15 years, as a result of intensive investigations, a great number of various models of the human body as an elastic system have been produced [ ~ I J- [27] struction of the models have been either

. The initial data for

con-

experimental measurements

of the relationship of the parameters of oscillation of the head and seat, shoulders and seat, etc., or measurements of the mechanical impedance of the human body as an integral indicator of the mechanical reaction of the system to the effects of vibration. Before going over to a description of certain models of the human body, let us attempt briefly to present the basic, experimentally confirmed peculiarities of the mechanical reactions of the human body to vibration. Below 2 Hz, the human body acts as a solid body. In the 2-100

Hz band, the mechanical energy propagates through the body i n the. form of waves, the length of which is significantly greater than the dimensions of the body. Based on this, the model should be one of an oscillating system with concentrated parameters and several degrees

of freedom. The basic resonant frequencies of vertical oscillation of the human body in the sitting position lie i n the 4-6 Hz area, in the starting position

-

in the areas of 5 and 12-15 Hz.

A t frequencies over 100 Hz, the human body acts as a more complex system with distributed parameters; the mechanical energy may propagate in the form of shear waves, surface waves o r compressive waves.

The type of waves propagating through the body depends

to a significant extent on the frequency and conditions of transmission

19

of vibrations. As the frequency of the exciting oscillations increases, ever smaller parts of the body become involved in the oscillating process, and the zone of mechanical effect of the vibration is. ever more localized. The mechanical properties of the human body depend bn the direction of the vibrations applied. When vibrations propagate in the transverse direction, the physical reaction differs significantly from the reaction to vertical vibrations. The basic resonant frequencies

of the human body with horizontal vibrations lie in the 1-3 Hz frequency band. The nonlinearity of the,elastic and damping properties of the human body is manifested in the form of the dependence of mechanical reaction of the human body on amplitude of external vibrations, The dynamic characteristics of the human body change as functions of the position of the body. Constant activity of the muscles can significantly influence the measured dynamic characteristics. In accordance with the above, all known models can be separated into a few classes

[is)

. Depending on the frequency range in

question, models are discrete, distributed o r combined (i. e.,

con-

taining both distributed and concentrated elements). Depending on the requbements of the problem at hand, models may be unidimensional, planar o r spatial. The conditions applied to the nature of elastic and dissipative connections in the human body result in the development of nonlinear models. The time of application of vibrations determines whether the model is stationary o r nonstationary. If, in addition to the elastic and damping properties of the body, we also considea the

contractive function of the muscles, the model is converted from a passive to an active model. Doubtless, a l l of these classes of models a r e independent of each other, i.e.,

models can be produced with a combination of the pro-

perties of various classes.

The need to study dynamic models of the body of a human operat o r f o r various working positions under the influence of vibrations

results from the changes in elastic properties and position of the center of gravity, which lead to changes in the resonant frequencies. This condition requires the development of new criteria and the r e -

finement of existing criteria f o r vibration protection. Our experiments have

eetablished .the fact of significant changes

in the amplitude-frequency characteristics depending on position. One of the basic structural elements of the human body is the. curved spinal column; therefore, it is convenient to utilizk an elastic rod with various masses attached to it (Figure 8). Thus, for a man seated on a chair in three different positions in Figure 9, we obtained the, amplitude-frequency characteristics shown in Figure 10. Analytic approximation of the experimental frequency characteristics produced the expressions f o r transfer functions of the human body establishing a relationship between accelerations measured at the head of the subject and at the seat

of the chair.

These depen-

dences can be expressed as a function of frequency. The synthesis of mechanical models with concentrated parameters, performed using a matrix method [8] , allowed determination of the parameters of three-mass, two-mass and one-mass models corresponding to the position in question. In a number of cases, a human operator must work standing up while being exposed to vibration. In [29J we presented our results of determination of the dynamic characteristics of the body in the sitting and standing position with various angles of the knee joint, Fig.

11, Fig.

12.

D. Models of the Human Arm Under the Influence of Local Vibra-

tion. Studies of the oscillating properties of

the human a r m began

to be developed intensively in the middle of the 20th century. The Peason for the increasing interest in this problem has been the wide

-

spread use in industry of mechanized hand tools with increased vibra-

21

tion danger. The next stage in the study of the a r m as a mechanical system involJed the appearance of the Dieckmann model in the form of an oscillating system with 2 degrees of freedom

[34J

.

The input im-

pedance of this model has a maximum at frequencies below 5 Hz and in the 35-40 Hz area, the effective mass of the a r m is approximately 1 kg, the compliance of the palmar tissue is estimated a s 2-10

8

c m/ dyn. When working with a mechanized hand tool, a man changes his working position and the degree of s t r e s s on the muscles of the arm.

As a result of this, the parameters of the equivalent mechanical systems, which replace the arms in theoretical investigations, obviously change with time. Therefore, investigators have recently concentrated their attention on estimating the influence of working position of the operator on the parameters of mechanical models of the human arm, Our investigations [25J

have shown that the amplitude

-

fre-

quency characteristics of the human a r m change significantly with various degrees of muscular stress. An increase in s t r e s s results i n an increase in the level of vibrations directly measured at various points on the human arm. The resonant frequencies of the system also increase, which is e s l a i n e d by the increase in equivalent rigidity of the entire system.

To investigate the dependence of the input mechanical impedance

of the system on the s t r e s s on the muscles of the a r m and the working position, Yu. Vasilyev

[SSJ

developed an experimental method

based on indirect measurement. First, the frequency characteristics of the f r e e oscillating system of an electrodynamic vibrator with the handle of a pick hammer attached to it were estimated. The test subject then imitated various working modes, grasping the handle w i t h his a r m straight o r bent and taking up various working posi-

tions. Comparison of the frequency characteristics of the f r e e vibrator and the vibrator loaded by the arms of the test subject allowed the oscillating properties of the a r m s to be calculated.

22

The mechanical parameters of the vibrator (rigidity, mass, dampingfactor) were similar in order of magnitude to the corresponding parameters of the a r m s (according to the data of Dieckmann).

Due

to this, the changes in frequency characteristics of the vibrator-arm system were significant, allowing the active and reactive components of the impedance of the a r m s to be calculated with great accuracy. E. Regulation of the Dynamic Characteristics of the Human Bodg

Under the Long-Term Influence of a Vibration Stimulus. When vibrations are applied over an extended time, a significant change occurs i n the dynamic properties of the human body. The changes are so significant that to ignore this fact may lead to basic e r r o r s , f o r example, in the development of means f o r vibration protection. In our studies

[37]

-

[41]

,

test subjects were subjected to

monoharmonic vibrations during sessions lasting from 2 to 4 hours. The amplitude-frequency characteristics of the body were measured before and after the sessions. The intensity and frequency of vibrations were constant during each session, but changed from session to session. The frequency range of 2-7 Hz was covered. Figure 13 shows selected experimental dependences of the amplitude of vibration accelerations on time, measured at the shoulders of

test subjects during one session. Figure 14 shows similar dependences of vibration displacement amplitudes, measured at the heads of the

test subjects. Comparison of these figures leads to very significant conclusions: 1. The amplitude of

vibrations of the human bodyincreases du-

ring the course of a vibration session, while the amplitude of vibration accelerations decreases. 2.

The rate of change of the amplitude of oscillations of the

human body depends on the frequency of the vibration stimulus.

The

maximum absolute value of acceleration is reached at the frequency of the human body.

The phenomenon noted in point 1 can be explained f r o m the

23

standpoint of the theory of oscillations, if we consider that the parameters of the ligaments of the skeletomuscular system a r e nonstationary, while the nonlinearity of the elastic ligaments is ttsoftt' in nature. With long term application of vibrations, the elastic ligaments become "softer".

According to the equation of motion for the system,

which can be written as:

where A a r e the relative vibration motions, the pnenomena described in point 1 can be expressed mathematically as follows. The behavior of the system corresponds to the condition min R i.e.,

m u t

II R ( A , A , i I ,

the maximum forces in the mechanical couplings of the sy-

stem must be minimal. To explain the phenomenon noted in point 2, let us analyze some additional information. During the tests, various tendencies were noted as to changes of the primary resonant frequency of the body of the test subject, depending on the frequency range of vibrations in relationship to the resonant frequency of the body, 4-5 Hz, measured before the beginning of a session. Illustrations of these tendencies are presented in Figures 14 and 15, in the form of amplitude-frequency characteristics produced with various frequency modes of vibration. The results of measurements were produced in a three-hour session with a vibrating frequency of 8 Hz, i. e.,

in the resonant mode. The frequency characteristic

numbered 2, produced after the end of the session, has a maximum which is displaced i n relationship to the initial frequency characteristic in the direction of higher frequencies by 1 Hz. In those cases when the frequency 'of the vibrations was between 0 and 4 Hz, i.e.,

in the subresonant zone, the maximum of

the frequency chcracteristic of human bodies after a vibration session

24

was shifted downward on the frequency range. Figure 16 presents the results of measurements performed for a session lasting 75 minutes, during which narrow-band random vibrations were applied, with their spectral density of power concentrated in the 0.2 Hz area, i. e.,

in

the subresonant area. We have here a shift of the maximum of the frequency characteristic toward the lower fl'equency end by 0.5 Hz. The results which we produced a r e summarized in Figure 14, where we s e e the dependence of the change in relative resonant frequency

W/W 0

of the human body under the influence of vibrations of

frequency p. The left branch of the graph, in the shaded area, corresponds to the transresonant mode, where p

7

w

0

while the right

branch of the graph corresponds to subresonant mode, i.e.,

p C wO.

The nature of the change in the natural frequency of the human body revealed in ourinvestigations can be formulated as follows. The natural frequency of the human body under longterm exposure to vibration, quite independently of any effort of the subject, changes i n such a way as to "detune" as far. away from the frequency of the vibration stimulus as possib1e;this can be described mathematically by the simple inequality

"[dt l*t This behavior of the biological system is quite "intelligent" from the standpoint of mechanics. We know in agreement with the results of the theory of oscillations, i n developing a vibration protection system the designer attempts to place the natural frequency of the protected

object, installed on shock qbsorbers, as f a r as possible from the frequency of the vibration stimulus. The results described above show that certain factual data on the dynamic properties of the system stu-

died cannot be explained by representing the human body as a certain passive mechanical system. In analyzing biomechanical systems, it is frequently considered that the functioning of such a system follows certain mechanisms of regula-

25

tion which provide the adaptive properties of biological structures. The

human body, from the mechanical point of view, is i n the f i r s t

approximation a system of'elastic bodies with couplings defined by the skeleto-muscular structure. The various regulation processes inherent in biological systems lead to changes of the mechanical properties of the human body. In accordance with these ideas, we can supplement the passive mechanical models of the human body and represent it a s a system a s shown in Figure 17. Here

the vector V characterizes the effect

of regulation, which is performed by the biological system, This vector can b e considered a certain control vector; each of its components corresponds to a specific regulation mechanism In this statement of the problem, we need not analyze the various mechanisms of bioregulation, but can consider that their joint effect is such that i t leads to certain changes in the dynamic properties of the mechanical system. Looking upon the vibration as a stimulus, we can assume that the behavior of the biomechanical system with longterm vibration is organized so as to minimize the influence of the unfavorable factor in the environment, for example by a local change of position. hypothesis i s also confirmed by the results of reference

This

[42J which

revealed search activity by the muscles. It i s thus seen that a more complete description of the dynamic characteristics of the human body

exposed to vibration

requires

the use of active dynamic models t h a t take i n t o consideration the processes of regulation of the biomechanical systems.

i W H, ~ ~ H B o TJ CR W ~ T9lllDUiHe XapaH T8pklC TMKM ~ P I b w f Ma

,qeficTsy~)wHa ~enosexa-onepa~opay n p a s m q e r o MamHam,

MeXaHM3MMH. YIHCTPyMeHTaMEI, TPaHCIlOPTHEJMH CPeJlCTBaMki, AHBJIPr3MPJWTCR AaH.We 3KCIIePMMeHTaJIbHMX MCCJI€?,Z~OBBH~~~ YeJIOBeXBoneparopa, no@ep;&esaoro c n y r l a t ~ o ~sk16pafiao~ao~y y no3zeBCTEMK)m-m ero P E I S ~ Y H K 1103. X [Ioxasaso Bmmzlle BpeMerm ~ e i CTBNR sndpaqmm Rx EHTeHC9lBHOCTM Ha 6ll0,lIkl~aMMve~~~Ie XapaKTepflcTmn nenosexa-onepa~opa, a !came ero @ y m ~ l g l o ~ a n bxs ~ e

@m~lonormecxmepeaxrwul.

RE'FERENCES Munin, A.G.

and V.Ye.

Kvitki

( E d i t o r s ) , Aviatsionnaya

(Aviation Acoustics ) , Mashinstroyeniye Press,

Akustika

Moscow, 1973 Ruderman, J., High Rise Steel Office Buildings in the Structural Engng., 43. Feld, J.,

u. s, ,

( 1 9 6 5 ) , N o 1,

Construction Failure, J.W.

and Sons, Inc.,

New

York, 1968, p. 151. Lange, K.O.

and FLR. Coerman, Visual Acuity Under Vibration.

Human Factors, Dennis, J.P.,

4, No. 5,

(1962), pp. 291-300.

The Effect of Whole-Body Vibration on a Visual

Performance Task, Ergonomics, 8, Vykukal, H.C.

and C.B.

Np.

2, (19651,

Dolkas, Effects of Combined Linear

and Vibratory Accelerations on Human Dynamics and Pilot P e r formance Capabilities, Madrid,

p. 107.

Chelovek v Kosmose (Man in Space)

, Mir

Press,

1971, p. 32.

Byndas, L.A., et al.,

Internat. Astronautical Congress,

1966, Life in Spacecraft,

Sharp, M., Moscow,

17th

K.K.

Glukharev, B.A.

Potemkin, K.V.

Frolov

Estimation of the Functional Condition of a Human Ope-

r a t o r Exposed to Vibration,

Vibrozashchita Cheloveka-Operatora

i Voprosy ModelirovaniyF (Vibration Protection of a Human Ope-

rator and Problems of Modeling), Nauka Press, MOSCOW,1973. Andreyeva-Halanina, Ye. Ts. et al.,

Vibratsionnaya Bolezn

(Vibration Sickness), Medgiz Press, Leningrad, Goldman, D.E., tion

and H.E.

1961.

Gierke, Effects of Shock and Vibra-

on Man, Shock and Vibration Handbook, Vol. 3, N. Y.,

Loeckle, W. E.,

1961.

The Physiological Effects of Mechanical Vibra-

tion, US Air Forces, German Aviation Med.,

1950, 11.

Clarac, J . and R. Kresmann, Conduite des Transports en Commun et Lombalgies,

Arch. Mal. Profess.,

28, No.3, (1967)

pp. 412-413.

27

[13] Butkovskaya Z. M.,

B. A. Potemkin and K. V.

Ye. N.Kadyskina,

Frolov, Study of the Influence of Vibrations of Machines and Tools on the Arms of a Human Operator with Various Initial Conditions, Vibroizolyatsiya Mashin i Vibrozashchita ChelovekaOperatora (Vibration Insulation of Machines and Vibration Protection of the Human Operator), Nauka P r e s s , MOSCOW,1973, pp. 5-16. Vorshchevskiy, I.Ya.

et al. Obshchaya Vibratsiya i Yeje

Vliyaniya na Organizm Cheloveka (General Vibration and its Influence on the Human Organism),

Medgiz Press, Moscow,

1963, p. 156. Megel, N.,

U. Wozmak, L.Sun,

Effects on Rats of Exposure

to Heat and Vibration, J. Appl. Physiol.,

17, No. 5, (19621,

pp. 759-762. Sackler, A.M.

et al. Effects of Vibration on the Endocrine

System of Male and Female Rats.,

Aerospace Med.,

37, No.2,

(19661, pp. 158-166. Vaysfeld, I.L.,

RF. Ilicheva, I.M.Khazen,

et al.,

Histamine

and Serotonin Metabolism when Vibration is Applied to the Body of a Human Operator,

Vliyaniya Vibratsiy Razlichnykh

Spektrov na Organizm Cheloveka i Problemy Vibrozatchity (The ‘Influence of Vibration with Various Spectra on the Human Body and Problems of Vibration Protection), Nauka Press, MOSCOW, 1972, pp. 132-136. Golubchikov, V.A.

The Mechanism of the Influence of General

Vertical vibration on the Urinary Tract in Man,

Vliyanie

Vibratsiy Razlichnykh Spektrov na Organizm Cheloveka i Problemy Vibrozatchity, Nauka Press, Moscow, 1972

,

pp. 184-

188. Wittmann, T.J. and N. S. Philips

Human Body Nonlinearity.

Mechanical Impedance Analysis, ASME publication 69BHF-2,

1969.

28

[20]

Obysov, A. S. Nadezhnost Biologitcheskikh Tkanei ( The Reliability of Biological Tissue), Meditsina Press, Moscow, 1971, pp. 37-48.

[21]

Gittke von, H.E.,

Biodynamic Response of the Human Body,

Applied Mechanics Reviews, [22]

Lippert, S. (ed.), P r e s s , N.Y.,

17, No, 2,

(1964)) pp. 95 1-958.

Human Vibration Research, Pergamon

1963.

1231 , Gierke von, H. E.

, Biodynamic

Models and Their Applications,

The Journal of Acoustical Society of America, 50, No.6, P a r t I, December 1971, pp. 1397-1413. 1245

Potemkin, B.A.,

and K.V.

Frolov, Model Representation of

the Biomechanical System of a Human Operator with Random Vibrations

,

Doklady Akademii Nauk SSSR

,

197, No.6,

1971,

pp. 1284- 1287, [25]

Potemkin, B.A.

and K.V.

Frolov, Experimental Study of the

Reaction of a Human Operator to Vibration, Nelineynyye Kolebaniya i Perekhodnye Protsessy v Mashinakh (Nonlinear Oscillations and Transient Processes in Machines), Nauka

Press, Moscow, 1972, pp. 67-74. 1261

Griganov, kS. and K.V.

Frolov,

The Problems of Estimation

of the Influence of Vibration of Machines and Tools on the Organism of a Human Operator, Kolebaniya i Ustoychivost Prioborov Mashin i Elementov Sistem Upravleniya ( Oscilations and Stability of Instruments, Machines and Elements of Control Systems), Nauka Press, Moscow, 1968, pp. 20-29. [27)

Potemkin, B.A.,

Some Problems of the Influence of Machine

Vibration on the Work of a Human Operator, Kolebaniya i U stoichivost Priborov Mashin i Elementov Sistem Upravlenia

(Oscillations and Stability of Instruments, Machine 8 and Element8 of Control Systems), Nauka Press, Moscow,

1968,

pp. 30-55.

29

Potemkin,

B. A. and K. V. Frolov, Construction of a Dynamic

Model of the Body of a Human Operator Subjected to Wideband Random Vibration, Vibrozolyatsiya Mashin in Vibrozachita Cheloveka-Operatora, Nauka Press, MOSCOW,1973, pp. 17-30.

P91

Panovko, G. Ya , B. A, Potemkin and K. V. Frolov, Determination of the Parameters of Models of the Body of a Human Operator Exposed to Vibration and Impact, Mashinovedeniye, 3, (19721,

pp. 31-36.

Stikeleather, L. F.,

G. 0. Ha. and A.O.

Radket, Study of

Vehicle Vibration Spectra as Related to Seating Dynamics, SAE Preprint No. 720001,

1972.

Bekesy von, G., Gber die Vibrationsempfindung, Akust. 2. , 4,

(1939),

p. 317.

Kuhn, F. and H. Scheftler, Beim Gebrauch von Druckluf t-

2. Angew.

Schlagwerkzeugen Einwirckende Krtjfte, Internat. Einschliesslich, Arbeitsphysiol. c3 33

15, (1954)

,

Kuhn, F., Uber die mechanische Impedanz des Menschen bei d e r Arbeit mit Presstufhammer, Internat. Einschliesslich Arbeitsphysiol.

C3 41

p. 277.

2. Angew. Physiol.

15, (1953), p. 79.

Dieckmann, D., Fin mechanisches Model1 fQr das Schwingserregte Hand- Arm-System des Menschen, Internat. Z. Angew. Physiol. Einschliesslich Arbeitsphysiol. Coermann, R.R.,

17, (1958), p. 125.

The Response of the Human to Low Fre-

qeuncy Vibration, Journal of Aerospace Med.

,

31, (1960),

p. 443. Vasilyev, Vu. M.

, Problems of the Dynamics of a System

Cosisting of a Human Operator and an Impact Tool, Nelineynye Kolebaniya i Perekhodnye Protsessy v Mashinakh, Nauka Press, MOSCOW,1972, pp. 74-88. Glukharev, K.K.,

B. A.

Potemkin and K. V.

Frolov,

Peculiari-

ties of the Biodynamics of the Human Body with Vibrations, Vibrozatchita Cheloveka-Operatory i Vo.prosy Modelirovaniya (Vibration Protection of the Human Operator and Problems of Modeling), Nauka P r e s s , Moscow, 1973, pp. 22-28.

30

[38]

Glukharev, K.K.,

B. A.

Potemkin and V. N. Sirenko, The Non-

l i n e a r and Unstable Characteristi cs of the Human Body, Mashinovedeniye, 4 (1972), pp. 9- 14. [39]

Glukharev, K.K.,

B.A.

Potemkin and K.V.

Frolov, Nonlinea-

rity and Instability as Manifestations of the Regulation of Dynamic Properties of the Human Body Vliyaniye Vibratsiy Razlichnykh Spektrov na Organizm Cheloveka i Problemy Vibrazatchity, Nauka Press, Moscow, 1972, pp. 46-60. [40]

Glukharev, K.K.,

B. A.

Potemkin and K. V, Frolov, The

Construction of a Simple Mechanical Model of the Human Body Exposed to Harmonic

Vibrations, Konf erentsiya PO Kolebani-

jam Mekhanitcheskikh Sistem ( Conference on Oscillations of Mechanical Systems), Naukova Dumka Press, Kiev

, 6-10

July 1971, Abstracts of Reports, Kiev 1972. [41]

Potemkin,

B.A.,

K.V.Frolov

et al.,

Unstable Dynamic Cha-

racteristics of the Human Body with Horizontal Oscillation, Vliyanie Vibratsiy na Organism Cheloveka i Problemy Vibrozatchity, Nauka Press, Moscow, [42]

1973, pp. 25-29.

Issledovaniye Protsessov Upravleniya Myshechnoy Aktivnosti (Study of Processes of the Control of Muscular Activity) Nauka Press, MOSCOW,1970, pp. 5-49.

31

t-

t-

t

=1.

Fig. 1. Examplee of idealized f o r m of vibrations.

32

Fig. .2. The orientation of the axes.

33

Fig. 3. Curves of equal resolving capacity of the eye without additional t i e -- - with a d d i t i o n a l t i e

--

0.10

-

-

8

0.08 -2.0 , . q 0.06 aoL -1.0

0.02 - '

-

0.

I

I

"

I

-

1

*

I XI result 61III 7lIII 16IIII 18IIII 261XI

Fig. 4. The l e v e l of histamine and the I1Dof1 a c t i v i t y o f the people affected by vibrations

34

A

f

1 r------------mechanical system I

V internal organs

I

I

B -

I I

central nervous system

I

J at terent signals

F i g . 5. The reactions o f the body t o vibrations.

--

+

0.2

Loadilb

Loading through back Loading through head

F i g . 6. Results o f experimental s t u d i e s .

35

t""'

10000 15000

a5 1

C

-

1.5 2 2 5 3 3.5 4 ~l(crn1

Fig. 7. The graph for the firet lumbar intervertebral d i s c

Position I

s

Position

I1

Position I11

Fig. 9. Different positions of the sitting m a n .

36

8

C

Position I1

m7km

Position I11

Fig. 10. Amplitude-frequency characteristics o f the three cases shown in P i g . 9.

Fig. 12. Dynamic characteristics.

37

I

a

I

1800

I1

1356

I11

900

IV

V

Fig. 11

38

.

Different p o s i t i o n s .

Pig. 13. Selected experimental results (measured at the shoulders).

39

12

_

1.4

_

_

~

1i

Fig. 14. Selected experimental results (measured at the head).

Fig. 15. Amplitude-frequency characteristics.

40

[rns-21 2

1

\ 0

'\.- --1

I

I

1L

16

18 20 Hz

Fig. 160 Amplitude-frequency characteristics.

Mechanical system

I

*

V

-

Biological system

I

h

Fig. 17. Human body as a system.

41

EF'FETS OF MUSCLE VIBRATION AND JOINT OSCILLATION ON HUMAN MOTOR MECHANISMS Gym C. Agarwal College of Engineering, Unlversiryof Illinois at Chicago Circle, chlcago. Ill ., U.S.A.

Gerald L. Gottlieb Department.of Physiology Rush-Presbyterian&. Luke's Medical Center, Chicago, Ill

., U.S.A.

SUMMARY The tonic vibration reflex (TVR) affects a joint's response to sinusoidal oscillation in the same facilitatory manner that is seen with tonic voluntary contraction.

In contrast, tonic voluntary

contraction facilitates the myotatic reflex while the TVR inhibits it in the soleus muscle.

The degree of myotatic reflex inhibition is

input frequency dependent.

In discrete tracking task, vibration

increases simple and choice reaction times.

However, the error

correction time is not influenced.

INTRODUCTION

The suppression of the patella reflex in human subjects seated on a vibrating platform was observed some forty years back (Coermann, 1938, cited by Goldman, 1948).

Interest in this vibration effect

was renewed by the studies of Hagbarth and Eklund (1966) and DeGail, Lance, and Neilson (1966). The tonic vibration reflex (TVR) and the suppression of both tendon-jerk and Hoffmannreflexeswere observed

42

in each of these studies.

Numerous studies since have shown that

vibration of the limb in animals as well as humans activates both monosynaptic and polysynaptic pathways in the spinal loops.

For

review of the earlier literature see Hagbarth (1973) and Lance, Burke

&

Andrews (1973).

Vibration of a tendon in the human causes a predictable increase in the contractile activity of the agonist, caused by autogenous reflex excitation of the alpha motoneuron pool.

This leads to

involuntary movement and illusions of movements (Goodwin, McCloskey &

Matthews, 1972; McCloskey, 1973; Craske, 1977). Recent studies by Godaux and Desmedt0(1975) have shown that

100 Hz vibration of the human masseter muscl& potentiates both the masseter tendon jerk and masseter H-refl'ex in contrast to the inhibition observed in the leg.

Agarwal

&

Gottlieb (1976) found the

effect of vibration on the achilles tendon,to be frequency dependent. The tendon jerk was inhibited at 60 and 100 Hz, but was facilitated at 160 and 200 Hz vibration.

The Hoffmann reflex was also inhibited

at 60 and 100 Hi vibration, slightly inhibited at 160 Hz and unchanged with 200 Hz vibration, There are two reflex pathways activated by muscle vibration through the primary afferent pathway. The relative contribution of monosynaptic and polysynaptic pathway is unclear in the generation of TVR, although the monosynaptic pathway plays an essential role in the vibration-induced timing of motoneuron discharge (Burke Schiller, 1976; Hagbarth, Hellsing Watanabe, 1972, Homma, Mizote

&

&

&

Lofstedt, 1976; Homma, Kanda

&

Watanabe, 1975).

The effect of high frequency vibration (above 5 0 Hz) applied to muscle or muscle tendon has received considerable attention in the neurophysiology literature but low frequency oscillation inputs

43

applied to a joint has attracted attention only recently (see Joyce, Rack

&

Ross, 1974; Agarwal

&

Gottlieb, 1977; Goodwin, Hoffman

Luschei, 1978 for references to other studies).

&

These studies have

provided-valuable information about the spinal mechanisms which may be important in the study of human performance. In man-machine system studies, the whole body vibration response is characterized in terms of a mechanical impedance.

Such studies

have focussed on overall input-output models rather than looking at the structural details.

For whole-body vibration, Coermann (1962)

and Von Gierke (1968) have been pioneers in this field (see Garg Ross (1976) for a recent review).

&

Similar approaches have been used

.to study the impedance of'the hand-arm system (for reviews see Taylor (1964); Wasserman

hi

Taylor (1977)).

In most of these studies linear,

lumped, mechanical models were obtained using curve fitting techniques from the Bode plot response. Extensive neurophysiological literature is available on the vibration effects on muscle spindles (see Matthews (1972) for a comprehensive review). However, our understanding of the effects of segmental vibrations on human workers in workplace situations is far from complete.

We need a more fundamental understanding of the

interactions of vibration with various "servo-systems" in the body which gontrol our motor activity. The human operator is prone to making errors in a quick, choice reaction time task.

The speed with which the operator can recognize

errors of choice and correct them is an important consideration in many industrial tasks.

Many studies have shown that subjects can

correct errors of movement more quickly than they can react to external stimuli (for review of the literature, see Schmidt (1976) and Angel (1976)).

44

Vibration which significantly modifies our

kinaesthetic perceptions is likely to influence our psychological processes and thereby will modify the human performance in the work3lace situation (Lewis

&

Griffin, 1976).

In this paper we will present the results of some of our recent studies on the. effect of vibration applied to the extensor and flexor muscles used for ankle joint rotation in plantarflexion and dorsiflexion. The ankle joint is anatomically convenient to work with and the electromyographic activity (EMG) of the major muscles is easily recorded using surface electrodes.

METHODS

Experiments were done on normal, adult, human subjects.

A

subject sat in a chair with his right foot strapped to a footplate which could rotate about a horizontal, dorsal-plantar axis through the medial maleolus.

The details of the experimental apparatus are

available in Agarwal & Gottlieb (1977a). The plate is*oscillated by a d.c. torque motor by sinusoidal signals in the frequency range from 3 to 30 Hz, superimposed on a mean motor torque level.

Measurements were made of the applied

torque, the angular rotation about the ankle joint and surface EMGs from the soleus and the anterior tibia1 muscles. wave rectified and filtered before recording.

A

The EMGs were fullcomputer (General

Automation SPC-16/65) generated the motor-drive signal and recorded the digitized data on magnetic tape. Hagbarth-type vibrator (TVR vibrator

Vibration was produced by a

-

Model #TMT-18, Heiwa Electronic

Industrial Corp., Japan), attached to the midpoint of the calf muscle with surgical tape.

Vibrator frequencies were selected at SO, 100 or

150 Hz.

45

Fourier series coefficients were computed from the torque and angular rotation data to calculate the effective compliance of the ankle joint.

A curve fitting procedure was used to estimate moment of

inertia of the limb, viscosity and stiffness of the joint (for details see Agarwal

&

Gottlieb, 1977b: Gottlieb

&

Agariral, 1977, 1978).

In the second experiment, pulses of torque lasting one second were applied to dorsiflex or plantarflex the foot.

The instructions

to the subject were to react as quickly as possible in opposition to the motor pulse and restore the foot to its original position.

For

details of the methods, see Gottlieb and Agarwal (1979). The rate of joint rotation and hence muscle stretch changes rapidly upon applicatior of a torque pulse.

The average velocity in the 16-24 msec interval

after torque onset was used as the independent variable in graphing EMG response versus stimulus intens’ity. The measure of the EMG response was the integrated EMG activity of the myotatic reflex. experiment was done without vibration and at three vibration

The

frequencies. In the third experiment, we studied the effects of vibration on the reaction time in a discrete tracking task.

Two vibrators were

attached on the calf and the anterior tibia1 muscles and were operated at 100 Hz continuously during the tracking task.

The methodology was

similar to that used by Angel (1976). For details see Jaeger, Agarwal &

Gottlieb (1978). The reaction times were measured to the onset of

the EMG activity in the appropriate muscle.

RESULTS

Figure 1 shows the compliance as a function of motor oscillation frequency under four conditions: no vibration, and vibration at 50,

46

100, or 150 Hz.

As the vibration was applied, the TVR produced a tonic

contraction (increasing with vibration frequency) which was counteracted by the torque motor bias so that the subject did not produce any voluntary tonic muscle force to hold the reference foot position. The solid lines in this figure are the best second order fit. The model's moment of inertia and viscosity coefficient remained nearly constant, their mean values at 0.021 Nm sec'/rad respectively.

and 0.28 Nm sec/rad

The elastic stiffness changed significantly.

The

values without vibration and at 50, 100 and 150 Hz were 26, 34, 47, and 56 Nm/rad respectively.

The resonant frequency increased with

vibration frequency and the values were 6.1, 6.6, 7.4, and 7.8 Hz for the four cages.

Similar results were obtained in all subjects.

Figure 2 shows the typical results of the second experiment. The stretch reflex magnitude is linearly proportional to the velocity

of stretch and is significantly reduced by vibration.

The two data

sets for the vibration-free case were taken before (x-points) and after (v-points) the vibration runs.

As

in the earlier experiment,

the subject was asked to relax and the tonic forces produced by the TVR were counterbalanced by the motor bias to maintain foot position.

The coefficient of the linear regression lines are 0.182 (no vibration before), 0.078 (50 Hz), 0.044 (100 Hz), 0.027 (150 Hz), and 0.i87 (no vibration after). In the third.experiment, we have compared the simple reaction time (SRT), choice reaction time (CRT), error reaction time (ERT) and error correction time (ECT).

ERT is the RT for those movements in

which the subject's initial choice of direction was in error.

These

reaction times may be defined with respect to foot angle, its first derivative or the EMGs of the respective muscle. measurements made using the EMG data.

Figure 3 summarizes

The table below shows the data

47

for one of the five subjects teated. Table: Reaction Times (GA) Normal

SRT CRT ERT ECT

Vibration

Mean

SD

N

219 253 257 143

39 80 62 72

233 -5.99 171 -5.58 47 -1.03 47 0.32

All the RTs are given in msec.

t

Mean

SD

N

246 317 274 137

45 111 60 69

150 131 19 19

The t-test analysis was performed

assuming the sample variances to be unequal and compared the RT between normal and vibration condition. DISCUSSION

The sinusoidal torques on the ankle joint has been shown to produce many nonlinear effects (Agarwal & Gottlieb, 1977a).

Driven

oscillations at frequencies near resonance show increasing amplitudes

of angular rotation exhibiting a limit cycle type phenomenon. Distortion of angular rotation from the sinusoidal wave shape is frequently observed with drive frequencies between 8 and 12 Hz. Self-sustaining oscillation (clonus) near the resonant frequency af the compliance is sometimes observed after the modulation signal to the motor is turned off.

This is most often seen when the

gastrocnemius-soleus muscles are fatigued. The vlsco-elastic properties of the ankle joint have been shown to be linear functions of the muscle contraction.

Vibration produces

a TVR and that tonic contraction of the muscle changes the muscle properties in a manner not distinguishable from voluntary contraction.

48

(Agarwal & Gottlieb, 1977a, Gottlieb 6, Agarwal, 1978.) In a recent study (Gottlieb

&

Agarwal, 1979) we have shown that

the myotatic component of the stretch reflex in the human soleus muscle is linearly and highly correlated with the rate of muscle stretch.

The slope of this response curve may be characterized as

a reflex arc gain which was shown to be-linearly proportional to the level of tonic voluntary activation.

The response curves in

Figure 2 show a linear relationship to the applied stretch.

However,

the tonic muscle activity of the TVR inhibits the.stretch response. This indicates different spinal mechanisms involved in TVR and voluntary tonic activity.

There are several known mechanisms which

influence spinal reflexes due to vibration inputs: a) busy-line phenomenon of the spindle fibers, b) presynaptic inhibition of the monosynaptic pathways, and c) changes in the spindle sensitivity via the gamma motor system.

The relative importance of these machanisms,

is still undetermined. In the tracking task study, the vibration input significantly increases the simple and choice RTs at P < 0.01 level in the t-test analysis.

This increase could be interpreted to indicate that large

irrelevant position signal input from the vibrated joint muscle. afferents delays processing of the visual information and command selection.

However, as shown in the table, the error correction time

is not significantly influenced by vibration.

This suggests that the

origin of the feedback from error responses is central rather than kinaesthetic. ACKNOWLEDGEMENT This work was supported by the NSF grant 316-7608754 and NIH grants 18-12877 and NS-00196.

49

Le r&flexe tonique & la vibration (W) ir?fluence la reponse a m oscillations sinusoidales clans la memo,fagOn facilitante, qu'on observe dans la contraction tonique volontaire. Au contraire, la contraction tonique volontaire facilite le riflexe myotatiyue t'andis que lo TVR la inhibe dans le muscle soleus. LO degxe 9'inh.ibition du rhflexe-myotatique depend de la friquence ds 1 excitation. nans doa taches do poursuite discrhte la vibraLion augmente les temps de,r&aotion simple et de choix. PourtanL le teiiips de correction d erreur n'est pas influent?&.

REFERENCES Agarwal, G.C. & Gottlieb, G.L., Effects of Vibration on Human Spinal Reflexes. In The Motor System: Neurophysiology and Muscle Mechanisms, M. Shahani (Ed'itor), Elsevier, 181-188, 1976. Agarwal, G.C. & Gottlieb, G.L., Oscillation of the Human Ankle J o i n t in Response to Applied Sinusoidal Torque on the Foot. J. Physiol. (London), 268, 151-176, 1977 (a)

.

Agarwal, G.C. & Gottlieb, G.L., Compliance of the Human Ankle Jpint. ASME Jour. of Biomechanical Engineerinq, 99, 1667170, 1977(b). Angel, R.W., Efference Copy in the Control of Movement. 26, 1164-1168, 1976.

Neurology,

Burke, D. & Schiller, H.H., Discharge Pattern of Single Motor Units in the Tonic Vibration Reflex of Human Triceps Surae. J. Meurol. Neurosurg. Phychiat., 39, 729-741, 1976. Craske, B., Perception of Impossible Limb Positions Induced by Tendon Vibration. Science, 196, 71-73, 1977. Coermann, R.R., The Mechanical Impedance of the Human Body in Sitting anEL Standing Position at Low Frequency. Human Factors, 4, 227-253, 1962. De Gail, P., Lance, J.W. h Neilson, P.D., Differential Effects on Tonic and Phasic Reflex Mechanisms produced by Vibration of Muscles in Man. J. Neurol. Neurosutg. Psychiat., 29, 1-11, 1966. Garg, D.P. & Ross, M.A., Vertical Mode Human Body Vibration Transmissibility. IEEE Trans. Systems, Man, and cybernetics, SMC-6, 102-112, 1976. Godaux, E. & Desmedt, J.E., Human Masseter Muscle: H Reflexes. Archives Neurol. 32, 229-234, 1975.

- and Tendon

Goldman, D.E. Effect of Mechanical Vibration on the Patella Reflex in the Cat. Amer. J. Physiology, 155, 78-81, 1948.

50

Goodwin, G.M., Hoffman, D. & Luschei, E.S., The Strength of the Reflex Response to Sinusoidal Stretch of Money Jaw Closing Muscles During Voluntary Contraction. J. Physiol. (London), 279, 81-111, 1978. Goodwin, G.M., McCloskey, D.I. & Matthews, P.B.C., The Contribution of Muscle Afferents to Kinaesthesia Shown by Vibration Induced Illusions of Movement and by the Effects of Paralysing Joint Afferents. Brain, 95, 705-748, 1972. Gottlieb, G.L. & Aqarwal, G.C., Two Methods of Measurinq the Dynamic Behavior.of the Stietch Reflex.in Man. Proc. San Diego-Biomed: Symp. , 16, 369-374, Academic Press, N.Y., 1977. rattlieb, G,L. & Agarwal, G.C., Dependence of Human Ankle Compliance on Joint Angle. J. Biomech., 11, 177-181, 1978. Gottlieb, G.L. & Agarwal, G.C., The Response to Sudden Torques About the Ankle in Man: The Myotatic Reflex. Jour. Neurophysiol., 1979. (in press) Haabarth. K.E.. The Effect of Muscle Vibration in Normal Man and in Patients.with Motor Disorders. In New Developments in Electromyography and Clinical Neurophysiology, J.E. Desmedt (Editor), vol 3, Karger, Basel, 428-443, 1973. Hagbarth, K.E. & Eklund, G., Motor Effects of Vibratory Muscle Stimuli in Man. In Nobel Symposium I - Muscular Afferents and Motor Control, R. Granit (Editor), Almquist & Wiksell, Stockholm, 177-186, 1966. Hagbarth, K.E., Hellsing, G. & Lofstedt, L., TRV and Vibration-Induced Timing of Motor Impulses in the Human Jaw Elevator Muscles. J. Neurol. Neurosurg. Psychiat., 39, 719-728, 1976. Homma, S . , Kanda K. & Watanabe, S . , Preferred Spike Intervals in the Vibration Reflex. Jap. J. Physiol., 22, 421-432, 1972. Homma, S., Mizote, M. & Watanabe, S . , Participation of Mono - and Polysynaptic Transmission During Tonic Activation of the Stretch Reflex Arcs. Jap. J. Physiol., 25, 135-146, 1975. Jaeger, R.J., Agarwal, G.C. & Gottlieb, G.L., Directional Errors of Movements and Their Correction in a Discrete Tracking Task. Proc. of the Fourteenth Annual Conference on Manual Control, University of Southern Claifornia, 1978. Joyce, G.C., Rack, P.M.H. & R o s s , H.F., The Forces Generated at the Human Elbow Joint in Response to Imposed Sinusoidal Movements of the Forearm. J. Physiol. (London), 240, 351-374, 1974. Lance, J.W., Burke, D. & Andrews, C.J., The Reflex Effects of Muscle Vibration. In New Developments in Electromyography and Clinical , J.E. Desmedt (Editor), vol 3, Karger, Basel, 444-462, Lewis, C.H. & Griffin, M.J., The Effects of Vibration on Manual Control Performance. Ergonomics, 19, 203-216, 1976.

51

Matthews, P.B.C., Mammalian Muscle Receptors and Their Control Actions. E. Arnold Publishers, 1972. McCloskey, D.I., Differences between the Senses of Movement and Position Shown by the Effects of Loading and Vibration in Man. Brain Research, 63, 119-131, 1973. Schmidt, R.A., The Schema as a Solution to Some Persistent Problems in Motor Learning Theory. In Motor Control: Issnes and Trends, G.E. Stelmach (Editor), 41-65, Academic Press, N.Y., 1976. Taylor, W. (Editor). The Vibration Syndrome, Academic Press, New York, 1974.

-

Von Gierke, H.E., Response of the Body to Mechanical Forces an Overview. Ann. N.Y. Academy of Sciences, 152, 172-186, 1968. Wasserman, D.E. & Taylor, W. (Editors). Proc. of The International Occupational Hand-Arm Vibration Conference. U.S. Department of Health, Education, and Welfare (NIOSH), Publication #77-170, Cincinnati, 1977.

A

'

w

0 z a

i

n 5 0 0 I-

z FREQUENCY (HZ)

Figure 1. Effective equivalent compliance for the ankle joint measured in rad/Nm as a function of the drive frequency at no vibration (x), and three vibration inputs: 50 Hz ( * I , 100 €12 (a, and 150 Hz ( A ) . The solid lines are for a best-fit, second-order mechanical model.

52

u

60 V.S.

STRETCH VELOCITY (GCA 6/22/76)

250

dews

Figure 2. Integrated soleus EMG response between 36 to 65 ms after the onset of torque input against the angular velocity of forced dorsiflexion. Velocity was measured 16 to 24 msec after the onset of torque input. The five data sets are no vibration (x) at the start of the experiment, vibration input applied to soleus muscle at 50 ( * ) I 100 (01 I and 150 ( A ) Hz, no vibration (v) at the end of the experiment. The solid lines are linear regression curves.

53

AT

P-

I Sec

Figure 3 . Typical response i n e r r o r movement and subsequent c o r r e c t i o n (normal, no v i b r a t i o n case). The e r r o r c o r r e c t i o n t i m e (ECT) are measured from t h e i n i t i a l b u r s t i n t h e a n t a g o n i s t and a g o n i s t muscle EMGs. The t a r g e t jumps a t t i m e z e r o and t h e t o t a l d i s p l a y i s one second.

54

EFFECT OF BASE OSCILLATIONS ON THE HUMAN SKELETAL MUSCLE AND JOINT FORCES IN A STANDING POSTURE A. Seireg, R.Arvikar* Deportment of Mechanical Engineering, The Universiw of Wisconsin, Madison, Wisconsin, U.S.A.

Sumnary A comprehensive computer model of the musculoskeletal system is utilized in conjunction with published data on human resporise and tolerances to vibration for the calculation of the muscle forces and the stress variation at different base frequencies. The results show that the peak pressures on the spinal column are approximately the same as those calculated at the limit of the subject's weight lifting capability.

Introducti on The response of the human structure to vibratory motion has long been an important area of study in biomechanics, physiology

and aerospace medicine.

The theoretical and experimental investi-

gations on the subject are too numerous to list; some of these studies can be found in references11-31. Among the areas which have considerable practical importance is the establishment of the limits of human tolerance to vibration.

This paper utilizes a compre-

hensive model of the musculoskeletal system developed by the authors to determine the stresses in the different skeletal joints as well

as the spinal disc pressures at the vibratory tolerance levels

.w

Presented at the Symposium by D. P. Garg.

55

.

available in the published literature [l]

The interest here is

to determine if such vibratory motions produce high levels of stress in the skeletal joints.

The Model The musculoskeletal model used in this study is the same comprehensive model developed by the authors and used in previous studies on the lower extremities [ 4 , 5 ] , the spinal column [6-81, and the upper extremities [9].

The model treats the skeletal elements, in-

cluding the individual intervertebral discs, as rigid bodies each having six degrees of freedom. The different skeletal segments are connected together by the various muscles and ligaments. The muscle actions are represented by single or multiple lines connecting their points of origin and insertion.

Theae lines are selected such that

they can adequately describe the different functions each muscle

is capable of performing.

The coordinates of the points of muscle

attachments are located with respect to reference axes fixed to the individual skeletal segments. A schematic representation of the model is shown in Figure 1 and a listing of the major muscles is given in Table 1. The mass distribution and the corresponding gravitational forces on the different segments for a 72.3-hg subject are proportioned according to the anthropometric data of Dempster [lo].

The model has provisions to incorporate the effect of dynamic

motions of the different body segments in the form of D'Alembert's forces on the segments acting through the centers of gravity. The reactions at the different skeletal joints are defined by three

56

orthogonal components along the reference axes. The reactions at the intervertebral joints are represented by normal disc loads as well as normal reactions at the articular facets. The ligament forces at the different joints are conveniently modelled as any unbalanced tensile reaction forces or moments. The model is essentially the same as that used in previous studies [ 4 - 9 ] .

Analysis o f Forces i n a Standinq Human Subjected t o V e r t i c a l O s c i l l a t i o n s a t t h e Base o f Support Relevant data on the vibratory response at the hip, shoulder and head of a standing subject due to vertical oscillations at the base of support is readily available in the literature (see reference[l],for

example).

This data was used to obtain the acceleration

data for the different skeletal segments at the considered frequency of oscillation by interpolation. The equilibrium equations for the individual segments can therefore be formulated in terms of the gravitational and inertial forces as well as the unknown muscle forces and joint reactions. The equilibrium in the case of sagittal plane motion or sagittal symmetry can be defined by approximately

120 equations with 420,unknowns. As in previous studies, linear programming is utilized to reduce the system redundancy to a unique solution which minimizes a merit criterion U = CF

+ 4CM + 2CRt

where, CF = sum of all muscle forces, CRt = sum of any tensile joint reactions and EM = sum of any unbalance joint moments. be noted that the use of M and R

t

It should

is a convenient way to describe

forces which have to be carried by the ligaments.

57

The muscle forces and corresponding joint reactions were calculated for the reported tolerance limit (for base vertical oscillations in standing posture) of 2g at 4 Hertz as giyen in reference [l]. The results are given in Tables 2 and 3 for some of the important muscles and j o i n t forces at the positive and negative peak values of the inertia forces.

The Tables also show similar results fox

the case of the subject's weight lifting capability in the 52'

for-

ward stooping position and lifting a total weight of 45.4 kg (100 lb.). It can be seen from the results that the peak joint forces at the tolerance limit (corresponding to the upward acceleration) are of the same order of magnitude as those calculated for the weight lifting act.

It can also be seen that during the peak downward

acceleration the vertebral joint reaction forces become zero.

Concl usi on The musculoskeletal modeling approach used in this study can be valuable in the analysis of muscle forces and joint reactions under different environmental vibration conditions. The technique is more comprehensive than the traditional gross mechanical analogs of the human body used for the analysis of impact, vibration or other dynamic situations.

RBsumB Un modele mathkmatique du systhme muscle-squelettique est utilisk en conjonction avec les donnkes publikes sur la reponse humaine et la tolerance a w vibrations pour la calculationdes forces et de la variation des tensions B diffkrentes frCquences de base. Les resultats montrent que les pressions maximales sur la

58

colonne vert6brale sont Q peu+res pour le sujet, au limite de

sa

les mhes que celles calculdes,

possibilit6 de soul&vement d'un

poids.

BIBLIOGRAPHY [l] Shock 6 Vibration Handbook (Ed. McCraw Hill, 1961.

[ 21

C.

M. Harris and C. E. Crede),

Symposium on Biodynamic Models and Their Applications. (a) Wright-Patterson Air Force Base, Ohio, Dec. 26-28, 1970; (b) Dayton, Ohio, Feb. 15-17, 1977.

[3] VonGierke, H. E.,"Biodynamic Response of the Human Body," Applied Mechaqics Reviews, Vol. 17, No. 12, Dec. 1964.

[4] Seireg, A. and Arvikar, R., "A Mathematical Model for Evalua-

tion of Forces in the Lower Extremities of the Musculoskeletal System," J. Biomech., 6:313, 1973.

[5]

Seireg, A. and Arvikar, R., "The Prediction of Muscular Loadsharing and Joint Forces in the Lower Extremities During Walking," J. Biomech., 8:89, 1975.

[6]

Seireg, A. and Arvikar, R., "A Comprehensive Musculoskeletal Model for the Human Vertebral Column," in Advances in Bioengineering, ASME, New York, 1975.

[7]

Arvikar, R. and Seireg, A., "Distribution of Spinal Disc Pressures in the Seated Posture Subjected to Impact," Aviation, Space 6 Environmental Medicine, Jan. 1978.

[8]

Arvikar, R. and Seireg, A., "Effect of Curvature on Spinal Stress During Lifting," 31st Annual Conf. on Engineering and Medicine in Biology, Atlanta, GA, Oct. 21-25, 1978.

[g]

Arvikar, R. and Seireg, A., "Evaluation of Upper Extremity Joint Forces During Exercise," in Advances in Bioengineering, ASME, New York, 1978.

[lo]

Dempster, W. T., "Space Requirements of the Seated Operator," WADC Technical Report, 55-159, July 1955.

59

1. Rectus capitis posterior major 2. Rectus capitis posterior minor 3 . Obliquus capitis superior 4 . Obliquus capitis inferior 5. Rectus capitis anterior 6. Rectus capitis lateralis 7. Longus colli 8 . Scalenus 9. Sternothyroid 10. Sternohyoid 11. Semispinalis capitis

1. Rectus abdominis

2 . External obliquus abdominis 3 . Internal obliquus abdominis 4 . Quadratus lumborum

1. Trapezius 2. Rhomboideus 3 . Levator scapulae 4 . Latissimus dorsi 5. Subclavius 6. Serratus anterior 7. Pectoralis major 8. Pectoralis minor 9 . Deltoideus 10. Supraspinatus 11. Infraspinatus 12. Teres major 13. Teres minor 14. Subscapularis 15. Coracobrachialis 16. Biceps bkachii 17. Triceps brachii ~

60

12. Splenius capitis 13. Longissimus capitis 14. Longus capitis 1 5 . Sternocleidomastoid 16. Longisaimus cervicis 17. Iliocostalis cervicis 18. Splenius cervlcis 19. Semispinalis cervicis 20. Multifidus cervicis 21. Rotatores cervicis

5. 6. 7. 8.

Multifidus lumborum Rotatores lumborum Psoas major Erectores spinae

Brachialis . Anconeus Supinator Pronator teres Brachioradialis Extensor pollicis longus Extensor pollicis brevis Extensor carpi radialis longus Extensor carpi radialis brevis Extensor digitorwn communis Extensor carpi ulnaris Flexor carpi ulnaris Flexor carpi radialis Flexor rollicis longus 3 2 . Flexor digitorum superficialis 33. Flexor digitorum profundus 3 4 . Abductor pollicis longus

18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31.

MUSCLES OF THE LOWER EXTREMITIES

Gracilis Adductor longus Adductor magnus adductor part Adductor magnus extensor part Adductor brevis Semitendinosus Semimembranosus Biceps femoris (long head) Rectus femoris Sartorius Tensor fasciae late Gluteus maximus Iliacus Gluteus medius Gluteus minimus Biceps femoris (short head)

Vastus medialis Vastus intermedius Vastus lateralis GastroQlemius Itledial head) GastroQlemius lateral head) Soleus Tibialis anterior Tibialis posterior Extensor digitorum longus Extensor hallucis longus Flexor digitorum longus Flexor hallucis longus Peroneus longus Peroneus brevis Peroneus tertius

I

TABLE 2 MlJSCLE F O R C E AT PFAK UPVARD iiESlVt?SE

Nuscle o r Huscle Group Rectus c a p i t i s posterior major Semispinalis cervlcfs

k s c l e Force ( k d

MUSCLE FORCES DIIRrNc STOOPING AND WEICHT LIFTING (45.4 Kgl

MUSCLE FORCh'S AT PEAX WUMARD RESPONSE

Muscle o r Huscle Group

Huscle Force

(kd

Muscle o r Muscle Group

Muscle Force ( k d

2.01

Semfspinal is capi t i s

1.3

Splenlus c a p i t i s

2.42

1.16

RectC abdominls

9.12

Semispinalis cervicis

1.95

Internal abdominal oblique

3.99

Levator scapulae

2.70

Levator scapulae

6.67

Rectus abdaninis

76.42

Erectores spinae

za .23

quadratus lumborum

60.06

External abdominal oblique

77.42

SenlWranosus

25.97

Nulifidus l u n b o m

7.04

8.19

Rotatores lumbom

Quadratus 1 - m Hultifidus lunborun Rotatores l u b r u n Adductor longus Gluteus medius

171.42 41.37 3.53 41.46 7.12

Sartorius Gluteus medius

26.46

127.61

Deltoid

1.19

Seninembranosus

135.45

Curacobrachial is

1.62

Blceps F m r i s (long head)

176.62

Triceps

1.49

Gluteus maximus

4.91

Gluteus medius

47.11

184.0

Oel toid

3.07

T i b l a l i s anterfor

Brachialis

3.68

Tensor fasciae l a t a e

11.73

Biceps F m r i s (short head)

Brachioradial is

4.31

Yastus l a t e r a l i s

39.54

Gastrocnemius

Gastrocnemius (medial)

141.86

Gastrocnemius ( l a t e r a l )

53.89

SOlWS

43.99

Gluteus maxims

10.98

Biceps brachii (long)

5.97

7.70

Erectores splnae

Iliopsoas

78.11 192.19 9.13

TABLE 3 JOIRT REACTIOS AT PEAX URlARD PRESSORE

I

Joint SkulllCl c1fC2 C2fC3 c3/c4 C4IC5 C51C6 C6/C7

28.29 27.93 19.02 27.29 34.59 34.59

C7lTbrax

33.59 31.71

ThoraxIL1 LlIL2 L2fL3 L31L4 L41L5 LSIPel v i s

305.74 305.21 309.32 335.65 384.76 444.36

Hip

X Y

Z Knee

X Y

Z Ankle

X

Y 2

m w

Reaction Force ( k d

4.49 -12.04 170.30 25.86 -0.93 351.23 34.29 2.89 391.73

JOIW REACTJO#S AT PEAK W U A R D RESMRSE

Joint

Reaction (kq)

A l l interveral j o i n t s Hip

Knee

Ankle

0

X

2.52

Y

-13.43

Z

2.49

x

10.94

Y

-3.75

2

0

X

8.87

Y

-3.71

Z

99.08

JOINT REACTIONS Dmm . ~ P I W G AND WICRT LIFTIWC (45.4 19)

Joint

Reaction Force

SkulllCl CllC2 C2IC3 C3IC4 c4ic5 C5lC6 C61C7 C7flhorax Thorax/ L1 LlIL2 L3lL4 L41L5 LB/Pelvi s Hip

230.06 296.52 344.23 363.44 371.75

X

-52.57 -17.99 412.29 -52.44

X

Y Rnkle

12.15 12.09

Y

Z Knee

8.83 10.14 5.75 11.12 12.08 12.23

Z

23.04 630.66

X

-a.sg

Y 2

a.62 249.63

(Id

64

n

MECHANORECEPTOR SYSTEMS OF THE ORGANISM FROM THE VIEWPOINT OF VIBRATIONAL BIOMECHANICS A. S. Mirkin, S. V. Petukhov* Mechanical Engineering R eseafch Institute, Moscow, U.S.S.R.

SUMMARY

The results of biomechanical investigations of functioning of two mechanoreceptor systems - vestibular apparatus and Pacinian corpuscules - under the conditions of vibration influences a r e discussed. Frequency characteristics of Pacinian corpuscles a r e presented. Special importance of the frequency 100 Hz f o r both systems is pointed out. A scale model of the man’s semicircular canal system constructed on the basis of the dynamical similarity theory is described. The model permits to establish that, due to purely mechanical reasons, und e r the condition of low frequency angle vibration of the head, false vestibular information enters the nervous system.

The experimental materials, presented in this paper, have been obtained in connection with the general problem of investigation on vibrational characteristics of different systems of the human organism

11.

This investigation is necessary f o r elucidating biophenomena me-

chanisms of negative and positive vibration influence on man. When mechanoreceptor systems a r e explored f r o m the point of view of vibrational biomechanics, the central questions a r e the following: establishing the particularities of different mechanoreceptors’ reactions to vibration exposure; discovering the reasons of the appearance of these particularities; finding out the connections between reactions on ; k Presented at the Symposium by

K. V. Frolov.

65

the level of mechanoreceptors and reactions of the organism as a whole; defining the p a r a m e t e r s of the corresponding vibrations. The paper includes the materials of r e s e a r c h from the viewpoint

of two mechanoreceptors: the vestibular apparatus and the Pacinian corpuscles. The Pacinian corpuscles, named after the Italian scientist of the XIXth century, a r e a highly specialized f o r m of incapsulated receptors (Fig. 1)

.

These corpuscles a r e widely s p r e a d in the hypodermic

tissue, connective tissue and envelopes of the organs of muscle-skelet a l apparatus, internal organs, blood vessels, nerve stems, vegetative and limphatic nodes endocrine glands. In o t h e r words, they a r e extero-, proprio- and interoreceptors.

These mechano-receptors a r e

the terminations of thick fast-conducting sensitive nerve f i b r e s and have a great informational value f o r the organism 12.31

.

The establishment of frequency c h a r a c t e r i s t i c s was the main task of o u r investigations on Pacinian corpuscles. F o r this purpose an individual mechanoreceptor, prepared f r o m the mesentery of a narcotized animal, was put on two e l e c t r o d e s so that the biopotentials were registered on the nerve f i b r e w i t h i n its capsule.

The

electrodes were mounted at the bottom of theiicup" which had t h e possibility to vibrate at various regimes of sinousoidal oscillations. If mechanical stimulations a r e absent, the mechanoreceptor does not generate nerve impulses. But vibrations of the cup, beginning f r o m a certain level of magnitude, which depends on the frequency, lead to the appearance of nerve impulses

-

potentials of action. We have

registered this threshold level of vibration for various frequencies of sinusoidal vibrostimulation and have discovered that it had a minimum value P

0

f o r the frequencies 100-105 Hz f o r all investigated Pacinian

corpuscles.

The results a r e shown in Fig.2: on the a b s c i s s a is pre-

sented the frequency of vibrostimulation, on the ordinate

-

the magni-

tude of the threshold level P. The discussion of the obtained r e s u l t s

is beyond the scope of this paper. Undoubtedly, special attention should be devoted to the 100 Hz frequency in the field of investigations on

"Man under vibrations". Now w e shall discuss the vestibular apparatus. Its investigation has a special practical value in connection with the growth of the

social need of a great number of specialists capable to fulfil normal work under conditions of vestibular stimulation, to which man is unaccustomed. It should be noted that the 100 Hz frequency so prominent in

frequency characteristics of Pacinian corpuscles is also characteristic f o r the functioning of vestibular receptors: approximately this frequency is observed in registrations of continuous spontaneous impulses in a m -

pullae nerves of monkey vestibular

apparatus [4],

which is built very

similarly to human vestibular apparatus. Some investigators show that.

a vibrostimulation with the 100 Hz frequency of human vestibular apparatus by means of applying a special vibrator to head bones is a highly productive vestibular stimulus which may be used f o r various clinical purposes [5J. But we were primarily interested in investigating the function of vestibular apparatus during low frequencp vibrations

(L

1 Hz)

.

Man

often meets these vibrations on transport, f o r example, during sea tossing. The effect of these vibrations on man is known to be usually accompanied by phenomena of motion sickness: giddiness, illusions of space perception, nausea, etc. In order to investigate the mechanisms of human vestibular diso r d e r s under these conditions we have studied the d'ynamics of processes i n the semicircvlar canal system of humanvestibular apparatus. This system informs the organism about angle parameters of head motions. The semicircular canal system consists of two symmetrical en&lopes with three connectionscontained ih the temporal bones of the head and filled up with endolymph. Three canals of each envelope a r e mutually perpendicular and there is a sensitive positional element

a cupula

-

-

i n each canal. When the head rotates with acceleration, the

67

cupulae together with the endolymph a r e displaced relative to the walls of the canals. These displacements of cupulae of six semicircular canals provide the organism with the information about t h e n a t u r e of head rotation. Modern concepts about the functioning of this system a r e based on Steinhausen's model [ 6 - 8 ] ,

grounded on the assumption that the

conduct of the endolymph in each semicircular canal is similar to the conduct of viscous liquid in a torus with an elastic partition.

Such

ideas a r e useful f o r the explanation of many particularities of vestibular reactions but they a r e rather simplified: they don't take into account the influence of the complex form of the semicircular canal system on the dynamics of processes in each canal. We have avoided this simplification: f o r the purpose of a more profound study of the hydrodynamical processes in the canals we have elaborated a scale physical model of the human semicircular canal system. The model enables simulation of the dynamics of natural processes(Fig. 3)

. The necessity of

creating this model was connected

with the high difficulty of investigations on the natural vestibular labyrinth, because of the tiny size of the labyrinth, opacity of its envelope, almost inaccessible location in the skull, etc. We have utilized the theoretical opportunity of reproducing the dynamics of endolymph motion in an artificial envelope having the form of the vestibul a r labyrinth. While creating the model we have taken into account that the envelope of the vestibular membranous labyrinth is practically rigid and smooth inside. For this reason its model, increased in size by a factor of 49, has been made of glass.

Taking into account the demands

f o r a dynamical similarity 191 to preserv,e the initial dynamics of intracanal currents i n new conditions of the scale envelope, the other physical parameters defining this dynamics have been accordingly scaled simultaneously with the envelope s i z e "1" the viscosityn hand density

9

. These parameters

are:

of the intracanal liquid; the elasticity a

of the cupulae; the angular accelerationp of envelope motions, the

time

t of the course of nonstationary processes. We have changed

all these parameters in such a way that the magnitude of three cri-

teria of process similarity in semicircular canal system 12e

Tt

;

.

t

7l

2

j?J t2

was preserved and the initial dynamics of intracanal processes was reproduced in the scale envelope. With due regard to these criteria the model envelope w a s filled up with glycerine. In the canals model analogs of cupulae with devices of automatical registration of intracanal cupulae displacements were placed. The model is described in detail in a special article

[lo].

The intracanal displacements of cupulae under the conditions of angular oscillations of the head with the amplitudes from 5' to 30' and- frequencies from 0.2 to 0.9 Hz have been investigated on our model. What new data were obtained from the model experiments? Formerly, on the basis of the linear Steinhausen's model it was considered that

-

under sinusoidal oscillations of the head each cupula,

informing the organism about the character of the head motion, was

also displaced in sinusoidal manner, and the nervous system received the semicfrcular canal information which strictly corresponded to the real motion. But model experiments refuted this opinion. Due to the form asymmmetry of each semicircular canal, the intracanal liquid flows easier in one direction round the canal than in the opposite direction. F o r t h i s reason the cupda displacement occurs not in a sinusoidal, but in a quasisinusoidal manner with the accumulation of a permanent component in the direction of the easier flowing liquid current

(Fig. 4). During the accumulation, this permanent component

( we shall call it "differential cupula displacement")

tends to some

limiting value which increases with the increase of the angular oscillation

frequency of the head. The discovery of differential cupula displacements acquire a spe-

cial meaning, if one takes into account that semicircular canals a r e

69

sensors of angular parameters of head motions and that cupula displacements of any origin are interpreted by the organism a s a result of the action of an angular acceleration. F o r this reason such displacements a r e accompanied by corresponding vestibular reactions of the whole organism: strictly defined eye motions, redistribution of the tonus of skeletal muscles, etc. It is natural to put forward the following assumption: permanent components of cupula displacements accumulated during head angular oscillations a r e interpreted by the organism as a result of the action of permanent angular accelerations, nonexisting in reality. On the basis of this assumption we have made an attempt to predict and explain quite a number of vestibulo-oculomotor reactions, which in essence cannot be explained on the basis of the concept of semicircular canals a s the complex of isolated tori. These reactions are: 1) differential vertical one-directional nystagm of eyes a s a result of head angular oscillations in sagittal-symmetric planes; 2) differential oculogyral illusion of one-directional motion in the sagittal plane of the head, i. e. a target luminous in the darkness as a result of head angular oscillations in sagittal-symmetric planes; 3) differential sagittal-asymmetric one-directional nystagm a s a result of head angular oscillation in sagittal-asymmetric planes; 4)

convergence o r divergence of eyes and accompanying illu-

sion of bifurcation of'objects (parallel to horizontal canals) i n the visual field as a result of head angular oscillations. These predicted differential vestibulo-oculomotor reactions have been discovered in special experiments with participation of subjects

[ 111

-

. This discovery confirms the initial thesis about the appearance

on the level of .semicircular canals

-

of reasons f o r space disorien-

tation of the organism. Finding out the disorienting role played by differential cupula displacements permits to s e e in these displacements one of the possible reasons f o r motion sicknees under the condition of angular oscillations of the head. Our results in the field of vibrational biomechanics of the vestibular apparatus may be useful f o r working out improved methods of

vestibular training and professional selection, for modelling disturbances of space and motion perception with the purpose of developing methods f o r eliminating these disturbances. Our results may be also useful f o r forecasting difficulties of work of man-operator under conditions of low-frequency vibration and for comprehending the origin of some forms of motion sickness. In addition we should l i k e to note that motion-sickness phenomenon, in aspects connected with the origin of space illusions, can be investigated from the viewpoint of mathematical theory of transformation groups. The space perception is based on psychophysical phenomena of perception constancy, having invariant-group character

[1 l]

In our opinion, the origin of space illusions is connected with the

.

disturbance of normal invariant-group structurization of space perception. Moreover, the study of space illusions, originating under conditions of vibration influence on man, provides a valuable possibility to research the principles of this invariant-group structurization in the limits of which the organism interpretes current information from various receptor systems. We think that in a subsequent development of the knowledge on the influence of vibrations, which a r e dispersed in time in complex manner essential assistance can be rendered by the research

on

group symmetries in phenomena of biological space-time structurization. There is a high probability that projective and conformal s p metries typical for a number of biological laws of space organization

[IZJ

play an important role in organism reactions, on time sequences

of stimdations, and in the laws of time organization of biological processes in the organism.

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ocodoe

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REFERENCES Frolov, K. V. : In: Vlijanie vibratsij n a organism cheloveka, Nauka. Moscow, pp. 15-17, 1977 in Russian

.

Otelin, A. A., Mashanskij, V. F.,

Mirkin A. S. : Teltze F a t e r -

Pacini, Nauka, Leningrad, 1976 (in Russian). Mirkin, A. S.

:

Resonansnie javlenia v isolirovannikh mechano-

receptorakh- teltzakh Pacini, Biophysika, 11, N4, (1966) pp. 638-643. Fernandes, C.,

Goldberg, J. M. : Physiology of peripheral neu-

rons innervating semicircular canals of the squirrel monkey, J. of Neurophysiology,

34,

N4,

( 197 l),

pp. 66 1-674.

LCicke, K. : Eine Methode zur Provokation eines pathologischen Nystagmus durch Vibrationsreize von 100 Hz, Zeitschrift f. Laryngologie, Rhinologie, Otologie, 52,

(1973 1, pp. 7 16-720.

,I

Steinhausen, W. : Uber die Beobachtung d e r Cupula, ~ f l G g e r s Archiv f. d. gesamte Physiologie,

232,

t 1933 ) , p. 500.

Groen, J. J.: The semicircular canal systems of the organs of equilibrium, I and I1 v.1,

N 2,

,

In: "Physics in Medicine and Biology",

(1956) pp. 103-117; v.1,

N3,

Kisljakov, V. A. ; Levashov, M. M.,

(1957)

pp.

225-242.

Orlov, I. V. : Vestibuljarnaja

sistema, In: "Physiologia sensornikh system",

Ch. 2,

1972

pp. 57-129 , ( i n Russian). Sedov, L. I. : Metody podobia i razmernosti v mechanike Nauka, Moecow,

1965 (in Russian).

,

[lo]

Petukhov, S. V. : Rezsultaty phyzicheskogo modelirovania systemy polukrusknikh kanalov cheloveka koi biologii, 31,

Nauka, Moscow,

,

Problemy kosmiches-

1975

pp.

14-64 ' ( i n

Russian).

[ 111

Akishige, Y. : Studies on constancy problem in Japan IIA, IIB

,

Psychologia: An International Journal of Psychology in the Orient [12]

,

11, (1968), N1-2,

pp. 43-55, N3-4,

pp. 127-138.

Petukhov, S. V. ; Organisatzi a senso-motornoj systemy i invarianti projectivnoj geometrii, Trudy XI Chtenij K. E. Tziolkovskogo. Sektzia "Problemi kosmicheskoi biologii i meditzini", Znanie, Moscow,

[13]

Pease, D. C.,

1978

pp. 71-80, (in Russian).

William, T. A. : Electron microscopy of the

Pacinian corpuscules, J. Biophysiol.

and Biochemical Cytology

3, (1957) pp. 331-342.

-

Fig. 1. The eoheme of a Pacinian corpusole with indication of the main dimeneions: AE-oapeule; BC the nerve termination# D the firet Ranvje interception; F and 0 Raxmje intercepthe tions outside the capsule (from l l 3 ] ) . OP the right light-optical image of the reoeptor (magnification 200)

-

-

-

73

Fig. 2. The threshold-frequency charaoterie ti08 (P/P~) of PIoinian oorpueoles un'der vibrostimulation.

.

Fig. 3. The eoale pbysioal model of the rremioiroular oanal ~ y a OUI t of the h..al.l ~ e 8 f i h I . map-fuo

Fig. 4. QuasiaimrsoiBal oupuZa oaoillationn with aoauPrulatioa of a permanent oomponent of di8plaaement under sinuaoidal stimulation.

IMMEDIATE EFFECTS OF VIBRATION TRANSMITTED TO THE HAND € Dupuis, I. G. Jansen Instilure of Occupational Health and Social Medicine, Johiannes-Gurenberg-University.Mainz, F.R.G.

SUMMARY

Three different research projects have been accomplishon the problems: biomechanical behaviour-of the hand-armsystem; subjective sensation; physiological changes.

ed

-

1.

Some of the main results were,: the wrist and with smaller amplifications the elbow show resonances at low vibration frequencies (10-20 Hz);

-

-

with constant acceleration subjective perception decreases with increasing frequency;

-

-

application of static grip force without vibration causes significant reduction of the skin temperature, which under vibration stress remains at the same lowered level.

Introduction

Vibrating tools, machinery and work pieces can produce high noise level as well as intensive mechanical vibration which may .be transmitted to the hands and arms of the operators. In order to protect the man from damage of health caused by such mechanical hand-transmitted vibration, knowledge on influence of mechanical parameters on human reaction is needed. Knowledge on the immediate effects is important not only for evaluation of short time Vibration exposure but also for interpretation of long-time effects. In the whole complex it seems to be reasonable to distinguish between three main fields of problems:

I. Vibration transmitted to the hand (vibration stress)

76

position of the hand and arm direction of vibration

amplitude of v i b r a t i o n frequency of v i b r a t i o n time-depending changes exposure t i m e coupling o f t h e hand t o t h e g r i p 11.

V i b r a t i o n effects t o t h e human being ( v 5 b r a t i o n s t r a i n ) immediate e f f e c t s :

biomechanical behaviour of t h e hand-arm-system s u b j e c t i v e perception p h y s i o l o g i c a l changes (nervous system, p e r i p h e r a l c i r c u l a t i o n , muscular r e a c t i o n s , biochemical changes) changes of t h e performance chronic e f f e c t s : damage of h e a l t h A p p l i c a t i o n of s c i e n t i f i c r e s u l t s

111.

-

technical protection against vibration vibration evaluation standards

T h i s p a p e r w i l l deal o n l y w i t h the f i r s t p a r t of t h e above s e c t i o n I1 a l t h o u g h t h e r e is close connection t o t h e s e c t i o n s I and 111. The immediate v i b r a t i o n e f f e c t s b e i n g t e s t e d may b e d i v i d e d i n t o t h r e e groups: biomechanical r e a c t i o n , s u b j e c t i v e p e r c e p t i o n and p h y s i o i o g i c a l e f f e c t s .

2,

Task The t a s k of t h e i n v e s t i g a t i o n was t o e s t a b l i s h

-

during

v i b r a t i o n exposure of t h e hand-arm-system t h e e f f e c t s of d i f & r e n t f r e q u e n c i e s , a c c e l e r a t i o n , amplitudes and elbow a n g l e s on t h e v i b r a t i o n t r a n s m i s s i o n t o c e r t a i n p a r t s of t h i s system, on s u b j e c t i v p e r c e p t i o n , on t h e muscle a c t i v i t y and on t h e p e r i p h e r a l blood c i r c u l a t i o n . Some s p e c i a l experiments f a r t h e r

77

more aimed to check the effects of combined noise and vibration stress on the peripheral circulation.

3.

Method

3.1.

Biomechanical behaviour

To produce vibration stress an electro-hydraulic shakersystem was used, takirlg sinusoidal vibrations between 8 and 500 Hz in up to 19 frequency steps. For all frequencies the 2 acceleration was kept constant: 14.1 m/s2 RMS (40 m/s peak to peak). These values of frequency and acceleration agree with the values found by us in electric drills and measured by Panzke, 1970, as predominant in pneumatic hammers. The elbow angle of the vibration strained arm was varied in the steps of 60°, 90°, 120°, 150° and 180°, while the forea m was kept in horizontal position in all cases, the direction of the vibration transmitted corresponding with the forearm. Grip force was choosen as 40% of maximal hand force, a quantity which under practical conditions at vibrating tools often appears, and allows a maximal duration of about 1.5 minutes ,[Rohmert, 1972) To keep invariable this grip force of 40% max. force the handle incorporated an inductive force transducer. The actual force could be observed by the subject at the screen of an oscilloscope and regulated according the demanded value. All tests were made with the hand in semiprone position. Acceleration measurements with inductive transducers (mass 12 grammes each, frequency range 0-1000 Hz) were made at 7 positions: forearm direction at the handle, on the surface of the wrist, dorsal beside albow, just above shoulder joint, and in three mutual perpendicular directions at the forehead. The measured values had been amplified and via a 'multichannel RMS detector fed into digital voltmeters. The full use of the results of the vibration transmission we got by the help on statistical analysis of variance.

..

78

3.2. Muscle a c t i v i t y

The p h y s i c a l c o n d i t i o n s of t h a t t e s t agreed w i t h t h e t r a n s m i s s i b i l i t y t e s t . Skin surface e l e c t r o d e s w e r e used t o measure t h e e l e c t r i c a l a c t i v i t y of t h e three muscle groups m. f l e x o r c a r p i u l n a r i s , m.biceps and m.triceps. To each p a i r of e l e c t r o d e s belonged an EEG a m p l i f i e r . S i g n a l s were c o n t r o l l e d on an o s c i l l o s c o p e o r an u l t r a - v i o l e t o s c i l l o g r a p h . Root-meansquare values were made from t h e s i g n a l s and fed i n t o an analog d i g i t a l converter. 2.5 samples per second were made of each s i g n a l . Mean of 1.0 samples w e r e c a l c u l a t e d , t h e r e s u l t s r e p r e s e n t i n g mean e l e c t r i c a l a c t i v i t y i n a period of 4 seconds f o r each of t h e three m u s c l e s . 3.3.

S u b j e c t i v e perception T e s t s on s u b j e c t i v e v i b r a t i o n perception s t a r t e d w i t h

exposure of a " r e f e r e n c e v i b r a t i o n " a t 16 Hz and three diffe'r2 e n t r e f e r e n c e v i b r a t i o n a c c e l e r a t i o n values: 7, 14 and 28 m / s RMS. For t h i s i n v e s t i g a t i o n a formerly developed method f o r whole body v i b r a t i o n , Dupuis, 1969, was used, which was employed by Lange, 1974, Dupuis, Hartung, and Louda, 1972, f o r t h e i r purposes too. F i r s t of a l l a r e f e r e n c e v i b r a t i o n w i t h a s t a t e d frequency and amplitude t o a l l subjects was submitted. The magnitude of perception t h e i n v e s t i g a t e d s u b j e c t had t o impress upon h e r memory. I n t h e following t e s t t h e subject had t o r e g u l a t e t h e amplitude of a presented, changed frequency, so a s t o g e t t h e same i n t e n s i t y of s u b j e c t i v e perception. By t h a t t h e v i b r a t i o n displacement a r b i t r a r y could be i n c r e a s e d o r reduced t o f e e l for euual perception. Duration o f each t e s t w a s some 20 seconds a t l e a s t , b u t was n o t l i m i t e d . 3.4.

Peripheral c i r c u l a t i o n

Ten male subjects were exposed t o 15 t e s t v a r i a t i o n s by a v i b r a t i o n and n o i s e simulator. S t a t i c g r i p f o r c e and push f o r c e were h e l d c o n s t a n t w i t h 25 N. Beside o t h e r p h y s i o l o g i c a l parameters f i n g e r p u l s e amplitude FPA on the n o t exposed l e f t

79

hand and s k i n temperature HT a t t h e v i b r a t i o n exposed r i g h t hand were measured. Exposure t i m e f o r v i b r a t i o n and/or n o i s e was 8 minutes. 4.

R e s u l t s and d i s c u s s i o n

'4.1.

Biomechanical behaviour

Comparing t h e measurements a t d i f f e r e n t body p a r t s t h e experiments showed t h a t w i t h i n c r e a s i n g d i s t a n c e from t h e p l a c e the? v i b r a t i o n were fed in an a t t e n u a t i o n of v i b r a t i o n a c c e l e r a t i o n i n t h e hand-arm-shoulder-head-system occurred. T h i s is shown i n F i g u r e 1, b u t could be proved up t o 500 Hz. The i n v e s t i g a t i o n concerning t h e i n f l u e n c e of frequency showed resonance a t t h e w r i s t and even a t t h e elbow between 10 and 20 Hz. A r e l a t i v e high stress of t h i s body p a r t s must b e expected. Raising t h e frequency up t o 250 Hz a p e r s i s t e n t deg r a d a t i o n of v i b r a t i o n happens a t a l l measured p l a c e s of t h e body. So f a r t h i s a g r e e s w i t h former r e s u l t s of Iwata e t a l . , 1972. A t t h e s h o u l d e r j o i n t and a t t h e head ( a t t h e head i n t h r e e d i r e c t i o n s ) t h e r e was found no resonance i n t h e lower frequency range, b u t w i t h i n c r e a s i n g frequency there w a s a r a t h e r l i n e a r d e c r e a s i n g of a c c e l e r a t i o n from 8 to 250 Hz. 4.2.

Muscle a c t i v i t y

-

comThe i n f l u e n c e of frequency on muscle a c t i v i t y is pared w i t h t h e other examined muscle groups o n l y obviously e f f e c t i v e a t t h e m . t r i c e p s .(Fig.2), showing t h e a r i t h m e t i c means of electrical a c t i v i t y diminishing when r a i s i n g t h e frequency. That means and v e r i f i e s t h a t t h i s group of muscles t a k e s a g r e a t p a r t i n t h e s t a b i l i z i n g t a s k . The m.biceps ( F i g . 3) h a s i t s b i g g e s t electrical a c t i v i t y between 30 and 50 Hz, u n l e s s t h e arm is f u l l s t r e t c h e d . The a c t i v i t y of m.flexor c a r p i u l n a r i s (Fig.4) is independent t o a l a r g e e x t e n t of t h e v i b r a t i o n frequency b u t is predominantly determined by t h e g r i p pressure.

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80

4.3.

Subjective perception

The magnitude o f p e r c e p t i o n corresponds t o a high d e g r e e t o t h e biomechanical and muscle-physiological behaviour: w i t h i n c r e a s i n g frequency e q u i v a l e n t t o t h e d i m i n i s h i n g mechanical v i b r a t i o n t r a n s m i s s i o n t h e a c c e l e r a t i o n must b e raised which produces t h e same s e n s a t i o n as t h e v i b r a t i o n w i t h lower frequency. T h i s i n c r e a s e o f a c c e l e r a t i o n for an e q u a l percept i o n approximately f o l l o w s t h e r u l e : 0 . 7 5 x frequency. This c o u l d be confirmed f o r three d e g r e e s of i n t e n s i t y ( F i g . 5 ) . For a n e v a l u a t i o n of human exposure t o v i b r a t i o n i n ergonomic g u i d e l i n e s i t may be proposed r e g a r d i n g t h e chosen c r i t e r i a of biomechanical behaviour (resonance a t t h e w r i s t and a t t h e elbow) t o f i t t h e e v a l u a t i o n contours proportioregarn a l t o a c c e l e r a t i o n i n t h e range of 8 t o 16 Hz, and increase d i n g s u b j e c t i v e p e r c e p t i o n and mechanical behaviour them i n t h e range > 1 6 Hz. This i t e m is r e a l i z e d approximately by a d r a f t p r o p o s a l of an i n t e r n a t i o n a l s t a n d a r d , IS0 DP 5349. A l t o g e t h e r from t h e r e s u l t s one can deduce t h a t , t o prev e n t hand and forearm from resonance, e x c i t i n g f r e q u e n c i e s i n t h e range below 20 Hz should be avoided. The h i g h e r t h e frequency a t t h e same a c c e l e r a t i o n t h e lower t h e biomechanical stress, t h e r e a c t i o n of m . t r i c e p s and t h e magnitude of subj e c t i v e p e r c e p t i o n w i l l be.

-

-

-

-

4.4.

-

Peripheral circulation

-

without vibration Even t h e a p p l i c a t i o n of s t a t i c f o r c e stress c a u s e s s i g n i f i c a n t r e d u c t i o n i n p e r i p h e r a l blood flow. The s k i n temperature shows s i g n i f i c a n t drop under stat i c load ( F i g . 6 ) . Under v i b r a t i o n stress as w e l l as under combined v i b r a t i o n and n o i s e exposure w i t h t h e same s t a t i c hand f o r c e t h e s k i n temperature remains a t t h e same low l e v e l , Dupuis and Weichenrieder, 1977. Under s t a t i c l o a d t h e f i n g e r p u l s e amplitude drops from t h e mean b u t t h i s change is n o t always s i g n i f i c a n t . Under add i t i o n a l v i b r a t i o n l o a d as w e l l as i n combination w i t h n o i s e exposure the FPA decreases s i g n i f i c a n t l y ( F i g . 7 ) . S i n c e t h e

-

81

-

noise stress alone leads t o t h e same d e c r e a s e - o f FPA as found by Jansen,1968 i t shows t h a t t h e f i n g e r p u l s e amplitude may be influenced mainly by vegetat'ive disturbances. I n conclusion t h e r e s u l t s show t h a t vascular c o n s t r i c t i o n is a more n o t i c a b l e e f f e c t of noise, b u t s t a t i c hand f o r c e and mechanical v i b r a t i o n mainly w i l l cause reduction of t h e s k i n temperature. Even a f t e r s h o r t period of t i m e these forms of stress can lead t o p e r i p h e r a l i n c a p a c i t i e s .

-

ZUSAMMENFASSUNG

Drei verschiedene Untersuchungsprojekte konnten zu den folgenden Problemen durchgeftihrt werdqn: biomechanisches Schwingungsverhalten des Hand-Arm-Systemes; subjektive SttLrke der Wahrnehmung; physiologische Wirkungen. Die wichtigpten Resultate haben folgendes ergeben: Resonanzen sind am Handgelenlc und mit geringerer Vergdsserung am Ellbogen bei niedrigon Frequenzen (10-20 Hz) vorgekommen; bsi konstanter Beschleunigung nimmt die sub'jektive Wahrnohmung mit ansteigencler Frequenz-ab; die Anwenrlung statischer Greifkrilfte olme SchwingungebeInstung verursacht eine signifikante Verminderung der Hnuttemperatur, d i e unter Vibrationsbelastun'c auf clem gleichen herabgesetzten Niveau bleibt.

-

-

-

-

-

-

-

LITERATURE Paneke, K.J.:

Mechanische Schwingungen bei handgefflhrten Vibrationsgeraten im Bauwesen und ihre Einwirkung auf den Menschen, Ergonomische Berichte, Schriftenreihe fOr Arbeitsstudium, Arbeitsgestaltung, Arbeitsschutz und Arbeitshygiene im Bauwesen, Nr.3, Berlin: Tribnne 1970.

Rohmert, W.:

Arbeitswiseenschaft I, Umdruck zur Vorlesung, T H parmstadt 1972.

Dupuie, H.:

Zur physiologischen Beanspruchung des Menechen durch mechanische Schwingungen, Fortschr. Berichte VDI Zeitschrift 11, Nr.7, 1-168 (1969).

Lange

82

, W.

I

-

-

Zur Beurteilung von Schwingungegemischen, die fiber die Sitzflache auf den Menechen einwirken, Europ. J. appl. Phyaiopl. 33, 151-170 (1974).

Dupu[is, H.,

Iwata, H.,

Hartang, E. und Louda, L.: Vergleich regelloser Schwingungen eines begrenzten Frequenzbereiches mit sinusfBrmigen Schwingungen hinsichtlich der Einwirkung auf den Menschen, Ergonomics 15, Nr.3, 237-265 (1972). Dupuis, H. und Hartung, E.: Gbertragung von horizontalen Sinusschwingungen auf die oberen Extremitaten bei Halbpronationsstellung und Reaktion des m.biceps, Int. Arch. Arbeitsmed. 30, 313-328 (1972). Hartung, E. tmd Hammer, W.: Biomechanisches Verhalten, Muskelreaktion und subjektive Wahrnehmung bei Schwingungserregung der oberen Extremitaten zwischen 8 und 80 Eiz, Int. Arch. Occup. Environ. Hlth 37, 9-34 (1976).

Dupuis, Ei.,

IS0 DP 5349:

Guide for t h e measurement and the evaluat'ion o f human exposure to vibration transmitted t o the hand (1978).

Dupuis, 8. und Weichenrieder, A.: Beeinflussung der peripheren Hautdurchblutung durch mechanische Schwingungen und Llrm, Ber. 17, Jahrestagung d. Dtsch. Ges. f.Arb.med., Gentner, Stuttgart, 1977. Jansen, G. und Thutewohl, W.: Zur Bestimmung vegetativer Schallreaktionen, Kampf dem LBrm 1 (1968).

8

10 12.5 16 20 25 3.5 40 50

63 80

F r e q u e n c y [Hz]

Fig.

1 . Vibration transmission t o d i f f e r e n t body p a r t s

83

I

Frequency

Fig. 2 . Electrical muscle a c t i v i t y of the m. triceps

----

........-.............

I -

Fig. 3. E l e c t r i c a l muscle a c t i v i t y o f the m . biceps

84

---.-

-....-. ..

."........_.._I

Pig.

4. Electrical

niuscle activity of the m. f l e x o r carpi

ulnaris

200

100

50 7 U

c 20

.-0

e

9

u 5 10

f

cn I : 5

a

I 8

10

= Reference

12.5 16 20 25 Frequency [ H f ]

vibation 31.5

40

50

63 80

Fig. 5. Subjective equal perception of hand-transmitted vibration

85

A HT

grd 0.2

0

- 0.2

- 0.L -0.6 -0.8

-1.0 -1.2 -l.L

I Istat* I I

Rest

load I

I

2

L

l

l

Noise 100 dBlA 1 and vibration stress I

8

6

I

I

I

1

10 min 12 13

F i g . 6 . E f f e c t of noise and vibration stress on skin- temper-

ature HT

FPA YO 100

90 80 70

60

50 LO

Rest

Noise 100 dB IA 1 1 vibration stress

Stat. load I

2

L

I

6 Time

I

8

I

I

10 min 12 13

Fig. 7 . E f f e c t of noise and v i b r a t i o n stress on finger-pulse-

86

amplitude FPA

BASIC PRINCIPLESFOR HYGIENIC RATING OF INDUSTRIAL WHOLEBODY VIBRATION IN THE U.S.S.R. A. A. Menshov Kiev Institute of Lcrbour Hygiene and Occupational Deseases. Kiev, U.S.S.R.

SUMMARY

author s i a g l e s out four main categorlee of the labour a c t i v i t y f o r a man-operatar and objects agalnst t h e f a c t t h a t s p e c i f i c charaoter of the labour a c t i v i t y was not included I n t o the r a t i n g c r i t e r i a of the International Stand a r d ISO-2631. He underlines the f a c t t h a t , in s p i t e of the s i m i l a r i t y I n reeonance frequencies, the basic principlea of the hygienic r a t i n g f o r the whole-body vibration in the USSR d i f f e r from those acoepted by ISO. They are baaed on t h e vibrovelocity (In octave bands), not on the ribroacceleration. 'phe

Great coNtingents of workers engaged I n industry, agric u l t u r e and traneport are expoeed t o whole-body vibration.

The whole-body vibration or the vibration o f working placee applied t o a standing o r seated man puts In action t h e complex o s c i l l a t o r y system

- our body - which i s the t o t a l i t y

of locomotor system, musoles and i n t e r n a l organs. Prom Waas'e etudy (1935) and the work of Volkov A.M.

, Chirkov

V. J. (1953,

USSR) many authors revealed and specified resonance zones of frequencies both for the body o s c i l l a t i o n in a whole and i t s p a r t i c u l a r p a r t s , ae well a s for t h e i n t e r n a l organs of a man

87

under the whole body vibration.

In most casee the-resonance of the body i n v e r t i c a l direction was detected in the frequency range 4 t o 8 He a t 12

Hz. The change of direction,for vibration transmitted i n t o

the horizontal plane, influences t h e resonance response of the body, namely the resonauce zone shift6 t o low frequencies 1-2

Ha. A t resonance frequenciee the oscillation8 of some

parts of the body may exceed the o s c i l l a t i o n s of the vibro-

platform and cause traumati.ting e f f e c t s of vibration. These data a r e p r i m a r i l y used f o r hygienic substantiation of the

whole-body vibrat ion ratlnge both by International Organizat i o n f o r Standardiz8tion and separate countries the USSR included. Thus, the International Standard IS0 2631 ltoUide f o r the evaluation of human exposure t o whole-body vibrationn provides f o r the lowest valuee of acceleration f o r v e r t i c a l vibration I n the range 4-8 Hz whereas f o r horizontal vibrat i o n these raluee a r e i n the range 1-2 Hz. These frequmcies a r e taken i n t o account as resonance frequenciee on hygienic r a t i n g of general i n d u s t r i a l vibration i n the USSR as well though they a r e expressed by vibroveloclty in SN 1102-73 "Sanitary r a t e s and r u l e s f o r the l i m i t a t i o n of vibration and noiee on the working places of t r a c t o r e , trucks, agricultural, land-reclamation and road building machinee" and in new GOS'E 12.1.012-78

Vibration. General s a f e t y requirementsn.

However, I n s p i t e of t h i s s i m i l a r i t y in resenance frequencies, the basic principles of hygienio rating f o r the whole-body vibration I n the USSR d i f f e r from those accepted

88

by IS0 and some countries, Thus, the International Standard I90 2631 "Guide f o r the evaluation of human exposure t o whole-body vibration" proceeds from the three r a t i n g c r i t e r i a : %xposure l i m i t v 1 , "fatiguedecreased proficiency boundary1' and Veduced comfort boundary". However i n the biomechanical system ltman-machlne-environmentll it is appropriate t o consider various k i n d s of labour a c t i v i t y from the point view of the i n t e r a c t i o n between a manoperator and a machine, taking i n t o account the degree of t h e p a r t i c i p a t i o n of a man I n the control of the machine which is t h e source of vibration (Suvorov G.A., al.,

19771 Menshov A.A.

et

1977). The operator of modern self-propelled machine is

an a c t i v e element and t o some extent may decrease the Intene i t y of v i b r a t i o n by the stops of short duration and the regulation of epeed. There is a s t r i c t regulation of the technological process when operating I n d u s t r i a l machinery and t h i s %iticks" t o the operator t h e speed and the rhythm of t h e

work and predetermines a c e r t a i n conetancy of t h e v i b r a t i o n a l exposure. Thus, t h e operators of d i f f e r e n t k i n d s of self-propelled 'machines a r e Influenced by vibration variable in l e v e l s and spectra due t o micro- and macropaueee, As t o the I n d u s t r i a l machinery here a continuous vibratlon takee place during t h e whole working day. The e i t u a t i e n may a r i s e when t h e v i b r a t i o n Is not oaueed by the process i t s e l f and the expoeure is ir-

r i t a t i n g and I n t e r f e r e s with t h e q u a l i t y of the working

prooeoe.

In view of the above oaneideratlon It i s appropriate t o

89

single out four main categories of labour a c t i v i t y for a man-

.

operator. These are: 1

The work on self-propelled vehicle6 (tractors, trucke,

a g r i c u l t u r a l , land-reclamatien and road building machinee) when the vibration transmitted t o t h e operator is caused by t h e driving over rough pasture or road during the technol o g i c a l proee8s. 2.

The work on self-propelled technological equipment

(excavators, various types of cranes, boring machinery) when the vibration transmitted t o the Working place of drivers and

.

operators i s due t o the technologioal process and p a r t i a l l y c ont ro 11e d

3. The operation of technological equipment o r machinery of various types I n industry when t h e vibration transmitted

t o the workers i s caused by the te*chnological prooess and does not depend on the operator's activity. 4. The work in premises without the source of vibration

(design officee, study-rooms, oontroiler'e offloe) when the vibration penetrating from the adjacent rooms cauees the irr i t a t i n g effect.

The r a t i n g o r i t e r i a of the International Standard IS0 2631 I n terme of w e ~ p ~ ~llmltpp, ure "fatigue-decreaaed profi-

ciency boundaryppand ppreducedcomfort boundary" do not amount f o r *he specificity of labour activity. Laboratory and f i e l d hygienic etudlee alomgeide with the meaeuremente of nervous sye8em of treater-drivers (Menshov L A .

limofeeva B.Tc

196701972) oonflrmed by Malinekaya lbl. e t al.

(1975) ehm t h e a o c e p t i b i l l t y of "fatigue-deereased proficiency boundary"

by IS0 2631 as the maximum allowable l e v e l s of whole-body vibration f o r the d r i v e r s of self-propelled vehicles whom labour correepoads t o the 1st eategory of labour activity. A t t h e same time i t was shown t h a t exceeding the allowable l e v e l s by 6 dB t o "exposure

Jlmittf

f o r t h i s category of workers is

imposeible, "Reduced comfort' boundarytt proved t o be on the point of maximum allowable l e v e l s of whole-body'vibration for t h e persons working w i t h technological equipment and machi-

nery I n industry. This group of workers ranks among the I I I d categsry of labour a c t i v i t y .

The p r i n c i p l e of evaluation according t o vibrovelocity in octave bands i s aseumed t o be the basis f o r the hygienic r a t i n g of vibration in the USSR. The expediency of the applic a t i o n of t h i s principle t o l o c a l vibration was substantiated experimentally and t h e o r e t i c a l l y by Rasumsv I . K .

Rasumov I.K.

e t al.

(1966).

(1967)

Thie t h e s i s was colnfirmed when

@omparing $he development of v i b r a t i s n a l diseasea among t h e

.

workers and the parameters of vibration f o r mechanized hand i n strumemts

The experimental ground f o r the use of the p r i n c i p l e of

evaluation accordirg t o vibrovelocity i n octave bands was given by Menshov A.A.

(1971). When studylng t h e Influence of

whole-body v i b r a t i o n on man a t the frequencies 4 and 8 He und e r equal vibroacceleration but d i f f e r e n t r i b r o v e l o c i t y and v i c e versa it was defined that the changes l h vibrsvelocity r a t h e r than in.vibroaccelerat1on f i t i n t o the mhifts of the indices of such physiolagical functisne. as conservation of s t a b l e equilibrium by t h e stabiloskopy data and Latenay period

91

f o r eimple and differentiating visual-motor reeponse ( ~ a b l e s1, 2, 3). In l i n e with the r e s u l t s of these invsstigatione the principles of the theory of energetic action of vibration s e t f o r t h by Rasumov I.K.

were extended t o whole-

body vibration. Thue, t h e hygienic r a t i n g of t h e whole-body vibration by vibrovelooity in octave bande has been already done in "Sanitary r a t e s and r u l e s f o r the l i m i t a t i o n of vibration and noise an the working places of t r a c t o r s , trucke, a g r i c u l t u r a l , land-reclamat ion and road-building machinesv1 SN 1102-73 and was r e f l e c t e d in a new GOST 12.1.012-78

"Vibra-

tion. General s a f e t y requirements".

ABTOP mnemeT geTbIpe ocsossrJe KaTeropaPl p a d o ~ e tnesTeJEti HOCTH q e ~ ~ o ~ e ~ a - o n e p aa~ ommmraer pa ~oapaxemen p o m Toro, ¶TO c I I ~ I @ pabowl! U ~ ~ ,QeRTeJlbHOCTHH e d~s~ra n#JeDreHa B KpHTepUl

~ m c c MemyHapomoro ~ m cTaysapra MCO-2631. IlomepmmeTCR TOT @KT, UTO, HeCMOTpJI Ht3 CXOJUIOCTb pe30H8HCHHX YaCTOT, ocsoBme n p k ~ ~ ~mcca][lcwawm ~~rn rPirtleHBvecxnx HOPM B cJIyrIae ~ ~ d p a q &Tern l senoBexa, npnmme B CCCP, OTmarncR OT IIPPIIISITHX B HCO. 0OCHOBalW Ha CXOPOCTR B B b p ~ m(B OKT~BHOM DOJIOCe ¶ ~ C T O T ) , a He Ha COOTBeTCTByrOqeM YCKOPeHllI4.

REFERENCES

[I] Waas , Ha, Messung van

K r e f t f ahrreugschwingungen, Zeite c h r i f t V D I 71 (7) , pp. 199-206.

[4] TOCT 12.1.012-78,

B n b w ,

C ~ C T ~CTaH,lWpTOB M ~

Odq~erpedoseaim

~ ~ ~ O ~ ~ C H OT C ,lW, T E I

desonac~oc~43, Mocxsa , 29Vg.

[5] Internatioaal Standard IS0 2631, Guide for the evaluation of human exposure t o whole-body vibration.

[6] Cyeopo~,1. A. n mp., Ax~yanbmeBonpoca rareRwecKoro HOPh4.KpOBaHllR padwero MeCTa. B KH. Te3acB JIOKJIaJIOB 111 Ha o p r a m s ~neBcecoroa~orocm~no3ay~a "Bmmne sadparl~lt~ nosexa a npobxem ~mdpoaa~qmm",Mocxm, 1977, c. 391-394.

Table 1 The change8 of physlolo$ical functions t o vibration expoeure (velocity

- 4.65

Indicee

om/.,

acceleration

-

1 ha a f t e r vibration

Init

116 cm/e2, 4 HZ) In 15 min

In 30 min

......................................... ~

f

m

~ t m

~

:

m

~

f

S a g i t t a l stabilogram i n conventional units 48,5f3*5

59f3.4

53.6:3.3

59.1f4.5

Frontal stabilogram i n conventional unite 54.0f2.9

6200z1.9

58.023.5

5406f2.3

Vieual-motor simple response l a t . per., 1/100s

30*0:1,5

30. 8:1,7

30.621.9

31 .0:2.0

Visual-motor diff. responee, lat. per., 1/100a 37.3z2.1

38,3:2,2

37.4t2.6

37.2f2.2

m

Table 2

The changes of physiological function8 t o v i b r a t i o n exposure (velocity Indicea

- 2.35

om//., a c c e l e r a t i o n Init

- 120 cm/e2,

1 h. a f t e r vibxat Ion ~ f m

8

HZ)

In15min

In30min

M f m

~ : l a

........................................... ~2rn

............................................................... Sagittal etabilogram i n conventio56.7f4.1 nal units

54.3f3.1

51.2:3,3

54*9!3&2

Frontal etabilogram in conventio61. lf2.1 nal m i t e

61.8f1.9

62.5f1.9

60.7f1.9

Vieual-motor simple reeponse la*. per., 1/100o 390 l_f2.3

3603f1.6

36.421

3608f2.0

Vieual-motor d i f f . reapenee, l a t . per., 1/100s 45 05z2.4

43.8f2.2

41.9f2.0

09

44.1:2.4

Table 3

The ohangea of physiologioal functions t o vibration expoeure (velocity

- 1.8 e m ,

Indices

acoeleration

Init

-

50 cm/e2, 4 HZ,)

1 h. after vibration

In 1 5 m i n

In30min

........................................... ~ trn ~ 2 m ~ : r n M t r n ............................................................... Sagittal stabilogram i n conventio45.2'2.5 nal units

51r0:3.1

49.6'2.7

50~0'2.5

Brontal stabilagram I n conventional unite 56,922 64

55.5z2.9

60,4:3. 0

55.8z1.9

Visual-motor simple response, 1st. per., I/?OOe

37.1~1.5

31~8'2.0

31,221~8

38-321.5

39.3'2.3

39r8t2.1

33.7f2.1

Visual-motor d i f f . reeponse, l a t . p e r * , 1/100e 42.1f2.6

...............................................................

EFFECTS OF VIBRATING TOOLS ON THE PERIPHERAL VESSELS AND THE PERIPHERAL NERVOUS SYSTEM IN WORKERS OF AN IRON FOUNDRY. PREVENTIVE SUGGESTIONS R. Gilioli, M. Tomasini, C. Bulgheroni, A. Grieco Clinica del Lavoro, Milano. lraly

Filippini Grazia Isrituro Neurologico"

C. Besra", Milono, Itoly

SUMMARY

The r i s k s and the p e r i p h e r a l angiological a s well as neurological impairment of the upper limbs i n workers using v i b r a t i n g t o o l s i n an iron foundry were investigated. Four c a t e g o r i e s according t o t h e t a s k s were obtained. Subjective symptoms were collected through an e s p e c i a l l y constructed questionaire. Objective s i g n s o f angiopathy, both i n b a s a l conditions and a f t e r cooling t h e hands i n running water, w e r e obtained through c l i n i c a l observation and photopletismography (FPC)

.

INTRODUCTION

This study is a p a r t of an ergonomical research carried o u t by the I n s t i t u t e of Occupational Health of t h e University

of Milan ( C l i n i c a l d e l Lavom) on the r i s k s and the d i s o r d e r s present i n an i r o n foundry; the purpose of t h e study is

to

f u r n i s h u s e f u l ilhdications t o design work environment and s t r u c t u r e s t o prevent a c c i d e n t s and occupational diseases. I n p a r t i c u l a r , the questions we t r i e d t o answer with t h e indica-

tions t h a t were more l i k e l y t o be u t i l i z e d d i r e c t l y i n t h e real foundry s i t u a t i o n refer to: a) t h e c l i n i c a l and epidemiological characteristics

0.f

t h e diseases from v i b r a t i n g t o o l s

97

i n the examined population i n r e l a t i o n to the length of esposure, the type of t o o l u t i l i z e d and the nature of work organization;

b) the l o n g e s t duration of Qxposure to vibra-

t i o n s t h a t does not r e s u l t i n c l i n i c a l symptoms o r signs;

c) the technological and medical means of prevention t o p r o t e c t the h e a l t h of the workers from s p e c i f i c occupational disorders. W i t h t h i s o b j e c t i v e , a group of workers a t p r e s e n t no longer exposed but w i t h former exposure to v i b r a t i o n s were also s t u d i e d so a s to i n v e s t i g a t e i n t o r e v e r s i b i l i t y i n time. I. PERIHIERAL A N G I O U G I C A L FINDINGS

Population examined The study w a s carried o u t i n the period March-April 1975

i n the i r o n foundry department of a North I t a l y s t e e l industry8

167 workers of the moulding and f i n i s h i n g s e c t i o n s were

in-

vestigated. Both s u b j e c t s s t i l l working and s u b j e c t s w i t h former exposure were examined.

Subjeots w i t h a t l e a s t one

year of exposure to the r i s k and s u b j e c t s who had i n t e r r u p t e d exposure no more than seven years p r i o r l y were studied. This choice was due to the d i f f i c u l t y of f i n d i n g s u b j e c t s who had stopped exposure before t h i s period. DescriDtion of the t a s k s and the t o o l s used Cast finishing:

by t h i s term we d e f i n e a l l the operations

a p t t o f i n i s h the c a s t already sandblast: removal of c r u s t s of moulding material and excess of f u s i o n , f i l l i n g of f u s i o n d e f e c t s by welding, smoothing of the cast surface. For n e a r l y

a l l t h e s e operations, v i b r a t i n g t o o l s of d i f f e r e n t type were employed a l t e r n a t i v e l y according to work demands ( c h i s e l l i n g , smoothing, milling) during t h e e n t i r e working hay, with exposure t o v i b r a t i o n s with d i f f e r e n t c h a r a c t e r i s t i c s o f workers who o c c a s i o n a l l y had non-exposing tasks. The workers used t h e v i b r a t i n g t o o l s about

$ hours d a i l y of

which 3

hours with t h e pneumatic c h i s e l . Moulding:

t h i s o p e r a t i o n c o n s i s t s i n p r e s s i n g foundry

m a t e r i a l i n t o wooden models r e p r e s e n t i n g t h e negative mould

o f t h e cast t o be obtained. Moulding may be mechanical o r manual; t h e former r e g a r d s c a s t s of minor dimensions ( u p t o 100 kg) and r e q u i r e s t h e use of pneumatic p e s t l e s of 4.7 kg

(850 beats/min) f o r t h r e e hours d a i l y . Table 1 shows t h e d i f f e r e n t types o f t o o l s employed i n the

various operations: it i s p o s s i b l e t o observe the d i f f e r e n t c h a r a c t e r i s t i c s r e l a t i v e t o the weight and t h e frequency of the b e a t s o r of the t u r n s developed. I n v e s t i g a t i o n of t h e p e r i p h e r a l c i r c u l a t i o n A physician c o l l e c t e d the h i s t o r y of a l l the s u b j e c t s w i t h

s p e c i a l reference t o t h e type of instrument used and t h e r e a l d u r a t i o n of exposure, the nature of symptoms and s i g n s and smoking h a b i t s .

I n t h i s phase, we used a s p e c i a l l y c o n s t r u c t e d

questionnaire. Each s u b j e c t has undergone photopletismography (FFG) by t r a n s i l l u m i n a t i o n of the f i n g e r s of the hands,

in

basal c o n d i t i o n s and a f t e r t h e cold t e s t . FPG w a s performed

i n a room n e x t t o t h e foundry between 6 a.m.

a d 7 p.m.;

the

99

ambient temperature varied, i n d i f f e r e n t days, from 14OC 18OC.

to

The subjects reached the examination room d i r e c t l y from

the foundry where the a i r temperature was generally 5OC lower. The subjects were asked t o refrain from smoking and work from the preceding evening or a t l e a s t four hours before. The .basal FPC was obtained f o r each finger with the subject relaxed and

lying down, a f t e r waiting 15 minutes; afterwards the subject put h i s hands i n running water a t a temperature between 10°C ard 12.5'C

f o r 15 minutes.

After immersion, the presence of ischemic pale aspects (Raynaud phenomenon) or of intense cyanosis i n the hands was observed and a new FPC was done; the f l a t tracing was considered i r d i c a t i v e of a significant impaihent of the d i g i t a l peripheral circulation: the examined workers were c l a s s i f i e d according t o two c r i t e r i a : a) the groups being homogeneous with regard t o ;the type of vibrating t o o l used ard the task; b) present or former exposure. The following groups were

therefore obtained: f i n i s h e r s , former f i n i s h e r s (who i n t e r rupted exposure seven years e a r l i e r ) , mechanical moulders ( w i t h the use of a li&t pestle), manual moulders ( w i t h the

use of a heavy pestle), former moulders (due t o the few subjects

of t h i s group, a f u r t h e r d i s t i n c t i o n was not considered) (table 2).

Results Finishers. lhis group consists of 43 subjects (mean age

31.4 yrs; range 24 from

100

I

15 t o

- 55)

with exposure t o vibrations ranging .

16 years (mean

4.6

yrs).

37 (86.05%) of the examined subjects complained of aymptoms a t t h e hands appearing i n 19 (51.35%) only w i t h exposure t o cold temperature and 18 subjects (48.6596) w i t h exposure to cold temperature a f t e r vibrations. The r i g h t hand was involved In 5 cases (13.51%) the l e f t hand i n 15 cases

(40.54%) both harrls in 17 cases (45.95%). The mean period of

latency f o r the onset of the disorders was 2.2 years (range 5 months- 5 years). Objective signs were present i n 26 subjects 160.46%), 4 a t the r i g h t hand (15.38%), 13 a t the l e f t hand

(5096), 9 a t both hands (34.62%) and appeared i n 19 cases, (73.1%) wYth exposure to cold, in 6 cases (23.1%) with expo-

sure t o cold temperature and vibrations, i n

1 case

(3.8%)

after Vibrations. The mean period o f latency f o r the onset o f these disorders was 3.3 y r s (range 1-14 yrs). FF'C was impaired a f t e r the cold test i n 21 subjects (48.84%), I n three of whom a t the r i g h t hand (14.28%), 12

.

cases a t the l e f t hand (57.14%), 6 cases a t both hands (28.57%).

"he cold t e s t was fourd positive (appearance o f the Raynaud phenomenon o r intense cyanosis) i n 12 subjects (27.996) none a t the r i g h t hands, 10 a t the l e f t hand (83.33%) and 2 a t b o t h hands ( I 6.67%). Former-finishers:

!be group i s composed of 52 subjects

(mean age 32.6 yrs; range 24-54 yrs) (mean exposure t o vibration 4.5 y r s , range 1-19 yrs), no longer exposed from 3 months

to 7 years (mean 3 years). The symptoms a t the hands (present and past) w e r e observed i n 37 subjects (71.15%) and appeared

in 16 cases (43.24%) w i t h exposure t o cold, i n 3 cases (8.12%)

101

a f t e r vibrations and i n 18 cases (48.64%) w i t h exposure to cold a f t e r vibrations. The ri&t hand was involved i n 4 cases (11.4%), the l e f t hand i n 13 cases (37.19(), both hands i n 18 cases (51.496)

.

“he mean period of latency f o r the onset of

the disorders was 1.9 y r s (range 6 months-6 yrs) signs (past and present) were seen i n

.

Objective

23 subjects (44.2%),

2 a t the r i g h t hand (8.7%), 13 a t the l e f t hard (56.5%) and 8

a t both hands (34.8%) and appeared i n 16 cases (69.6%) w i t h exposure only t o cold and i n 7 cases (30.496) w i t h exposure to cold a f t e r vibrations. The mean period of latency f o r the onset o f these disorders was 2.6

y r s (range

6 months-7

FFG was altered a f t e r cold t e s t i n 15 subjects (28.8%),

yrs).

2 at

the r i g h t hand (13.3%), 6 a t the l e f t hand (406) and 7 a t both hands (46.7%). “he cold t e s t was positive i n 5 cases (9.6961, none a t the r i g h t hand, 4 a t the l e f t hand (80%) and 1 a t both hands (20%). The symptoms disappeared i n 10 cases (28.57%) in various periods .(mean 6 months, range 2 months- 2 yrs), diminished i n 11 ( 31.43%) and remained present i n 14, (40%); the signs disappeared i n 6 cases (29.09%) i n various periods of time (mean 8 months, range 6-18 months), and remained present i n 17 cases (73.91%). Mechanical moulders:

The group i s composed of I 8 subjects

(mean age 32.6 yrs; range 22-50 yrs) (mean duration o f ex= 1 posure 10.4 yrs; range 13 29 yrs). O f the examined subjects,

-

8 (44.4%) complained of symptoms a t the hands t h a t appeared

w i t h exposure t o cold i n 3 cases (37.%), a f t e r vibrations i n

I case (12.5%), w i t h exposure t o b o t h f a c t o r s i n 4 cases (50%).

102

The r i g h t hand was involved i n 1 case (1 2.5%), the l e f t hand i n 1 case (12.5%), both hands i n 6 cases (75%). The mean period of latency f o r the onset o f these disorders was 3.7 yrs (range 1-7 yrs). Three subjects (16.7%) complained of d i s t u r bances a t both hands t h a t appeared i n a l l o f them only with exposure to cold temperature. The mean period of latency f o r the onset o f signs was 4 years (range 1-11 y r s ) . FPG was found a l t e r e d a f t e r cold test i n 2 cases ( l l . l % ) , I a t the r i g h t hand and 1 a t both hands. 'Ihe cold t e s t was negative i n a l l subjects.

Manual moulders: The group is composed of 45 subjects (mean age 30.5; range 21-57 yrs) (mean exposure 7.9 yrs; range 1-27 yrs). O f the examined subjects, 15 (33.3%) complained of

sjmptoms a t the hands t h a t appeared i n 6 cases (4090 with exposure t o cold, i n 3 cases (2096) a f t e r vibrations, i n 6 cases (40%) w i t h exposure t o both. The right hand was involved i n 4 cases (26.7961,

the l e f t hand i n 3 cases (20%), both hands

i n 8 cases ( 53.3%).

The mean period of latency f o r the onset

o f these disorders was 4.1 y r s (range 3-9 yrs)

.

The objective

signs w e r e present i n 2 subjects (4.4%), i n on@a t the r i g h t hand and i n one a t both hands, and appeared i n one w i t h exposure t o cold, i n one a f t e r vibrations. !he mean period

of

latency for the onset of these disorders was 6 years (range 5-7 yrs). FPG was a l t e r e d a f t e r cold t e s t i n 5 cases (11.1%),

of which 3 (8096) a t the r i g h t hand a d 1 (20%) a t both hands. !he cold t e s t was negative i n a l l subjects.

103

Former-moulders: The group is composed of 9 subjects (mean age 39.8; 16.5 yrs, range

range 22-56 yrs) (mean exposure t o vibrations 1 15

- 30 yrs);

with no f u r t h e r exposure (mean

non-exposure period 24 years; range 6 months-7 years). 4 s u b j e c t s (44.496) complained o f subjective symptoms a t the hands (present and past) which appeared i n 2 cases (5096) w i t h exposure t o cold, i n I case (25%) a f t e r vibrations and I case (25%) with exposure t o both. The l e f t hand was involved i n 1

case (25%), a left-handed subject, i n the remaining 3 cases

(75%) both hands were involved. The mean period of latency f o r the onset of these disorders was 10.4 years (range 6 months23 yrs).

Only one sub3ect (11.1%) complained of objective

signs t h a t appeared 13 years after beginning of work a t t h e l e f t hand due to exposure t o cold temperature. FPG and the cold t e s t were negative i n a l l cases. The subjective disorder had disappeared in one case (25%) a f t e r CWO months.

I n Table 3 and 4 some of the most i n t e r e s t i n g r e s u l t s a r e summarized. I n order t o furnish useful indications a s t o the severity of the d i f f e r e n t pictures of angiopathy considered and also i n order t o suggest preventive and medico-legal measures

t o be adopted, we thought appropriate to c l a s s i f y the subjects, within each homogeneous group, i n 5 categories according t o the presence o r absence a t the moment of the study of signs and symptoms and according to the type of the observed a b normalities. I t was therefore possible t o define the following categories !

- no sign o r symptom, past o r present, of angiopathy 1 - subjective symptoms of angiopathy present a t the moment

0

104

of t h e study (suspected i n i t i a l angiopathy)

2

- s u b j e c t i v e symptoms of

angiopathy and abnormalities of

FPG a f t e r cold test ( i n i t i a l angiopathy)

3

- s u b j e c t i v e symptoms, abnormalities

of FPC and appearance

of Raynaud phenomenon o r cyanosis a f t e r cold t e s t ( c l e a r angiopathy)

4

- p a s t presence of

s i g n s o r symptoms of angiopathy, a b s e n t

a t the moment o f the study, with FPG negative a f t e r cold t e s t ( p o s s i b l e past ang iopathy)

Table 5 shows the c l a s s i f i c a t i o n of the s u b j e c t s according

to t h e above criteria. D i scu ssi o n

The a n a l y s i s of ?able82 and 3 suggests the following con-

s i d e r a t i o n s . The ages of t h e d i f f e r e h t homogeneous groups are n e a r l y t h e same both f o r mean and extreme v a l u e s ( w i t h t h e o n l y exception of the mean age of the group of former moulders). The p e r i o d s of exposure t o the r i s k o f v i b r a t i o n s are rather unequal ( w i t h t h e exception of t h e two groups of p r e s e n t and former finishers).

4 the FFQ

If we consider i n t h e following order:

presence o f o n l y s u b j e c t i v e symptoms; b> a l t e r a t i o n s of c)’ p o s i t i v e cold test, a s a progressive.expression of

i n c r e a s i n g s e v e r i t y of angiopathy, one can r e a l i z e t h a t -be prevalences of t h e above parameters decrease i n the proposed o r d e r , for each homogeneous group. However, i f the above parameters are i n d i v i d u a l l y considered, i n r e l a t i o n t o the d i f f e r e n t homogeneous groups, we

105

can r e a l i z e t h a t they decrease f r o m the group of nfinishersw t o the one of former f i n i s h e r s ; this i s probably the expression of a p a r t i a l r e v e r s i b i l i t y of the disorders. !he same

parameters, i f the two groups of Vnechanical and mama1 moulders" a r e compared, show a g r e a t e r prevalence o f subj e c t i v e symptoms and o b j e c t i v e signs i n the former w i t h re* p e c t t o the l a t t e r , while FPG behaviour is the same. As f o r subjective and objective disorders, t h e i r g r e a t e r prevalence i n mechanical moulders may be due to the higher number of beats/min developed by t h e u t i l i z e d p e s t l e s and to the d i f f e r e n t way o f holding them, However, the same frequency of a l t e r a t i o n s o f FPC cannot be explained. If the finishers and former finishers on the one h a d and the mechanical or manual moulders on the o t h e r hand are c o l l e c t i v e l y confronted it is possible t o remark t h a t , on t h e whole, the c i t e d parameters show more evidence i n the f i n i s h e r s with r e s p e c t to the moulders (where the cold test was always negative). zhis is probably due t o both the higher attendance and duration of the d a i l y work load i n f i n i s h e r s (even though t h e period of exposure i n years i s always longer f o r t h e moulders), and t h e d i f f e r e n t c h a r a c t e r i s t i c s of the instruments used by the tyo c l a s s e s of workers ( f i n i s h e r s and moulders) w i t h r e l a t i o n t o the number of beatdminute and turndmin. The scanty number

o f former moulders d i d n o t permit t o c i n s i d e r them. The o v e r

a l l judgement of the degree of angiopathy by c a t e g o r i z a t i o n o f t h e homogeneous groups, a s can be seen i n Table 5 , sub-

s t a n t i a l l y confirms the above considerations.

Table 4 permits some considerations on t h e period of latency o f the subjective and o b j e c t i v e angiological disorders. I n two homogeneous groups, present and former f i n i s h e r s , the subjective symptoms appear a f t e r two years o f exposure while the o b j e c t i v e d i s o r d e r s (expression of a more advanced s t a g e

of t h e disease] appear about three years l a t e r . I n the two homogeneous groups o f mechanical and manual moulders, subj e c t i ve symptoms appear a f t e r about 4 years while the o b j e c t i v e d i s o r d e r s appear a f t e r 4-6 years. The d i f f e r e n t type of employed instruments and the higher work attendance may explain, a l s o i n this case, t h e e a r l i e r appearance of the d i s o r d e r s i n f i n i s h e r s ( p r e s e n t and former) w i t h r e s p e c t to moulders (manual and mechanical) and i n p a r t i c u l a r mechanical moulders within the two groups of present moulders. Also w i t h regard t o this, it does not seem appropriate to consider t h e group o f former moulders for the reason a l r e a d y mentioned. W e would like now t o p o i n t o u t t h a t i n present f i n i s h e r s ,

the mean time of exposure for the appearance o f a l t e r a t i o n s i n FPG a f t e r cold t e s t w a s 5.4 y r s ( t h e lowest value was 1.5 yrs) while f o r mechanical moulders the mean time f o r an i m pairment of FPC was 3.5 y r s (lowest value 2 yrs); I n manual moulders, t h e scanty number of s u b j e c t s does not permit any consideration. As for the r e s p o n s i b i l i t y of cold temperature or vlbra-

t i o n s o r both f a c t o r s together f o r causing the angiological d i s o r d e r s , according to nearly a l l t h e interviewed workers, the exposure to cold

or the combined a c t i o n of cold and vibra-

t i o n s can cause both s u b j e c t i v e and o b j e c t i v e d i s o r d e r s , while

107

exposure t o vibrations was often considered negligible. This ;s

confirmed by the f a c t t h a t i n present and former f i n i s h e r s

the l e f t hand, t h a t was more heavily exposed t o the cold j e t of a i r given out by the exhaust of the instrument, was

more

frequently affected by both subjective and objective disorders with respect to the right hand. Five volunteers, chosen among the workers who had shown a f t e r the cold test and impairment of FFG and the Raynaud phenomenon, received FPG immediately after working w i t h a vibrating tool.

None showed any s i g n i f i c a n t FPG a l t e r a t i o n o r appearance of the Raynaud phenomenon. Immediately afterwards, t h e cold t e s t was performed a t the hands: i n a l l of them F R a l t e r a t i o n s and the Raynaud phenomenon appeared. With reference t o r e v e r s i b i l i t y of both subjective and objective disorders, it can be seen from Table 4, t h a t i n former f i n i s h e r s reversibil i t y was observed i n 28.57% and ?9.09% of the cases(+

former

moulders only one case of disappearance of subjective symptoms was seen)

.

These subjects had been exposed t o vibrations from 1 t~ 7,1 years (mean value 4 yrs). Ihe time i n t e r v a l between cessation of exposure and disappearance o f disorders varied from 2 months t o 2 years f o r subjective symptoms and from 6 to 18 months for objective ones.

.

I1 NEUROLOCICAL PERIEHERAL FINDINGS

Ihe population examined was the same as was the object of the angiological study.

108

!he neurological study consisted of:

- analysis of

subjective complaints collected w i t h the help

of a specially constructed questionnaire including both unspeckfic (headache, malaise, insomnia, vertigo, etc.)

" specific"

and

symptoms (paresthesias, dysesthesias, cramps?

indicative of peripheral nerves involvement. !he time of appearance of the disorders and t h e i r reduction or recovery w i t h removal f r o m exposure was also considered. D a t a per-

t i n e n t t o smoking h a b i t s , aZcohol consumption and the use

-

of protective means, were collected; a neurological examination was performed p a r t i c u l a r l y directed t o the brachial plexus and the nerve trunks of the upper extremity and t h e i r branches;

- an electromyographic (EMC) and electroneurographic

study

to determine the conduction velocity of the f a s t e s t (MCV) and slowest

(SFCV) motor nerve fibres.

ENG, MCV and SFCV were carried out on the r i g h t or l e f t s i d e

according t o the c l i n i c a l examination and the worker's

report;

when no subjective o r objective signs were present, EMG was done on the l e f t upper extremity (the r i g h t side f o r l e f t handed), t h i s side being more affected by vibrations. EMG that permits t o evaluate axonal function was done on m. abductor m i n i m i d i g i t i of the hand ( u l n a r nerve), m. opponens pollicis

(median nerve) and also on the m. t i b i a l i s anterior and m. extensor digitorum brevis of the foot (peroneal nerve). MCV and SFCV permit to study the function of .Ule myelin sheath

of the nerve fibre; they have been determined on the ulnar, median and common peroneal nerves. Skin temperature was

109

obtained w i t h a thermocouple. A score was given to each c l i n i c a l and e l e c t r o p h y s i o l o g i c a l parameter. Results I

- S u b j e c t i v e complaints:

lhe frequency of u n s p e c i f i c

symptoms was not s t a t i s t i c a l l y d i f f e r e n t i n the examined groups. The f r e q u e n c i e s of s p e c i f i c symptoms t h a t were given a progress i v e l y i n c r e a s i n g score are: a) f i n i s h e r s : 29 (78.3%)

o u t of

the 37 s u b j e c t s complained of p a r e s t h e s i a s a t the hands., 7(19%)

l o s s of t h e s t r e n g t h of c o n t r a c t i o p i n f i n e movements of t h e hands. P a r e s t h e s i a s were mainly p r e s e n t i n the V and IV f i n g e r

of t h e l e f t hand, and, r a r e l y , b i l a t e r a l l y and on the medial s i d e of the forearm. P a r e s t h e s i a s were mainly p r e s e n t i n the morning, i n t e r m i t t e n t l y , of t e n t r i g g e r e d by cold temperature and always t r a n s i e n t . Motor d i s o r d e r s c o n s i s t e d i n d i f f i c u l t y

i n making f i n e movements. Subjective important l o s s of s t r e n g t h was never reported. These d i s o r d e r s appeared g e n e r a l l y a f t e r 1.9 years of work (6 months-6 yrs).

12 s u b j e c t s (32.496)com-

plained of pains a t the w r i s t , . I 3 (34.6%) a t t h e elbows, 19 (51.35%) a t the shoulders. The p a i n s appeared a f t e r

years of work (6 months-13 yrs).

4.9

b) former f i n i s h e r s :

18 (38%) o u t of t h e 47 s u b j e c t s examined had p a r e s t h e s i a s a t

the hands, 7 (14.8)

motor impairment of t h e hands p r e v a l e n t on

the l e f t s i d e , The p e r i o d of l a t e n c y f o r their o n s e t was

1.9

years of work. 5 s u b j e c t s 60.5%) complained of wrist pain, , 3 (6.3%) a t the elbow, 15 (31.8%) a t the shoulders. The period

of l a t e n c y f o r t h e i r o n s e t was 4.9 years of work.

Specific

symptoms were t h e r e f o r e more frequent i n t h e group o f f i n i s h e r s with r e s p e c t t o former f i n i s h e r s . Bone and j o i n t s p a i n s a p

110

peared a f t e r specific symptoms and w e r e i n d i c a t i v e of a neurogenic l e s i o n . c) moulders

(mechanical, manual and

former). S p e c i f i c a d u n s p e c i f i c symptoms were n o t s i g n i f i c a n t l y p r e s e n t i n this category. Objective Clinical Neurological Findings

(Table 6)

a) F i n i s h e r s : 23 (71.8791) o u t of the 37 examined s u b j e c t s hand a n u l n a r neuropathy, 6 (16.21%) a median neuropathy.Five

s u b j e c t s (13.5%) had combined u l m r and median n. neuropathies,

-

-

which w e r e p r e v a l e n t l y on the l e f t side both f o r the u l n a r (11 cases

48%) and f o r the median nerves (4 cases

66.6%).

The me abductor d i g i t i m i n i m l and the abductor p o l l i c i s w e r e

p a r t i c u l a r l y involved and become hyposthenic b u t not hypot r o p h i c and o f t e n , on t h e contrary, showed l o c a l i z e d hypertrophy. Hypotrophy w a s r a r e l y seen and only a t the f i r s t i n t e r n s s e u s without corresponding hyposthenia. Motor impairment f o r f i n e movements o f the hands was o f t e n seen without hyposthenia o r hypotrophia. A motor d e f i c i t o f the f l e x o r u l n a r i s c a r p i o r o f the f l e x o r digitorum proFundus was r a r e l y seen. The m. o p p n e n s p o l l i c i s was found hyposthenic i n d i c a t i n g median neuropathy. A sensation d e f i c i t was observed i n the f i f t h and fourth f i n g e r s of the hand up

t o the s t y l o i d process. Rarely, s u p e r f i c i a l hypoesthesia was a l s o seen a t the u l n a r s i d e of t h e fore-arm up t o the elbow. The s e n s a t i o n impairment was g e n e r a l l y s u p e r f i c i a l , hypoalee-

sia o r hypodyseethesia. Hypopallesthesia was unfrequent. I n 8 s u b j e c t s (34.3%) motor u l n a r neuropathy was found, i n 9 (39.1%) sensory and i n 6 (26.6%) combined sensory-motor u l n a r

111

neuropathy w e r e found. Mononeuropathies w e r e seen i n single cases w i t h no relation t o exposum. b) Former sinishers:

17(36.17%) o u t o f the 47 examined

subjects had ulnar neuropathy; 5 (10.63%) had a median neuropathy. The lesions were prevalently b i l a t e r a l both f o r the ulnar (9 cases = 52.9%) and f o r the median nerve (3 cases = 6096). The motor and sensory areas involved were the same seen

i n finishers. A fine motor ulnar neuropathy was found i n 5 subjects (29.5%), purely sensory i n 9 cases (52.9%) and sensory-motor i n 3 subjects (17.6%). No pure median neuropathies were seen, while 4-pur-e sensory (80%) and 1 (20%) sensory-motor neuropathies were seen ( t a b l e 6). c) Moulders

(mechanical, manual, former) : No abnormal

r e s u l t s were seen.

3. PIC ard nerve c o d u c t l o n velocity results The mean and standard deviation (s.d.)

values of MCV and

SFCV of t h e ulnar and median nerves f o r a l l t h e homogeneous groups of workers are reported i n tables 7 and 8. The values found can be considered a t the lower border of normality. The following are the r e s u l t s f o r the iniividual groups. a) Finishers:

The population examined consists of 36 s u b

jects since only the subjects exposed f o r a t l e a s t 5-6.hours daily were considered. 20 (55.55%) out gf the 36 examined subljects showed a slowing o f ulnar MCV, 13 subjects (36.1%)

of median MCV and 8 (25%) showed a slowing of both median and

112

ulnar MCV. The ulnar nerve was therefore more frequently involved even though the median nerve was often involved and prevalently a t t h e l e f t side. For both nerves SFCV values were p a r t i c u l a r l y diminished even i f also MCV was significantly low ( t a b l e 9). b) Former finishers:

The population examined was reduced

to 42 subjects f o r the same reason indicated f o r finishers. 14 subjects (33.3%) showed a slowing of ulnar'MCV, 22 (52.38%) of MCV of both nerves (tab. 9). c) Moulders (mechanical, manual and former): Ihe r e s u l t s of this group f a l l within normal limits and are not a n a l y t i d

l y reported. Discussion The r e s u l t s o f t h e c l i n i c a l and EMG study c l e a r l y indicate t h a t a peripheral neurogenic lesion w a s frequently found i n the groups of finishers and former f i n i s h e r s , while moulders (mechanical, manual and former) had normal neurological findings.

The neurogenic lesion was consistant w i t h a peripheral neuropathy affecting the ulnar a& the median nerve, while the common peroneal nerve was always normal.

We believe that the neuropathy observed is due t o the long-term vibratory trauma f o r the following reasons: I)the

known damaging action of vibrations on the nerve fibres; 2)

the h i s t o r y of the subjects demonstrating long-term expo-

sure t o vibrations; 3) the absence of other possible cau8es

113

of the neumpathy (endogenous or exogenous i n t o x i c a t i o n s , i n f e c t i o u s diseases, etc.) ; 4) the s t a t i s t i c a l d i s t r i b u t i o n of the neuropathieg i n the various groups; 5 ) the normal f i n d i n g s

of the common p e m n e a l n e r v e , a nerve of t h e lower extremity. However, i n addition t o i n v e s t i p a t i o n o f the c l i n i c a l a s p e c t s this study had two o t h e r objectives: 1) the determination of a

s a f e period of exposure and 2) the study of t h e r e v e r s i b i l i t y of the lesion. For t h i s purpose, each s u b j e c t received a score

of the l e s i o n , progressively Increasing w i t h s e v e r i t y , according t o a c l i n i c a l c r i t e r i o n .

--

Four s t a g e s of increasing involvement were obtained: stage 0 stage 1 stage 2

no l e s i o n mild neuropathy

neuropathy

s t a g e 3 = severe neuropathy By adopting t h i s c r i t e r i o n , t h e s u b j e c t s were d i s t r i b u t e d a s follows:

3

Finishers- t o o b t a i n comparable d a t a , the population

considered was reduced t o 32 subjects, because only workers exposed over 5-6 hours p e r day were included. This population was then divided i n t o two "homogeneous subgroups".

'The first

subgroup comprised I 0 subjects w i t h 4 3 years of-work attendance, while t h e second subgroup was composed of 22 s u b

jects with

> 3 years

of work attendance. I n t h e first

subgroup, o n l y 1 s u b j e c t (10%) is a t s t a g e 0,7 (70%) a t s t a g e I,2 (20%) a t stage 2 and none a t s t a g e 3. I n lhe second sub-

group, none is a t s t a g e 0, 5 (22%) s u b j e c t s a t s t a g e 1, 13 (60%) a t s t a g e 2 and 4 (18%)a t stage 3. A q u a n t i t a t i v e

114

analysis of subjective symptoms is i n apeement w i t h t h e

c l i n i c a l results4 in f a c t , 20% of the population with work attendance

< 3 years and 47% o f the population with work

attendance

> 3 years complained of specific symptoms indica-

t i v e of a neurogenic lesion. I n graph 1, subjective symptoms and objective signs are compared. b) Former f i n i s h e r s

- f o r the same reason indicated f o r

f i n i s h e r s , the population examined was reduced t o 45 subjects.

Two "homogeneous subgroups" were also obtained: the first subgroup comprised 14 subjects with

C 3 years of work atten-

dance while the second subgroup was made o f 29 subjects w i t h

>3

years o f work attendance. I n the first subgroup, 12

subjects (86%) are a t stage 0, 2 (14%) a t stage 1, none a t stage 2 and 3. I n the second subgroup, 9 subjects (79%) a r e

a t stage 0, 9 (29%) a t stage 1, 9 (29%) a t stage 2 and 4 (13%) a t stage 3.

I n order to study the r e v e r s i b i l i t y of the lesion, we investigated lhe differences existing between present and former

finishers. The two subgroups w i t h work attendance < 3 years were then compared with the t w o subgroups with work attendance

> 3 years;

former f i n i s h e r s were also subdivided i n to sub-

j e c t s who had been removed f r o m the work one year p r i o r l y and subjects removed two years p r i o r l y (graph 3a and 3b). one can realize considering the group 3a, t h a t the percen-

,

tage of f i n i s h e r s a t stage 0 is lo%, while 70% are a t stage 1 20% a t stage 2 and none a t stage 3, f o r former f i n i s h e r s re-

moved. I year priorly, 8Q6 a r e a t stage 0, 20% a t stage 1

(therefore 5096 recuperated with respect t o finishers) and

115

none a t t h e o t h e r stages. The former f i n i s h e r s removed two y e a r s p r i o r l y are a l l a t s t a g e 0. From t h e graph 3b, one can realize t h a t rn f i n i s h e r s

are a t s t a g e 0, 22% a t s t a g e I,60% a t s t a g e 2, and 18%a t s t a g e 3. -Among former f i n i s h e r s removed I y e a r p r i o r l y , 25% are

a t s t a g e 0, 22% a t stage 1, 10%a t s t a g e 2 and 40% a t s t a g e 3. Among former f i n i s h e r s removed 2 years p r i o r l y 35% are a t

,

s t a g e 0, 35% a t stage I 15% a t s t a g e 2 and 15% a t s t a g e 3.

W e may conclude t h a t , f r o m a c l i n i c a l standpoint, a complete recovery i s p o s s i b l e o n l y f o r s u b j e c t s with work attendance

b e l o w t h r e e years. For the same reasons mentioned e a r l i e r , each s u b j e c t was given a score p r o g r e s s i v e l y

increasing with s e v e r i t y also f o r

t h e EMG and nerve conduction values.

-

For MCV and SFCV, f o u r s t a g e s were obtained: stage 0

normal MCV

s t a g e I = mild reduction of MCV s t a g e 2 = r e d u c t i o n of MCV s t a g e 3 = severe reduction of MCV

-

For EMC three s t a g e s were obtained: stage 0 stage 1

-

normal EMC mild EMC a b n o p n a l i t i e s

s t a g e 2 = severe EMC abnormalities The obtained d a t a are t h e following: a)

Finishers:

The population c o n s i s t s

of 36 subjects.

The d i s t r i b u t i o n f o r s t a g e s o f s e v e r i t y i s reported i n t a b l e 10.

116

Motor conduction v e l o c i t y of the common peroneal nerve was always normal (MCV = 45-55 d s e c . : SFCV = 40-50 m/ sec.) ; t h e r e f o r e a n a l y t i c a l data a r e n o t reported. This population was divided i n t o two homogeneous subgroups, t h e same way as

f o r the c l i n i c a l f i n d i n g s . The f i r s t subgroup comprised 9 subjects w i t h

4

3 years of work attendance, while t h e second

subgroup was composed of 27 s u b j e c t s w i t h work attendance

>3

years. The r e s u l t s can be seen i n group 4 f o r t h e nerve

conduction and 5 f o r t h e EMG. I n the f i r s t subgroup (graph 4)

3 s u b j e c t s (33.3%) a r e a t stage 0, 5 (55,596) a t s t a g e 1 , 1 (11.1%) a t s t a g e 2, none a t s t a g e 3. I n the second subgroup,

11 s u b j e c t s (40.74%) a r e a t s t a g e 0, 6 (22.2%) a t s t a g e I,

6 (22.2%) a t s t a g e 2 and 4 (15%) a t s t a g e 3.

EMC data show a behaviour s i m i l a r t o nerve conduction; i t can be seen, however, t h a t t h i s t e s t i s less s e n s i t i v e w i t h r e s p e c t t o nerve conduction which must be considered a f i r s t choice test. b) Former finishers: "he population is composed of 42

subjects. 'Ihe d i s t r i b u t i o n f o r s t a g e s of s e v e r i t y i s reported

in table 12. Nerve conduction of the common peroneal nerve was always normal (MCV = 45-55 m/sec; SFCV = 40-50 d s e c ) . A n a l y t i c a l data are n o t reported. This population w a s a l s o divided i n t o two "homogeneous

subgroups".

The f i r s t subgroup comprised 10 s u b j e c t s w i t h work

attendance

> 3 years while t h e second subgroup i s composed

of 32 s u b j e c t s w i t h work attendance

> 3 years. R e s u l t s a r e

reported i n graph 6a. I n t h e first subgroup 1 s u b j e c t (10%)

is a t s t a g e 0, 6 (6096) a t s t a g e 1 , 3 (30%) a t s t a g e 2 and none

117

a t s t a g e 3. I n t h e second subgroup, 4 s u b j e c t s (12.2%) are a t s t a g e 0, 19 (59.37%) a t stage I,6 (18.43%) a t s t a g e '2 and 3 (10%) a t stage 3 . Therefore, t h e r e is no s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e between the groups of finishers and former finishers f o r work attendance

4

3 years a s well. These r e s u l t s are

shown i n graph 6b, where the f i r s t "homogeneous subgroups" (work attendance

4 3 y e a r s ) of the two populations a r e com-

pared w i t h each o t h e r , by d i v i d i n g t h e population of former f i n i s h e r s according t o when they ceased t o work (one or two years). From graph 6b, one can see t h a t t h e r e is no s i g n i f i c a n t d i f f e r e n c e between t h e two curves. These r e s u l t s may be explained by t h e f a c t t h a t a subjective and c l i n i c a l recovery of a p e r i p h e r a l l e s i o n o f t e n does not coincide with t h e recovery of t h e neurophysiological parameters (MCV, SFCV and EMC) which may become mrmal l a t e r on.

N euro l o a i c a l conclusions This study shows t h a t t h e neuropathies observed i n this

s p e c i f i c s i t u a t i o n are due t o v i b r a t i n g t o o l s and t h a t they a r e p r e v a l e n t on the l e f t side i n r e l a t i o n t o the hand holding t h e t o o l . lhese r e s u l t s a l s o permit t o advance t h r e e cons i d erat i o n s :

I)

2)

-

-

a c l e a r neurological symptomatology i s never p r e s e n t before two y e a r s of exposure f o r p e r i o d s o f exposure up t o t h r e e years severe neump a t h i e s a r e never seen

118

3)

-

a r e l e v a n t clinico-functional recovery i s observed

i n s u b j e c t s with work attendance

4 3 years a f t e r they

ceased to work, while f o r higher exposure r e v e r s i b i l i t y i s i n s u f f i c i e n t o r absent.

Freven t i v e measures

As f o r the preventive measures t o be adopted i n the s p e c i f i c s i t u a t i o n o f o u r study, the r e s u l t s suggest the f 0110wing i n d i c a t i o n s :

a b

-

-

t h e work phases preceding f i n i s h i n g must be improved;

t h e tools used must be improved t o reduoe v i b r a t i o n s

and t o deviate the a i r j e t

c

- the h e a t i n g of

o f the exhaust;

the work environment must reach s a t i s f a c -

tory levels;

d

- exposure time of

workers t o v i b r a t i o n s must be reduced

t o a t l e a s t 50%.

On a examin; leu risques, et les altbrations ph6Yiphdriques angiologiques et neurologiques dans l e s membres superieurs d e s oyvriers qui emploient d e s outils vibrants dans une fonderie d acier. 09 a obtenu quatre ca;6gories selon l e s diffbrentes t k h e s . Symptomes subjectifs ?nt ete rocuellis avec un questi.onnaire speciallenient organise. Ind+cations objectives de angiymthie, dims c o n d i t i y basalos et egalement aprhs avoir rafraichj. les mains dans 1 eau courante, ont 6 t h obtonuos avec observations cliniques et ph?t?pletism?graphye. Indications objectives neurologiques ont 0te observeos avec examens cliniques et eloctroneuromyographiques.

119

REFERENCES

, Nlssardl C.P., Spinazzola A., Cherchi P., P a t o l o g l a da v i b r a z l o n l , A t t i d e l XXX Congress0 Nationale SOC. I t a l . Med. Lavoro, Palermo, sett. 1967.

1. Casula D.

2. Kllmkova-Deutschova E. , Neurologische Aspekte d e r V l b r a t i o n s k r a n k h e l t , I n t . Arch. Cewerbepath. 22 (1966) PP. 297-305,

,

3. Lukas E. , Kuzel V.,

Klinlsche und elektromyographische Dlagnostlk d e r Schandigung d e s p e r i p h e r e n Nervensystems durch l o k a l e v i b r a t i o n , I n t . Arch. Arbeltsmed. 28 (1971) pp. 239-249.

,

4. Russo L., Lena P., Le a r t r o p a t i e da microtraumatismo v i b r a t o r l o , Ed. Minerva Medica, Torlno, 1964.

5. Seppalalnen A.M.,

Nerve conduction i n t h e v i b r a t i o n syndrome, Work envlron. h l t h . 7 (1) (1970) , pp. 82-84,

6, Tomaslnl M., Chiappino C., Castano P., Ambrosini A., Le l e s i o n i v a s c o l a r l d a strumenti v l b r a n t i , Med. Lavoro, 63 (19721, p. 332. Objective neurological signs I o/o 1 of finishers according l o exposure 1 in yrs t ( 5 - 6 hrs/day 1

O/o

subjective neurological symptoms of finishers according to exposure ( in yrs. I ( 5 - 6 hrs/day I

80

70 60

50 10 30 20 10 n "

b

st.0

sl.1

*-+-+ P =

120

9.2

L

sw

Finishers with exposure

3 years

Finishers with exposure *3 years Score of subjective symptoms

Objeetik neurdogical signs Io'/ of former finishers according expowre 1 in yrs 1

'/a

I

Subjective neurological symptoms of former finishers according to exposure ti n yrs)

70

'/o

70

60

60

50

50

40 30 20

Lo

30 20

lo

0

st.0

e---o--+

st.1

st.2

10 n"

st.3

Former finishers with exposure Former finishers with exposure

3 years 3 yearS

Fig.

PO

P1

P2

2

objective neurological signs in finishers and former finishers removed respectively 1 or 2 years priorly ; exposure.* 3 years Objective neurological signs in finishers and former finishers removed respectively 1 OT 2 years priorly ; exposure P 3 years

30

-

St.0

*-*-a

&----6--d

st.1

st.2

st.3

20 10 n

Finishers Former finishers removed 1 yr. priorly Former finishers removed 2 yrs. priorly

1

st.0

st 1

st.2

st.3

Fig. 3

121

MCV and SFCV I % 1 of finishers

EM6 results ( Y o )of finishers

according to expowre (in yrs 1

40 30 20 10

0 Fig.

4

MCV and SFCV in former finishers

-

Former finishers exposed(3years

c+-e Former finishers expowd>3years

Fig. 6

122

MCV and SFCV O/O in finishers and former finishers removed 1 . 2 and 3 years priorly

-

Finishers

c ++ Formerfinishers removed from 1 year

n--+-* Fbrmcrfinishersremoved from2years c-.4-4 Former finisherrmrwcd from 3ycars

Table

Type of vibrot ing tool

Producer

1

Commerc iaI name

0

P' ieumatic hcimmers

up-right grinders

horizontal grinders -

vettical grinders

Consolidated Pneumatic Tool CO.

Simplate 2'

C onsol idated Pneumatic Tool CO. Breberg-BRB

weight in k g

.

3050

5.9

2600 ----

A .7 -I-

18000

5-SDN-6&R/M

5500

5,15-5*85

CP-3221-5-6OOO

6000

5'5

2,3

Depmg

- 6,2

DE- 180

7500

4*1

DE- 200

6000

4*1

3190-A-6000

6000

Consol idated Pneumatic

-3

2-SDN-180-R Calzoni

Tool CO. Pneumatic pestles

Simplate 1

beats or turns/min

5

-63

VSt -1 6-R

850

4*7

VSt-1211

800

93

VSt-8/1

650

11

123

Table Categories

mean age mean exposure and range and range in yrs.

no. subjects (tot. 167)

F inishers

43

F ormer Finishers

52

MechanicaI moulders

18

Manual moulders

45

Former moulders

9 Table

Categories

2

symptoms

(%I

1

19 (4,5)

2 1-57 (30,5)

1

27 (7,9)

-

3 signs

(%)

FPG impairment after cold test

positive cold test

12 (2~9)

(%I

37 (86,Q9

26 (6046)

21 (48,841

Manual moulders

13 (28,8)

2 (4,4)

(111)

F ormer

4 (44,4)

1 (11,l)

Finishers

-

24-54 (32,6)

(W

Former Finishers

moulders

124

5

0

0

Table 4

Categories

meon and range

of latency for

the appearonce of the symptoms

mean and mnge

of latency for

the appearance

of signs

Finishers

6 months4 years (2,2 F.)

1 year-14 years

Fm e r F inishen

6 months-6 years (1,9 F.)

6 .months-7 years (2,6 yn.1

Mechanical moulden

1 year-7 years (3,7 F.)

1 year-11 years (4 Y " J

ManuaI madden

3 years-9 years (4,1 p.1

Fm e r moulders

6 months-23 years (10,4 m.)

meon time for symptoms disappeared disappearance (%)

signs

disappeared

(%I

m w n time for disuppearance

(3,3 F.)

10 cases (28,571

2 months-2 years (6 months)

1 case

2 months

5 years-7 years (6 yn.1 13 years (1 case only)

(U)

6 cases (29,091

6-18 months (8 months)

Table Categories of severity

Finishers

Former Finishers 52 cases

43 cases

(%I

a

6 (13,9)

1

5 Mechanical moulders 18 cases

(%I

Manual moulders 45 cases

(%I

Former moulders 9 cases

(%I

(96)

15 (28,9) 10 (55,6)

30 (66,7)

5 (55,6)

16 (37,3)

14 (26,9) 6 (33,3)

10(22,2)

3 (33,3)

2

9 (20,9)

10 (19,2) 2 (11,l)

5 (11,l)

0

3

12 (27,9)

5 (9,6)

0

0

0

4

0

8 (15,4)

0

0

1 (11,1)

Table 6

- Prevalences of neurological peripheral findings in present and former finishers

Finishers (37) Ulnar n. neuropathy

left right bilat.

TOTAL

11

2 10

48.00% 8.60% 43.40%

1 9

7

41.30% 5 ;80% 52.90%

23

71.87% 17

36.17%

motor 8 sensory 9 sensory-motor 6 left Median n. neuropathy right bilat.

126

Former finishers (47)

4

2

34.30% 39.10% 26.60%

5

9 3

29.50% 52.90% 17.60%

66.60%

2

40.00%

33.40%

3

60.00%

-

-

-

TOTAL

motor

sensory sensory-motor

6

16.21%

5

1 4 1

16.60% 66.80% 16.60%

4 1

10.63%

-

80.00% 20.00% -

~~~~

Ulnar and median n. neuropathies

5

13.50%

3

6.30%

Long thoracic neuropathy Inferior trunk neuropathy Radicular neuropathy Superior trunk neuropathy Thoracic outlet Axillary n. neuropathy

4 3 2 1 1

12.50% 9.37% 6.25% 3.12% 3.12%

1 -

1

2.12%

Table 7

-

-

- Mean and standard deviation (5.d.)

L

2.12% L

8.51% 2.12%

4 1

values of MCV and SFCV

of the ulnar nerve.

SF CV

MCV (m/Sec

ULNAR NERVE

.I

(mhec .)

.d.

mean

s.d.

57,47

7'76

42

45,69

8,74

41

58,m

8,50

45

48,88

9,83

44

Mechanical moulders 56,25

7,78

17

43,M

8,31

16

Manual moulders

60,74

8,12

45

46,46

8,50

44

Former moulders

60,03

4,8

9

47,55

7,0

F inishen ~~

mean

5

no. cases

~

Farmer ~~

no.cases

F inishen

~~~

0

127

Table 8

- Mean and standard deviation (5.d.)

values of

MCV and SFCV of the median nerve.

MCV

MEDIAN NERVE

Finishers Former finishers

SFCV

(m/sec .)

(m/sec

.)

.

mean

s.d.

no. cases

mean

s .d

55,60

8,31

42

47,09

8,91

38

7, 91

50

44,40

0,64

48

52,26 ~~~

~~

no .cases

~~

Mechanical moulders

55,20

8,16

17

43,12

0,44

15

Manual moulders

58,50

7,92

45

46,83

8,42

41

Farmer moulders

52,82

4,40

9

45,CQ

3,2

Table 9

- Slowing o f MCV and SFCV o f the

7

u l n a r and median nerves i n

finishers and former finishers

MCV and SFCV

- Total Median neuropathy - Total Ulnar nerve

Median and u l n a r nerves

128

Finishers (36)

Former finishers (42)

No cases

x

No cases

x

20

55.55

14

33.33

13

36.11

22

52.38

8

25.00

7

16.66

Table

10

- Distribution of the subjects of the five groups according to the stage of EMG and/or conductive velocity alterations.

Stage 0

no. cases

1

Stage

%

Stage

%

no. cases

Finishers

16

44,44

7

19,44

Former Finishers

20

47,61

3

7,14

Mechanical moulders

13

72,22

4

77,n 88,88

Manual mouIders

35

Former moulders

8

2

Stage

%

no. coses

3

no. cases

%

9

25,OO

4

11,ll

11

26,19

8

19,04

22,2

1

5,s

0

0

9

20,o

1

2,2

0

0

1

11,l

0

0

0

0

129

COMPARATIVE ANALYSIS OF HUMANAND SUBHUMAN OPERATOR PERFORMANCE IN A CONTROL LOOP P. K. Bhagat, V. N. Gupta and D. F. McCoy Wenner Gren Research Laboraaoty, Universlly of Kentucky, Lexlnglon, Ky. U S A .

sumruy Using electric shock as a negative rehforcement, three Rhesus wnkeys wre trained on a custan-designed pre-programable electronic visual tracking facility in an effort to coapare t h e h performance with those of hunan operators. Describing functions for these animals were estimated from input, output and error t-lm records obtained under a coupematory tracking task. A Gaussian random noise generator was used to generate the forcing function aver the frequency bandwidths of 0.05 and 0.15 W.. A paramter optimization a l g o r i h was used to compute a generally accepted five parameter performance model w i t h the a h describing function data. For carparison purposes, data for tm humn subjects were also collected and analyzed for the 88me tracking task. !l%e describing function data and values of caqmted model parameters for these t w o species s h no signiCicant differences. Typically, the t r a n q o r t a t h lag ranged betmen 0.08 and 0.19 seconds. These similar fmctional relationships observed bemeen hunm and subhunm operators lend suppoa for monkey-man extrapolations in stressful tracking situaths.

I MRODUCTION

An understanding of the effects of vibration on human performance i s

essential for specifying optimum design for systems such a s piloted aircraft and other transport vehicles. The chief effects of vibration are seen as alterations of physiological function and general decrement in performance

130

capabilities.

Laboratory studies done w i t h man are often compromised by the

fact that only low levels of vibration can be employed and access t o invasive physiological variables i s n o t feasible.

Animal experimentation, on the other

hand, i s relatively free from the above constraints.

Human performance, i s

usually described i n terms of mathematical models derived from sllbjects performing a tracking task. An essential feature of thesemodels i s the use of

quasi-linear describing functions derived from time domain i n p u t o u t p u t data. The parameters defining the describing function are adapted t o the task variable defined i n the particular operator machine configuration.

Recently subhuman

operators (Rhesus monkeys) have been trained to perform visual tracking tasks w i t h a view t o future studies of performance degradation due t o vibration,

radiation and other physiologic stresses.

Because of scarcity of this type

of data there are few mathematical models of primate performance. A need exists,

t o develop a comparative model of performance for subhuman operators performing the same tracking task as humans.

W i t h this model as a basis performance

degradation i n subhuman operators under various stresses may be quantified i n terms of. variations i n model parameter values and the results extrapolated t o human performance under defined conditions.

The study reported here describes

the development of an optimum parametric model of primate operators performing a compensatory tracking task.

MATERIALS AND METHODS A.

Tracking System The electronic system used i n tracking experiments was custom-

designed and built a t Wenner-Gren Research Laboratory. The machine i s fully programnable i n t h a t all parameters like "Test", "Rest" and "Grace" periods, and number of "Test/Rest" cycles can be externally preprogramned.

In addition, the machinecan be used either i n the Pursuit o r

131

Compensatory mode, Figure 1 i s a f l o w c h a r t of the developed system which primarily cons i s t s of hybrid-analog and d i g i t a l signal conditioners designed t o control the X, Y and Z axis display of a Cathode Ray Tube (CRT).

The s t a t i o n a r y

pattern on the CRT screen, shown i n Fig. 2, i s generated i n t e r n a l l y using analog c i r c u i t s .

The analog i n p u t signal, stimulus x ( t ) , i s used t o provide

movement o f the central cursor (dot) along the X-axis. The operator, through use of the s t i c k attempts t o control the motion o f the cursor. The p o s i t i o n o f the s t i c k corresponds t o operator's output; y ( t ) .

An e r r o r signal e ( t )

i s generated when the cursor crosses boundary l i m i t s which turns shock on and simultaneously causes the cursor t o b l i n k .

A l l these signals x ( t ) , y ( t )

and e ( t ) are i n t e r n a l l y conditioned t o l i e w i t h i n 0-2 v o l t s and are made available t o the Raytheon-704 computer f o r d i g i t i z a t i o n . The d i g i t a l section i s b a s i c a l l y a quad-time-state l o g i c machine.

'Ex-

ternal manual controls "Clear" and "Go" enable the machine t o be reset, and i n i t i a l i z e d before s t a r t i n g the experimental session.

"Clear" signals

the machine i n t o the "Ready" s t a t e and simultaneously t r i g g e r s the CRT pattern o f Fig. 2.

The "Go" signal takes the machine t o "Test" state.

In

t h i s s t a t e the machine waits f o r "Grace" period T1, and then checks t o see i f the subject i s on traget. I n an o f f t a r g e t condition, the cursor i s caused t o f l a s h and shock i s applied t o the subject. Shock continues u n t i l

the subject i s back on t r a g e t a t which time both l i g h t - b l i n k s and shock signals are turned o f f .

During the e n t i r e "Test" period the machine keeps,

track of time and a t the end o f T2 seconds "Rest" s t a t e i s entered and a l l . a c t i v i t y ceases f o r Tg seconds.

-

The ltRest" s t a t e i s followed by "Increment"

s t a t e i n which the machine checks ifpreset numbers o f "Test/Rest" cycles have been completed, ifnot, a new cycle i s i n i t i a t e d .

A t t h e end o f the l a s t

cycle the machine halts. The "Grace" period T1 may be preset as a m u l t i p l e o f 1 second.

132

"Test"

T2 and Tg respectively can be preprogramned as m u l t i p l e s

and "Rest" periods o f 10 seconds.

The input used for e x c i t i n g the system (causing t h e cursor t o move) was Gaussian-random i n nature and was derived from a Random Signal generator (Hewlett Packard).

The primary reason f o r using random i n p u t signals was t o

remove the element o f p r e d i c t a b i l i t y from the operator's response.

In t h i s research, the analog random signals o f frequency bandwidths 0.05 Hz and

0.15

B.

Hz were used.

DATA ACQUISITIGN AND\ ANALYSIS

During each experimental session, random i n p u t x ( t ) t o the c o n t r o l l e d element and s t i c k output y ( t ) were d i g i t i z e d every 16 msecs on the Raytheon

704 d i g i t a l computer.

The computer was programed t o recognize "Rest" periods

and discontinue data acquisition.

I n b r i e f , data was recorded f o r 15 minutes

on magnetic tapes f o r o f f - l i n e analysis on the I B M 370/165 computer.

The

sampling r a t e o f 16 msec was chosen t o include a l l higher frequencies i n the subject's response.

The cross-spectral estimates Qio

input and output) and Qie from subroutines

(cross-spectra between

(cross-spectra between i n p u t and e r r o r ) were computed

i n l i t e r a t u r e [l].ai0 and Qie estimates were used t o

calculate t he describing function as gjven by

C.

MODEL IDENTIFICATION SCHEME The l a s t phase o f the analysis was matching the describing function

estimates w i t h a s u i t a b l e model.

,

Model i d e n t i f i c a t i o n s t a r t s w i t h t h e

assumption o f a known model based on a v i su a l judgement.

Since the model

tr ansf er function G ( j w ) can be expressed as a complex number: G(jw) = G'(w)

+j

G"(w)

(2)

an alogrithm was devised t o determine optimal values o f various model

133

parameters t o minimize t h e sum squared e r r o r

S (A)

(Gi i

= C

Y;)

2

+

S defined by (Gi

-

(3)

Y;)2

where i i s a frequency index, G; and G i are data computed f o r t h e assumed model and Y; and

Yi

are experimentally observed data.

G; and G i a r e computed

f o r t h e chosen model using a r b i t r a r i l y chosen values o f unknown parameters A, t h e dimension o f which depends on t h e number o f parameters i n t h e model. The. program begins w i t h an a r b i t r a r i l y chosen parameter vector, ?. The upper and lower l i m i t s on t h e unknown parameters are provided both t o

l i m i t t h e search area and p h y s i c a l l y t o i n t e r p r e t t h e data.

The steepest

descent method [2] i s used i n i t i a l l y f o r minimization o f t h e sum-squared e r r o r ,

S. I n t h e event of the steepest decent method f a i l i n g , a second order gradient technique known as Newton Raphson technique [2] has been incorporated which has good convergence p r o p e r t i e s i n t h e v i c i n i t y o f a minima. The program i s convergent f o r various s t a r t i n g values chosen i n t h i s study.

It should be noted, however, t h a t since t h e program i s based on t h e

search f o r a l o c a l minima i t i s e n t i r e l y

p o s s i b l e t h a t a b e t t e r f i t t o data

may r e s u l t through choice o f a d i f f e r e n t s t a r t i n g vector.

This i s known i n

t h e l i t e r a t u r e as s t a r t i n g parameter bias. I n order t o o b t a i n l i m i t e d assurances o f uniqueness o f t h e s o l u t i o n , several computer runs were made f o r each equation w i t h d i f f e r e n t s t a r t i n g parameter vectors.

The f i n a l

parameter vector selected was one t h a t y i e l d e d t h e lowest sum-squared e r r o r within t h e group.

There i s a l s o a p r o v i s i o n w r i t t e n i n t h e program random-

l y t o s e l e c t t h e s t a r t i n g v e c t o r i n t h e hope o f i d e n t i f y i n g several s t a t i o n -

a r y points, thus assuring a b e t t e r choice among t h e f i n a l parameter,vectors. The program as developed was checked for. accurate r e s u l t s through i d e n t i f i c a t i o n o f known open loop and closed loop t r a n s f e r functions. For a g e n e r a l l y accepted f i v e parameter model defined by G(s) = Ke'ts(l t T l s ) (1 + T2s)(1 + T3s)

134

(4)

[S]

With parameters chosen as

K

= 2.0;

T =

0.2 sec; T1 = 0.2 sec; T2 = 0.5 sec;

T3 = 5.0 sec; input-output data was generated and from t h i s raw data a t y p i c a l s e t o f papameters i d e n t i f i e d using the i d e n t i f i c a t i o n schemes was T =

0'.20012 sec;

K

w i t h S = 0.31970 x

= 1.9990; T i = 0.2005 sec; T2 = 0.5008 sec; Tg = 4.995 sec;

lo'!

As can be observed t h e e r r o r i n system i d e n t i f i c a t i o n

i s very low.

RESULTS AND DISCUSSION I n the i n v e s t i g a t i o n d e t a i l e d here, three Rhesus monkeys Butch, Hoppy snd B i g Boy were used as subhuman operators i n a shock contro l e d compensatory tracking s i t u a t i o n .

For each o f the animals, f i v e tapes were randomly chosen,

both i n .15 Hz and .05 Hz ranges.

One of the three monkeys, namely B i g Boy,

was t r a i n e d f o r only a few days on 0.05 Hz.

Consequently, the number o f r e -

cordings made were n o t enough t o estimate h i s describing function i n the .05 Hz range.

Typical describing function data f o r these animals are shown i n Figure 3

which shows both magnitude and phase p l o t s , estimates obtained f o r human subjects

Representative describing functibn

are shown i n Figure 4.

Notice the

remarkable s i m i l a r i t y i n the shape o f the raw t r a n s f e r function data i n both o f these figures.

Figure 5 shows the coherence function f o r a l l both human

and subhuman subjects.

The trend o f data was s i m i l a r i n a l l cases except

f o r t h a t o f B i g Boy (open c i r c l e s ) .

The p2-(w), from a c o n t r o l ' s viewpoint,

i s a measure o f t h e l i n e a r i t y i n the operator's response. A l t e r n a t i v e l y , 2 [l p (w)] i s a measure o f the "remnant" present i n the operator's response.

-

The observed inconsistency i n Big Boy's response can, i n part, be explained i n terms o f "shock avoidance'' response.

I n t h i s case t h e animal

manipulated the s t i c k so as t o place the cursor on the boundary o f the window ( f i n i t e width) .[3] Using the model i d e n t i f i c a t i o n scheme w i t h the describing function data

135

and equation 4 t h e unknown parameters were computed f o r both human and subhuman operations shown i n Table 1.

The range o f t h e parameters was same f o r

both humans and primates v a l i d a t i n g our i n i t i a l hypothesis. are consistent w i t h those c i t e d by Bachman e t a 1

These r e s u l t s

f4] who estimated t h e transfer

functions through v i s u a l i n t e r a c t i v e computer graphic approach.

These s i m i l a r

f u n c t i o n a l r e l a t i o n s h i p s lend support f o r monkey-man e x t r a p o l a t i o n f o r performance decrement studies under v i b r a t i o n . The model i d e n t i f i c a t i o n scheme developed here can a l s o be used t o define f u n c t i o n a l r e l a t i o n s h i p between v i b r a t i o n and a f f e c t e d p h y s i o l o g i c a l v a r i a b l e s w i t h appropriate modifications. ZUSAMMENFASSUNC

Mit elektrischom Stoss a l s negative Verstlrkung warden drei Rhesusaffen trainiert mit einem speziell entworfenen vorprogrammierten elektronischen visuell folgenden Einrichtung; in einem Bestrebon,die Loistung mit einem nicht-mensohlichen Operateuren z u vergleiohen. Die beschreibenden Gleichungen far diese Tiere wurden von den Daten geschtltzt. Efn Gaussian Gereuschgenerator wurde benutzt,um die zwingende Funktion im Bereicli von O , O 5 und 0 , 1 5 He zu produzieren. Eine Paramotoroptimation wurde benutzt,wn d a s gewblmliohe flhf Parametermodoll niit den oben emvCLhnten Daten zu erhalten. FUr Vergleichszwecke ivurden imch die Daten von zwei Menschen far die gleiche A u f gabc aufgenommen und ausgowertet. Die boschrcibenden GleicHungen, die Daten und die Werte far beide Vorsucher zeigen keinQn wesentlichen Unterschied. Die typische Verzbgerungszeit lag zwischen 0 , 0 8 und 0 ; l g Sekunden. Dieso vergleichbaren FunktionsverhPltnisse zwischen don menschlichen und den nicht menschlichen Operatoren unterstatzen eine weitere Ausdehnung. far die Affen-Mensch Vergleiche in druckfolgenden Situationon. Bibliography 1.

Reid, L. D. "The measurement o f human p i l o t dynamics i n a p u r s u i t plus-disturbance t r a c k i n g task," UTIAS Report No. 138, A p r i l , 1969.

2.

McGhee, R.B. , some parameter o p t i m i z a t i o n techniques, i n D i g i t a l Computer User's Handbook. McGraw-Hill, New York, 1967.

3.

Gupta, V. N. " A mathematical d e s c r i p t i o n o f primate operators i n compensatory t r a c k i n g s i t u a t i o n , " unpublished M.S. thesis. Univ e r s i t y of Kentucky, Lexington, Kentucky 1977.

4.

Bachman, J. A., Jaeger, R.J. and NewSon, T.J. "Human and nonhuman operators i n manual c o n t r o l systems," A v i a t i o n Space Environmental Medicine, 1976, 7, 311-315.

136

cr' Start

System Initialization Press "Clear" Lights on Shock wires Clear

Stop Computer animal

-

Preliminar

Record digital

1

Shock, door closed, comp Test Controller

Start Test

Press "Go" Check: display dot response to stick, etc.

Shock, Parameter Setup Set shock level T l -grace time Test, Rest times # of tests Compensatory or Pursuit

Remove shock and animal

Pre; - ' oG" Last Ani maI

I

"Test" State Test LED on TI delay before shock

Display off.

* Turn off and

Secure Computer

Input signal Magnitude and frequency

Last test

Reset Control Box

Rest period state. "Last

b Fig. I. Flow chart of the tracking system

137

Fig. 2. V i a u a l tracking target o n CRT

DESCRIBING FUNCTION - BUTCH SIGNAL BANDWIDTH .15 Hz

--

30.001

H

-

Observed Calculated

m 3

c C

cn 0

t

J.

rp -10.00

cl)

0

-20.00 too

i

4 i

idG9',()1

i

5

z

i6+i9',(f

Frequency [HZI o 122.6 Fig. 3. Typical describing function data for subhumans

138

DESCRIBING FUNCTION SIGNAL BANDWIDTH o

x

-m aJ

HUMAN 2 . 1 5 HZ

Observed

Calculated

30.00 I

0

7 c

-

-

-

1000

-

-10.00

J

C

cn

s

Fig. 4. Typical. d e s c r i b i n g function data f o r humans

139

1.00

X

++$*

0.80

+

* 0.60

CORRELATION FACTOR AS A FUNCTION OF FREQUENCY 8.

0 + 0.40

0 Big Bo

0

0

0.00 1

I

2

I

1

I

3

I

x

0

I

I 1 1 1 1

5 6709'

Frequency

Butch

+ HOPPY

10'

Hzl

I

2

1

3

I

1

Human$ Human3

I l l 1

4 58789'

lo2

122.6

Fig. 5 . Test for system linearity of performance data

Table 1 Freq. Ran e

Subject Name

0.15

140

Parameters K

Remnant

(sec)

T1 (sec)

T2 (sec)

T3 (sec)

H2

.16

18.01

28.99

3.99

18.97

418.2

H3

.16

18.00

28.99

3.99

'18.77

288.3

Butch

.09

18.01

28.99

4.59

13.00

398.4

HOPPY

.09

18.01

28.88

3.99

13.00

365.0

H 2

.09

18.00

28.99

3.91

13.70

22.9

H3

.17

18.00

27.10

3.98

18.98

276.7

Big Boy

.19

18.00

28.98

3.99

13.00

187.9

Butch

.10

16.50

24.36

4.5

11.99

25.1

HOPPY

.08

18.00

25.00

3.99

18.99

336.6

(HZB

0.05

T

- Model

DIFFICULTIESOF THE EVALUATION OF STRESSDUE TO MECHANICAL VIBRATION SUFFERED BY MANKIND H.Schnauber Gesomthochschule, Fochbereich Moschinentechnik, Siegen. F.R.G.

SUMMARY It is mechanical vibration brought to bear on the human physique that i,apart from noise phenomena is assuming an ever increasing significance. Frequencies of slightly above 0 Hz up to slightly 100 Hz bear on the whole body, o r on parts thereof, to an extent that depends on the intensity and frequency of the vibration. Since the evaluation of' s t r e s s due to mechanical vibrations suffered by man is not sure, the difficulties of the evaluation for exampleof impacts o r vibrations of longer period a r e investigated.

-

-

It is mechanical vibration brought to bear on the human.body that apart from noise phenomena

-

a r e assuming an ever increasing

significance at work places and in residential environment Frequencies of slightly above 0 Hz up to' slightly above 100 Hz bear on the whole body, o r on parts thereof, to an extent that depends on the intensity of the vibration.

This applies to the whole-body vibrations and also to the vibra'

tions of part of the body, and it includes all directions of introduction, that is, the horizontal X and Y directions a8 well as the vertical

Z direction whereby due attention must be given to the varying bowdary lines of evaluation.

141

Whereas the possibilities f o r evaluating and assessing whole-body vibrations have been established on an international basis in the IS0 Document 2631-1974 ( E 1 (61,

additianal assessments,

as well

as defined schematics for evaluating a r e lately being applied on a national basis

(see e. g. VDI-Richtline 2057

171 or DDR-Standard TGL

22312, L8J). A l l procedures employed up to date for assessing vibrations have

in common the representation of actual amplitudes of acceleration as subject to frequency. In this context the ISO-Document, e.g.

exempli-

fies the safe periods of exposure as depending on the following csiteria: comfort, fatigue, exposure limit, and VDI-Richtline 2057 employs K-Values which are data reflecting similar perceptive volumes. The DDR-Standard TGL 2 2 312 .is modelled on ISO-Document 2631 and records safe daily periods of exposure depending on the acceleration of vibration reflected in t e r m s of frequency. Whithout wishing to enlarge on the well-known proceedings employed in assessing that have already been mentioned, at this stage it is far more necessary to point out the difficulties which a r e still

encountered in assessing mechanical vibrations. It has e. g. not yet been clarified whether unmodified application of the ISO-Document and the VDI-Guidelines is still feasible,when the crestfactor is above 3

-

a s it is often the case of practical investi-

gations. It should, in this instance, be kept in mind that the assessing curves valid today stem from investigations conducted with sinusoidal excitations, whereas stochastic vibratory progressions which a r e frequently interspersed with abrupt excitations produce considerably mo-

re unexpected reactions in the human body than sinusoidal excitations.

And

their assessement by means of the procedure gover-

ning the assessment of sinusoidal excitations would therefore appear

pro bl e matic.

A reduction of the crest factor f o r the purposecof obtaining an improved means of assessing would therefore also constitute a questionable approach. Whereas it would be missing the initial issue of the procedure f o r assessing if an evaluation of vibratory progressions were taken into consideration in t e r m s of frequency, and c r e s t factor: of up to 6 were in addition allowed.

-

It may be assumed to be probable that in the case of vibration similar to the case with sound

in the form of K-values

- differing perceptive

volumes (e.g.

[I] o r also of varying periods of exposure)

.

may be l a i d down as boundary s t r e s s depending on the type of activity in order to take

into account the classification of the individual

tasks in conjunction with the influence exercised by vibration. DDRStandard TGL 22312 may be referred to here a6 an example. This standard offers a break-down into 4 categories. Existing initial data f o r evaluating mechanical vibrations as expressed in the documents o r guidelines resp.

mentioned a r e now the

subject of intensified discussions. Publications by Beitzer Henkel [3J , Meier-Darnberg [4J and Meister [5] out the

-

-

a s yet

e.g.

[2]

~

have pointed

incomplete evaluation which requires supplementa-

tion and refining. So far, the current procedures of evaluating do not preclude different approaches cerned. This there exist no

-

e.g.

where the assessing of the K-value is con-

as a matter of fact

-

is evidenced by the fact that

binding provisions regarding the duration of analyses.

As a result hereof a short-period analysis only may indeed indicate a c r e s t value

ranging below 3 although there exists a high vibratory stress, since

-

as

the case may be

-

a high amplitude of vibration was

registered at the very moment, or a high crest factor may occur whilst the corresponding vibratory s t r e s s is low, since the one high"peak" (maximum amplitude)

143

is faced by many visibly lower amplitudes.

Since there is a lack of work-place-investigations

covering longer

periods of influence by vibration, and since there is no proof as to

-

when evaluated

on the grounds of a f e w minutes dedicated to analysis

may be con-

whether the overall s t r e s s of an 8-hour working day

-

sidered a s reflecting the man/day period a s a whole, s e v e r a l long period mensurations a r e prepared in consequence [S].

The results

are evaluated by different procedures Short-period analyses, a s have already been prepared previously (vibration progressions a r e singled out of long-period mensurations and evaluated on the grounds of a break-down by random figures) ; Long-period classifications of actual values ( evaluated, non- evaluated)

-

-

whereby classifications should be to values of

5 seconds,

10 seconds,

15 seconds, and

- 30 seconds

and on over all K-values should be prepared f o r follow-up.

This proceeding allows in the same way the Assessment and classification of the maximum values of the same s ection gnd it is possible to compare all other methods of evaluation,

the evaluation procedure laid down in VDI 2027 o r IS0 2631, the evaluating procedure offered by Beitzer (procedure based on the maximum level of cycle) , the equivalent permanent level of vibration as laid down by

Henkel. A comparison of the results of theinvestigations allows f o r

offering indications and suggestions towards assessing whole-body vibrations,

asserting the scope of random tests indicating the problems governing evaluation of vibrations offering information regarding the influence impactlike vibrator y excitations exert on mankind Indications are, however, expected in particular with regard to practical close-up investigation of xibratory stress, and with regard to the period of recording and the requisite methods of evaluation. The investigations show, that the determination of vibrations in X-Y-direction o r i n 2-direction filtered higher frequencis and also the impacts, (Fig. 1 + 2 :

Z (evaluated, non-evaluated

)

(Fig. 3 + 4 : X ( evaluated, non-evaluated) differences will be caused by the durationof analyses, and so it is importagt to change representative parts, to analyse these parts and to consider higher amplitudes of acceleration, (Fig. 5

+

6 : 2, 5- end 15-second-values)

the vibrations should be classified in all determinations and hereof an equivalent permanent level of vibration can be determined. I have. shown these facts, because I think there a r e also many

questions about the determination and evaluation of stress due to mechanical vibration suffered by mankind. KURZFASSUNG In zunehmendem Masse werden neben Schallereignissen z. B. auch mechanische Schwingungenvon knapp oberhalb 0 Hz bis wenig d b e r 100 Hz bedeutsam. Sie werden auf den menschlichen Kdrper als Ganzkkhperschwingungen oder Teilkdrperschwingungen in den verschiedenen Richtungen ubertragen und beelnflussen diesen je nach Intensitk und Frequenz mehr oder weniger stark.

145

Da die Beurteilung d e r mechanischen Schwingungen derzeit noch nicht in ausreichendem Masse gesichert ist, werden Schwierigkeiten d e r Bewertung insbesondere stossartiger und l b g e r d a u e r n d e r Schwingungsbelastungen d arzustellen ve rsuc ht.

REFERENCES

113 Diekmann,

D. : Einfluss vertikaler mechanischer Schwingungen auf

den Menschen, Int. Z. angew. Physiol. 16, (1957)

Id Beitzer,

,

p.

einschl. Arbeitsphysiol.

16 ff.

H. W. : Zur Beurteilung zeitlich schwankender Schwingungs-

einwirkung mit Hilfe eines aquivalenten Dauerschwingwertes, VDI-Berichte Nr. [3]

284, (19771, pp.

19-22.

Henkel, W. : Schwingungsbewertung mit Hilfe d e r aquivalenten

Dauerschwingbeschleunigung, Z. f. d. ges. Hygiene und ihre Grenzgebiete 22, [4]

(19761

, pp. 330-332.

Meter-Dornberg, K. E. : Zur Beurteilung stossartiger, transien-

ter Einwirkungen, Kriterien, K enngrbssen und Modellvorstellungen, VDI-Berichte N r . 284,

151

(1977)

pp.

13-18.

Meister, F.J.: Kritische h m e r k u n g e n zur Bewertung d e r Schwingungsbelastung nach VDI 2057-1st eine Vereinfachung des

VDI-Richtlinien-Entwurfes VDI 2057 fur messtechnische Zwecke d g l i c h ? VDI-Berichte Nr. 284, (19771, pp. [6]

37-40.

ISO: Guide for the evaluation of human exposure to whole-body vibration, First edition 1974-07-01, IS0 2631-1974 ( E l

[7J

.

VDI: Beurteilung der Einwirkung mechanischer Schwingungen

auf den Menschen, Blatt 1: Gmndlagen, Gliederung, Begriffe, 2/1975; Blatt 2: Schwingungseinwirkung auf den menschlichen Kdrper, I/ 1976; Blatt 3: Schwingungsbeanspruchung dea Menschen,

Vorlage 1211977.

146

1: 83

D D R Wirkungen mechanischer Schwingungen auf den Menschen, TGL 22 312: Blatt 1: Begriffe, 6/1971; Blatt 2: Grenzwerte fur Ganzkdrperschwingungen, 6/ 197 1; Blatt 3: Messmethodik fur Ganzkdperschwingungen, 6/19? 1.

[a

Brand, H. und H. Schnauber: Untersuchung d e r Schwingungsbelastung des Menschen an Arbeitsplktzen d e r Eisen-und Stahlindu-

strie und technische Mdglichkeiten zur Belastungsminderung, Forschungsbericht 01 VA 075-2-13-TAP 0006. Humanisierung des Arbeitslebens.

147

a0

LO

20

S O

(10

XO

60

RU

80

Amplitude of arcelemtion {rn Jec-7

Fig. 1 . Frequency d i s t r i b u t i o n o f a c c e l e r a t i o n amplitudes 2 (evaluated). (Spaces o f about 100 sec.)

1. I

0. J

Fig. 2. Frequency d i s t r i b u t i o n of a c c e l e r a t i o n amplitudes Z (non-evaluated). (Spaces o f about 100 sec.)

148

0. J 0

C a,

g

0. 01

2!

Y-

p

o. ou1

u

3 -0

g 0. wo1 0. DoDm ao

LU

2 0

so

go

J;O

so

xo ao Acceleration [m/sec2)

-

F i g . 3. Frequency d i s t r i b u t i o n o f the instantaneous accelerat i o n values x (estimable) (spaces o f about 100 sec).

2 H

0.1

a, 3 u-

0.

7.72 8 7a o

0. o1

woo1 ao

o

LO.

au

so

rlo

su

-

ao Acceleration 1 m /sec2] so

zo

Fig. 4. Frequency d i s t r i b u t i o n o f the i n s t a n t m e o w amelerat i o n values x (inestimable) (spaces of about 100 sec).

149

A-

- 1.3

N

u

-

UI

-E \

-

=0 1' 0 -

c

-uI 8

! -

L

-

u

0

c E

-

a5

a

-

-

O

r

I

I

I

I

I

I

I

Fig, 3. Z-direc t i o n (evdluated), 5-sec-effectiveamplitudes.

0.

c

I

I

I

I

0.

.

I

I

500. lime (secl

I

I

acceleration-

I

1ooO.

Fig. 6. Z-direction (evaluated), 5-aec-eff ective-acoalerationamp1it udes

150

HAND-MMvlBBATIONINSIIIpyABDCAuLgEBS M. Bovonzi, L.Potronio, B Di Marino Vnhmtwsf mute,ItarV

The results of a survey performed on Rhipyard caulkers exposed to had-arm vibration are reported.Percussive(chipping hamner)and rotatory(grinders)hand held tools have been examined. Frequency apectrum of the chipping hammer shows high acceleration levels whiah exceed IS0 acceptable boundaries for the exposnire time of caiilkers.Accelerat€on .levels of the grinders,m the contrary,exceed IS0 limits only in a few third octave bands. Medical investigations included 169 caulkers and 60 controls. The results of medical eminations demonstrate: 1 )a high prevalence (78,75&)0f neurovascular complaints in the upper limbs of the caulkers; 2)among 169 caulkers,53(31.3$)are

suffering from vibration white

finger,while a prevalence of 6.65 is found in the control group; 3)X-ray of the right upper limbs of the caIllkers show a moderate prevalence of typical carpal cysts(31.3$)

(lO.O$);$)the

and olecranon exostoses

measurement of basal skin temperature of the hands

and the recovery time of basal skin temperature after cold test

reveal a statistically significant difference between caulkers and controls.At conclusion,some preventive considerations are reported.

151

-

Workers exposed t o hand-arm vibration develop a complex of d i s a b i l i t i e s named V i b r a t i o n Syndromett[5]. Vibration syndrome c o n s i s t s of o s t e o a r t i c u l a r l e s i o n s , vascular (Raynaud's phenaPemn) and neurological disorders i n t h e hand-Rrm segment. The most important provocative f a c t o r s include: f , t h e physical charact e r i st i c s o f v i brs. t i on ( accelera ti on versus frequency 1: ii, t h e exposure time of operators; iii, cold and ergonomic condit i o n s ; iiii, t h e technical aspectR o f t h e work [6]. I n the -present paper t h e authors r e p o r t an epidemiological survey performed a t a shipyard ( I t a l c m t i e r i o f Monfalcone) i n o r d e r t o determine the prevalence of v i b r a t i o n Ryndrome among caulkers working w i t h pneumatic hand-held t o o l s . MATERIALs

m METHODS

T t a l c a n t i e r i is a yard of s h o p b u i l d i n g Rnd h u l l assembly i n dock. Caulking ( r i v e t i n g , c u t t i n g , s c a l i n g , etc.) hss h e l d a more important r o l e in past building. A t t h e present arc-welding, gas welding and c u t t i n g are t h e main work i n shipyard. Caulking haa been reduced to: chipping and s c a l i n g metal shavings of f i l l e d weld, chamfering t h e manhole borders, scouring and grinding a t e e l sheets

.

The pneumatic hand t o o l s used by caulkers were chipping hammers of'one model type a n d portable grinders of small, medium and large s i z e s (between 2.0 and 6.6 kg). The caulkers work w i t h t h e hand-arm segment end t h e body i n d i f f e r e n t postures, o f t e n i n t i g h t spaces (i.e. c e l l u l a r double bottom). The exposure time of caulkers t o aegmental v i b r a t i o n is about 5-6 hours during a s h i f t of 8 hours. Vibration analysis of pneumatic portable t o o l s was performed i n two steps: 1. Vibration measurement i n t h e f i e l d , during work operations. A reoording equipment with accelerometer c a l i b r a t o r ( W e 1 &

152

Kjaer 4291 ), pick-up

(MK 4367 and 8309), charge amplifier

(B&K 2635); narrow bmd spectrum analyzer (B&K) 2031) and X-Y recorder (B&K 2308) were used. The accelerometers were d i r e c t l y screwed i n t o t h e , t o o l handles o r were placed on a t h i n metal sheet fastened with cyanoacrilate glue. Vibratfons were recorded i n a t r i a x i a l system X, Y, Z.

2. Laboratory a n a l y s i s of recorded vibration spectra.

Constant bandwidth spectrograms (2.5 Rz) recorded i n t h e field were t m s f o r m e d t o one-third

nctave bandwidth spectrograms

w i t h a c a l c u l a t o r - p l o t t e r system (HP 9825 and

HP 9872).

Vibration s p e c t r a were compaired w i t h maximum a c c e l e r a t i o n boundaries proposed by IS0 ( m a f t Proposal n o 5349) 131. Medioal i n v e s t i g a t i o n s w e r e performed on 169 caulkers and on a c o n t r o l group o f 60 workers of t h e same shipyard, n o t exposed

t o hand-arm vL bra t i on. The mean age o f CqulkerR w a s 40.7 years (SD 5 6.5) a g a i n s t 34.8 years (SD 2 7.9) of t h e c o n t r o l groiip. The mean v i b r a t i o n time expomre o f c a u l k e r s w s 7.3 y e a r s (SD

2 6.9);

only 10.6% o f caulkers had an exposure time of more

than 10 years. The medical i n v e s t i g a t i o n s included:

- s p e c i f i c questionnaire with t e c h n i c a l ,

ergonamical and medicaY

quest i o n s ;

-a -

complete medical examination;

X-ray o f upper limb (usually r i g h t ) ;

basal s k i n thermometric map, recorded (by a r e s i s t a n c e them?

meter) i n 16 p o s i t i o n s per hand:

I

thermometric curve, monitored every 3 up t o 40 minutes a f t e r provocative oold t e s t (immersion o f hands and wrists i n melting

ice for 2 min.)

153

Vibration spectra of the pnewnatic portable tools Vibration spectrum of the chipping hammer during work on a a t e e l aheet is reported i n Figure 1. The IS0 acceptable acceleration l i m i t s f o r various exponure time- (different correction factors) a r e drRwn by R thin l i n e i n the background of the graphe. Vibration arnpliiudefl recorded on chipping hammer wi dely exceed, i n ell freqiiency ranges, the maximum IS0 l e v e l s (correctjon f a c t o r 1) aaceptable f o r ixmal exposure time of caulkers (5-6 hours per Bhifk). ~n acceleration l e v e l of 30 m/sec2 can be seen a t fundamental frequency of the chipping hammer (40 H5). Other acceleration peaks a r e present a t multiple upper frequencies (80 Bz and 160 Hz) The epectrograma recorded on the main and l a t e r a l haslilles of the grinder of medium s i z e (4.6 ks, 6000 rpm) a r e ahown i n Fis6m 2 and 3. Acceleration levels of t h i R grinder exceed TSO l i m i t ourve(fc 1) only i n a few t h i r d octave bands, namely a t 80 and 160 H5 which represent the netural rotatory motion of the tool. The d i f f e r e n t vibration amplitude@recorded along t h e triaxial syatem of the t w o handles of the grinder a r e p r o b b l y due t o the impulsive mechanical reaction o f the workpiece. The vibration spectra recorded on large grtnders do not: exceed the IS0 acceptcLble levela, whereas tho amall grindere showed a very small increase. Therefore they a r e not reported. Medical examination resultm The answers t o the quemtionnaire (Tab.1) Bhow t h e t t h e prevalence of j o i n t and neurovascular complaint@ wa8 higher i n the CRulkers than i n the control group.F?eponderance of j o i n t symptoms i n caulkera may be due not only t o vibration,but t o other f a c t o r s such as uncomfortable working posture and s t a t i c tension i n upper limb muscles due t o the strength of the grip.TherePore, musaular fatigue c m simulate the symptom of @*arthralgiatt .This

154

hypothesis was confirmed hy X-ray of t h e upper 1imb.h f a c t , the r a d i o l o g i c a l examination demonatrated

moderate prevalence

R

of wrist and shoulder a ~ t e o a r t h r i t l s ( 2 0 . 1 F ) and elbow exostosea ( 10 .O%) .Cysts of carpal bone8 ' were found i n 31.396 o f the caulkero

Wrist vacuoles a n d olecranan exostoae8 a r e , f o r Rome a u t h o r s

.

[ 1,4], t y p i c a l i n v i b r a t i o n syndrome.

Seven caulkerp( 4 .l$)were a f f e c t e d w i t h Dupuytren contracture, w h i l e t h i s f e a t u r e was found i n none o f t h e controls.

The &nRwerR t o t h e questionnaire point out a l s o t h e preponde-

.

rance of nmirovaecular complaints i n t h e exposed group: 78.7% of caulkers experienced p a r e s t h e s i a i n t h e i r h m d s Raynaud's phenomenon of o c c u p a t i o n ~ lo r i g i n ( o r Vibmtion White Finger) was found i n 31.3% of workers. Both parestheeia and VWF were highly correlateti w i t h exposure

timereleven of the f i f t e e n c m l k e r a who worked more than 12 y e a r s , were a f f e c t e d by v i b r a t i o n white finger.In Table 2,data o f t h e s u b j e c t s w i t h VWF a r e reported.

Cold and v i b r a t i o n exposure neem t o be t h e most i m p o r t m t provocative f a c t o r s o f t can be seen t h a t the caulkers Ruffering f r o m VWF matnly uRed t h e chipping hammer(42.5$ of t o t a l time).As reported before,the chipping hammer i s t h e t o o l t h a t Senerntee t h e highest a c c e l e r a t i o n 1evels.The d i f f e r e n t u t i l i z a t i o n time of each tool may, therefore,confirm t h e c r i t i c a l importance of v i b r a t i o n i n the pathogenesis of Raynaud

8

phenomenon of occupa-

t i o n a l origin.The f i n g e r s of t h e r i g h t hand seem t o be more affected than those of t h e l e f t aide.!Fhe duration o f ischemic t r a n s i t o r y a t t a c k in the hands is 10-19 minutes i n about a half of c a u l k e r s with W. TO

diagnose vamailar d i s o r d e r s due t o v i b r a t i n g t o o l s ,

we recorded t h e s k i n temperature of t h e h m d s of the 169 CRulkers and the 60 controls.We have chosen the temperature measurement t e s t becauee of its SemPliCitY and R e n s i t i v i t y

f o r epidemiological purposes.

155

Skin temperature was measured in the shipyard during the winter of 1978.The mean temperature of the room was 21.0 O C (SD f 1.50C).A basal thermometric map was recorded with a resistance thermometer on the Aorsal side of the hands, using 16 positions per hand.The mean temperatures are reported in fig.4.The difference between the mean basal &in temperatures of the 169 caulkers and the 60 controls (Student's t-test) was highly significant in all the positions (P\

sw2

- Wide band receptance: QF = Gl - S t a b i l i t y : QF = max Re ( u r ) . r

Z;(CJ)

d o I

There a r e a l s o numerous o t h e r p a r t i c u l a r q u a l i t y f a c t o r s

t h a t apply t o p a r t i c u l a r systems. Obviously, very o f t e n , n o t

only one q u a l i t y f a c t o r is being considered. Usually we have a s e t of them, sometimes r e p r e s e n t i n g c o n t r a d i c t o r y aims. The problem of t h e c o n s t r u c t i o n of a unique, g e n e r a l q u a l i t y f a c t o r has not y e t been e n t i r e l y solved. The V i b r a t i o n Control c r i t e r i o n may be defined as:

Where

$,

$+,

f

a r e a d m i s s i b l e l i m i t s of t h e q u a l i t y f a c t o r

grade o r class of q u a l i t y . v a l u e f o r . t h e llkll If f o r a machine t h e i n e q u a l i t y ( 3 ) i s n o t s a t i s f i e d , t h i s suggests t h a t V i b r a t i o n Control technique would be

welcome

.

The e f f i c i e n c y of a V i b r a t i o n Control method

i8

often

expressed by t h e r a t e of response a f t e r and b e f o r e V i b r a t i o n Control treatment. This q u a l i t y , o r a f u n c t i o n of i t (e.g., t h e sum o r product in t h e case of s e v e r a l responses) r e p r e s e n t s a measure of e f f i c i e n c y , which may be taken i n t o account, when c o n s i d e r i n g t h e g l o b a l g a i n from t h e a p p l i c a t i o n of t h e V i b r a t i o n Control technique ( b e a r i n g i n mind d i f f i c u l t i e s of i n t r o d u c t i o n of V i b r a t i o n Control t r e a t m e n t , the c o s t of i t on one hand, and t e c h n o l o g i c a l , p h y s i o l o g i c a l , s o c i o l o g i c a l and economical p r o f i t on t h e o t h e r ) . The q u a l i t y f a c t o r may s e r v e a l s o as an index of performance t o be minimalized in problems of optimum design.

295

It i s r a t h e r d i f f i c u l t nowadays t o formally d e f i n e t h e whole problem of V i b r a t i o n Control as a problem of optimization. Usually a p a r t i c u l a r V i b r a t i o n Control technique i s s e l e c t e d by some means ( a f t e r having passed from s i m p l i e r t o more d i f f i c u l t and expensive techniques, accordi n g t o t h e above mentioned hierarchy). However, t h e problem of i d e n t i f y i n g the open design parameters of t h e chosen Vibration Control technique, t o g e t t h e b e s t r e s u l t s i n system performance remains. The optimum r e f e r s , t h e r e f o r e , t o t h e performance that can be achieved by t h e p a r t i c u l a r c l a s s of t h e V i b r a t i o n Control technique under c o n s i d e r a t i o n and may be defined as an optimal design parameter s y n t h e s i s . The optimal design must a l s o s a t i s f y c o n s t r a i n t s imposed on diff e r e n t a s p e c t s of t h e system response and on t h e parameters of t h e chosen V i b r a t i o n Control technique. The i n e q u a l i t y (31 may s e r v e as an example of response c o n s t r a i n t s ( w h i l e a n o t h e r q u a l i t y f a c t o r t o be minimized has been chosen). Now l e t us d i s c u s s i n d i v i d u a l V i b r a t i o n Control techniques, c l a s s i f i e d by t h e scheme proposed i n t h e I n t r o d u c t i o n and defined above on t h e b a s i s of t h e mathematical model ( I ) . The S i r e t p o i n t has been a l r e a d y considered. Below, t h e o t h e r Vibration Control techniques w i l l be discussed. 4. P A R m T E R MODIFICATION If t h e n a t u r a l frequency of t h e s t r u c t u r e of a machine

c o i n c i d e s w i t h the frequency of t h e a p p l i e d f o r c e , v i b r a t i o n c o n d i t i o n s may be made much worse, as a r e s u l t of resonance.

296

Under such c i r c u m s t a n c e s , i f t h e f r e q u e n c y of e x c i t a t i o n i s s u b s t a n t i a l l y c o n s t a n t , i t is o f t e n p o s s i b l e t o a l l e v i a t e v i b r a t i o n by changing t h e n a t u r a l f r e q u e n c y , i.e.

t h e mass

and o r s t i f f n e s s p r o p e r t i e s of t h e s t r u c t u r e . However, t h e problem of modifying p a r a m e t e r s i s u s u a l l y n o t s o s i m p l e ,

n o r is i t always p o s s i b l e (e.g.

f o r broad f r e q u e n c y band

e x c i t a t i o n , as i n s o n i c f a t i g u e e t c . ) . If t h e e x c i t a t i o n c o n d i t i o n s a r e n o t unfavourable,. t h e

problem s t i l l remains complex. There are many p a r a m e t e r s t o be modified and s e v e r a l c o n s t r a i n t s . The problem i s determined i n e x c e s s u s u a l l y w i t h c o n t r a d i c t o r y r e q u i r e m e n t s . To o b t a i n

a s o l u t i o n of t h e p a r a m e t e r m o d i f i c a t i o n problem, one may a n a l y s e t h e s e n s i t i v i t y o f p a r a m e t e r s t o t h e v a r i a t i o n of t h e r e q u i r e d f e a t u r e , t h e n s e l e c t and change t h e i r v a l u e s by app l y i n g a n i t e r a t i v e procedure. More g e n e r a l l y , one may choose a q u a l i t y f a c t o r and l o o k f o r a s c t of ttoptimnltt p a r a m e t e r s ,

a t which t h e g i v e n f a c t o r r e a c h e s i t s extremum. The procedure of i n t r o d u c i n g t h e p a r a m e t r i c a l m o d i f i c a t i o n s t o t h e system may, a l s o , be performed i n a more complex way, t a k i n g i n t o a c c o u n t t h e r e a l e x c i t a t i o n i n t h e r e a l structu1.e w i t h s i m u l t a n e o u s i d e n t i f i c a t i o n of t h e system. The scheme of such

a procedure i s p r e s e n t e d i n Fig.

1.

5. S T R U C T U R A L M O D I F I C A T I O N S

5.1.

A n t i v i b r a t i o n mountings: dynamic a b s o r o e r s . The

method of r e d u c i n g t h e v i b r a t i o n of t h e r e s p o n d i n g system b y a t t a c h i n g an a u x i l i a r y mass t o t h e system by means of' a s p r i n g ,

297

i s one of t h e o l d e s t techniques of V i b r a t i o n Control. With proper tuning, according t o the frequency of e x c i t a t i o n , t h e a u x i l i a r y mass v i b r a t e s and reduces t h e v i b r a t i o n of the p r i n c i p a l system, t o which i t i s attached. This kind of dynamic a b s o r b e r has, however, one important drawback: i t i s e f f e c t i v e , w i t h proper tuning, f o r only a steady nonharmonical e x c i t a t i o n . The a u x i l i a r y system i n t r o d u c e s a new n a t u r a l frequency t o t h e composite system apd may b r i n g i t i n t o resonance f o r o t h e r kinds of e x c i t a t i o n . Damping i n t r o d u c e s some a t t e n u a t i n g e f f e c t t o the motion.

It i s p o s s i b l e t o provide a dynamic absorber t h a t i s e f f e c t i v e f o r two o r more f r e q u e n c i e s by a t t a c h i n g a u x i l i a r y mass systems t h a t r e s o n a t e at t h e s e f r e q u e n c i e s which a r e objectionable. The p r i n c i p l e t h a t would make such an absorber e f f e c t i v e , may be u t i l i z e d i n the d e s i g n of t h e e l a s t i c systems. 5.2.

V i b r o - i s o l a t i o n b r i n g s about a r e d u c t i o n i n shock o r

vibratory effects.

A v i b r o - i s o l a t o r may be considered a

r e s i l i e n t member connecting two p a r t s of a mechanical s t r u c t u r e and impeding v i b r a t i o n propagation from t h e source t o the r e c e i v e r . The f u n c t i o n of t h e i s o l a t o r i s t o reduce t h e magnitude of motion t r a n s m i t t e d from a v i b r a t i n g foundation t o t h e s t r u c t u r e (kinematic e x c i t a t i o n by movement) o r t o reduce t h e magnitude of f o r c e t r a n s m i t t e d from t h e s t r u c t u r e t o i t s foundation ( f o r c e e x c i t a t i o n )

.

The term llfoundationl'

should be understood h e r e i n a more g e n e r a l sense, as a v i b r a t i o n source o r r e c e i v i n g p a r t of t h e s t r u c t u r e . The e s s e n t i a l f e a t u r e s of an i s o l a t o r a r e r e s i l i e n t load-

supporting means and energy d i s s i p a t i n g means. I s o l a t o r s g e n e r a l l y a r e mass-spring-dashpot

systems w i t h parameters

chosen t o minimize t h e t r a n s m i s s i o n of v i b r a t i o n .

6. DISSIPATION OF MECHANICAL ENERGY D i s s i p a t i o n of energy accompanies every motion. The phenomenon of d i s s i p a t i o n i s however complex and depends up on many f a c t o r s . D i s s i p a t i o n of energy may roughly be class i f i e d as e i t h e r d i s s i p a t i o n due t o boundary e f f e c t s , c r e a t e d during r e l a t i v e motion of m a t e r i a l elements o r d i s s i p a t i o n due t o i n t e r n a l e f f e c t s a r i s i n g during deformation of s o l i d s , as a consequence of t h e i r non-ideal e l a s t i c i t y ( F i g . 2 ) .

Obviously t h e s e p a r a t i o n between l l i n t e r n a l l l and f l e x t e r n a l f l e f f e c t s i s very conventional. Except f o r r a d i a t i o n damping, a l l o t h e r d i s s i p a t i o n mechanisms a r e connected w i t h an i r r e v e r s i b l e conversion of mechanical energy i n t o heat. This b r i n g s about an a t t e n u a t i o n i n f l u e n c e on t h e motion. D i s s i p a t i o n of energy during shocks of m a t e r i a l elements has been c o n v e n t i o n a l l y c l a s s i f i e d as a boundary e f f e c t . This

kind of d i s s i p a t i o n , however, i s more complex and a c t u a l l y i n v o l v e s many mechanisms of d i s s i p a t i o n ( i n t e r n a l e f f e c t s of d i f f e r e n t o r i g i n s and r a d i a t i o n damping i n p a r t i c u l a r ) . Furthermore, t h e amount of shock energy d i s s i p a t i o n changes i n time due t o wear and p o l i s h i n g of t h e p a r t s . I n mechanical systems damping f o r c e s a r e u s u a l l y much

s m a l l e r than i n e r t i a and e l a s t i c i t y f o r c e s . These small f o r c e s

p l a y , however, an important r o l e i n V i b r a t i o n C o n t r o l at

s t e a d y s t a t e c o n d i t i o n s of motion and u n d e r s t o c h a s t i c e x c i t a t i o n as w e l l . Damping a t t e n u a t e s t r a n s i e n t p r o c e s s e s , d i m i n i s h e s resonance peaks. Damping a l s o d e t e r m i n e s t h e v e r y important boundary between s t a b l e and u n s t a b l e motion, when s e l f - i n d u c e d v i b r a t i o n s may occur i n t h e system. 6.1.

R a d i a t i o n damping. R a d i a t i o n damping i s connected w i t h

energy r a d i a t i o n from a v i b r a t i n g element t o t h e environment through boundary mountings ( e l a s t i c waves) and f r e e s u r f a c e s ( a c o u s t i c waves). The e f f e c t i v e n e s s of t h i s k i n d of damping ( i n t h e s e n s e of a t t e n u a t i n g of v i b r a t i o n s of mechanical e l e m e n t s ) i s n0.t g r e a t . Moreover, i t can cause some unprofit-, a b l e e f f e c t s ( n o i s e o r e x c i t a t i o n of v i b r a t i o n i n some d i s t a n t elements due t o t r a n s m i s s i o n of e n e r g y by e l a s t i c wave). V i b r a t i o n C o n t r o l t r e a t m e n t aims t o l o c a l i z e and c o n v e r t r a d i a t e d energy i n t o h e a t . Damping l a y e r s , j o i n t s and s e p a r a t o r s f u l f i l l t h e p o s t u l a t e s of V i b r a t i o n Control.

6.2.

M a t e r i a l ( i n t e r n a l ) damping. M a t e r i a l damping i s t h e

name g i v e n t o t h e complex p h y s i c a l e f f e c t s t h a t c o n v e r t k i n e t i c and s t r a i n energy i n a v i b r a t i n g mechanical system c o n s i s t i n g of a volume of macrocontinuous ( s o l i d ) m a t t e r into heat. Energy d i s s i p a t i o n due t o i n t e r n a l e f f e c t s depends up on a great number of f a c t o r s such as: i n t e r n a l f a c t o r s : t y p e of m a t e r i a l , chemical composition, i n t e r n a l c r y s t a l l i n e o r nonc r y s t a l l i n e s t r u c t u r e 1 e x t e r n a l f a c t o r s : temperature, p r e s s u r e ; motion f a c t o r s : amplitude and f r e q u e n c y of deformation, s t a t e

of s t r e s s , pre-load,

i n t e r n a l s t r a i n 1 specimen f a c t o r s :

geometry, s c a l e , s t a t e of s u r f a c e , bounding,... M a t e r i a l damping of s t r u c t u r a l m e t a l s and a l l o y s is not high ( f o r s t e e l , the l o s s f a c t o r

7

is l e s s than

and i t

cannot be considered a powerful V i b r a t i o n Control t o o l . Some m e t a l s o r a l l o y s (as l e a d , bronzes) have a h i g h e r l o s s f a c t o r , b u t t h e i r c o n s t r u c t i o n p r o p e r t i e s (mainly r e s i s t a n c e ) a r e u s u a l l y poor. They can, however, be s u c c e s s f u l l y a p p l i e d i n sandwich c o n s t r u c t i o n s ( m e t a l l u r g i c a l t r e a t m e n t ) . Polymers, enamels and g l a s s have high damping p r o p e r t i e s

7

> l ) , but o b v i o u s l y ' t h e y may be u t i l i z e d only as a u x i l i a r y

s t r u c t u r a l materials. The damping p r o p e r t i e s of m a t e r i a l s ( t h e l a t t e r group, i n p a r t i c u l a r ) depend s t r o n g l y on temperature and frequency of v i b r a t i o n . By choosing t h e chemical composition, they may be "tunedff t o a r e q u i r e d c o n d i t i o n (temperature, frequency), and used as s u r f a c e c o a t i n g s o r s e p a r a t i n g adhesive of metal elements, a t t e n u a t i n g t h e i r v i b r a t i o n . An important c o n t r i b u t i o n of t h e p a s t s e v e r a l y e a r s should be mentioned here: t h e e l a b o r a t i o n of t h e reduced temperature

i d e a f o r data p r e s e n t a t i o n of damping p r o p e r t i e s of m a t e r i a l s w i t h l i n e a r r h e o l o g i c behavior ( r u b b e r , polymers, enamels...). This is a simple i d e a of g r a p h i c a l p r e s e n t a t i o n , b u t i t i s a v e r y important a i d i n g i v i n g d e s i g n e r s information on t h e damping of many materials, and f o r t h e development of chemical s u b s t a n c e s f o r use i n t i r e s , epoxies, bonded s t r u c t u r e s and t h e m a t r i x of composite s t r u c t u r e s .

301

6.3.

S l i p damping. S l i p damping a r i s e s d u r i n g f l e x u r a l

deformation from boundary s h e a r e f f e c t s at mating s u r f a c e s o r j o i n t s between d i s t i n g u i s h a b l e p a r t s . A s t r u c t u r e b u i l t from a number of component p a r t s e x h i b i t s a marked degree of energy d i s s i p a t i o n d u r i n g v i b r a t i o n , compared w i t h a similar one-piece s t r u c t u r e . The manner of j o i n i n g elements i n f l u e n c e s t h e degree of energy d i s s i p a t i o n . Bolted and r i v e t e d j o i n t s a r e more e f f e c t i v e i n d i s s i p a t i n g energy, because they permit l i m i t e d s l i p p a g e a t i n t e r f a c e s between p a r t s i n c o n t a c t , while maintaining p r e s s u r e a t t h e i n t e r face. Welded j o i n t s a l s o e x h i b i t c o n s i d e r a b l e damping, which a p p a r e n t l y i s t h e r e s u l t of same s l i p p a g e between p a r t s i n c o n t a c t , n o t f u l l y r e s t r a i n e d by t h e weld. S q i p damping u s u a l l y b r i n g s about t h e most damping i n mechanical s t r u c t u r e s (system 100s f a c t o r

'2 =

0.1

-

2).

Its

q u a n t i t a t i v e o r even q u a l i t a t i v e d e s c r i p t i o n i s , however, very d i f f i c u l t . S l i p damping depends on many f a c t o r s such as geometrical and s t r u c t u r a l amplitudes and f r e q u e n c i e s of' v i b r a t i o n , l o a d , normal and s h e a r f o r c e s between elements and c o n d i t i o n of f r i c t i o n . S l i p damping as a source of d i s s i p a t i o n of energy i s

r e l a t e d t o t h e problem of wear due t o f r e t t i n g o r c o r r o s i o n and t h e consequent i n c r e a s i n g c l e a r a n c e s which may l e a d t o changes i n t h e dynamic p r o p e r t i e s of t h e system. To minimize t h i s e f f e c t , f l u i d o r s o l i d i n t e r l a y e r s (adhesive s e p a r a t o r s )

t r a n s f e r r i n g t h e s h e a r s t r e s s e s a r e introduced between the parts.

302

6.4.

F l u i d pumping a t j o i n t s . When a s t r u c t u r a l j o i n t i s

n o t t o o t i g h t and t h e two p a r t s of t h e j o i n t v i b r a t e , a r e l a t i v e motion takes p l a c e between t h e

mating s u r f a c e s .

This motion depends on t h e j o i n t c o n s t r u c t i o n and t h e a p p l i e d

l o a d i n g s b u t , as i t t a k e s plzce, it causes o r f o r c e s t h e a i r ( o r o t h e r f l u i d ) in the gap t o move i n t o o r out t h e j o i n t s . F l u i d pumping removes some of t h e v i b r a t i o n a l energy and r e p r e s e n t s a s p e c i a l s t r u c t u r a l d i s s i p a t i o n mechanism. This mechanism i s widely used i n f l u i d dashpots.

6.5.

Damping t r e a t m e n t : Damping c o a t i n g s , sandwich

c o n s t r u c t i o n s , damping j o i n t s . The a p p l i c a t i o n of sandwich c o n s t r u c t i o n s and damping c o a t i n g s i s one of t h e most u s e f u l and powerful techniques of V i b r a t i o n Control. The p a r t s made from s t r u c t u r a l m e t a l s a r e joined w i t h v i s c o e l a s t i c m a t e r i a l l a y e r s having h i g h damping p r o p e r t i e s . The e f f e c t s d u r i n g v i b r a t i o n are t h e following:

- reduction

of s t e a d y - s t a t e amplitudes, e s p e c i a l l y a t

resonances ( r e d u c t i o n of s t r e s s e s , lowering of n o i s e l e v e l s ) ;

- a t t e n u a t i o n of

t r a n s i e n t motion and corresponding n o i s e

g e n e r a t e d by impacts and random impulses;

- damping of

e l a s t i c waves, impediment of t h e i r propaga-

t i o n , damping of a c o u s t i c waves. The l i t e r a t u r e on Damping Treatment i s very large. I n [ l ] a b r i e f d e s c r i p t i o n of t h i s V i b r a t i o n Control Technique can be found.

303

6 . 6 . A n t i v i b r a t i o n mountings w i t_-_h damping. -. I n S e c t i o n 5.1 c o n s e r v a t i v e a n t i v i b r a t i o n mountings were discussed; I n r e a l systems some d i s s i p a t i o n of energy i n v i b r a t i n g elements always occurs. This l e a d s t o an a t t e n u a t i o n of v i b r a t i o n amplitudes. Furthermore, t h e e f f e c t of r e d u c t i o n of v i b r a t i o n may be amplified by i n t r o d u c i n g some s p e c i a l energy d i s s i p a t i n g d e v i c e s i n t o t h e a n t i v i b r a t i o n mountings. Such mbuntings a r e u s u a l l y r e f e r r e d t o as damped absorbers. A n t i v i b r a t i o n damped absorbers a r e used when t h e e x t e r n a l e x c i t a t i o n does not have a simple monoharmonic c h a r a c t e r and when t h e a p p l i c a t i o n of a conservative dynamic a b s o r b e r would introduce t h e danger of a d d i t i o n a l resonance.. D i f f e r e n t kinds of damping mechanisms a r e used i n absorbers: viscous f l u i d o r electromagnetic damping, dry f r i c t i o n , h y s t e r e t i c m a t e r i a l damping. Acceleration dampers a r e a s p e c i a l group of damped absorbers. They c o n s i s t of small mass elements ( m e t a l l i c b a l l s o r s h o t , q u a r t z sand, tungsten powder, etc.)

f r e e t o move o r s l i d e i n a s e a l e d

c o n t a i n e r t h a t i s a t t a c h e d t o the v i b r a t i n g system. I n c i p i e n t v i b r a t i o n i s reduced by t h e m u l t i p l e c o l l i s i o n s and f r i c t i o n between t h e mass elements w i t h consequent t r a n s f e r of momentum and conversion of mechanical energy i n t o heat. It should be n o t i c e d , however, t h a t such dampers may i n c r e a s e a c c e l e r a t i o n l e v e l s as a r e s u l t of impulsive loadings.

7. ACTIVE TECHNIQUES OF V I B R A T I O N CONTROL Growing v i b r o a c t i v i t y of machines r e n d e r s p a s s i v e methods of V i b r a t i o n Control i n s u f f i c i e n t ; more and more o f t e n they

304

a r e completed o r r e p l a c e d by a c t i v e methods. Active methods, i n t r o d u c i n g a u t o m a t i c c o n t r o l s y s t e m s , can s o l v e t h e problem Of

c o n t r a d i c t o r y r e q u i r e m e n t s o f e f f i c i e n c y of t h e main

p r o c e s s of t h e machine, low l e v e l of p e r t u r b i n g v i b r a t i o n and 8 t a b il i t y

.

The system is " a c t i v e t 1 i f t h e r e i s an e x t e r n a l energy supply, which a m p l i f i e r s g e n e r a t e d c o n t r o l s i g n a l s , t o r e d u c e

t o an a d m i s s i b l e l e v e l t h e v i b r a t i o n r e s p o n s e c h a r a c t e r i s t i c s a t chosen pointB o r s p a c e s of t h e s t r u c t u r e , w i t h i n a g i v e n band of f r e q u e n c y o r an i n t e r v a l of t i m e , f o r a p r e d i c t e d c l a s s of e x c i t a t i o n . Let u s now mention somc c h a r a c t e r i s t i c f e a t u r e s d i f f e r e n t i a t i n g a c t i v e systems from p a s s i v e ones. P a s s i v e systems can d i s s i p a t e e n e r g y o r t e m p o r a r i l y s t o r e

i t and t h e n r e t u r n i t . Active s y s t e m s , c o n t a i n i n g an e x t e r n a l c o n t r o l l e d power s u p p l y , may c o n t i n u o u s l y p r o v i d e o r a b s o r b energy from any p a r t of t h e machine i n t h e r e q u i r e d manner. P a s s i v e elements g e n e r a t e a c t i v e o r d i s s i p a t i n g f o r c e s , which a r e r e l a t e d t o l o c a l motion v a r i a b l e s . Active systems can g e n e r a t e l o c a l f o r c e s , which are r e l a t e d t o d i s t a n t motion v a r i a b l e s and/or e x t e r n a l command signals. They a l s o have t h e p o t e n t i a l of r e s p o n d i n g t o i n p u t c o n d i t i o n s and changes i n t h e desired behavior

of t h e system i n ways f a r more complex

t h a n t h o s e p o s s i b l e w i t h p a s s i v e systems. P a s s i v e systems a r e

g e n e r a l l y optimized by c h o o s i n g p a r a m e t e r s w i t h i n a g i v e n s t r u c t u r e . A c t i v e systems a r e much more f r e e # t h e r e i s no imposed s t r u c t u r e f o r feed-back c i r c u i t s and a c t u a t o r s . L i m i t a t i o n s i n t h e c h o i c e of a s t r u c t u r e a r e connected w i t h

305

value bonds f o r f o r c e s , displacements o r v e l o c i t i e s and s e l e c t i o n of e f f i c i e n c y c r i t e r i o n . Among t h e advantages of passive systems a r e t h e i r

s i m p l i c i t y , contained weight, low c o s t , high r e l i a b i l i t y . Active systems a r e used where passive means f a i l t o d e l i v e r t h e r e q u i r e d performance, or where t h e o p e r a t i n g c o n d i t i o n s vary so widely t h a t v a r i a t i o n s i n t h e s t r a t e g y of c o n t r o l a r e f r e q u e n t l y ’ c a l l e d f o r . Together w i t h t h e development of technology, as experience with a c t i v e systems grows, and progress ia made in s i g n a l processing equlpment, t h e time w i l l s u r e l y come when an a c t i v e l y c o n t r o l l e d system may even be s u p e r i o r t o a p a s s i v e system a l s o as f a r a s p r i c e , weight and r e l i a b i l i t y a r e concerned.

According t o t h e p r i n c i p l e of o p e r a t i o n one can c l a s s i f y a c t i v e systems as f u l l y a c t i v e , semiactive (Fig. 3) and systems with v a r i a b l e s t r u c t u r e s . F u l l y a c t i v e systems usuall y g e n e r a t e f o r c e s , and t h e i r a c t u a t o r s a c t d i r e c t l y on t h e c o n t r o l l e d o b j e c t , p a r a l l e l t o t h e p e r t u r b i n g f a c t o r s . Such systems a r e v e r y o f t e n completed by p a s s i v e elements w i t h con-

stant c h a r a c t e r i s t i c s . In semiactive systems t h e executing devices continuously

o r unevenly modify some parameters of t h e s t r u c t u r e . I n comparison w i t h f u l l y a c t i v e systems, semiactive ones a r e simpler, c h e a p w , more s e n s i t i v e , l i g h t e r , r e q u i r e moderate power. S y s t e m w i t h v a r i a b l e s t r u c t u r e s a r e m u l t i c i r c u i t feedback systems g e n e r a t i n g f o r c e s , and/or changing v a l u e s of parameters of t h e s t r u c t u r e . A command c o n t r o l s t h e a c c e s s t o

t h e o p e r a t i o n of t h e s e p a r a t e circuits, corresponding t o a k i n d of p e r t u r b a t i o n , v i b r a t i o n a l responses and t h e i r r e q u i r e d l e v e l . V i b r a t i o n Control systems w i t h v a r i a b l e s t r u c t u r e s are n o t y e t w e l l e l a b o r a t e d 1 they do have, however, some good prospects. According t o a n o t h e r c l a s s i f i c a t i o n , one can d i s t i n g u i s h a c t i v e feed-back systems c o n t r o l l e d by movement in closedl o o p c i r c u i t s and compensating systems c o n t r o l l e d by i n p u t p e r t u r b a t i o n s (Fig. 4). Systems c o n t r o l l e d by movement ( o u t p u t ) do n o t r e q u i r e much knowledge of p e r t u r b i n g f a c t o r s . They a r e e f f e c t i v e f o r resonance bands of frequency. F o r nonresonance f r e q u e n c i e s t h e p a s s i v e means a c t i n g t o g e t h e r w i t h t h e a c t i v e one improves t h e operation. This kind of a c t i v e system should be c a r e f u l l y analysed from t h e p o i n t of view of s t a b i l i t y , and i f n e c e s s a r y completed w i t h some c o r r e c t i o n c i r c u i t s , f i l t e r s .

o r combined c o n t r o l . Compensating systemn a r e a p p l i e d when it i s p o s s i b l e t o measure p e r t u r b i n g f a c t o r s . The a c t i o n of t h e s e systems i s independent from t h e responses, so t h a t t h e i r a p p l i c a t i o n r e q u i r e s a f u l l knowledge of t h e c o n t r o l l e d s t r u c t u r e . Usuall y , compensating systems a r e also completed by p a s s i v e elements and by c o r r e c t i o n c i r c u i t s (e.g. active vibro-isolation,

i n t h e c a s e of

the correction c i r c u i t s control the

i n f l u e n c e of s t a t i c o r dynamic l o a d s t h a t vary slowly i n time), There a r e a l s o hybrid compensating

- feed-back

systems

and systems w i t h programmed c o n t r o l s i g n a l s . The t h e o r e t i c a l background of a c t i v e V i b r a t i o n Control

307

systems is given by t h e Control Theory. Let us b r i e f l y d e s c r i b e t h e optimal c o n t r o l method. The l i n e a r mathematical model of t h e c o n t r o l systems is:

where x is an n-dimensional column v e c t o r of s t a t e v a r i a b l e s , A i s an ( n x n ) matrix, d e s c r i b i n g t h e i n t e r n a l p r o p e r t i e s

t h e c o n t r o l l e d Bystem ce.g.

of

a combination of t h e matrices

I, K, C, s e e Eq. ( l ) ) , u is an m-dimensional v e c t o r of i n p u t q u a n t i t i e s , B is an ( n x m) matrix, y i s an r-dimensional column v e c t o r of output v a r i a b l e s response and C , D are

( r x n) and ( r x m) m a t r i c e s r e s p e c t i v e l y . I n t h e open loop case we seek time f u n c t i o n s f o r t h e i n p u t q u a n t i t i e s i n t h e u-vector, which have some d e s i r e d e f f e c t on t h e system t o be c o n t r o l l e d . In the c l o s e d loop

case we t r y t o r e l a t e t h e input q u a n t i t i e s t o the measured a s p e c t s of t h e system response i n o r d e r t o t a i l o r t h e o v e r a l l system dynamics, so t h a t t h e system responds i n a d e s i r a b l e manner. For elementary systems which i n p u t q u a n t i t i e s would be u s e f u l f o r c o n t r o l l i n g the system is o f t e n i n t u i t i v e l y e v i d e n t , b u t i n more complex case8 this l e not always c l e a r . For l i n e a r systems t h e simple c r i t e r i a of c o n t r o l l a b i l i t y a r e formulated. The next important s t e p i s connected w i t h t h e problem of c o n t r o l e f f i c i e n c y . As an example, t h e i n t e g r a l f a c t o r of q u a l i t y (performance i n d e x )

J

0

should be minimized (Q,R

- weighting m a t r i c e s ) .

Problem ( 4 ) w i t h determined o r random p e r t u r b a t i o n and w i t h t h e performance index

(5) taken i n t o account has been

solved by t h e modern c o n t r o l theory. while r e l i a n c e on a q u a l i t y f a c t o r as t h e b a s i s f o r o p t i m i z a t i o n seems t o be unavoidable, l i m i t a t i o n s t o t h e g e n e r a l i z i n g of t h e o p t i m i z a t i o n as a consequence of comparison w i t h a l i m i t e d c l a s s of a l t e r n a t i v e s can be

SUP

mounted. Optimization techniques of modern c o n t r o l theory, when a p p l i e d t o s y n t h e s i s i n the time o r frequency domain make i t p o s s i b l e t o e s t a b l i s h limits on t h e q u a l i t y f a c t o r f o r a l l a d m i s s i b l e c a n d i d a t e V i b r a t i o n Control concepts. Moreover, a p p l i c a t i o n of t h e optimal c o n t r o l method g i v e s t h e advantage of avoiding a d d i t i o n a l s t a b i l i t y a n a l y s i s : systems c a l c u l a t e d by t h i s method a r e always s t a b l e . This approach, however, s a y s n o t h i n g about t h e elements d e s i r a b l e from a device o r i e n t e d p o i n t of view t o achieve optimum performance. The d e s i g n e r i s f r e e t o choose a convenient system, and he a l r e a d y has v a l u a b l e information, which he almost never p o s s e s s e s otherwise. The a c t i v e techniques of V i b r a t i o n Control have y e t t o be p e r f e c t e d b e f o r e t h e i r g e n e r a l a p p l i c a t i o n , much more r e s e a r c h w i l l be necessary. In p a r t i c u l a r , i t should be mentioned that comparative e s t i m a t i o n s of d i f f e r e n t k i n d s

309

of a c t i v e systems, which would suggest a proper choice a r e s t i l l lacking. 8. CLOSING REMARKS

The methods of t h e V i b r a t i o n Control described i n t h i s paper p r i m a r i l y concern t h e problem of mechanical v i b r a t i o n i n machines. However, t h e technfques involved a r e e q u a l l y a p p l i c a b l e , w i t h proper s c a l i n g , as necessary, t o l a r g e s c a l e c i v i l , a s t r o n a u t i c a l and marine engineering problems, and a l s o t o small s c a l e problems, such as v i b r a t i o n c o n t r o l of sporti n g and games equipment, where p r o t e c t i o n of human f a t i g u e i s t h e d i r e c t aim. Among t h e "large s c a l e " problems we have Vibration Control and s t a b i l i z a t i o n i n s h i p s , aircrafts and s p a c e c r a f t s , c o n t r o l of wind earthquake o r ground induced v i b r a t i o n i n b r i d g e s , masts, buildings. In many of t h e s e problems, t h e approach adopted toward

V i b r a t i o n Control is a p u r e l y mechanical one, i n which t h e human being i s regarded as a p a s s i v e s u f f e r e r of t h e v i b r a t i o n o r n o i s e environment, and where t h e g o a l of design i s t o keep t h e environment w i t h i n s a f e l i m i t s .

I n o t h e r c a s e s , the human o p e r a t o r is an a c t i v e , v i t a l p a r t of t h e system (aircraft, automobile, s p o r t i n g equipment)

and man-machine i n t e r a c t i o n is a n e c e s s a r y p a r t of any v i b r a t i o n o r n o i s e r e d u c t i o n p r o j e c t . It i s important t o d i s t i n g u i s h between t h e s e two t y p e s of problems, because t h e approach is c o n s i d e r a b l y influenced by t h e i n t e r v e n t i o n of t h e human o p e r a t o r who makes t h e system behave l i k e a system w i t h f eed-back.

What i s important, I s that the technology f o r c o n t r o l l i n g

310

v i b r a t i o n s and n o i s e ( a n a l y s i s , V i b r a t i o n Control techniques, advanced d i g i t a l measurement systems, damping, i s o l a t i o n and a b s o r p t i o n m a t e r i a l s , m i c r o e l e c t r o n i c systems f o r a c t i v e control,

..

.) e x i s t s , i n g e n e r a l , a t a very advanced l e v e l

today, but i t i s n o t being used a s w e l l a s i t could be i n p r a c t i c e , because of t h e wide d i s p e r s i o n of r e l e v a n t information

...

worldwide, i n hundreds of j o u r n a l s and i n t e r n a l

documents. The task,which p r e s s e s many engineers and d e s i g n e r s today, is t o c o l l e c t i d e a s and m a t e r i a l s now a v a i l a b l e and u s e them t o develop p r a c t i c a l and economical s o l u t i o n s ( o r p a r t i a l s o l u t i o n s ) f o r t h e most s e r i o u s problems a t hand. D i r e c t i o n f o r new r e s e a r c h work, n o t s o much geared t o today's problems, b u t r a t h e r toward t h o s e we might expect t o s e e by t h e end of t h i s century, should be c a r e f u l l y sought, examined, debated, and a r t i c u l a t e d , s o t h a t r e s e a r c h i n s t i t u t e and u n i v e r s i t i e s can begin from now on t h e slow t a s k of c r e a t i n g new technology. This p r o c e s s of i n t e r a c t i o n between r e s e a r c h and a p p l i c a t i o n i s very important; u n f o r t u n a t e l y i t i s n o t found a s f r e q u e n t l y a s i t should be.

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311

REFERENCE 113 Muszyfiska A . ,

V i b r a t i o n c o n t r o l methods, Nonlinear

V i b r a t i o n Problems (Zagadnienia Drgafi Nieliniowych) 21 (1980)

CONTROLLED EXClTATl ON RESPONSE

EXCITAT I 0N

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. .,,)EL I

MOD1FlCAT1ONS K+K+AK M+M+ AM

REQUIRE1 4

Fig. 1.

3 12

I

I-

. . .

A)

Fig.

COP~TROLLED OBJECT

INPUT

STRESS RELAXATION

DISLOCATION MOVEMENK WONOELECTRONIC EFFECT PHASE PROCESSES

EDDY CURRENTS MAGNETOSTRICTION EFFECT

HYSTERESIS

MAGNETOELASTIC EFFECT MAGNETOMECHANICAL

THERMAL FLOWS

THERMAL DIFFUSION

LUBRICATED SLIDING

DRY SLIDING

LUlD PUMPING AT JOINTS

I

-n rn

rn

i

u)

-I

0

W

DISSIPATION OF MECHANICAL ENERGY

Bl CONTROLLED OBJECT

SYSTEM

INPUT

3

313

INPUT

I

ACTUATOR

INPUT

314

OUTPUT (MOVEMENT)

OBJECT

#

t AMPLlFl ER

MEASURING DEVICE

CONTROLLED OBJECT

OPTIMIZATIONOF STOCHASTICMAN-MACHINE SYSTEMS R. I. Furunshiev, A. G. Ismailov Byelorussian Polytechnic Institute, V.S.S.R .

SUMMARY I n t h e r e p o r t we d i s c u s s t h e r e s u l t s o f c o m p a r a t i v e s t u d i e s on t h e e f f i c i e n c y of seven a l g o r i t h m s o f s t o c h a s t i c o p t i m i z a t i o n s e q u e n t i a l l y on t e s t f u n c t i o n s , t e s t models o f s t o c h a s t i c v i b r a t o r y s y s t e m s and r e a l m o d e l s of w h e e l e d v e h i c l e s w i t h a n o n l i n e a r v i b r o - i s o l a t i o n s y s t e m a t random d i s t u r b a n c e s .

1.

INTRODUCTION The a d v a n t a g e o f u s i n g c o m p u t i n g t e c h n i q u e f o r t h e a n a -

l y s i s and s y n t h e s i s o f v i b r a t o r y s y s t e m s , r o l e i s p l a y e d by t h e m a n - o p e r a t o r ,

i n which an i m p o r t a n t

and t h e n e c e s s i t y o f u s i n g

o p t i m i z a t i o n m e t h o d s f o r d e s i g n i n g s u c h s y s t e m s h a v e been d i s cussed i n t h e quoted l i t e r a t u r e [1-8]

and b y o t h e r a u t h o r s .

The n o n l i n e a r c h a r a c t e r o f m a t h e m a t i c a l m o d e l s , random n a t u r e o f tem’s

input effect;

the

and t h e dependence o f t h e s y s -

p u r p o s e f u n c t i o n s o n many p a r a m e t e r s i s a c h a r a c t e r i s t i c

f e a t u r e o f t h e p r o b l e m o f t h e optimum d e s i g n i n g o f v i b r o - i s o l a t i o n systems. Presented here a l g o r i t h m s o f s t o c h a s t i c o p t i m i z a t i o n , though n o t u n i v e r s a l ,

c a n be u s e d f o r t h e s o l u t i o n o f t h i s p r o -

b l e m c l a s s o r a n o t h e r one and i n p r a c t i c e q u e s t i o n s a r i s e c o n n e c t e d w i t h t h e c h o i c e o f optimum methods f o r t h e s o l u t i o n o f pa r t I c u 1 a r p r o b 1 ems. An i m p o r t a n t p r o b l e m i n c r e a t i n g s o f t w a r e ( p a c k a g e s o f a p p l i c a t i o n program) f o r t h e o p t i m i z a t i o n o f parameters,

which

315

significantly ctioning,

i n f l u e n c e t h e q u a l i t y o f m an-m ac hi ne

system fun-

i s t h e d e v e l o p m e n t o f t e s t f u n c t i o n s and m o d e l s t o

e s t i m a t e t h e e f f i c i e n c y o f t h e methods used. 2.

T H E ALGORITHMS OF STOCHASTIC O P T I M I Z A T I O N Let us consider the studied algorithms.

I n computer m i n i m i -

zation of the quality c r i t e r i o n the stochastic optimization a l g o r i t h m s were g i v e n by t h e f o l l o M i n g r e c u r r e n t r a t i o s : Kiefer, Wolfowitz

= A[k-11-

A[k]

-

[lo]:

,...,

a[k]a,

k=1 ,2

a[n]v,

nsk, n=1,2

q,

a[k]=

(2. 1

Kesten [ll]: A[k]

A[k-11-

,..., a[n]= fi, nY

Kesten w i t h Fabian's m o d i f i c a t i o n :

= A[k-11-

A[k]

-

i = l,m,

a[n].Ssign{Uil,

(2.2)

(2.3)

a l g o r i t h m s u s i n g t h e m e t h o d s o f random s e a r c h w i t h o n e o r double t e s t i n g steps i n c a l c u l a t i n g the gradient

= A[k-11-

A[k]

[12]:

a[n]Vl,

(2.4)

modified algorithms w i t h the coordinate wise descent ai[k]

=ai[k-l]

-

,

i==

-a[n].Sjsign{Uil,

learning algorithms of stochastic optimization A[k] Z[n]

z

[n]

A[k-I]-

Z[n]4slgn{~}

ZIIOJ

ma[n]diag(ZI), a1

Ail"[

z [n-1 ] + [1-a1]

-

1

E,

,

-

A In]

uI[n]uI[n-l]

l/m,

,

i

-l,m,

l/m,

ml

(2.6)

0,

random s e a r c h a n d t h e q u i c k e s t random d e s c e n t

316

[14]:

$0,

u , [ ~ ] u ~ [ ~ - >I o] ,

-

(2.5)

O

~ ~ ( =6 ) where P 3 ,

sign

,

LC

are constants

i ,

M are constants;

where

Y,

where k t ,

m

M/m,

6

a

Y-q,

n2= Ct/m,

6c=

(~+m) 9 Ct

s

m are constants.

D i s t u r b a n c e q ( t ) was f o r m e d a s r e a l i z a t i o n o f t h e n o r m a l random p r o c e s s w i t h t h e e x p o n e n t i a l - c o s i n e

correlation function

I n t h e c a l c u l a t i o n we assumed a = 2 . 5 cm. T The o p t i m i z e d p a r a m e t e r v e c t o r A = (lo, Y, Yo), where va-

(3.10).

l u e s lo, Y c and Y o ,

when a p p l i e d t o t h e p r o b l e m s o f v i b r o - i s o -

lation,

lo

have t h e f o l l o w i n g p h y s i c a l meaning:

v a l u e w h i c h c h a r a c t e r i z e s gas volume

i s a nonlinear

i n t h e working c a v i t y o f

i n t h e s t a t i c s t a t e and Y c a n d Y o a r e

a hydropneumatic element

relative coefficients of aperiodicity,

respectively correspon-

d i n g t o m i n o r v i b r a t i o n s o f t h e s t r o k e s damped a t c o m p r e s s i o n and r e l e a s e . The d i f f e r e n t i a l e q u a t i o n s w e r e s o l v e d b y R u n g e - K u t t a m e t h o d o f the 4-th order with step h

-

0.005 C .

For t h e e f f i c i e n c y cri-

t e r i o n we u s e d t h e e x p r e s s i o n :

=

W(A,q)

+ 13P(*),

US-

X

(4.2)

w h e r e a% i s the standard decrease

i s the penalty coefficient:

13

-P

o f t h e s p r u n g mass a c c e l e r a t i o n ;

i s t h e a l l o w a b l e p r o b a b i l i.ty o f t h e r e s i l i e n t e'lements b r e a k

down;

P(*> = E [ x 1

(t)],

x,

w h e r e E i s a symbol o f m a t h e m a t i c a l e x p e c t a n c y ;

(t> i s a chs

racter i s t i c function:

A Ad

W(*)

-

=

0.66 t o , A,=

1 ~ ~ 1 ,

A ~ -

i s t h e g i v e n v a l u e o f t h e d y n a m i c movement o f t h e p l u n g e r . was t o be m i n i m i z e d : W(A

3t

,

q)

= m i n W(A,q)

AEA

w i t h r e s t r i c t i o n s o f t h e 1 - s t and 2 - n d a b l e parameter area.

type;

-A

i s the allow-

The f o l l o w i n g r e s t r i c t i o n s w e r e imposed

on t h e o p t i m i z e d parameters: 12

322

Q

lo$25

cm,

O,l$

\y

C

d 1,

0,1$

Yo


=

Yio,

Yi(to)=

io ,

i(to)=

Iji(t0)

4o , = ii0 ,

w h e r e i i s t h e number o f t h e m a c h i n e s u p p o r t ; of

J i s t h e number

t h e s u s p e n s i o n element c h a r a c t e r i s t i c s between t h e sprung

and u n s p r u n g masses o f t h e i - t h s u p p o r t responds t o t h e r e s i l i e n t element,

. ..

v i b r a t i o n absorber,

J =

( t h e v a l u e o f J-1

J = 2 corresponds t o the

3 corresponds t o the d r y f r i c t i o n ) ;

X,X,X

are v e r t i c a l movements (cm), s p e e d ( c m / s e c ) ( c m / s e c 2 ) o f t h e s p r u n g mass, and v e r t i c a l

$,4,;

movements ( r a d ) ,

cor-

speed ( l / s e c )

acceleration are angular 2 o f the

and a c c e l e r a t i o n ( l / s e c

.. a r e

>

s p r u n g mass a r o u n d t h e l a t e r a l a x i s p a s s i n g t h r o u g h t h e c e n t r e *

o f gravity (pitching axis); speed ( c m / s e c )

and a c c e l e r a t i o n ( c m / s e c

o f the i - t h support;

Bi

Y,Y,Y

F,)

P5

-

v e r t i c a l movements (cm), 2 o f t h e u n s p r u n g mass

>

n o n l i n e a r c h a r a c t e r i s t i c s (cm/sec?);

i s t h e c o e f f i c i e n t c h a r a c t e r i z i n g t h e p a r t o f t h e sprung

mass w h i c h i s o n t h e i - t h s u p p o r t ;

hi

i s the c o e f f i c i e n t taking

i n t o a c c o u n t t h e e f f e c t o f t h e i - t h s u p p o r t on a n g u l a r v i b r a t i o n o f t h e s p r u n g mass;

324

yi

i s t h e c o e f f i c i e n t e x p r e s s i n g t h e sprung

and u n s p r u n g mass r a t i o o n t h e i - t h s u p p o r t .

These c o e f f i c i e n t s

are calculated according t o the expressions:

Bi

xi

= Mi/M,

= Biei/P;,

yi

= Mi/mi

,

i - t h support, M i s the 2 s p r u n g mass o f t h e w h o l e m a c h i n e ( k g s e c / c m ) ; m i i s t h e u n 2 s p r u n g mass o f t h e i - t h s u p p o r t ( k g s e c / c m ) ; x i i s t h e d i s t a n -

where M i

i s t h e s p r u n g mass o f t h e

ce between t h e

i t h s u p p o r t and t h e c e n t r e o f g r a v i t y o f t h e

s p r u n g mass (cm);

po

i s t h e r a d i u s o f t h e s p r u n g mass i n e r t i a

r e l a t i v e t o the p i t c h i n g a x i s . L e t u s c o n s i d e r now t h e n o n l i n e a r c h a r a c t e r i s t i c s i n t h e system ( 5 . 1 ) .

involved

The c h a r a c t e r i s t i c o f t h e t e l e s c o p i c

dropneumatic r e s i l i e n t element o f

the i - t h support

hy-

i s given

by t h e e x p r e s s i o n :

where

A’

= AiAi,

Ai

= X + ti$

-

Yi,

Ai=

{1,

with i=l,

a:b,

w i t h i=2.

H e r e toi i s t h e l i n e a r v a l u e c h a r a c t e r i z i n g t h e g a s v o l u m e t h e work ng c a v i t y o f t h e r e s i l i e n t e l e m e n t o f t h e i n t h e s a t i c s t a t e (cm);

in

i - t h support

k i s the r a t i o o f the forces effec-

t l n g the i - t h support r e s i l i e n t element’s

plunger from t h e

back p r e s s u r e c a v i t y and t h e w o r k i n g c a v i t y ,

respectively;

i s t h e r a t i o o f t h e h e i g h t s o f t h e gas column i n t h e back pi pressure c a v i t y L a n d t h e w o r k i n g c a v i t y l? respectively; oi oi x i i s p o l y t r o p e i n d e x , x i b e i n g u s u a l l y 1.25; A ; i s t h e r e s i l i e n t element d e f o r m a t i o n which c a r r i e s

information about the

suspension k i n e m a t i c s . I n t h e expression (5.2)

k i = 0 s h o u l d be t a k e n f o r t h e s u s -

pension w i t h hydropneumatic r e s i l i e n t elements w i t h o u t back pressure. The v i b r a t i o n a b s o r b e r k h a r a c t e r i s t i c s i s g i v e n b y t h e f o l l o wing expression:

325

where

Here Yci,

\Yoi

are r e l a t i v e aperiodicity coeff cients corres-

p o n d i n g t o m i n o r v i b r a t i o n s a t c o m p r e s s i o n and r e l e a s e s t r o k e s o f the i - t h support. The c h a r a c t e r i s t i c s o f t h e d r y f r i c t i o n c o n d t i o n a l o f the i - t h support

Fgi(Af)

Here

P

3i

element

is

,

= AiFji(ii)

i s the dry f r i c t i o n a t

the i - t h support

(kg).

The r e s i l i e n t r a d i a l c h a r a c t e r i s t i c s o f t h e t y p e F q i ven by a t a b l e .

is gi-

The a l g o r i t h m o f t h e f o r m i n g o f t h i s c h a r a c t e -

r . i s t i c s was d e s c r i b e d

in

[8].

The d i s s i p a t i v e r a d i a l c h a r a c t e r s t i c s o f t h e t y p e

s given

by the expression:

Fgi(ki)

kti/mi, =

si(t> = Y i W

where H e r e 6cl

,

-

i f 6 i ( t ) \ < dCi

,

if 6i(t)

,

q i w

.

i s s t a t i c d e f o r m a t i o n d e r ved f r o m t h e r e s i l i e n t cha-

r a c t e r i s t i c s Fbi;

qi(t)

i s the d sturbance e f f e c t i n g

the i - t h

.

w i t h a2= 37.0 cm2 q a d e t a i l e d scheme f o r c a l c u a t i n g a n d b u i l d i n g t h e m o d e l

support modelled according t o the I n [8]

>CjCi

aw ( 3 . 1 0 )

i s given. For o p t i m i z a t i o n standard,

acce e r a t i o n values o f t h e sprung

mass a t t h e p o i n t o f t h e d r i v e r ' s efficiency criteria:

326

seat f i x i n g a r e taken as the

where

eC

i s t h e d i s t a n c e between t h e c e n t r e o f g r a v i t y o f t h e

mass a n d t h e p l a c e o f t h e d r i v e r ' s

s e a t m o u n t i n g . We h a v e a s -

sumed LC = 491 cm. Taking

i n t o account the r e s t r i c t i o n s ,

the accepted q u a l i t y

c r i t e r i o n has t h e f o l l o w i n g form:

w = where

PTi

W'

+

0.1.10~, with

W'

+

O.l.10~, with

W'

+

0.1.107,

W'

+

0.1.10~q with

with

-

PAi

PAi

< PAi,

0..

x1,2

Yci

>

>. l g , Yoi

,

i s the accepted p r o b a b i l i t y o f t h e ab-

sence o f t h e s u s p e n s i o n break-down.

PAi= 0.995.

< PTi,

i s the given p r o b a b i l i t y o f non-separation o f t h e

s t e e r a b l e wheels;

-

-

PTi

We h a v e assumed F T i =

0.92;

The r e s u l t s o f t h e o p t i m i z a t i o n u s i n g a l g o r i t h m

P-A a r e g i v e n i n T a b l e 5 . 1 .

The s t u d y r e s u l t s h a v e shown c o m p a r a t i v e e f f i c i e n c y o f using s t o c h a s t i c o p t i m i z a t i o n methods i n optimum d e s i g n t i c machine-systems.

However,

o f stochas-

i n o r d e r t o reduce machine t i m e

consumption i n designing r e a l o b j e c t s ,

it

i s necessary t o c a r -

r y o u t e x p e r i m e n t s on c o m p a r a t i v e e s t i m a t i o n s o f t h e used a l g o r i t h m s convergence. designing,the

Preliminary

i n v e s t i g a t i o n s showed t h a t

in

s t o c h a s t i c v i b r a t o r y o b j e c t m e t h o d p r o v e d t o be

t h e b e s t as f o r

the convergence time (see Table 4.1).

method r e q u i r e s a b o u t f i v e hours o f "Minsk-32"

This

t i m e f o r asymp-

t o t i c o p t i m i z a t i o n o f a r e a l man-machine system.

-Number of successful steps

0-

a1

um-

Step length

er f teP

- - 4.1 N

n

EffiOptimized parameters

-

ciency c r i ter ior

w=lJ.

XB

+pena 1t Y cm/sec

,

-

I I

- 'A1

'0i

V i b r a t i o n parameters

Restrictions

I PA2

3

T l -

,

11

12 I

I

I

i

i1

-0;c2

aY1 9

.J

1

0.29

2.04,

1.2

0.34

1.9

1.48

110.33

0 -44

2.0

1.76

a; 1P . 1/sez g 1 1

9 -

y2 9

0

0

0.364

512.4

1.0 b . 0

I .o

1.0

1

4

0.185

483.9

1.0

1.0

I .o

I .O 10.27 1.0

1

4

0.18

552.8

1.0 1.0

I .o

1.010.3 I

2

12

0.38

512.1

1.0 b . 0

I .o 1.0 I0.24

0.99

10.36

0 -3

2.06

1.25

478.1

1 .o 11 .o

I .o

I

1.010.23

D.99

10.31

0 -31

1.9

1.2

0.31

1.8

1.3

0.33

1.76

1.35

3

4

-

18 20 24 28

33

34 --

0.25 0.18 0.14 0.14 0.21 0.21

-

0.2 0.21 0.31

I 10.4

10.71 I (14.7115.1 I

I

I

1

1

10.42 10.71 114.7 j15.1 (

10.42,0.71

114.7 j15.1

458.9

447.9 493.6 480.7

447.8

-

i

I

I I

I 1 .o '1 .o I .o I I

I

0.23

I

I

I .O 10.24 0.43

1.010.25

I

1 .o I1 .o 1 .o 1.010.26 1 I

I

1 .o ;1 .o 1 .o 1.010.25 I

-

1.3

I

I 1 .o 11 .o I .o I .010.25 I I 1 .o (1 .o I .o

1.004 10.34

0.96

0.33

1 10.31 1 i0.3 1

1.1

I

0.36

1.52

1.03

r3'

1.9

10.32

0.35

1.9

1.5

0.95

110.29

0.33

1 .8

1.3

REFERENCES P a u l I . J . : On t h e o p t i m i z a Karnopp D.C., Bender E.K., t i o n o f v e h i c l e s u s p e n s i o n u s i n g random p r o c e s s t h e o r y , A S M E P a p e r No 67 Tran. 12.

-

-

Bender E.K.: Optimum l i n e a r r a n d o m v i b r a t i o n P r e p r i n t s 1967 JACC.

isolation,

T r i k h a A.K.: Comparative study o f o p t i m i Karnopp D.C., z a t i o n t e c h n i q u e s f o r s h o c k and v i b r a t i o n i s o l a t i o n , A S M E P a p e r No 69 Vibr. 45.

-

-

T r i k h a A.K., Ka.rnopp D . C . : A new c r i t e r i o n f o r o p t i m i z a t i o n l i n e a r v i b r a t i o n i s o l a t o r systems s u b j e c t t o random i n p u t , A S M E P a p e r No 69 Vibr. 45.

-

-

A p e t a u r M . , J a n a k K., Skrinvanek I., V a c i k D . : Computer o p t i m i z a t i o n suspensions parameters, Automative Design Engng., 1968 December.

COBpeMeHHOe COCTORHne HayqHblX MCCJleAOBaHMfi @pOnOB H.6.: B o 6 n a c ~ na n 6 ~ 0 3 a u n ~ b i 0 . c 6 . B n n f l ~ n e~ n .6 ~. a u Ha ~ f om-ai H H ~ Mqe n o a e u a ' n flpO6neMbl Bn6pO3auMTbt. " H a y u a " , MocAaa, 1974. OypyHmnee P.M. : IlpoeuTMposaHne OnTMManbHbix ~ n 6 p o 3 a u n ~ Hbix cncTeM, "BblUehUafl tunona", MnHcu, 1971. ABTOMaTM3MpOEaHHOe flpOeUTMpOBaHMe H one@ypyHMHeB P.M.: 6aTenbHblX CMCTeM. "BblUekLuafl WUOna", M n H C u , 1977. R o b b i n s H . , M o n r o S.: A s t o c h a s t i c a p p r o x i m a t i o n m e t h o d , Ann. M a t h . S t a t . 2 2 (19511, 1 . K i e f e r J., W o l f o w i t z 1 . : Stochastic estimation of the Maximum o f a r e g r e s s i o n f u n c t i o n , An n . M a t h . S t a t . 23,

(19521, 3.

K e s t e n H.: A c c e l e r a t e d s t o c h a s t i c a p p r o x i m a t i o n , M a t h . S t a t . 2 9 , (1958).

Ann.

P a c r p n r M H A.A.: CnyranHbtR n o n c u a n p o q e c c e aAanTaqnn, PMra, "3nHaTHe", 1 9 7 3 . Mcmannoe A.R.: 0 6 O A H O M anropnT m e O n T F OypyHmnee P.M., ManbHoro npoenTnpoaaHnfl CTo xa c T nqec nnx Bn6pO3auMTHblX CwcTem. 0 c 6 . BnnflHMe a n 6 p a u n f i Ha o p r a ~ n 3renOaeHa ~ n u o n e 6 a ~ n f lMatunH, " Ha yu a " , Mocnaa, 1 9 7 7 . Mcmannoe A.R.: MoAnOnqMpoaaHHnfi a n r o p n T M Oypynmnee P.M., c 0 6 y ~ 1 e ~ nne e~r o npnMeHeHne n 3a~accar-1o n ~ n m n 3 a u ~ M w nAeHTMOnnaunn c r o x a c r n q e c n n x cMcTeM. B c 6 . Y c nopenne BHeApeHMfl MeToAoB n cpeAcTe a ~ ~ o ~ a ~ n 3npoeuTnpoeaHMfl a ~ n n n ynyrweHnR n o A r o r o e n n cn e q n annc T oe, M ~ H C U , 1 9 7 8 . D v o r e t z k y A.: On s t o c h a s t i c a p p r o x i m a t i o n , P r o c e e d i n g s o f t h e T h i r d B e r k e l e y Symposium o n M a t h . S t a t . a n d P r o b a b i l i t y , v o l . 1 , 1956.

329

EXPERIMENTAL METHOD FOR THE IDENTIFICATION OF DYNAMIC PROPERTIES OF A VIBRO-ISOLATIVE SYSTEM WITH A RUBBER SPRING

P.Tirinda, R.Chmurny Institute of Machine Mechanics of the Slovak Academy of Sciences, Bratislaba, Czechoslovakia

SUMMARY The contributioq deals with problems of the experimental method of measurement and identification of vibroisolation effe'cts of a mechanical system with a rubber spring. Although cases of passive vibroisolation have already been well elaborated, new possibilities in the methodical and practical handling of some problems regarding identification of dynamical properties of the vibroisolation system with real viscoelastic elements are presented. The contribution consists of two thematic parts:

-

the first part includes methodical aspects of solution and some actual results achieved by experimental measurement and identification of dynamical properties of a rubber spring,

-

the second part handles problems of automating the scientific experiment by a minicomputer and an up-to-date CAMAC. modular interface system of measuring devices

-

Introduction "The world we live in is full of vibration; technology and transport are the chief causes of dangerous vibration". These sentences could be read in the advertising leaflets of this Symposium. We identify ourselves with them and thus wish to be enrolled among those efficiently combating these problems of environment. The entire gamut of problems of man's protection against undesired vibration is very sophisticated and at the same time heterogeneous. To master them not only

diverse branches of science are to be involved but the achieved results in the individual stages of solution are also to be efficiently amalgamated. This contribution deals with the problem of automating the experimental research into the passive isolation of vibration with the view to suppress its effect upon man or equipment. Cylindrical rubber springs are considered in this case as elements of passive vibroisolation. Rubber is being produced all over the world in large quantities and production continues to rise each year. In spite of this no reliable and universal methods are hitherto known to determine the dynamic properties of real rubber springs Ill2 , 3 , 4 , 5, 6, 71 . It should be emphasized, as a matter of fact, that to handle the overall problem of man's protection against undesirable vibration successfully presumes a thorough knowledge not only of the structure and the parameters of the substitute dynamic model of man but also of the substitute model of the vibroisolating system. It is just this that has induced us to present at this Symposium our results achieved in the area of the indentification of dynamic properties of rubber springs as elements of passive vibroisolation.

1.

The methodical procedure and the results achieved in the identification of dynamic properties of a mechanical system with a rubber spring

In investigating the dynamic properties of a rubber spring it is necessary to load this spring in a suitable way and to observe its response. From among the curPent harmonic modes of spring loading the following two may be possibly considered: 1.

loading by a hydraulic exciter,

2.

loading by the inertial force of the mass fixed at one end of the rubber spring, its other end being mounted

33 1

to a vibrating electrodynamic exciter. The first of these modes is applicable in the law frequency domain since with hydraulic loading machines the increasing frequency lowers the.capacity of inducing a sufficiently large vibration amplitude (in the order of a few mm), currently required in loading rubber springs. The second mode fits the area of higher fequencies since electrodynamic exciters are not capable of developing a sufficiently large load at low frequencies. In investigating the dynamic properties of a rubber spring it is necessary to reckon with the fact that the vibrating system with such a,springwill be nonlinear. when working with a rubber spring shaped cylindrically (Fig.la) with vulcanized metallic clamps at the ends, it may happen that the measured static characteristic of such a spring will be linear within the whole range of the permissible load [6J Leaning upon certain our experiences [6! it may be stated that the dynamic characteristics will exhibit nonlinear features. They will depend on the level of load and on the direction offrequency change (the jump phenomenon in the amplitude frequency characteristic at a low frequency alteration a phenomenon characteristic for some nonlinear syshas not been observed in our experiments). This nontems -linearity is due to two causes:

.

-

-

1.

to the change in the spring shape by the loading effect ,

2.

to the change in-the mechanical parameters of the spring due to temperature changes.

The shape of the spring which is cylindrical when unloaded, may change from a "quasihyperboloid" up to a "barrel-like" shape (with short springs), or from a combination of a cylindrical (in the centre of the spring length) and "quasihyperboloid" (at the spring ends) up to a combination of a cylindrical and "barrel-like" shape (with slender springs). Thence it follows that the non-linearity caused by this change of the shape will make itself manifest mainly at

332

larger deformations. With the spring working under vibration, i.e. as it springs and damps, vibration energy transfer to heat increases the temperature of the spring. Increase in the spring temperature brings about changes in the mechanical properties of the spring as follows [I1 :

a) spring stiffness declines, this making itself manifest by the lowering of resonance frequency, b) spring damping declines, this making itself manifest by a higher peak in the amplitude frequency characteristic. Our experiments have shown that room temperature (environmental temperature) strongly affects internal temperature, too. A difference of several degrees of environmental temperature brings about a manifold difference of inside temperature. Thus external temperature indirectly affects the mechanical properties of the rubber spring. TO define the role of temperature in the nonlinear properties of the rubber spring, the spring was cooled by a stream of cold air so as to maintain an approximately constant temperature in it, i.e. to hinder its warming up. It appeared that under such conditions the response of the rubber spring system would not depend largely on the excitation level, nor on the direction of frequency change, so that such system approximately behaves as a linear one also under dynamic conditions. Further, it was our gndeavour to find an adequate mathematical model of the rubber spring shaped according to Fig.la, that would fit both the static and dynamic properties of the rubber spring as a real body, at least under conditions.of constant temperature. Since the dynamic stiffness of the rubber spring appeared to be greater than the static stiffness (by 2 0 up to 4 0 % ) and rose along with increasing frequency, we abandoned the model with one degree of freedom and chose

333

a model structure with one and a half degree of freedom according to Fig.lb, following some experiments with a more general structure. Parameter c1 (static stiffness) was defined by static measurement, parameters c2 and x were defined in the course of the optimization process. The sum of the squares of the differences between the measured complex frequency characteristics and the complex frequency characteristics of the model were taken as the optimization criterion, i.e. we minimized the expression

k=1 where U , ( uk), UM( dk)are the values of the real frequency characteristics, VEC dk), VM( uk)the values of the imaginary frequency characteristics experimentally ascertainsd (index El or calculated from the substitute model (index M), the parameters being c2, aC and the excitation frequency ak. Frequency characteristics measurement as well as parameter optimization were carried out with one spring having several diverse masses. The optimized parameters were subsequently averaged and with these mean values the frequency characteristics were calculated for the same load masses and plotted for comparison into a diagram together with the measured characteristics [6] It appeared that the model with one and a half degrees of freedom according to Fig.lb dislayed the dynamic properties of the rubber spring according to Fig.la relatively well up to a loading level of approximately 50% of the permissible load and in the domain outside resonance, when spring temperature would rise only slightly and, in consequence, its mechanic properties would not be changing much.

.

334

2.

The engineering provision of the automated measurement

and the estimation of

input and output signals of the

dynamic system by means of the CAMAC system In experimental investigations of the dynamic properties of vibroisolation systems and in identifying the mathematical models of any dynamic systems it is always necessary to measure and evaluate a large number of data (hundreds by order of magnitude), both in the time and frequency domains. This work is rather cumbersome, scarcely productive, the presence of the human factor being the source of errors, it literally calls for automation by modern technology. We are going to point out here the feasibility of applying an automated laboratory system for experimental data collection and processing controlled by a current minicomputer equipped with an external memory and standard peripheral input-output devices [8] The connection of the CAMAC crate to the minicomputer is presumed. To inform briefly: the CAMAC system is a universal interface system providing for on-line process control in real ,time at a very high level. Its basic principles are: modularity, independence on the hardware of the chosen computer type and of the measured or controlled process, multiplexity, compatibility. The CAMAC system is thoroughly standardized with accurately defined rules at the individual compatibility levels. It is a mechanical compatibility, i.e. the individual modules manufactured by diverse producers in the world may find application in arbitrary configurations. The compatibility of the connector is given by the use of unified types of connectors. Further there is the power supply compatibility, i.e. the units are .supplied by a unified line of power.from the crate source. The same is the case with signal and transfer compatibility, i.e. the levels of diverse signals and their timing are accurately defined.

...

.

335

The axis of the system is the standard information channel, the so-called crate dataway direct couplings to the active elements of the system, the so-called functional units. These are input-output units such as amplifiers, filters etc.

-

-

so-called crate controllers which connect control units the given system with the computer by mearls of the information channel, data processing units, such as analog-to-digital converters the digital-to-analog converters etc. The basic crate dataway provides for the interface between the functional units and the crate controller. The mechanical basic of the CAMAC system is thus a unified crate which, apart from the control unit and the power supply, may additionally include up to 23 diverse modules. In a current arrangement, the crate may be positioned either at the computer or at a maximum distance of 15 m from it. To program the system the CAMAC-BASIC language is available and it is possible to incorporate a subroutine written in assembler into the FORTRAN compiled program. The CAMAC system rests upon a broad international background, it has been set up and continues to be developed by the European organization ESONE (European Standards on Nuclear Electronics) , in cooperation with the American Committee for Electronics NIM. It has also been established as a IEC standard (International Electrotechnical Commission). It is gaining ground not only in Europe, but also in the USA, in Japan and Canada. At present, there are 1000 different functional units and modules available on the international market, produced by approximately 80 different firms. The socialist countries are taking their share by 100 types of different functional units supplied by four countries (Hungarian Peoplels Republic, Polish People's Republic, Union of Soviet Socialist Republics, Czechoslovak Socialist Republicl. The circuit diagram of a minicomputer-CAMAC set capable of performing, among others, the automated measurement of frequency characteristics, is shown in Fig.2.

336

Such system allows not only to measure and evaluate the measured values but also to control the set represented by the excited dynamic model. It also provides for a qualitatively new approach in following up the frequency characteristics at a constant spring temperature equal to the temperature of the environment, without artificial cooling, since it manages to scan frequency characteristics so quickly that the rubber spring practically cannot grow warm. The system can be similarly utilized in following up the dependence of frequency characteristics on temperature: the system with a cooled rubber spring will be set swinging at a fixed level of excitation and at the required frequency: the system keeps track of these parameters, retains aqd follows up the rise of temperature in the spring and, the defined value attained, it reads the corresponding quantities and evaluates the corresponding point of the frequency characteristic. It then lowers the excitation level, lets the spring cool down, resets the excitation frequency and repeats the cycle. Conclusion In our contribution we wished to underscore that in experimental research in problems of vibroisolation aside from current means of automated data collection and processing by coupling the device to programmable portable calculators or by minicomputers equipped with a more or less specialized interface for the experiment the CAMAC system linked up with a minicomputer has acquitted itself especially well. The advantages of the CAMAC system lie in its universality and in the wide range of manufactured modules, from which those can be chosen that best comply with the requirements of the given experiment that may be controlled by the minicomputer, through CAMAC, also in a closed loop.

337

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References [l]

Gabl, E.F.: Gummifedern, Berechnung und Gestaltung, Springer Verlag, Berlin - Heidelberg - New York, 1969.

[z]

Meltzer, G.: Die Beachtung nichtlinear Federkennlinien bei der Berechnung des dynamischen Verhaltens von Triebwerksaufhangungen in Kraftfahrzeugen, ATZ 71 (1969) 6, pp. 201-206.

131

Jenitzsch, J., Dresig, H., Horn, K., Krause, K.H.: Deformationsmechanisches Verhalten von Gummi, wiss. Z d. Techn. Hochsch. Karl-Marx-Stadt 1 5 (1973), pp. 359 379.

[4]

Poturaev, W. N., Dyrda, W.I., mechanika reziny, Kiev 1975.

[5]

Malter, G., Jenitzsch, J.: Gummifedern als Konstruktionselement, Teil 1 und 2 , Maschinenbautechnik 25 (1976) 3 und 5 , pp. 109-121, 225-228.

[6]

Krush, 1.1.

:

Prikladnaya

~ h m d r n yR., Tirinda P.: Dynamic properties of a System with rubber spring (In Russian), Proceedings of the XI-th Conference on Machine Dynamics, pp. 167-172, Liblice 1977.

[7]

[8]

Tirinda, P.: Contemporary problems of projection and application of rubber springs (In Slovak), In: Proc. of the Conference on "Damping and vibroisolation problems of mechanical systems", pp. 113-118, Smolenice 1977. Tirinda, P., Stein, J.: System CAMAC - the technical provisions of automating scientific experiments in machine dynamics (in Slovak), Proceedings of the Conference on "Dynamical and stiffness problems in machinery", pp. 216-221, Pezinok 1978.

a)

D x

b'

Fig.1

c1

cz

The shape of the investigated rubber spring and its dynamic model

339

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Diagram of automated experiment control by a minicomputer and the CAMAC system

BIFIXATION A S A DYNAMIC SELF-REGULATING SYSTEM E. S. Avetisov, A. M. Kotliarsky,V. A. Mochenov, I. L. Smolyaninova, K. V. Frolov, K. K. Glukharev, M. A. Belsky Helmholtz Research Institute of Eye Diseases and Mechanical Engineering Research Institute, Moscow, U.S.S.R.

SUMMARY A device has been created for recording binocular movements with electromagnetic transducer built into a contact lens. The position of the transducer is measured simultaneously along X and Y coordinates. A composite record of the movements of two eyes during fixation of a target has allowed to outline for the first time the a r e a of bifixation. Studies of eye movements in the act of bifixation may contribute to a fuller understanding of the various aspects of binocular vision and, in particular, of some compensatory oculomotor mechanism which operate s under vibration.

The conventional methods of studying the oculomotor and visgsl systems allow to record only monocular movements. Lately a device has been designed for registering binocular movements (V. I. Guselnikov, A.M.

Kotliarsky, E.S.

Kivayev, V. A. Barkov,

1975).

Avetisov, I.L.

Smolyaninova, A.A.

An electromagnetic transducer built into

a contact lens serves as the sensor. It operates in the field of coils fed from generators of sinusoidal voltage of variable frequency. This permits to measure the position of the transducer both in the horizontal and vertical planes with an accuracy of

-+

10 seconds of arc.

The

results of the measurements a r e processed in a computer and then the trajectories of eye movements a r e transmitted to an X-Y recorder.

341

Using the device, we have obtained for the first time a composite record of the movements of two eyes in the act of binocular fixation. The new method was employed to examine 11 normal subjects and 9 patients with disorders of binocular vision. It could be established that the movements of the same eye differ considerably during monocular and binocular fixation.

The composite

graph representing the divergence between the trajectories of the right and left eyes during binocular fixation outlines an area termed bifixation area. Normally, it consists of two parts: a dense central zone, or receptive fusion field, is surrounded by a rarefied peripheral zone, or reflexogenic corrective field. The farther the visual axis of an eye deviates from the dense zone, the greater a r e the chances of a corrective eye movement to return i t into this zone.

The bifixa-

tion area is oriented horizontally, Evidently this is due to higher sensitivity of the binocular visual system in the horizontal direction. The dense zone of the bifixation area has in average a vertical dimension of 3-4,

and a horizontal dimension of 5-10 minutes of arc.

In Figure 1 a r e shown the monocular movements of the right and the left eye: the right eye is fixing an immobile point, the left is closed. There is an analogous recording, but with the left eye fixing and the right

eye closed. The analysis of these two recordings dis-

closes substantial differences between the movenieiits of the closed and the fixing eye. The movements of the latter are characterized by the presence of a zone of consolidation (field of. monocular fixation) and a horizontal trend. Figure 2 shows the movements of the right and the left eye in the process of binocular fixation of an immobile point.

Attention is

attracted by the fact, important in its principle, that the movements of one and the same eye differ substantially under conditions of monocular and binocular fixation. Of particular interest is Figure 3 in which the movements of the right and the left eye coincide in the process of binocular fixation of the test object.

This coincidence permits to recognize a central

consolidated part which, evidently, corresponds to the zone of fusion

of monocular images, i. e. characterizes the receptive fusion field. Thus f o r the first time it became possible to obtain the field of bifixation.

The farther the visual axis of one of the eyes deviates from

the field of bifixation, the greater is the possibility of the generation of a corrective eye movement which will return t h e visual line into the field of bifixation. Two-dimensional histograms we r e constructed to demonstrate the distribution of probabilities f o r the position of visual axis during monocular and binocular fixation of a stationary point.

The histogram of

the dominating eye has a sharp peak, reflecting precise fixation and a low amplitude of movements (Fig. 4).

The histogram of the other

eye is flattened due to coarser fixation (Fig.5).

Even flatter is the

binocular histogram. Evidently the movements of two eyes in the act of bifixation a r e more variable than those of one eye duking monofixation.

This means that the receptive fusion field is wider than the

receptive field of one eye (Fig. 6). In subjects with normal binocular vision eye movements may be described as purposeful activity striving to place the eyes into the unique position which allows fusion, i. e. transfer of the image of the target being fixated on the foveae. Bifixation,

which may be defined

as a dynamic selfregulating system, maintains the image of the target within the fusion field during the entire period of viewing. (Fig. 7). This purposeful activity corresponds to a complicated sequence of events which may be briefly enumerated a s follows: (1) displacement of the image towards periphery, out of the foveal fusion field; ( 2 ) a change in the excitation (gradient and area) of visual cortex neurons; (3) a change in the discharges of motoneurons of oculomotor nerves; (4)

contraction or relaxation of the appropriate extraocular muscles;

(5) return of the image onto the foveal fusion field.

In patients with disorders of binocular vision the bifixation area is substantially altered: i t is oriented in the vertical direction, i t s di-

mensions are considerably larger ( 2 6 x 100 minutes of arc) than in

343

normal subjects, and, l a s t but not least, there is no rarefied zone. Since the latter zone functions as a reflexogenic corrective field surrounding the receptive fusion field, its absence means that no feedback signals a r e delivered to the visual cortex, evidently due to suppression of visual impressions in one eye. Interaction between the sensory and motor systems of the visual analyzer is clearly manifested in the phenomenon of binocular vision: fusion of monocular images is only possible if the eyes a r e placed in a certain position by the extraocular muscles, and their activity, in turn, depends on the regulatory influences of the sensory visual system. Bifixation is the link connecting the two systems. The above concepts of the role of bifixation in the physiology and pathology of binocular vision have led to the development of diploptics (E. Avetisov, 19771, a basically new system of treatment aimed at

restoration of binocular cooperation. Studies of eye movements in the act of bifixation may greatly contribute to a fuller understanding of the various aspects of binocular vision and, in particular, may help to elucidate some compensatory oculomotor mechanisms which operate under vibration.

P a s p a d o ~ anprndop ~ JIJIS p e r M c T p a y l l m ~NHOKYJIIIPH~IXABIUBHN l'JEt3 C 3ReKTPOMaPHETHhIM PBTPKKOM, BMOHTMPOBPHHbIM B XOHTPHTHYIO m~3y.M ~ M ~ P ~ H I nU o~ n m e m f l mmma 0 6 e c n e w ~ a ~orno)~c~ EPeMeUHO B OCRX X-Y. C O B M ~ I Q ~ H H B98IIPICb R ~ ~ ~ O ~HO E ~Pl'83 X I ~ ~ B I I P O ~ ~ C C Bdmox mp~ofi @mcaw~ 0 6 n e ~ ~1103~omna a BnepBHe nonysara none ba&uccaqlla. Ylayne~nee s a r e r t M rnss B npouecce dbI@HKcm MOXeT RaTb bICKJIH)rlEITeAbHO 48HFIfl ~ ~ H @ o P M B @ ~AJlR ~ D BbIa C H 0 k E W F3JIElYHbIX CTOPOH MeXaHP13Ma ~~IHOKYJUIPHOSQ3 p e H l l f f , B PaCTHOCTfl, HeKOFOPHX KOMIIeHCaTOPHbIX hRXaHM3MOB JLB~lgeHJllfi rm3 npn ~ m r d p a u m .

REFERENCES Guselnikov, V. I., nova, I. L.,

Kotliarsky, A.M.,

Kivayev, A. A.,

Avetisov, E. S.,

Smolyani-

Barkov, V. A. : Authors' certificate No.

5 17298, 1975. Avetisov, E.S. : Diploptics;

A new approach to the treatment

of concomitant strabismus. Vestnik oftalmol.

a

6, (1977

17-24.

Y

26"

d

a

Fig, 1.

X

Monocular recording of eye movements. a) right eye

b) left eye

-

-

during fixation of immobile point.

closed.

Y

~

X

Fig.2.

Recording of eye movements during binocular fixation of immobile point,

345

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-4

AY

-

AX

Fig.3.

Coinciding recording of the movements of both eyes during binocular fixation of the immobile point.

1

~ ( x , y ) ,minutes ( of arc)-*

om55 0.0044

"' Fig. 4.

Probability distribution histogram of trajectory movements in bifixation of dominating eye.

346

x. minutes of arc

P(x.y),(minutes of arc)-2

4W&I

4 4

x, minutes of arc

Fig. 5.

The other eye histogram.

x. minutes ot arc

Fig. 6-

Two-dimensional probability distribution of coinciding trajectory movements of both eyes during bifixation.

.

VISUAL CENTER

I Fig. 7.

+

TARGET

-

r-i

- EYE MUSCLE

-

RECEPTOR

EFFECTORS

A

REVERSE AFFERENTATION

FINAL SYSTEM EFFECT AND ITS DEVIATIONS

t J

Schematic representation of the functional self-regulating system of bifixation.

347

VIBRATION MACHINES AND MAN E. I. Shemyakin, N. P. Benevolenskaya, A. Ya. Tishkov The Mining Institute of the Siberian Branch of the Academy of Sciences ofthe U.S.S.R..Novosibirsk, U.S.S.R.

SUMMARY A review of the application of vibration machines in mining i s

givenzhe data of peculiarities of t h e i r effect on the human o r g a n i s m a r e analyzed; the t r e n d s of t h e i r development with due r e g a r d to the human factor a r e considered. In underground mining, the man-machine s y s t e m h a r d l y a p p e a r s favorable to human conditions and the struggle to achieve good conditions was complicated by a number of circumstances. The underground environment i s r a t h e r specific: n a t u r a l lighting i s absent, r e l a tive a i r humidity i s high, the oxygen content in i t i s reduced, the a i r coz tains few charged ions. Constant advancement of the face can r a t h e r considerably change environment medium and r e q u i r e s a l a r g e mobility of a l l the s y s t e m . The m a t e r i a l being worked upon is one of the m a i n s o u r ces of unfavourable f a c t o r s ; i t s c h a r a c t e r i s t i c s m a y a l s o a l t e r substantially with the changing physical and chemical p r o p e r t i e s of m i n e r a l s and t h e i r i m p u r i t i e s , The m a s s i v e solidity, the underground working s t r u c t u r e , the change in a i r density a t i n c r e a s i n g depths c r e a t e particul a r conditions f o r spreading of wave p r o c e s s . Automation and mechanization of a number of p r o c e s s e s s o m e t i m e s cannot be r e a l i z e d because of explosion hazards. A l l t h e s e complexities hinder the struggle against unfavourable f a c t o r s in mining which a r i s e when operating with vibration machines. Nevertheless, the Mining Institute of the S i b e r i a n B r a n c h of

the USSR Academy of Sciences has been conducting r e s e a r c h f o r y e a r s in unmanned ways of solving this problem. P a r t i c u l a r attention

has

been dedicated to the problem of the effects of vibration. P r o f e s s o r B. V. Sudnishnikov in his work a t the a b o v e m e n t i o n e d Institute, suggested and theoretically substantiated a new method to inc r e a s e the s a f e t y f r o m explosion of p e r c u s s i v e machines [ l ] . The method p r a c t i c a l l y excludes a main s o u r c e of vibration and a t the s a m e t i m e considerably reduces the n e c e s s a r y value of the p r e s s u r e . High production pick h a m m e r s , designed according to this principle, a r e light (50-

6 0 N), p r e s s u r e effort does not exceed 150-200 N, vibration p a r a m e t e r s on the h a m m e r handle a r e within l i m i t s p e r m i s s i b l e in the USSR. A t p r e s e n t the Institute is developing s e v e r a l b a s i c c i r c u i t s of pneumatic machines with dynamically'balanced percussive m e c h a n i s m that p e r m i t s realization of the mentioned method on a wide b a s i s in the production of p e r f o r a t o r s , concrete b r e a k e r s and otHer machines. In a number of c a s e s d e s i g n e r s have completely eliminated cont a c t of the o p e r a t o r with the machine. F o r instance, in semiautomatic d r i l l s HKP-lO,OM, the o p e r a t o r has no contact with the vibration and the application of an a i r and w a t e r m i x t u r e a s e n e r g y c a r r i e r has solved the problem of prevention of dust formation when drilling. R e s e a r c h of the Physiology Laboaatory [Z] m a d e i t evident that the d r i v e r s of mine e l e c t r i c locomotives, a t l o n g - t e r m work in underground conditions, m a y be subject to professional pathology with p r i m a r y involvement of o s t e o a r t i c u l a r apparatus and disturbances of the n e r vous, c a r d i o v a s c u l a r and m u s c u l a r s y s t e m s . Evidence of t h e s e changes depended upon the period of s e r v i c e in a given profession. I n the c a s e of the o s t e o a r t i c u l a r apparatus common effects w e r e : osteochondrosis, o s t e o a r t h r o s i s , l o r d o s i s , with the g r e a t e s t injury to the 4th and 5th l u m b a r v e r t e b r a e and d i s k s . According to the data of o u r r e s e a r c h e s t h e s e changes w e r e mainly generated b y the action of g e n e r a l and local vibration. To eliminate this a i l m e n t the Mining Institute of the S i b e r i a n B r a n c h of the USSR Academy of Sciences developed a s y s t e m of a u t o m a t i c control of mine e l e c t r i c locomotives, which f r e e s a considerable num_

349

b e r of w o r k e r s in this field f r o m underground work. A high percentage of the work t i m e of the m i n e r s i s given to

loading and supplying operations where vibration, noise and physical efforts a r e dominating f a c t o r s . A s e r i e s of vibrating supplying and loading devices, belts and conveyers, designed by the Mining Institute of the Siberian B r a n c h of the USSR Academy of Sciences, gives an example of the highly mechanized loading and supplying equipment. These m a chines g r e a t l y reduce the number of m i n e r s employed and eliminate h a r d manual labour. Vibration levels on the job f o r o p e r a t o r s of these machines a r e lower by 16-32 dB than the l i m i t s s e t in the USSR. In a number of c a s e s , f o r example a s c r a p e r used f o r o r e supply, the o p e r a t o r i s subjected to the action of local vibration which often exceeds p e r m i s s i b l e values, to considerable physical efforts, dense dustiness of a i r and various possibilities of t r a u m a . Another way to s h a r p l y reduce the vibration on m a n i s the c r e ation of s y s t e m s with d e c r e a s e d vibrating activity. We give, a s an ex ample the vibration machines of the Mining Institute of the S i b e r i a n Branch of the USSR Academy of Sciences, which u s e the principle of a travelling wave. A

thin long m e t a l plate can be compared with a c e r -

tain d e g r e e of approximation to a flexible band which can be considered s i m i l a r to a flexible thread. By applying variable loads to the band end oscillations o c c u r in it. During the f i r s t half-period (Fig. l ) , when the disturbing force is directed upwards, the band r i s e s to s o m e height above its support. In the section

Q - a,

a bend i s f o r m e d which i s displaced towards an op-

posite end a t a speed of vibration propagation along the band a s a r e s u l t of i t s elasticity. In the f i r s t half-period the disturbing f o r c e , moving along the band, r a i s e s by s t a g e s a l l the portions of the band above i t s support. In the following half-period the v i b r a t o r a t t r a c t s the band end to the support. The bend r i s e s in the p a r t which is propagated towards the opposite end. Thus in the band two f o r c e s a r i s e , equal in value and opposite in direction which a r e displaced relative to e a c h o t h e r in phase

by a half-period. These f o r c e s c r e a t e a t r a n s v e r s e travelling wave. A s i s shown in the diagram, to obtain the n e c e s s a r y oscillation

amplitude, the f o r c e applied need only be that required to bend the band a t the wave length and o v e r c o m e the m a s s of bulk load. This f o r c e i s considerably l e s s than that required f o r translational oscillations of the rigid t r a y of a vibrating f e e d e r under load. Consequently, the effect of this f o r c e on the support is also l e s s than that resulting in the i m p r o v e ment of the working conditions of an o p e r a t o r . L a r g e - s c a l e i n d u s t r i a l testing of vibration machines actually in use confirmed the fitness of the mentioned trend to c r e a t e vibrating f e e d e r s , conveyers and s c r e e n s . Such equipment finds m a n y applications in mining. The a f o r e s a i d examples proved the possibility of reducing the levels of acting vibration to s a f e values, A n o t h e r l o n g - t e r m direction m a y be the effect on p r o p e r t i e s of the object being m a d e and exactly on a m a s s i f . Our experience proves that moistening the coal in the s e a m not only reduces dust, but a l s o vibration p a r a m e t e r s by 3 - 8 dB and n e c e s s a r y p r e s s u r e on the pick h a m m e r by 50-70 N. The Mining Institute of the Siberian B r a n c h of the

USSR Academy of Sciences i s studying the p r o p e r t i e s of the m a s s i f and and creating s y s t e m s f o r forecasting i t s behaviour. However, in the fundamental effort to avoid vibration pathology, it i s n e c e s s a r y to introduce a sufficiently reliable o p e r a t o r into the "man-machine" s y s t e m . He need not p o s s e s s occult r e s i s t a n c e o r individual predisposition to vibration action. To improve the selection of o p e r a t o r s f o r vibration hazardous professions, we have c r e a t e d a s p e c i a l section

-

a L a b o r a t o r y of Prophylaxis of P r o f e s s i o n a l Pathology and a

number of additional t e s t s f o r diagnosis. The s a m e l a b o r a t o r y can diagnose peculiarities a r i s i n g in the c o u r s e of an adaptation p r o c e s s , depending on the duration of s e r v i c e i n a given profession. Thus o u r r e s e a r c h on the effect of vibrations on a l l the sections of the "man-machine

- object being m a d e - environment" s y s t e m allow

us to provide s a f e and reasonably comfortable working conditions, even if t h e r e should be an i n c r e a s e in range of the employment of vibration

machines in mining.

351

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REFERENCES

1.

Sudnishnikov B. V. a n d E s i n N. N.

- E l e m e n t s of D y n a m i c s of P e r c u s -

s i v e M a c h i n e s , Mining I n s t i t u t e of the S i b e r i a n B r a n c h of the USSR A c a d e m y of S c i e n c e s , N o v o s i b i r s k , 1965, 84 p. 2.

Benevolenskaya N. P.

-

Action of V i b r a t i o n i n O r g a n i s m of D r i v e r o f

Mine E l e c t r i c Locomotive. P r o b l e m s of Struggling Against Dust and Vibration i n I n d u s t r i a l P l a n t s , Nauka, Novosibirsk, 1 966.

Pt

Fig. 1

KINEMATICTYPE ACTIVE VIBRO-ISOLATION DEVICES

K.V.Frolov, A. V.Siqjov, V. S.Solovjov,J. G. Safronov Mechantcal Englneerlng Resmrch Institute, Moseow. V.S.S.R.

SUMMARY The p a p e r shows t h e a d v a n t a g e s of a c t i v e v i b r o i s o l a t i o n d e v i c e s of a s p e c i a l c l a s s , c a l l e d t h e v i b r o i s o l a t i o n systems based on a k i n e m a t i c p r i n c i p l e of o p e r a t i o n . The d e v i c e s a r e in te n d ed f o r t h e p r o t e c t i o n of an o b j e c t from t h e v i b r a t i o n s of a baoe. Fundamental e q u a t i o n s f o r h y d r a u l i c and pneumatic v i b r o i s o l a t i o n systems a r e given. Contemporary development of means of t r a n s p o r t , and especially the increase of

it5

speed, c a l l f o r q u a l i t a t i v e l y

new methods of combating t h e harmful e f f e c t s of v i b r a t i o n s on a human o p e r a t o r .

The i n v e s t i g a t i o n s c a r r i e d out a t t h e V i b r a t i o n s C o n t r o l L ab o r a to r y a t Gosniimash and o t h e r domestic a s w e l l as f o r e i g n r e s e a r c h c e n t r e s , show t h a t t h e f u n c t i o n a l i t y , and co n s e q u en t l y t h e e f f i c i e n c y and s a f e t y of a v e h i c l e o p e r a t o r depend c o n s i d e r a b l y on t h e i n t e n s i t y of v i b r a t i o n s r a n g i n g from 1 t o lOHz, which o v e r l a p s t h e main res o n an ces of t h e human body. Obviously, the- e x i s t i n g systems of v i b r o i s o l a t i o n w i t h

353

natural frequencies from 1 to 3Hz cannot significantly subdue the vibrations of the driver's

seat. This is why the

development and investigations of the active vibration control systems received recently so much attention. The active devices for vibration isolation implemented

In the transport and the production machinery consist of pneumatic, hydropneumatic and hydromechanical systems with mechanical feedbacks

- the relative position of

the base and

the object being the controlled variable. A detailed description of these systems can be found in

the literature 14, 6, 7, 0, 151. The proper operation of these systems ia ensured by special hydraulic dampers [ l J or throttle valves, arranged between the complementary and the act-

capacitance

elements of the pneumatic and hydraulic servo-controlled systems [4, 6, 7, 8 , 15, 161. The vibroisolating properties of the systems result from the presence of spring elements and dampers. The automatic-control system only maintains the relative static position of the isolated object and the vibrating base on the constant level regardless of the varying mass of the system. This is especially important in case of suspension systems of buses, fast through-trains, d e lux cars, multiwheelers (133, and vibration isolated operator's

seats and cabins.

There are some suggestions, given in the domestic papers 12, 5J, how to improve vibration isolation in the transport

and production machinery by the use of additional pick-ups and sophisticated regulators. However, the implementation of

354

the proposed s o l u t i o n s i s d i f f i c u l t because of t h e s p e c i f i c demands concerning r e l i a b i l i t y , c o s t , maintenance and energy d i s s i p a t i o n . Moreover, t h e r e i s no evidence t h a t new systems a r e s u p e r i o r t o t r a d i t i o n a l passive and a c t i v e means of vibroiso l a t ion.

The o b j e c t i v e of t h i s paper i s t o show t h e advantages and p o s s i b l e a p p l i c a t i o n s of one s p e c i a l c l a s s of a c t i v e

v i b r a t i o n c o n t r o l devices, r e f e r r e d t o as kinematic systems of v i b r o i s o l a t i o n , mainly used t o i s o l a t e an o b j e c t from t h e v i b r a t i o n s of a base. A g e n e r a l diagram of a similar one-way system i s shown

i n Figure 1. Picks-ups

3, 5

, regulator

6

and power u n i t

7 can employ any p r i n c i p l e of operation and can be arranged

i n a r b i t r a r y order. So, t h e outstanding f e a t u r e of the systems under c o n s i d e r a t i o n , i n comparison t o the used ones, a r e accelerometer ( 3 , 4 in F i g u r e 1). If an o b j e c t can be t r e a t e d as a r i g i d mass, t h e equa-

t i o n of equilibrium can be w r i t t e n as:

The r e l a t i o n s h i p between t h e f o r c e exerted by t h e power u n i t and t h e s i g n a l s generated by t h e pick-ups can be written i n double form: a ) without an i n t e g r a t i n g block i n the feedback loop:

b) w i t h a n i n t e g r a t i n g block i n t h e feedback: J.

355

Combining equation (1) with ( 2 a ) and (2b) we o b t a i n :

(kCa

+ m) 2 +

&+k where:

x

u

pa;

+

C,k

(i

Cv (x

-

+

- u ) + Cd

- o b j e c t displacement, - base displacement,

- o b j e c t mass, F - f o r c e exerted by

Cdk

(X

i"

-

(X

U)

(3a 1

= a(%

- U) dt

= O L q (3b)

0

m

K

-

Umg

the power u n i t upon t h e o b j e c t ,

s t i f f n e s s of t h e power u n i t ,

- weight

load i n s t a n t l y a p p l i e d t o t h e system,

- overload f a c t o r , g - a c c e l e r a t i o n of g r a v i t y ,

cc

Ca Cv Cd

- gain f o r the - g a i n for t h e - gain f o r

o b j e c t a c c e l e r a t i o n feedback path, r e l a t i v e v e l o c i t y feedback path,

t h e r e l a t i v e displacement feedback path.

For t h e h y d r a u l i c o r pneumatic d r i v e s t h e g a i n Cv c o n s i s t s of two components: one a s s o c i a t e d with t h e t h r o t t l i n g p r o p e r t i e s of t h e spool-type o r solenoid-type v a l v e , and t h e o t h e r ass o c i a t e d w i t h d i f f e r e n t i a t i o n of t h e r e l a t i v e displacement s i g n a l i n t h e feedback loop. Should a system be composed according t o eqn. output power a m p l i f i e r connected t o r e g u l a t o r

6

(3a) the could be a

p r o p o r t i o n a l block. A n e g l i g i b l y small e f f e c t of mass weight and i n e r t i a

f o r c e s r e s u l t s from t h e f a c t t h a t i n eqn.

(3a) t h e c o e f f i c i e n t

CaK i s much g r e a t e r t h e n m.

In t h e case of a system composed i n accordance t o eqn. (3b) an a d d i t i o n a l i n t e g r a t i n g block i s indispensable. The

356

Integration present In eqn. (2b) is performed in this case directly by a spool-type or solenold-type valves Incorporated

In the system. In the case of an electromagnetic drive, which shows no Integrating properties, eqn. (3b) can be obeyed by proper processing of the signals in the regulator. Small effect of gravitational and inertial forces is due to the fact that the term

in the equation is of higher

order, and is small in comparison with the other terms of eqn. (3b).

Now, we shall discuss eqn. (3b) in more details. The Laplace transform of eqn. (3b) yields the absolute transfer function of the system at

a =0 :

The displacement corresponding to the weight load at u = 0 13:

The notation used in formulae (4) and (5) is explained below: p = s/oo, s

- Uplace

transform variable,

1 /2

-

= (Cd/ca ) -

natural frequency determined by the control system,

5.: Cv/2w0Ca - nondimensional damping factor, oo =

(K/m

y/*-

natural frequency of the system: "moss suspended from the elastic drivett,

4t

=I

g/a?

- static displacement under full

load for a passive system of vibroisolation having natural frequency (do, ;K

1 7 . ~0 - nondirnensional psrameter, ("n a o d0

=(-

where Cawo I s another nondimensional parameter.

357

Analysis of formulae ( 4 ) and ( 5 ) permits t h e following conclusions t o be drawn. Unlike t h e passive systems, t h e systems under c o n s i d e r a t i o n a r e p r a c t i c a l l y i n s e n s i t i v e t o loads, and weights of elements i n p a r t i c u l a r . If t h e s t a t i c d e f l e c t i o n f o r t h e passive system subject-

ed t o t h e load (armg) i s a&., then t h e corresponding s t a t i c d e f l e c t i o n f o r t h e system under c o n s i d e r a t i o n would be n i l , as i t r e s u l t s from formula ( 5 ) , due t o t h e astatic p r o p e r t i e s

of t h e system [15J. The m a x i m u m d e f l e c t i o n from t h e pre-set p o s i t i o n is of t h e o r d e r of

*4t.

becomes s m a l l e r a8 t h e r a t i o

The c o e f f i c i e n t

aO/u1,

decreases and t h e nondimensional parameter Cawo increases. It i s evident from eqns. (3b) and ( 5 ) t h a t small

displacements following t h e a p p l i c a t i o n of the load, r e s u l t from t h e f a c t t h a t t h e i n e r t i a l f o r c e e n t e r s t h e equation as t h e term including time d e r i v a t i v e of

x of h i g h e r order,

which t o g e t h e r with proper s e l e c t i o n of c o e f f i c i e n t s Ca, Cv and c d makes t h i s term i n s i g n i f i c a n t i n t h e equation. Eventually, dynamic p r o p e r t i e s of t h e v i b r o i s o l a t e d object

.

influence, i n a *small degree, t h e o v e r - a l l v i b r o i s o l a t i o n

charac t e r i s t i c s

It should be noted t h a t t h e s t a b i l i t y condition 2 5 > %

(6) i a always f u l f i l l e d w i t h a g r e a t margin. We s h a l l consider now, a p p l i c a t i o n s of v a r i o u s types of

drives. Hydraulic power control. If we assume t h a t t h e l i q u i d i s incompressible then K

P

a0

, ‘K, =

0 and equations ( 1 1 and ( 2 )

are independent from each other. Formula (5) shows that the system is not displaced upon application of load. This simplified case i o widely used in the study of electrohydraulic means of vibroisolation 19, 141. Pneumatic power control. Consider a numerical example of vibroisolated seat for a human-operator with the following data :

The attenuation plot for the system TA = I W ( j 3 d i s shown in Figure 2, In the same picture the attenuation plot for the passive system with rigidly fixed mass and natural frequency

s=

2% l/sec (1.5Hz) and 0.35 is given. n =coo = J.5 Figure 3 shows the response of the operator’s seat in

0

the active system to the stepwise application of the load (the operator sitting down on the seat). calculated from formula (5) for

a=

The displacement was

57+20 c 7 / I

0.75,

For comparison a displacement for the passive system is plotted so that the superiority of the active system is clearly seen. The pneumatic power control system discussed in the example shows that the advantages of the active means of vibroisolation based on the kinematic principle consist in the fact that the stiffness of the pneumatic drive, treated as an elastic member, can be increased until it affects the geometric and force conditions, (For the natural frequency on o 3He the attenuation add displacements have smaller

359

v a l u e s t h a n corresponding v a l u e s f o r t h e passive system w i t h t h e n a t u r a l frequency

Wn

= 1.5Hz). The s t a b i l i t y of t h e

system i e ensured by accelerometer 3 (Figure 1 ) . No h y d r a u l i c darspers o r a d d i t i o n a l c a p a c i t a n c i e a a r e u t i l i z e d i n t h e system, s o t h a t t h e o v e r - a l l dimensions of t h e v i b r o i s o l a t i n g devices can be c o n s i d e r a b l y reduced a s i d e from e l i m i n a t i n g some design components. The improvement of v i b r o i s o l a t i n g p r o p e r t i e s of t h e considered means of v i b r a t i o n c o n t r o l i s a l s o p o s s i b l e by u t i l i z i n g t h e a c c e l e r a t i o n s i g n a l from pick-up

4

, attached

t o t h e o s c i l l a t i n g base (Figure 11,. This accelerometer gen’erates a s t a b l e s i g n a l , s o t h a t high g a i n s i n t h e c o n t r o l system l o a d i n g t o i t s i n s t a b i l i t y can be avoided [l21. (If t h e accelerometer i s mounted on t h e i s o l a t e d o b j e c t , t h e s i g n a l becomes weaker as t h e v i b r o i s o l a t i o n becomes more eff ec t i v e

.

I n t h e c a s e of multidimensional o b j e c t s improvement of t h e a c t i v e v i b r o i s o l a t i o n devices can be achieved by applicat i o n of multi-input-output

r e g u l a t o r s , with s i g n a l s from a l l

t r a n s d u c e r s worked out i n a r e g u l a t o r and s e n t t o a l l power u n i t s of t h e system [ l o , 1 1 , 123. The s t r u c t u r e of t h e a c t i v e means of v i b r o i s o l a t i o n based on kinematic p r i n c i p l e p e r m i t s t o a d j u s t mass, damping and s p r i n g c h a r a c t e r i s t i c s of the system w i t h t h e purpose t o f i n d i t s optimum p r o p e r t i e s .

CONCLUSION

The a c t i v e means of v i b r o i s o l a t i o n based on t h e kinematic

p r i n c i p l e of operation combine a q u a l i t a t i v e l y new e f f e c t of highly e f f i c i e n t v i b r o i s o l a t i o n p r o p e r t i e s with a g r e a t s t i f f n e s s t o f o r c e s exerted by t h e object. They a r e recommended f o r a wide a p p l i c a t i o n i n v a r i o u s f i e l d s of technology, e s p e c i a l l y i n t h e suspension systems of t r a n s p o r t v e h i c l e s , o p e r a t o r ' s c a b i n s and v i b r o i s o l a t e d s e a t s .

A. n. Re a p e m e p , ranpaanasecxtle aMo TEsaTopN aaroMob ~ e f i ,'$ma8OCTPOelul~", M O C R B ~ , 1969, %7 C [2] m a m a ciaorem mq o r a - w a - e ~ ~ o ~ o ~ m b - ~ o non ~ ~ epea. nb, A. A. XePeqpo~e, ~maaocrpoetlsett,Mooxsa, 1976, 535 c. [3] M a 3. K O J I O B C K ~ , Eienmema~Teopm mbposawrmx CKCTeM, "Ha a" , I ~ O C K B1966, ~, 317 C Me n b m o s , A. A, Y c n e ~ c x a ,II o e ~ ~ a p o n a mmes~ae L4] A. TFleCKIM POl[BeCOX, ~ O P M 1965, ~ , F! C [i]

.

F-Y

. Pymma [9]

ge

AxTasme sabpo3aq1lTme cmTem, 3xcn CC-PIHM c D H T ~ T ~ ~ ! ~ HnpLlb0PH EI~ a CTeertym 1 (1969)

B&TM,

D. r. c a g o ~ o ~A. , B. c m e ~ ,B. C. C O ~ ~ B M EMccxenosame , O ~ P I PBJIOaxexrportWpam.mecx& CzcTerm B ~ ~ ~ O P I B cmzesexa-onepazopa. B cb. nBmmme mbpaxwfi sa opramsM zrenosexa a upobmm mdposanwnrw, "Hay~a", Moc~sa,1974, 643655.

,

@] A. B. CaHeD, IIpA'l CJI

CmHTe3 BEbpO3a~THO~ CBCTeMbI TBepAOrO TeJIa afiHHX BO3nefiCTEllRx B ,ZI,BYXMePHO~ 3aJlaP8, &UXHOEe-

AeHXe r(1973) , 29-34

[la A B

CkWeB, CRHTe 3! I'IpClCTpaHC TEeHHOfi CkzC TeEH 9116p03aWTar TBepAOrO TeJIa DpZl C T w O H a p H H X CJrysa&iHX B03nefiCTssuut9

Hamqecxaa npomocri ~ J I ~ M ~ R T MBWH", OB "€Ia91(a0,HOCXBEL, 'I9 6, 7-29. BZ] A. B. CsmeB, B. C. Conosben, K. B. @OJIOB, Mccaegosahe a ~ x e ~ ~ p o r a ~ p a ~cncTew ~ ~ a ~ ecc ynpasmemeha xo~ no soshayrya~b q e g p o p e ~ ~ l r rB, . cb "BlIbp0381~pnfaYenoBexa-oneparopa n KQAe6aEIIIR B MaPIEIHBX" , "HayKatt, MOCKSM, 1977, 12-46 @YPYH;dCtleB, ~pO2IcTWpOBaHMe OIITPIMaJIbHbIX B t l d p O S ~ T ~ X b3] P, CtlCTeM, "BJm3~mamonatt, WCH, 196'7, 3i5 C. b4] 11. B. lllgdepT, P;a. PyxFiKa, TeOpeT91YeCKOe 'II 3KcnepHMeHTZUIbH O ~accaeAosaHme 3ae~~por1q1,pasmecxk!xBPI~POS~UIPITHHX mcTeM KomTpyRpomme M TeXHOAOrtlR M a ~ H O C T p O e H ~4R (4969) , 62-$4

B cd. ttKoae6am PI

B

.

[I

51 R.D.

.

.

Cavanaugh, Air suspension snd servocontrolled isolation systems, Shock and vibration Handbook, Harris and Crede, 1963, Vol. 2, Chapter 33, 33-1, 33-35.

[I 61 J. I. Soliman, Tajer-Ardabily, Self-damped pneumatic isolator for variable froquency excitatfon, J. Mech. Eng. Science, Vol. 8, No 3, (1966) pp. 264-291.

1171 G. Schulta, Active multivariable vibration isolation for an helicopter by decoupling and frequency domain methods, VII International Congress IFAC, Helsinki, 1978,

Fig. 1.

1.

Object to be isolated. 2. Vibrating base.

3, 4. Accelerometer. 5. Relative displacement pick-up. 6. Regulator. 7. Power control.

362

Fig. 2

X. cm

7.5

5.0

2.5

0 0

1.0

2.0

3.0

4.0

5.0

6.0

t.sec

Fig. 3

363

MINIMIZATIONOF TRACTOR-OCCUPANT'S TRAUMATICVIBRATIONAL RESPONSE BY MEANS OF THE" PATIL-PALANICHAMY-GHSTA" (PPG) TRACTOR SEAT SUSPENSION Mothiram K. Patil Biomedical Engineering Dlvision, Indian Institute of Technology. Madras, India

M. S . Palanichamy Structural Engineering Depenment, College of Engineering, Guindy, Madras. India

Dhanjoo N. Ghista Department of Mechanical Engineering and Engineering Mechanics, Michigan Technological University, Houghton, Michigan, U.S.A.

Summary It is shown that a newly developed ("PPG") tractor seat suspension system drastically improves the tolerance to high intensity vibrations in the 0.5-11 Hz range experienced by tractor occupants, by reducing (i) the maximum amplitude ratios and relative displacements of the body parts to 0.0876 and 0.12 mm respectively, and (ii) the body parts' acceleration to levels much below the IS0 specified discomfort limit.

INTRODUCTION

A tractor occupant is exposed to high intensity vibration levels in the 0.5-11 Hz (discomfort) range for extended periods of time, which he is not physically equipped to tolerate.

It is there-

fore, not surprising that a survey by orthopaedic surgeons in USA (Radke, 1957) establishes that truck and tractor drivers suffer from a number of disorders of the spine and supporting structures. Infact, high incidences of osteoarthritis, traumatic fibrositis, herniated disks, coccygodynia, lumbosacral pain, abdominal pain and intestinal disorders occur in drivers of trucks, tractors, motor cycles and other vehicles or machinery in which appreciable vibrations and jolts occur (von Gierke, 1959).

364

Vibration intensity is characterized by the amplitude ratio, acceleration level, and relative amplitude between the different segments of the body.

Any isolation of vibration by providing a

suspension should reduce all these characteristics.

It is seen

(Radke, 1957) that the acceleration levels in conventional tractors are of the order of 1.5g to 0.5g in the frequency range of 2 to 7 Hz, and standard seats (of different suspension parameters) give rise to amplitude ratios of 2.5 to 4.5.

These vibration

acceleration levels are of much higher intensity than the one minute '''exposure limits" proposed by the International Standard Organization (ISO).

It is no wonder that a tractor operator, who

has daily prolonged exposure to these vibration levels, suffers from a number of disorders of the spine and supporting structures. By suitably selecting the parameters, of a "standard" tractor seat suspension, the authors (Patil et a l l 1977) were able to reduce the amplitude ratio to 1.55 and the acceleration level to 0.99.

However, this is still higher than the one minute "exposure

limits" (in the frequency range 4

-

8 Hz).

Therefore, in this

paper, a new type of seat suspension (namely, the "Patil-PalanichamyGhista", or the "PPG" suspension, shown in Figure 1) is provided at the plane of the centre of gravity of the tractor, and its parameters are chosen such that the occupant vibration intensity (characterized by human body acceleration levels, amplitude ratios and relative displacements) is reduced to a minimum in the 0.5

-

11 Hz frequency range.

ANALYTICAL MODEL AND SIMULATION It is found that the measurement of vibration on the seat alone does not truly reflect the vibration level to which the

365

human body is exposed (Mathews, 1973).

Therefore, we have modeled

the occupant and the tractor (incorporating the "PPG" seat suspension) as a composite unit (idealized as a lumped mass system, interconnected by springs and dashpots); this composite model is analyzed by computer simulation for vertical vibrations of body parts and the seat. The tractor occupant is idealized as a lumped parameter nonlinear model of Muksian et al. (19741, which is modified in our study to also include the damping and elasticity of the buttocks. As shown in Figure 1, the lumped masses (of head, back, torso,

thorax, diaghragm, abdomen and pelvis) are connected by springs and dashpots, representing the elastic and damping properties

of the connective tissue between the segments.

The validity of

this model is established (Palanichamy et al,, 1978) by good agreement between our model response and that recorded experimentally by other investigators. The tractor is idealized (as shown in Figure 1) by the seat, chassis body and tire masses (lumped together).

The para-

meters for the tractor (namely the inertia properties of the components, the tire elastic and damping coefficients) are adopted from Mathews (1967). The tractor seat is provided with the "PPG" suspension (as shown in Figure 1, at the plane of the centre of gravity of the tractor), consisting of a compression spring (Ksb) and a leaf spring (Kst) in parallel with a dashpot (Cst), acting in opposite directions to each other.

The PPG seat suspension

parameters are determined (by computer simulation) so that the resulting responses of the human body parts (characterized by acceleration responses, relative displacements between body parts and amplitude ratios) are minimized.

366

The composite model of the human occupant seated on the tractor seat (schematized in Figure 1) is analyzed (by computer simulation) for ( 2 ) steady state vertical responses (characterized by amplitude ratios and acceleration levels) of body parts, to sinusoidal vertical vibrational inputs applied to the tractor tires (representing the dynamic ground reactions due to the traversing of the tractor’s wheels over a furrowed field), and (ii) transient vertical vibrational responses of the body parts and the seat, to a suddenly applied disturbing force to the tires (idealized as a trapezoidal shaped function), due to a sudden obstruction encountered by the tractor. The governing equations of motion for each mass consists of the inertia force term (due to the acceleration of the mass) and the force exerted on the mass (by the inter-connecting springs and dashpots) due to its relative motion with the adjacent masses. The resulting coupled nonlinear ordinary differential equations are programmed on the IBM 370/155 computer and, by using the Continuous System Modelling Programme (CSMP), are solved to give

i.I0

(the accelerations of body parts) and yi (the body displacements

at different frequencies of vibrations).

The resulting responses

of the body segments are further studied in order to select the best parameters of the suspension system, by ensuring that the acceleration responses, amplitude ratios and the relative displacements between body segments are uniformly minimized in the 0.5 to 11 Hz frequency range.

It is found that the body segments’

vibration intensity responses are minimum for the I’PPG” seatsuspensionpara:neters values of K st = 686.7N/cm, Ksb = 689.2N/cm, and Cst = l.l16N/cm/sec.

367

RESULTS AND CONCLUSIONS

Herein, only representative results are presented.

Figure

2 shows the variations of amplitude ratios of the diaphragm,

thorax, torso and head with the frequency of vibration, when the tractor is equipped with the "PPG" seat suspension at the plane of its centre of gravity.

It is found that, among the body

parts, the torso has the highest amplitude response (at a frequency of 3 Hz) and the new (PPG) suspension (with the optimal selection of parameters, reported above) reduces the maximum amplitude ratio of the body parts to a value of 0.0076. By way of comparison, Figure 3 represents the variations of amplitude ratios of the thorax, diaphragm, torso, and head with the frequency of vibration, when a standard seat suspension is provided to the tractor.

It is seen that the provision of a

standard seat suspension could only reduce the amplitude ratio to a value of 1.55.

In fact, by comparing the responses of the

amplitude ratios obtained by the optimized @'PPG" suspension system with those obtained by other suspension systems, it is found that the PPG seat suspension is the most effective suspension: it reduces the maximum amplitude ratio to a near zero value, thereby effectively isolating the tractor occupant from the harmful vibrgtions. It is also seen that the maximum relative displacement between body parts (torso and back) is of the order of 0.012 cm for the "PPG" seat suspension (provided at the plane of the center of gravity of the tractor), as compared to a value of 0.11 cm in the case of the "standard" seat suspension. Figure 4 represents the variations of acceleration levels

of the diaphragm, thorax, torso and head with the frequency of

368

vibration, for the "PPG" seat suspension (provided at the plane of the C.G. of the tractor).

Also plotted in this figure is

the 8 hour "reduced comfort boundary curve" proposed by the International Standards Organization (ISO). It is noted that the peak acceleration response, recorded with the "PPG" system, is outside its discomfort zone.

Indeed, the maximum acceleration

level for the body part (thorax) is only of the order of 11.8 cm/sec2 (for the above suspension) a s compared to a value of 9 m/sec2 in the case of standard seat suspension (Patil et al,

1977), demonstrating an order-of-magnitude improvement afforded by the "PPG" system. From the computed steady state and transient responses, it is found that provision of the "PPG" seat suspension at the.plane of centre of gravity of the tractor, with an optimal selection of its parameters, reduces (i) the amplitude ratios of body

parts to 0.0076, (ii) the relative displacements between body parts to a value of 0.12 mm, and (iii) the acceleration of body parts to levels below the 8 hour "reduced comfort boundary curve'' proposed by ISO, thereby providing best riding comfort to the tractor driver.

On montre qu'une suspen5ion pour si&ges de tra7tcur de nou( ~ ~ P P G I I )autl iore rorteuieii t l a tolerance a.ux vibrations d haute inkensite dins Ic doiuainy 0 , 5-11 Hz ress e n t i e s par l e ? occupants clu tracteur. L'amelioration e s t ohtenue par l a reduction (i) des r a p p o r t s n i a x i m a w s d'auiplitude 0,0076 e t des displacements r e l a t i f s dcs parties du corps e t 0 , 1 2 min respectivenlent, e t (ii) ,de l ' a c c & l & r a t i o nd:s part i e s du corps a un niveau tres inforiour & l a l i m i t e d inconf o r t specifide par ISO. voile conception

369

REFERENCES 1.

Mathews, J., "An analogue computer investigation of the potential improvement in tractor ride afforded by a flexible front axle", Journal of Agricultural Engineering Research, 12 (11, 48-54, 1967.

2.

Mathews, J., "The measurement of tractor ride comfort", SAE Meeting, Milwaukee, Wisconsin, paper No. 730795, 1-16, 1973.

3.

Muksian, R., and Nash, C. D., "A model for the response of seated humans to sinusoidal displacements of the seat", Journal of 'Biomechanics, 7, 209-215, 1974.

4.

Palanichamy, M. S., Patil, M. K. ation of the vertical vibrations ator, by provision of a standard Annals of Biomedical Engineering 1978.

5.

Patil, M. K., Palanichamy, 14. S. and Ghista, D. N., "Dynamic response of human body seated on a tractor and effectiveness of suspension systems", SAE Meeting, New Orleans, Lousiana, Paper No. 770932, 755-792, 1977.

6.

Radke, A. O., "Vehicle vibration ASME paper, 57-A,' 54, 1957.

7.

von Gierke, H. E., "Transmission of vibratory energy through human body tissue", Proc. First National Biophys. Conference, Yale University Press, New Haven, Connecticut, 647-688, 1959.

370

and Ghista, D. N., "Minimizsustained by a tractor opertype tractor seat suspension" (In Press), Vol. 6, No. 2,

. . . . man's

environment",

1

-

Fig. 1 Occupant t r a c t o r model with a'sPatil-Palanichamy-Ghista" s u s p e n s i o n system.

0.009 ' 0008-

-

Fig. 2 Amplitude r a t i o s of dlaphragm, t h o r a x , t o r s o and head f o r t h e PPG t r a c t o r seat s u s p e n s i o n p r o v i d e d a t t h e p l a n e of c e n t r e of g r a v i t y o f c h a s s i s .

8 HOURS 'REPWED COHFORT

t

.~

Fig. 3

-

FICOULNCV

IN Ha

Amplitude r a t i o s of ( a ) t h o r a x and diaphragm, ( b ) t o r s o and head f o r t h e s t a n d a r d t y p e of t r a c t o r s e a t s u s p e n s i o n (from P a t i l e t a l , 1977).

FREOUENCV

N

HX

-

F i g . 4 - Comparison of IS0 8 h o u r s ' r e d u c e d c o m f o r t boundary' c u r v e and t h e a c c e l e r a t i o n r e s p o n s e s of human body p a r t s f o r t h e PPG seat s u s p e n s i o n a t p l a n e of C.G. of c h a s s i s .

371

THE NIAE SUSPENDED CAB TRACTOR A. K.Dale The National Institute of Agricutural Engineering, Silsoe, England

The problem o f v i b r a t i o n i n the operation of a g r i c u l t u r a l t r a c t o r s i s discussed with reference to surveys o f the medical and workrate aspects i n addition t o surveys o f t r a c t o r usage and measured v i b r a t i o n levels under f i e l d conditions. An experimental suspended-cab t r a c t o r , which has been designed and b u i l t a t the National I n s t i t u t e o f Agricultural Engineering (N.I.A.E.), described.

is

Results are presented of r i d e measurements made on this vehicle,

w h i l s t towing a loaded 2-wheel t r a i l e r , which showed an improvement i n r i d e quality when the suspension was operating compared with when i t was locked.

Introduction The high incidence of s p i n a l disorders amongst t r a c t o r d r i v e r s has been reported by several researchers. i n Germany.

The f i r s t of these[l]

Two comprehensive s t u d i e s were made

showed t h a t t r a c t o r d r i v e r s were more

l i k e l y t o s u f f e r spinal and i n t e s t i n a l disorders than almost any o t h e r group of workers.

372

The second study [2] examined a group of t r a c t o r d r i v e r s using

X-ray photography a t the o u t s e t of t h e i r c a r e e r s and again after 5 years.

This showed a s i g n i f i c a n t increase i n s p i n a l damage or abnormality.

The

increased damage occurred predominantly i n the lumbar region o f the s p i n a l column.

The high l e v e l s of vibration experienced by the d r i v e r s

was considered t o be an important contributory f a c t o r .

I t has been shown [3] [ 4 ] that r i d e v i b r a t i o n d i r e c t l y influences working speed of the t r a c t o r by inducing discomfort and l o s s of control i n a number of a g r i c u l t u r a l tasks.

T h i s e f f e c t l e a d s t o under r e a l i s a t i o n of

the c a p a b i l i t i e s of t r a c t o r and machine because speed i s r e s t r i c t e d t o keep vibration t o acceptable levels.

I n a recent survey by Stayner and Bean 151,

l i n e a r v i b r a t i o n was measured on the pan, between s e a t and d r i v e r , i n 3 mutually perpendicular d i r e c t i o n s : v e r t i c a l , l a t e r a l and longitudinal r e l a t i v e t o the motion of the t r a c t o r .

The vibration was weighted by the

human s e n s i t i v i t y functions defined i n the I.S.O. N.I.A.E.

Guide [6] using the

Mk I1 Ridemeter [7I.

The N.I.A.E.

has expended a large e f f o r t i n a continuing research

p r o j e c t to improve operator r i d e comfort i n t r a c t o r s and a p a r t of t h i s work has r e s u l t e d i n an experimental t r a c t o r on which the complete d r i v e r ' s cab is suspended from the t r a c t o r chassis.

T h i s paper describes the

suspended cab t r a c t o r and demonstrates the improvement i n r i d e which i t gives f o r the common a g r i c u l t u r a l task of hauling a t r a i l e r .

The suspended cab t r a c t o r The design, development and operation of the suspended cab t r a c t o r has been comprehensively described elsewhere [8]

191.

B r i e f l y , the experimental

vehicle i s based on a standard 95 kW 2-wheel drive t r a c t o r , on which the cab

373

i s suspended i n t h e 3 axes of v e r t i c a l , r o l l and p i t c h .

A g e n e r a l view of

the t r a c t o r i s shown i n Figure 1 and the d e t a i l s of t h e suspension a r e shown i n Figure 2 . The cab i s supported on an Lnclined p e d e s t a l a t the r e a r of t h s t r a c t o r chassis, which can be incorporated without i n t e r f e r i n g with the 3-point linkage and l i f t arms,

P a r a l l e l links guide the v e r t i c a l motion of the cab

controlled by rubber t o r s i o n s p r i n g elements, mounted on the rear pedestal. On the forward ends of the l i n k s i s c a r r i e d a l a r g e Booke's j o i n t , the bearings of which are replaced by rubber t o r s i o n springs. j o i n t c g r r i e s the cab.

T h i s Hooke's

Separate p a i r s o f hydraulic dampers are provided f o r

each suspension freedom.

The n a t u r a l f r e q u e n c i e s of the suspensions a r e

0.8 Hz, 0.6 Hz and 0.5 Hz i n v e r t i c a l , p i t c h and r o l l r e s p e c t i v e l y . A study of s u b j e c t i v e t r a c t o r d r i v e r s ' opinions of t h e suspended cab t r a c t o r '1103 has l e d t o the r o l l suspension being locked because t h e operators f e l t too i s o l a t e d from the machine and l e s s a b l e t o c o n t r o l operations. Experimental measurements Some comparative measurements of the r i d e performance of the suspended cab t r a c t o r have been made f o r a small number of a g r i c u l t u r a l t a s k s which did n o t include towing t r a i l e r s .

Exact s t a t i s t i c s of times s p e n t by t r a c t o r s

on various t a s k s are d i f f i c u l t t o o b t a i n b u t one important trend, which has been noted i n some attempts t o o b t a i n these s t a t i s t i c s [ll][12J [t3] i s the high percentage of time spent on t r a n s p o r t tasks.

Much of t h i s time will be

spent coupled with a t r a i l e r , s o t r a c t o r r i d e v i b r a t i o n and the e f f e c t on t h e operator under these c o n d i t i o n s i s of considerable importance.

In t h i s s t u d y the r i d e i s o l a t i o n of the suspended cab t r a c t o r was measured when towing a loaded 2-wheel unbalanced t r a i l e r a t h i g h speed over

a consolidsted farm track.

The r i d e was messurod with the cab suspension

o p e r a t i n g i n t h e v e r t i c a l and p i t c h freedoms and again with t h e suspensions locked.

374

The speed chosen f o r the experimental runs was 221an/h and was the

f a s t e s t a t which the d r i v e r f e l t reasonably comfortable f o r short periods. Vibration was measured i n v e r t i c a l , l a t e r a l and longitudinsl d i r e c t i o n s using the Ridemeter and i n v e r t i c a l , l a t e r a l , longitudinal, r o l l and p i t c h recorded on a portable F.M.

tape recorder for subsequent analysis.

A full

description o f the measurement equipment and procedure i s given elsewhere [14]. A l l accelerations were measured a t the base of the d r i v e r ' s s e a t

The o v e r a l l dimensions and weight d i s t r i b u t i o n s of the t r a c t o r and t r a i l e r a r e shown i n Figure 3. Experimental r e s u l t s The tape recorded r i d e accelerations were frequency analysed and t h e r e s u l t s f o r the t r a n s l a t i o n a l axes

are shown i n Figures 4 and 5 and f o r the

r o t a t i o n a l axes i n Figures 6 and 7 .

These s p e c t r a were each averaged over

41 seconds and the trequency r e s o l u t i o n i s 0.048

Ez.

Table 1 shows the comparison of Ridemeter r e s u l t s f o r the two experimental conditions. Table 1 .

Ridemeter frequency-weiphted r i d e accelerations. Speed = 22 km/h

lateral

vertical

longitudinal

Suspension operating

0.09

0.1

0.13

Suspension locked

0.12

'0.16

0.15

Discussion The cab suspension was designed t o give the lowest n a t u r a l frequencies practicable.

These n a t u r a l frequencies are limited because the lower the"

frequency the g r e a t e r the suspension t r a v e l and hence the l a r g e r a r e the necessary clearances,

Additionally a t low frequencies the phenomena of

motion sickness i s encountered and the d r i v e r may a l s o experience c o n t r o l ,

,

375

difficulties.

I n f a c t , the n s t u r a l frequencies of the suspended csb t r a c t o r

wera governed by cab clearance c r i t e r i a . The r i d e s p e c t r a i n F'igures4-7 give d e t a i l e d inforlustion on the dynmic behaviour of the vehicle.

To a s s i s t with the i n t e r p r e t a t i o n 3f these f i g u r e s

the frequencies of the two p ~ d o m i n a n tpeaks f o r esch s p e c t r a a r e given i n Table 2. Table 2.

Major s p e c t r a l peaks

-------

-----,

Suspension locked

Suspension f r a e

-

Axis msin peak

second peak

msin pesk

second peak

2.8 Hz

2.2 az

1.6 Hz

3.0 Hz

vertical

1 1

--

longi~~dinal

1. 5 Hz

3.5 Hz

2.8 Hz

lateral

1.0 Hz

5.9 HZ

1.0 Hz

3,OHz

2 L - 1

L~~[-[~~EIZ

2.2 Hz

2.8 Hz

1.0 Hz

-----

5.1 Hz

!

2.8 Hz

The three axes of v e r t i c a l , longitudinal and p i t c h a r e coupled and a r e b e s t considered together.

I n the case of v e r t i c a l and p i t c h the r e s u l t s are

f a i r l y straightforward producing i n esch case an a t t e n u a t i o n i n the s p e c t r a and a reduction i n frequency of the main s p e c t r a l peaks.

The a c t i o n i n the

longitudinal a x i s is l e s s easy t o understand a s the predominant frequency increases.

The behaviour with the suspension locked i s i n accord with other

findings [15] i n showing a r e l a t i v e l y low (1-2 HZ) main fraquency.

When the

suspension i s released this motion i s heavily attenuated by the p i t c h fnedom and shows up a s energy i n the p i t c h spectrum.

However, the coupling of the

system now produces a peak a t 2.8 Hz i n l o n g i t u d i n a l r e l a t e d t o the p i t c h and v e r t i c a l motion of the t r a c t o r .

376

The spectra of l a t e r a l and roll accelerations show l i t t l e differance i n

the t w s experimental conditions.

I n roll the spectra i s broad-band w i t h the

l a r g e s t peaks between 2 and 3 Hz. 5

n a i n peak a t 1.1 Hz.

The l a t e r a l spectra a r e a l s o broad-band with

I n both r o l l and l a t e r a l there i s a peak a t about 6 Hz.

which i s heavily attenuated when the suspension i s operating.

T h i s seems

strange i n view of the f a c t t h a t v e r t i c a l and p i t c h suspension should have l i t t l e e f f e c t on e i t h e r roll or l a t e r a l and t h i s may be due t o a C o r i o l i s e f f e c t 3s suggested i n an e a r l i e r report [g]. The performance o f the cab must be judged by the difference i n ride q u a l i t y experienced by the d r i v e r and t o t h i s end the spectra i n f i g u r e s 4-7 should be c o n s i d e n d with the i n f o r m t i o n i n IS0 2631 [16].

T h i s guide applies

only t o the t r a n s l a t i o n a l axes and i n the cases of v e r t i c a l and longitudinal the main frsquency content i s moved t o a less s e n s i t i v e region of the spectra. T h i s r e s u l t is r e f l e c t e d i n the ridemeter r e s u l t s .

The advantage o f the

Ridemeter i s t h a t i t gives a quick. estimate o f r de s e v e r i t y which i s e a s i l y understood.

Reference t o Table 1 a f f o r d s a simple conparison o f the r i d e

q u a l i t y o f the t r a c t o r under the two experimental conditions and shows a reduction of the v e r t i c a l and longitudinal R.M.S.

31% respectively.

accelerations by 25% and

There i s a s l i g h t reduction i n the l a t e r a l acceleration.

These r s s u l t s appear t o be disappointing i n the l i g h t of previous results

[

1.

Table 3 shows Ridemeter R.M.S.

alone over the N.I.A.E.

vibration l e v e l s for the t r a c t o r

undulating t r a c t o r t e s t tracks [17] [l8].

Tne high a t t e n u a t i o n found here of up t o 7% has also been obtained for a limited range r e a l of a g r i c u l t u r a l operations. T h i s t e s t was d e l i b e r a t e l y an extreme test of the c a p a b i l i t i e s of :his

machine.

A comparison of the weighted R.M.S.

the survey data ( t a s k 16)

given in [ 51 shows

this experiment were very high.

accelerations i n Table 1 with t h a t the levels encountered i n

Accelerations i n both horizontal axes without

suspension were higher thsn any encountered i n the survey and the v e r t i c a l

377

Direction of vibration

Suspended cab t r a c t o r

Conventional t r a c t or

t

Suspension locked

suspension free

Vertical (m/s2)

1.25

1.25

0.45

Pitch ( rad/s2)

1.45

1.35

0.80

Roll ( rad/s2)

1.40

1.50

1.50

Direction ofvibration

Conventional tractor

Suspended cab t r a c t o r Suspension locked

V e r t i c a l (m/s2)

1.75

1.15

Pitch ( rad/s2)

1.70

1.30

Roll ( rad/s2)

1.05

1.45

7, suspension f Fee

The reasons why the suspension i s less e f f e c t i v e i n the r o l e of t r a i l e r transport merit f u r t h e r i n v e s t i g a t i o n i n view of the importance of t h i s task. The sus ension i s now becoming s l i g h t l y worn and t h i s may be a contributory factor.

The machine will be overhauled during the winter of 1978/9 and i t

i s hoped t h a t a comprehensive investigation of the tractor/trailer/suspension system w i l l then be done i n order t o understand the complex dynamics of t h i s configurstion and so a i d the deslgn of a 2nd generation suspension. Conclusions The suspended cab t r a c t o r has been shown t o s i g n i f i c a n t l y reduce r i d e vibration levels i n

378

B

severe case of a very comnon t r a c t o r operation.

The suspension does n o t simply a t t e n u a t e the r i d e a c c e l e r a t i o n s but

alters the frequency s p e c t r a o f the v i b r s t i o n i n a favourable manner from the point of view of the o p e r a t o r ’ s vibration s e n s i t i v i t y . Attenuation of the ride i s not as e f f e c t i v e i n this p a r t i c u l a r operation

as has been encountered i n o t h e r tasks.

Le prob1.ihe de 15 y i b r a t i o n dans 1’ophra;ion des t r a c t e u r s a g r i c o l ? s e s t considere en rapport avec des etudes des a s p e c t s de l a medicine, de l a cadelme du t r a v a i l , des heures de t r ? v a i l du t r a c t e u r e t d e s niveaux de v i b r a t i o n e n r e g i s t r e s sous regim e de marche normale. Une cabine exp6rimentale s u r p l a t e - f o r a e susp?ncp~e, cr?npua e t r e a l i s & au N.I.A.E. e s t d d c r i t e . L a yabine a e t e montee s u r un t r n c t e u r qui remorquait un wagon a deux roues: Le l e c t y e des instruments a t t a c h h s & c e t t e cabine a montre +a d i f feren$e quand l a suspension G t a i t l i b r e e t qu-d e l l e etait bloquee. L e s . r & s u l t a t s ont indiqu6 une am6lioration i m p o r t q t e en ce qui concerne l e c o n f o r t du conducteur avec l a suspension libre.

References Rosegger, R. and Rosegger, S. Health e f f e c t s o f t r a c t o r driving. agric. Engng. Res., 1960, 5, 3, 241.

J.

Dupuis, H. and C h r i s t , W. Untersuchung der Moglichkeit von Gesundheitsschadigungen i n Bereich der Wirbelsaule bei Schlepperfahrern. (Study of the r i s k of s p i n a l damage t o t r a c t o r d r i v e r s ) , 1966, Report, Max-Planck-Institute Landarb., Landtech, Bad Kreuznach. Ministry o f Agriculture, Fisheries and Food. The use o f large horsepower wheeled t r a c t o r s 1966-1 968, 1968, NAAS Technical Report No. 17. Gibbon, J.M. and Boyce, D.S. T r s c t o r operators survey, Dep. Note DN/SY/I23/1952, Natn. I n s t . agric. Engng., Silsoe, 1971 ( m p u b l . ) . Tractor r i d e i n J e s t i g a t i o n s : a survey Stayner, R.M. and Bean, A.G.M. of v i b r a t i o n s experienced by d r i v e r s during f i e l d work. Dep. Note DN/E/578/1445, N a b . I n s t . a g r i c . Engng., S i l s o e , 1975 ( m p u b l . ) I n t e r n a t i o n a l Standards Organisation. Guide f o r the evaluation of human exposure t o whole-body vibration. I S 2631, 1973. Stayner, R.M. and Hartshorn, R.L. The N.I.A.E. Note DN/E/564/1445, Natn. I n s t . agric. Engng.,

Mk I1 Ridemeter. Silsoe, 1975

379

[8]

Stayner, R.M.; Hilton, D.J. and Moran, P. P r o t e c t i n g the t r a c t o r d r i v e r from low-frequency r i d e vibration. tlOff-highway vehicles, t r a c t o r s and equipment.”, Vol. CP 11/75 I. Mech. E. London.

[91

Hilton, D . J . ; Moran, P. Experiments i n reducing t r a c t o r r i d e vibration with a cab suspension. J. agric. Engng. Res. (1975)20, 4.

[lo]

Barber, T.S. The“ suspended cab t r a c t o r : Subjective assessment of the Natn. r i d e with and without r o l l danpihg. Section Note 3/77/1445. I n s t . a g r i c . Engng., S i l s o e , 1977 (unpubl.).

[ll]

Farm transport requirements and t h e i r e f f e c t on t r a c t o r F y e r , M.J. design. Dep. Note DN/TC/426/1400, Natn. I n s t . agric. Engng, S i l s o e , 1973 (unpubl. )

[12]

Moran, P.; Manby, T.C.D. Materials handling i n a g r i c u l t u r e . Traffics b i l i t y of vehicles and demountable container systems. Dep. Note DN/ER/705/1300, Natn. I n s t . agric. Engng, S i l s o e , 1976 (unpubl.).

[13]

The t r a c t o r requirements of a sample of large farms Taylor, U.3.H. i n England and Wales. MSc. Thesis, University of Manchester, 1972.

[14]

Dale, A.K. The measurement and s p e c t r a l a n a l y s i s o f a g r i c u l t u r a l vehicle r i d e v i b r a t i o n s a t N.I.A.E. Dep. Note DN/E/835/02005, Natn. Inst. a g r i c . Engng, S i l s o e , 1978 (unpubl.).

[15]

The r i d e v i b r a t i o n of t r a c t o r t r a i l e r Crolla, D.A.; Dale, A.K. combinations. Dep. Note DN/ER/915/OT005, Natn. I n s t . agric. En-, Silsoe, 1978 (unpubl.).

[16]

The I n t e r n a t i o n a l Standards Organisation (ISO) A guide f o r the evaluation of human exposure t o whole-body vibration. Geneva: IS0 2631 -1 974.

.

[I71 B.S.I.

B.S. 4220 Part 1 , 1974. Methods of tests f o r seats on agricult u r a l wheeled t r a c t o r s . P a r t 1 : Tests on a r t i f i c i a l track.

[18]

380

Dale, A.K. Spectral a n a l y s i s of the N.I.A.E. undulating t r a c t o r test track. Dep. Note DN~/897/02005, Natn. Inst. agric. Engng, Silsoe, 1978 (unpubl.)

.

Fig. 1. Diagrammatic view of the suspended cab t r a c t o r .

F i g . 2. The cab 8U8penslon.

381

D

1,

I

2060 kg

Fig. 3. T r a c t o r - t r d l e r parameters.

382

LATERAL

LO.000

-

N

I \

hl

m

0

s

-

0

fn n

-

5.0000 A *

0.0

-_

Hz

I

I~

12.000

LONGITUDINAL

15.000

r

\ (v

en

0

s

a

n

5.0000

0.0

HZ

12.001

VERTICAL

90.000

10.000

Fig. 4. T m n s l a t i o n a l r i d e s p e c t r a w i t h locked suspension.

383

45.000

LONGlTUDl NAL

1

0.0

Hz

12.00(

VERTICAL

90.000 L

P

& cn

(*

8 P

u)

n

10.000

0.0

HZ

Pig. 5. Translational ride spectra w i t h free suspension.

384

12.N

ROLL

7,0000

c

N

% -e 0

P)

52

0 v)

n

1.0000 0.0

'1L .ooo

12.000

HZ

PITCH I

N

I

Fig.

6 . R o t a t i o n a l r i d e s p e c t r a with locked suspension.

385

ROLL

7.0000 I N

I \

N,

c

N

U

e

1.oooo

12.000

11.000 N

-

2

-

-e

-

I

2

U

m

n v)

Q

I

-

2.0000 0.0 Fig.

386

Ht

7. Rotational r i d e s p e c t r a with f r e e suspension.

12.000

VIBRO-ISOLATION IN PORTABLE TOOLS (SCIENTIFIC CONCEPTS AND METHOD, DEVELOPMENTOF CONCEPTUALLY NEW VIBRATION-SAFETOOLS, FURTHER IMPROVEMENTS)

B. G. Goldshtein VNIISMI,Moscow, U.S.S.R.

SUMMARY

VNIISMI and other organizations in the USSR undertook investigations aimed at developing scientific and methodical concepts of vibroisolation in portable tools. A range of radically new vibration-safe portable tools which has no equal i n the world has been developed and put into production. New promising developments aimed at further improvement of vibro-isolation and output performance of portable tools a r e under way.

The problem of vibration protection f o r operators of portable tools has acquired a p r i m a r y importance, owing to its vast scale and evergrowing acuteness. Millions of portable tools

-

pick, chipping,

riveting, rotary and other types of hammers, concrete breakers, tampers, impact wrenches, drills, grinders, etc.

-

a r e used in

various fields of industry, construction and transport. The potential vibration hazard of such tools increases with the continuous increase in working part velocities, output and performance. The opportunities offered by partial measures of vibration protection a r e mainly exhausted and entirely inadequate f o r many applications. Future advance in the development of vibration-safe tools will only 'be achieved by means of deep penetration into the c o r e of the

387

problem, a comprehensive approach and the use of opitimization techniques. With these considerations in view, a comprehensive program Ll] aimed at eliminating the adverse effects on operators of vibration in portable tools has been started and developed on a l a r g e scale in the USSR. It includes: 1. Better standardization of admissible levels of vibrations tran-

smitted from portable tools to operator. 2. Development and improvement of methods and means f o r an

objective evaluation of the vibration performance of portable tools. 3. Development of methods and means f o r vibroacoustic diagno-

stics, and techniques f o r establishing structural, production and operation factors causing increased vibrations in portable tools. 4. Development and improvement of theoretical calculation tech-

niqes f o r the analysia and optimum synthesis of portable tools, as well as methods and means f o r vibration protection, and the creation, on this basis, of vibration-safe portable tools that give an optimum performance with the most advantageous structural realization. 5. Elaboration and improvement of rules establishing safe opera-

ting conditions for portable tools. 6. Elaboration and improvement of techniques for the evaluation

of technological, economical, sanitary and health results of the reduction of portable tool

vibrations

transmitted to operators.

A decisive part in the whole system of vibration protection of

operators is played by the fourth group of measures aimed at the creation of vibration-safe portable tools. The vibration safety of a portable tool is determined at the stage of development of its general structure. This process continues in the course of the theoretical studies of the dynamics of the tool, calculation of basic parameters and development of the structural solutions, during manufacture of the parts, assembly, adjustment and testing of the tool parts and of the tool as a whole. The problem of vibration protection consists in reducing vibratory

388

effects of a tool on the operator to levels that do not exceed the limits stipulated by sanitary and hygienic norms and standards. This problem may be solved by different methods. The first and main method is to reduce the intensity of the sources of harmful vibrations.

A l l sources of vibrations cannot, however,

be completely suppressed under real conditions, althoug in some instances the intensity of generated vibrations may be considerably reduced. It should, however, be kept in mind, that even weak sources of vibration may cause inadmissible phenomena should resonances appear i n the tool at frequencies of induced vibrations. The second method of vibration protection,therefore, consists in design and structural measures aimed at preventing resonances in the tool, and reducing the vibration intensity of resonating elements when complete elimination of the resonance phenomena is either impossible or impractical. The third method of vibration protection applicable to portable tools involves dynamic damping of vibrations, that is, the suppression of vibrations using auxiliary devices ( dynamic dampers ). The fourth and most widely used method of vibration protection involves vibro- isolation tion absorbers

-

by

means of

defornlable elements -vibra-

placed between the oscillating member and the

object to be protected. A characteristic feature of vibro-isolation in that it offers protection against vibrations over a wide frequency range-

All these methods of vibration protection a r e passive methods: protection against vibration is achieved without spending additional energy from an energy source. In certain applications, vibration protection

an active

(automatic vibration control) may prove more

expedient. Finally, vibration protection may be effected by using individual means

-

vibration absorbing mittens.

Development of vibration- safe portable tools often requires non-conventional methods to evercome difficult and complicated problems

since the vibration safety of personnel must be ensured under conditions characterized by stringent manufacture requisites and maintenance for the tool: low total weight, small size, high output and intensity of performance, long service life and durability, easy handling, simplicity and effectivenes. In many instances, it is not enough to use only one method o r element f o r vibration protection. Much more fruitful, and sometimes even the only possible method, is a comprehensive approach to the problem of creating efficient dbration- safe portable tools that includes an optimum combination of various methods of vibration protection chosen according to the type, size, dynamic and functional features of the

tool

[ZJ.

It is on the basid of such a comprehensive approach that a whole range of radically new vibration-safe portable tools which hare no equals in the world have recently been developed and commercially introduced in the USSR by the All-Union Scientific Research Institute of Portable Tools (VNIISMI) i n cooperation with a number of other institutions and enterprises. Among these tools is a range of chipping and riveting hammers with complex vibration protection of the operator' s hands, so-called rare-blow electric and pneumatic impact wrenches f o r torque tighteiing of high-tensile threaded joints, electric hammers and rotary hammers, tampers and other tools.

These de-

velopments have been patented i n leading industrial countries. Pneumatic chipping, riveting and other hammers a r e widely used in many industries. Conventional pneumatic hammers are, however, seriously deficient because of the great feed force required to ensure stable and efficient performance, and the high level of vibrations transmitted to the operator's hands. According to medical statistics, up to 60% of the cases of occupational white hands disease occur in operations involving pneumatic hammers. Optimization of the free-body diagram and increase in the impact velocity of hammer piston hitting against the working tool shankin the vibration- safe chipping and riveting hammers developed by the VNIISMI

390

Institute result in considerably lower feed force and reduced reaction, eliminating the main source of vibrations of the hammer casing. Moreover

complex vibration protection of the operator’s hands is

ensured, with the employment of modular a i r and spring vibration absorbers of original design. In the a i r and spring vibration absorber, a pneumatic elastic part and a metal spring function in parallel. Owing to low rigidity and considerable initial force, the former absorbs the major part of the constant component of the feed force.

The metal

spring, which is much more rigid and has a low initial force, absorbs the major part of the alternating component of the load. The hammer handle and casing integral with the handle form a vibration prgtected assembly. An impact mechanism is housed in the handle and casing assembly f o r movement in special low-friction guides, considerably improving the efficiency of the vibration protection system. The main structural feature of the pneumatic chipping hammers with complex vibration protection is a vibration-safe manipulator designed not only to protect the operator’s left hand against strong vibrations, but also to keep the chisel f r o m being shot from the tool in case of idle blows, so that the danger of injury t e the operater is elimink ed. The possibilities of improving the shape of the free-body diagram in portable percussive tools of the convential single-hammer piston type a r e limited; they may be greatly enhanced by using an auxiliary inertial part to transform the reaction of alternating forces associated w i t h hammer piston acceleration into a constant ( o r quasi-constant )

reaction force.

Tools of this type, which permit the realization of

theoretically minimum values of feed force and casing vibrations, are referred to as dynamically balanced tools. Tools of this class include those with partial and complete dynamic balancing. The latter feature the resultant (reaction) force determined by dl exciting forces acting on the tool casing, which is constant during the whole working cycle.

391

Concrete structural solutions of this type a r e primarily developed f o r pneumatic percussive tools

f 3 1 . It should be noted,however,

that

electric percussive tools also offer an opportunity of complete or partial dynamic balancing

[4].

In particular, in electromagnetic ham-

m e r s and rotary hammers with complex vibration protection, having an electromagnetic drive with an armature functioning a s hammer piston, partial dynamic balancing is ensured with the u s e of an inertial reaction impulse transformer i n the form af a "heavy" spring-lo-

aded shock absorber.

Additional vibration protection of the electro-

magnetic hammers and rotary hammers developed by the VNIISMI Institute in cooperation with the Mining Institute of the Siberian Branch of the USSR Academy of Sciences is ensured by a passive vibration isolation of the tool casing, employing a spring f o r the elastic suspension of the impact mechanism. Vibration-safe electropneumatic hammers and rotary hammers with a single-phase commutator motor a r e built around an original impact mechanism with optimized parameters ensuring the reduction of feed force and vibrations transmitted to the operator's hands. They also incoEporate a return-stroke shock absorber, to take up blows of t h e working tool hitting the casing, and local vibro-isolation of the handle UShg elastomers that provide substantial energy dissipation. In the course of the development of vibration-safe electric tampers, studies showed that minimum forces in the drive and impact mechanism were obtained with a predetermined nonlinear characteristic of a spring coupling between the drive and shoe. Efficient vibration reduction at the tamper casing is achieved by using rotary counterweight balancers. The tamper handles a r e provided with vibro-isolation systems.

A new promising development in creating vibration- safe percussive portable tools with a guaranteed margin of vibration and output performance consists in a synthesis of impact mechanisms with optimized structure of impact output

[4 J.

This optimization technique was used in the VNIISMI Institute to

c r e a t e radically new vibration-safe electric and pneumatic rare-blow impact wrenches f o r torque tightening of vital threaded joints with a s m a l l number of stable powerful blows. Not only were vibrations and noise reduced, but the performance of the impact wrenches a s a whole improved

[51

.

In rare-blow impact wrenches, the blow frequency, a t which the major oscillatory energy i s released, i s chosen well below the ranges specified by health rules (0.5-3 blows p e r s e c o n d )

, and vibrations

induced by higher harmonics within the specified octave hands prove to be substantially below admissible levels.

Rare-blow impact wren-

ches exhibit ten and m o r e t i m e s g r e a t e r impact energy, they a r e much lighter in weight and have lower motor input compared with conventional tools. Rare-blow impact w r e n c h e s with optimized s t r u c t u r e of the output power a r e protected by a number of USSR Inventor's Certific a t e s and foreign patents. At present, the VNIISMI Institute is conducting r e s e a r c h to c r e a t e vibration-safe r a r e - blow hammers, rotary h a m m e r s and conc r e t e breakers. The commercial introduction and development of manufacture of a new generation of dynamically balanced and rare-blow vibration- s af e portable tools with a guaranteed margin of vibration and output performance is an important step towards a f u r t h e r reduction of the harmful effects of vibrations on man in t h e production environment.

REFERENCES

Ill

Goldshtein B. G.,

Goppen A. A.,

System for Ensuring Vibration

Protection of Portable Tool Operators, TsNIITEstrojmach Publishers, MOSCOW, 1977 r21

Bykhovsky I. I.,

,

p.53.

Goldshtein B. G.,

Principles of Design of

Vibration-Safe Portable Tools, TsNIITEstrojmach Publishers, Moscow,

[31

1977, p.60.

Tupitsyn K.K.,

Problems of Dynamic of Pneumatic Tools with

Balanced Impact Mechanism, Nauka Publishers, Novosibirsk,

1974, p.86. 141

Goldshtein B. G., Optimization of Free-Body Diagram and Impact Output Structure of Electric Percussive Portable Tools Aimed at Improving their Vibration and Output Performance. Collection articles "Vibration Protection of Operator and Oscillations in Machines", Nauka Publishers, Moscow, 1977, pp. 150-154.

I: 51

Gelfand M. L, Goldshtein B. G., Tsypanyclk Y a. I. , Vibration-safe Electric Impact Wrenches and Efficient Ways of their Application TsNIITEstrojmach Publishers, Moscow, 1976, p. 60.

394

MAN-MACHINE-OBJEaBEING WOBKED-ENYIBO"T SYSTEM AND VIBRATION N. P. Benevolenskaya, T. T. Basova, L. L. Lysenko* The Minlng Institute of theslberian Bmnch sfthr Academy sfSciences sfthr U.S.S.R.,Novoslbirsk, U.S.S.R.

S U m Y

The methods of investigating the 'lman-machinelt system involving the methods for measuring the biomechanical values are described in the paper. The influence of the elements of this system on the vibration factor in quantitatlve sense is shown. The results of the physiolozical-hygienic oboemations are analyzed. At the present state of development of the society, one of the main criterion used to evaluate the perfection of a machine or manufacturing process is to provide safe and comfortable operating conditions as well

as

to preserve the

environment. Currently, a real hazard to the health of man resulto from the use of machines producing impacts which, in some cases, lead to pathological changes of the human tienue. Between the man and the machine producing vibrations the highly complex interrelations occur. They are considerably affected by the object being worked and the environment.

A

variety of these interrelations and their importance justify

*Presented at the Symposium by E. I. Shemyakin.

395

t h e attempt t o present them u s

8

diagram of t h c system o f f e r e d by

system. J'itgrc 1 shows a US.

A t t c n t i o n i o drawn t o

t h e element " o b j e c t b e i n g worked" and t h e s u b d i v i z i o n of the element tQmanlti n t o t w o l i r , k s I1operator1l and tlpersons involved i n t o t h e system but unconnected w i t h t h e c o n t r o l and maintenance of the given machine". F u r t h e r , an i n v e s t i g a t o r should always take i n t o account t h e exogenetic e f f e c t s . The o b j e c t being worked such

LIB

workpieces, s o i l s , cargos

e t c . has a s i g n i f i c a n t i n f l u e n c e on t h e i n t e n s i t y and t h e c h a r a c t e r of t h e unfavourable f a c t o r s produced d u r i n g t h e machine operation. In some c a s e s , a worked on o b j e c t can become a source i t a e l f

.

For i n s t a n c e , v a r i o u s packets (Fig. 2)

can predetermine t h e d i f f e r e n c e of v i b r a t i o n l e v e l s , measured on t h e handle of a r i v e t i n g hammer, which may r e a c h 20 dB. Transporting a v i b r a t i n g c o n t a i n e r by a bridge c r a n e is accompanied by t h e t r a n s m i s s i o n of o s c i l l a t i o n s from t h e c o n t a i n e r v i a suspension c a b l e s t o t h e crane o p e r a t o r ' s c a b i n (Pig. 3). The p r o p e r t i e s of t h e o b j e c t being worked can a f f e c t

t h e o t h e r c o n d i t i o n s of t h e i n f l u e n c e of t h e unfavourable f a c t o r s on t h e operator. So, t h e i n c r e a s e i n t h e c o a l hardness n o t only r i s e s t h e v e l o c i t y of v i b r a t i o n s and t h e magnitude of t h r u s t f o r c e , but prolongs t h e exposure time t o a c t u a l v i b r a t i o n s , i n c r e a s e s the n o i s e and p h y s i c a l s t r a i n , by 1520 seconds p e r cycle, i.e.

d r a s t i c a l l y changes t h e s t r u c t u r e

of t h e working time of t h e operator. It i s important t o d i s t i n m i s h t h e group of lfpersons

involved i n t o t h e system" as a group of persons s u b j e c t e d t o t h e unfavourable f a c t o r s who may be excluded from t h e system

396

by p r e v e n t i v e measures and h e a l t h c a r e . The r a t i o of t h e number of theee persons t o t h e number of t h e workers d e a l i n g w i t h t h e vibration-hazardous p r o f e s s i o n s is one of t h e

q u a n t i t a t i v e i n d i c e s of t h e q u a l i t y of o r g a n i z a t i o n of t h e l a b o u r p r o c e s s on a p a r t i c u l a r object. To study t h e i n t e r i o r o r g a n i z a t i o n of t h e system and t o

p r e d i c t its behaviour under v a r i o u s working c o n d i t i o n s we propose t h e c l a s s i f i c a t i o n of t h e r e l a t i o n s i n s i d e t h e system, based on t h e f e a t u r e s of t h e connections between t h e o p e r a t o r and t h e machine, t h e o b j e c t being worked and t h e environment. It determines t h e o b j e c t , means, t y p e s , p l a c e of a c t i o n and

i t s source [I]. Long i n v e s t i g a t i o n s of t h e v a r i o u s t y p e s of t h e machines under n a t u r a l and l a b o r a t o r y c o n d i t i o n s made i t p o s s i b l e t o o f f e r t h e technique which provides, i n our opinion, t h e o b j e c t i v e information about t h e machine being evaluated. As t h e main f a c t o r s of t h e machines under c o n s i d e r a t i o n a r e t h e v i b r a t i o n and t h e p h y s i c a l s t r a i n , p a r t i c u l a r a t t e n t i o n i s g i v e n t o t h e means of observing t h e s e f a c t o r s . To measure and analyze t h e v i b r a t i o n a l p r o c e s s e s a p o r t a b l e measuring s t a t i o n was made ( F i g . 4 ) f i t t e d w i t h a v i b r o a c o u s t i c a l a p p a r a t u s by B m e l & Kjaer, and o t h e r s p e c i a l d e v i c e s , i n c l u d i n g an automatic c o n t r o l unit f o r a t a p e r e c o r d e r ( i t e m 7). It is intended f o r switching t h e t a p e r e c o r d e r a t a given i n t e r v a l (from 0.3 t o 3 0.1

8.)

8.

a f t e r each

from p o s i t i o n llrecordingll t o p o s i t i o n llstopll or

Veplay".

The presence of t h i s device makes p o s s i b l e t o

i n v e s t i g a t e t h e v i b r a t i o n a l parameters of t h e hand impact t o o l s used i n production o p e r a t i o n s w i t h d u r a t i o n no l e e s

397

than 1

8.

It is w e l l known t h a t t h e comparative hygienic e v a l u a t i o n of t h e machines should be done f o r t h e same o p e r a t i n g cond it i o n s

.

Thus, t h e hand impact t o o l s a r e s u b j e c t e d t o t e s t when they a r e o p e r a t i n g under t h e main l i m i t i n g conditions. These c o n d i t i o n s a r e c h a r a c t e r i z e d by t h e minimum r e g u l a r time of c o n t a c t i n g t h e t o o l housing w i t h t h e working member correspondi n g t o t h e frequency of t h e o p e r a t i n g cycle. To determine t h e main l i m i t i n g c o n d i t i o n s f o r t h e o p e r a t i o n of t h e hand impact t o o l s , t h e method of e l e c t r i c c o n t a c t was used (Fig. 5).

The v a l u e of t h e t h r u s t f o r c e e x e r t e d on t h e t o o l was determined by means of a f o r c e p l a t e s u p p o r t i n g t h e operator. The v a l u e of t h e t h r u s t f o r c e was maintained a t a c o n s t a n t level. This made p o s s i b l e t o s t a n d a r d i z e t h e t e s t conditions. The o p e r a t o r i n f l u e n c e s t h e v i b r a t i o n a l parameters of t h e machine. So

our d a t a show t h a t t h e v i b r a t i o n a l parameters of

t h e machinetdetermined in s e p a r a t e octave bands, can d i f f e r i q v a r i o u s o p e r a t o r s working under t h e 8ame t e s t c o n d i t i o n s by only 6 dB. This probably r e s u l t s from t h e dynamic c h a r a c t e r i s t i c s of t h e human body. It is purposeful t o make up an a t l a s of t h e most t y p i c a l working p o s i t i o n s of t h e human-operator w i t h p a r t i c u l a r dynamic c h a r a c t e r i s t i c s of t h e human body and i t s e q u i v a l e n t models,which would make i t p o s s i b l e t o develop a mechanical model of t h e human body f o r t e s t i n g t h e v a r i o u s t y p e s of t h e machines

.

The p h y s i o l o g i c a l r e a c t i o n s of t h e o p e r a t o r a r e widely used when t h e comparison h y g i e n i c e v a l u a t i o n of t h e machines

is performed. Not always t h e y r e v e a l a main unfavourable f a c t o r , as t h e i n d i v i d u a l parameters such as v i b r a t i o n a l c h a r a c t e r i s t i c s , t h r u s t f o r c e , weight may d i f f e r i n v a r i o u s t y p e s of t h e t o o l s . I n experiments on t h e s e p a r a t e and g l o b a l i n f l u e n c e of t h e t h r u s t f o r c e and weight on t h e o p e r a t o r , i t has been e s t a b l i s h e d t h a t the weight of t h e hand impact t o o l s i g n i f i c a n t l y a f f e c t s t h e p h y s i o l o g i c a l r e a c t i o n s . However,

it' i s not p e r m i s s i b l e t o i n c r e a s e t h e weight of t h e t o o l i n o r d e r t o subdue v i b r a t i o n s of t h e t o o l . To e v a l u a t e t h e g l o b a l i n f l u e n c e of t h e unfavourable f a c t o r s on t h e o p e r a t o r Dwe introduce a concept o f t h e discomfort c o e f f i c i e n t ( Table I 1. The proposed formula permits

u8

t o take

i n t o account t h e v a l u e s of unfavourable f a c t o r s i n d i v i d u a l l y

a s w e l l as g l o b a l l y . The g l o b a l a c t i o n of t h e f a c t o r s may e i t h e r i n t e n s i f y o r weakcn t h e p h y s i o l o g i c a l e f f e c t [l

1.

I n our opinion, p a r t i c u l a r emphasis should be put upon

t h e choice of t h e persons f o r t h e p h y s i o l o g i c a l t e s t s . For t h i s reason we e s t a b l i s h e d i n o u r i n v e s t i g a t i o n s t h e r o l e of psychophysiofogical mood of t h e o p e r a t o r on t h e r e s u l t s of t e s t i n g of new machines. Changing t h e p h y s i o l o g i c a l r e a c t i o n s

of t h e s k i l l e d o p e r a t o r w i t h a c o n s t a n t dynamic s t e r e o t y p e t o manipulate t h e machine of s p e c i f i c d e s i g n cannot s e r v e a s a c r i t e r i o n f o r t h e o b j e c t i v e e v a l u a t i o n of t h e advantages of t h e new design.

In our opinion, t o compare t h e o l d machine and t h e new one,the choice of t h e " i n t a c t t 1 workers f o r t e s t i n g i s es-

399

s e n t i a l . T h i s i s a l s o t r u e f o r t h e evaluation of t h e poss i b i l i t y of mastering t h e machines by inexperienced workers. I n our opinion, t h e evaluation of t h e impact t o o l s imparting v i b r a t i o n s t o t h e man should include a s e r i e s of t h e prolonged production observations. I n doing so, i t i s advisable t o summarize t h e data from t h e hygienic, physiol o g i c a l , c l i n i c a l and s o c i a l economic i n v e s t i g a t i o n s on a s i n g l e s p e c i a l c h a r t used l a t e r f o r t h e data procesaing performed on a d i g i t a l computer. The a n a l y s i s should be s t a r t e d w i t h t h e choice of the b e s t informative f e a t u r e s . Our i n v e s t i g a t i o n s make use of t h e algorithm of an adaptive random s e a r c h developed a t the I n s t i t u t e of Mathematics of the S i b e r i a n Branch of t h e USSR Academy of Sciences [2]. With noninformative f e a t u r e s , t h e method determines t h e t r e n d f o r t h e r e l a t i o n between t h e f e a t u r e s which

i8

t e s t e d by a s e r i e s of t h e narrow-directio-

n a l i n v a s t i g a t i o n s . This f a c i l i t a t e s o b t a i n i n g t h e t r u e r e s u l t w i t h a s u f f i c i e n t confidence l e v e l . To r e v e a l t h e f a c t o r s e f f e c t i n g the hazards of t h e

operator,we propose t o improve t h e system of dynamic medical supervision by introducing a s p e c i a l l i n k , L e e t h e Laboratory of Prevention of P r o f e s s i o n a l Pathology. Speaking about t h e hazardous f a c t o r s , we would l i k e t o focus a t t e n t i o n on t h e c o n s t i t u t i o n a l f e a t u r e s of t h e man because o u r data is i n d i c a t i v e of t h e i r influence on the course of t h e

adaptive process of the workers [2,3]. For i n s t a n c e , when manipulating t h e hand powered t o o l , t h e persons with t h e v e n t r a l type of t h e frame have t h e most favourable course of

t h e a d a p t i v e process, while t h e s i m i l a r p r o c e s s f o r t h e persons with t h e p e c t o r a l type of t h e frame i s t h e l e a s t favourable. The same r e l a t i o n is observed f o r t h e groups of workers with l o n g e r experience i n t h e vibration-hazard profeas i o n (Fig. 6). The percentage of persons w i t h

a pectoral

type of frame i s reduced from 31 t o 12% and t h e p e r c e n t a g e of persons w i t h t h e v e n t r a l type of frame i s increased from 15 t o 53% as t h e l e n g t h of work i n c r e a s e s . Therefore, when t h e h y g i e n i c i n v e s t i g a t i o n s and t h e p r o f e s s i o n a l choice a r e performed,it i s e s s e n t i a l . t o t a k e i n t o account t h e psychol o g i c a l and p h y s i o l o g i c a l , a s w e l l a s anetomical f e a t u r e s of t h e operator. Thus, a system approach sl~oulclbe taken i n t h e invest i g a t i o n s of t h e i n f l u e n c e of v i b r a t i o n on t h e human organism. The a n a l y s i s of t h e vman-rnachine-object

b e i n g worked-environ-

ment" system makes i t p o s s i b l e t o determine t h e r o l e of i t s i n d i v i d u a l l i n k i n any p a r t i c u l a r case. Based on t h e long experience of the Mining I n s t i t u t e of t h e S i b e r i a n Branch of the USSR Academy of Sciences, an e f f o r t was made t o o f f e r t h e means f o r providing t h e o b j e c t i v e information about t h e f u n c t i o n of t h i s system under t h e s p e c i f i c conditions.

REFERENCES

[l] N. P. Benevolenekaya, Sketches on Ergonomics, ltNaukalt, Novosibirsk, 1977, p. 142.

121 N..P. Benevolenskaya, T.T. Basova, G.A. Vanag, e t a l . , Problems of Labour Protection during Riveting Operations, tlNaukafg,Novosibirsk, 1978, p. 136.

131 A Hand Mechanized Tool. Hygienic Evaluation. Proceedings of the Mining I n s t i t u t e of the Siberian Branch of the USSR Academy of Sciences, Novosibirsk, 1978, p. 96.

402

Table 1

Vi

- coefficient of conform-

- quantitative value of i-th.unfavourable factor; $ig - admissible value of i-th factor; @i

- coefficient of significance, Ki e: - limit value for unfavourable factor1 rp- subset of combinations of physiologically interrelated Ki

=I

aig

factors of set of all possible combinations,taklug into account unfavourable factors, for instance:

a;

v i j ('pi rl,

+

'Pj) 9

Ki

+

Kj

i#2 where

- positive or negative functions, assuming definite numerical values for given combinations of factors, taking into account the trend of global influence of the factors of a man.

403

Fig. 1. Diagram of relations in system "man-machine-ob j e c t being made-surrounding mediumtg.

Fig. 2. Dependence of parameters of v i b r a t i o n of axial component of r i v e t i n g hammer from p r o p e r t i e s of o b j e c t b e i c g made. 1 P e r m i s s i b l e l e v e l i n acc. with GOST s t a n d a r d s 15996-70; 2 l e v e l of r i v e t i n g of laminat i o n 14 3 the same of lamination 2.

-

-

Holding up of vibrating container, crane is stationary

-

Holding up of vibrating container, crane moving

Fig. 3. I n f l u e n c e of o b j e c t on v i b r a t i o n s of c r a n e o p e r a t o r ' s cabin.

405

I1

Sound

U 6

-

Fig. 4. Block-diagram of movable meaeuring station. 1 Accelerometer# 2 integrator# 3 cathode follower; 4 amplifier with set of octave filters; 5 meaeuring tape recorderr 6 recorder1 7 tape-recording automatic control device# 8 set of octave filter81 9 aound meterr 10 microphone.

-

-

406

-

-

-

-

-

-

-

F i g . 5, Diagram of location of man and equipment at d e f i n i tion of limit main duty. 1 Pick hammer8 2 indicator of pressure effort1 3 measuring platform1 4 pressure gauge1 5 pressure regulator1 6 frict i o n absorber8 7 stem type instrumenti 8 slip ring1 9 oscilloscoper 10 light-beam oscillograph.

-

-

-

-

-

-

-

-

-

-

407

Share ( % ) of investigated persons with different body feature types for riveters

I

11-

-1

- Pectoral type - Muscular type - Ventral type

IV

III

I1

I - Professional length of service

I

- 6 - 10 years

I1 - Professional length of service

I1 - 11-15 years

111 Protessional length of service

III- 16-20 years IV- 21 - 25 years

IV- Professional length of service

Fig. 6.

PROPERTIES OF NON-LINEAR VIBRATION-PROTECTION SYSTEMS WITH DIFFERENT DISSIPATIVE CHARACTERISTICS Z. Cherneva-Popova The Higherlnstirute of Electricol and Mechonicol Engineering" Lenin", Sofia. Bulgaria

SUMMARY The properties of vibration-protection systems whose structure involves non-linear forces o f resistance, such as dry friction of the Coulomb type have been studied. Using the methods of the theory of non-linear vibrations, the laws of motion of the isolated object were obtained and the criteria of vibration-protection efficiency were investigated. Their formulae of calculation were constructed with respect to the parameters of the system. The characteristic properties of vibration-protection systems in the resonance regimes were shown and a comparative analysis was carried out.

To evaluate the qualities of a vibratiop-protection system whose structure involves non-linear elements, the approximation methods of the theory of non-linear vibrations [l] have successfully been used. Some of these methods furnish good accuracy and are inevitable in engineering calculations. The purpose of the present work was to study with their help the qualities of vibration-protection systems which involve non-linear dissipative forces, such as forces of dry friction of a Coulomb type, for example. It is known that the basic characteristic of the vibration-protection qualities of an active vibration-protection system is the dynamic coefficient:

I

409

which represents a ratio between the amplitude of the force transmitted by the system to the vibration-isolated object and the amplitude of the harmonic exciting force (vibration influence). The system is efficient if K C: 1. In order to juxtapose the properties a€ non-linear systems involving forces of Coulomb friction with those of the linear type, the dependence K ( z ) for the following linear vibration-protection system is given in Fig.1: x

+

2nx

+ K 2x

= ho sin W t

(n,K,U,h,=constants).

(1)

K (z) has the structure:

Herein

ho =

3

Ho ' -6-, (msystem)i is the inertia characteristic of the

= -9K

-

dimensionless resistance in the system.

There follows from (2) that a linear-protection system is efficient at z 2 > 2. The presence of resistant forces lowers 2 the efficiency of the vibration protection at z > 2, but it improves its qualities in the resonance domain (at z zl). Keeping in mind the high possibilities for the natural occurrence or constructional modelling of the dry friction force, one sees its great number of advantages as a resistance force in a vibration-protection system. Furthermore, it could be synthesized as a function of various kinematic and other parameters, such as deformation, velocity, time, which ensures various dissipative properties of the system. The following cases of dry friction force created in a vibration-protection system are of interest in the practice: 1)

410

A.force T, constant in magnitude. The differential

equation of motion for the system is:

x + K2x + To sign x wherein To

--

T = ----pH --m mO

h, sin a t ,

=

;

(3)

p C = constant.

This case has been considered in detail by Kolovski [l] The solution of equation (3) was obtained in the form:

.

The function K ( z ) in this case is represented by (Fig.2):

The study of ( 5 ) shows that there is an efficient vibration protection at

The function (Fig.3) :

K(F)

with z as parameter has a maximum at

A dry friction force with magnitude T o = P o I red to a u n i t of mass. Such a force is possible for 2)

I , refer411

example, when a normal pressure is present upon the friction surfaces, due to the availability of Coriolis's forces of inertia. The differential equation of motion for the system will be:

..x + K2 x +polx!sign x

=

ho sinwt.

.

(7)

It becomes evident, in representing sign = ---, that IX I with a dry friction force of this type, the problem is reduced to the linear vibration-protection system with equation (1) (Fig.1). X

Pol

dry friction force of the type To= X Isign %. A similar force is introduced in the construction of vibration-protection systems in railway vehicles. The equation of motion is: 3)

A

'*x + K 2x + l J o I x l sign 2

=

ho sinwt.

(8)

The problem is analogous to the one of studying the dissipative qualities of a system at the expense of the inner absorption of energy in the material of the isolators [23 It is known that in this case, to have an efficient vibration protection it is necessary that z2, 2 . The function K ( z ) has the same characteristic properties as in the case of a linear system.

.

4)

A dry friction force of a "harmonic" type with magni-

tude T =

I

To + p h o cos o t l

.

Such a force could be employed in the vibration-protection systems of vehicles, in which there often occurs a periodically changing force as a normal pressure upon the friction surfaces [3] The differential equation of motion for the system is the following:

.

412

2 +

2 K x

+

ITo

+

r h o cosOtIsign 2

a) Let us consider the case of ITo

+

p h o coswtl =

To

-k

=

ho sinwt.

(9)

T o > p h o , hence p h o cosot

.

The solution. of equation (9) is searched for by method of harmonic linearization, i.e., by representing the dry friction force in the form:

wherein

is amplitude of the solution of equation (9) accepted in the form: A

for the amplitude A and the phase p one obtains the expressions (4a), it becomes evident that in this case the problem is reduced to the model described already in item 1). Consequently, the periodically changing component of the friction force magnitude has no influence upon the vibration-protection qualities of the system and the latter are represented by the function K ( z ) according to (5) and (6). As

b)

Case To = 0. By the method of harmonic linearization one finds the solution of equation ( 9 ) in the following form C41 : (13)

413

herein

For the law of alteration of the dynamic coefficient one obtains (Fig. 4) :

In order to fulfil the condition of efficient vibrationprotection it is necessary that the motion be realized at. the following z:

The function

K(P) is

shown in Fig.5.

As a partial case of the relationships (6) and (16) one

obtains the well known condition for an efficient vibrationprotection of a linear type according to equation (1):

On the basis of studies thus carried out, the following conclusions could be drawn: A.

On introducing a dry friction force o f the type 11, 4a), 4b) the frequency's ratio z for an efficient vibration-protection becomes a function of the resistance parameters (JIA respectively), whereas with a linear resistance force and cases 2 ) and 3) it is independent of them ( z > = const).

B.

The functions

C.

The mechanical systems are similar in their vibration-

414

K(

p

1

have extremum.

protection properties in the following cases: T = const

to

T =

~hOIcos~t)signx,

D. In the region of efficient vibration-protection the resistance forces of any type lower this efficiency. In the resonance region, however, they appreciably decrease the dynamic coefficient K. E. Under the conditions of resonance, with resistance forces of T=const. and T= I TO+ U / . hOcos at I the amplitude of vibrations and K ( z ) , respectively, have a possibility of increasing infinitely. And vice versa, with forces ~=jllil and T= ,p l x I , the amplitudes have finite values.

[3

.]Oponoe,

.

K B.,

Heno~oprenpo6mer~napare=pxueemr xone-

bawa# aneMeHTo8 MamnH. B HBIDHH,

CT.

K o n e d a m ~H

~ C T O ~ ~ ~ U B O C T ~

I1Hayxat1, Mocxsa, 1968, cTp.5-19.

Ha n e n a ~ e f i ~cncTeMa a npu Hannvwe

cyxo TpHeHe o T " x ~ ~ M o H uT ~H~n , ~H C T"~ 29-35, . CO@HR I r0a. B y 3 - T ~ x H H ~ ~ c Ha

Ka MeXaHHKB, T.9, KH.~, v T e x w ~ ~ a w CO@R, , 1974.

C6.J

R o s e a u , M.: V i b r a t i o n s n o n l i n 6 a i r e s et t h 6 o r i e d e la stabilit8, S p r i n g e r - V e r l a g , 1966.

C7.J

~ h e r n 8 v a - P o p o v a , 2 . : N o t e s u r q u e l q u e s p r o p r i 8 t b s des v i b r a t i o n s n o n l i n 4 a i r e s d e s y s t 6 m e s d e s o l i d e s en pr&se.nee d e f r o t t e m e r t see, J o u r n a l d e M b c a n i q u e No.5, D u n o d / Gauthier-Villar, Paris, 1976, pp. 877-885.

Fig. 1

Fig. 2

417

Fig. 5

418

DISCUSSIONS

GENERAL LECTURE (presented by K. V, Frolov) B.M.

NIGG: You d i s c u s s e d i n your p r e s e n t a t i o n t h e e f f e c t s

o f e x t e r n a l v i b r a t i o n s . We know t h a t t h e r e a r e i n t e r n a l vibrations

- such as micro-vibrations - too.

Could you

e x p l a i n t h e r e l a t i o n between t h e i n t e r n a l and t h e e x t e r n a l v i b r a t i o n s and could you comment on t h e i r importance? AUTHOR: I n my l e c t u r e I described only e x t e r n a l vibra-

t i o n s because of o u r s p e c i a l i n v i b r a t i o n s a t head. of course,

we worked with i n t e r n a l v i b r a t i o n s , f o r example, w i t h bones

as I have demonstrated h e r e , and some r e s u l t s r e l a t e d t o blood, muscles and o t h e r similar systems.

D.P.

CARG: Your p r e s e n t a t i o n gave an e x c e l l e n t survey of

p r o j e c t s and d e t a i l s of experiments. Could you comment on t h e method of attachment of measuring instruments, such as acc e l e r o me t e r s t o human s u b j e c t s ?

AUTHOR: The q u e s t i o n i s v e r y i n t e r e s t i n g , indeed. It is not

80

e a s y t o measure a c c e l e r a t i o n . W e calibrated our ap-

p a r a t u s w i t h a s p e c i a l scalp frame on t h e v i b r a t i n g t a b l e , and we have s t u d i e d .the spectrum of n a t u r a l frequencies of

41.9

the scalp. This method helps t o avoid p o s s i b i l i t i e s of introduction of e r r o r s i n our measurements. We have an a r r a y of scalps f o r various n a t u r a l frequencies. A.OLJfDZKI:

I n your i n t e r e s t i n g l e c t u r e you mentioned the

investigation on the influence of vibration on a man in v e r t i c a l position. Do you think, professor Frolov, t h a t i t is possible: a) t o design s p e c i a l boots f o r people who a r e suff e r i n g from serious pains i n knie-joints caused by c l i m b i n g mountains ( s e r i e s of impacts during the ascension of slopes and rocks), jumping w i t h parachute, etc? b) t o invent boots o r special protecting devices f o r industry workers who have t o work i n very c r i t i c a l conditions (forging, f o r instance)? AUTHOR: Yes, i t is possible t o use our r e s u l t s f o r

designing s p e c i a l boots f o r people who a r e suffering from pains i n the knie-joints,

but it is necessary t o Investigate

t h i s s i t u a t i o n f o r people of d i f f e r e n t age.

H. DUPUISt May I add some remarks t o vibration e f f e c t s on v i s u a l acuity.-Since there was no knowledge on the n a t u r a l frequency of the eye-balls, we have done some research last year. I n animal t e s t s w i t h monkeys we fixed miniature accelerometers at the cornea of the bulbus and a t the bone of the forehead. Exciting the head by a v i b r a t i o n simulator we could f i n d t y p i c a l t r a n s m i s s i b i l i t y curves f o r the eye-balls w i t h maximal resonances between 20 and 30 Hz. Texts with

human beings using a s p e c i a l TV-traching system confirmed these r e s u l t s . In addition, research on the e f f e c t of vibrations on visual acuity shows r e l a t i v e higher decrease of performance i n t h e same vibration frequency range.

PAPER: SESSION I/4 (paper presented by H. Dupuis) D.P.

GAtlG:

The paper g i v e s d a t a f o r v i b r a t i o n s t r a n s m i t t e t

t o t h e hand. However, hand-held t o o l s a l s o t r a n s m i t v i b r a t i o c t o o t h e r p a r t s of t h e body. How does t h e d e s i g n e r r e s o l v e the c o n f l i c t i n g requirements f o r p r o t e c t i o n of v a r i o u s body p a r t s ? AUTHOR: As f a r as it belongs t o t h e trunk, f r e q u e n c i e s

below 15 He would be of i n t e r e s t . But most of t h e v i b r a t i n g hand-held t o o l s w i l l produce h i g h e r frequencies. Frequencies above 10 H s may be t r a n s m i t t e d t o t h e head. If 2 0 t o 30 H z v i b r a t i o n reaches t h e head, resonances of t h e e y e - b a i l s may occur. B.M.

ITIGG: You d i s c u w e d i n your paper t h e r e l a t i o n

between t h e a c c e l e r a t i o n and the frequency. From t h e amplitude you have t o make t h e s t e p t o t h e danger of t h i s a c c e l e r a t i o n amplitude. How and f o r what reason can you do that? krample ( 1 ) amplitude 3 cm/s2 frequency 30 Hz (2)

I1

5 crn/s*

I1

20 He

which example i s more dangerous? AUTIIOR: A l l r e s u l t s of t h e r e s e a r c h I presented were

c o n t r i b u t e d t o the I n t e r n a t i o n a l Standard IS0 DP5349, i n which you w i l l f i n d r e l a t i o n s between a c c e l e r a t i o n and frequency.

Evaluation curves depending on frequency, a c c e l e r a t i o n and exposure time g i v e you a measure of the probable r i s k of damage t o h e a l t h . As f o r your examples you can f i n d out from t h e IS0 e v a l u a t i o n curves t h a t case ( 2 ) i s more c r i t i c a l t h a n case ( I ) * E.I.

SHEMYAKIN: 1) Since your p i c t u r e ( t h e last s l i d e i n

421

your r e p o r t ) i s mainly demonstrating t h e influence of noise, can you compare the influence of v i b r a t i o n w i t h that of n o i s e ( s t i l l v i b r a t i o n , but with d i f f e r e n t frequency!) ? 2) How

would change your data on t h e influence of v i b r a t i o n on t h e temperature of the hand s k i n with another e x t e r n a l temperature? AUTHOR: 1) Using @other s l i d e I can show you t h a t the

e f f e c t of t h e chosen v i b r a t i o n i n t e n s i t y :in a l l v a r i a t i o n s ) on the f i n g e r pulse amplitude is q u i t e smallcr than t h e eff e c t of 100 dB (A) noise. That i s why the f i n g e r p u l s e r e a c t i o n ks a v e g e t a t i v e e f f e c t . 2) We cannot answer t h i s question, because i n a l l o u r experiments i n l a b o r a t o r y the temperature was kept constant a t 20'

C.

PAPER: SESSION I/5 (paper presented by A. A. Menshov) H. DUPUIS: I n $our paper you considered micro- and macro-

pauses. Was some r e s e a r c h c a r r i e d out on t h e e f f e c t of v i b r a t i o n pauses, i. e. i n t e r r u p t ion of v i b r a t i o n exposure? AUTHOR: Yes, such r e s e a r c h has been c a r r i e d out. In f a c t ,

GOST 12. 1. 012-78 V i b r a t i o n . General S a f e t y Requirements" proposes high allowable l e v e l c of whole-body v i b r a t i o n s f o r t h e 1 s t category of labour a c t i v i t y , ( d r i v e r s of t r a c t o r s ,

t r u c k s , road b u i l d i n g machines, etc.)r who have some pause s during t h e i r work. PAPER: SBSSION I/6 (paper presented by R. G i l l o l i )

D.P.

GARG: Could you comment on the a v a i l a b i l i t y of any

r e s u l t s which show that t h e use of preventive measures sug-

422

gested in your paper do indeed reduce neuro~ogicalhPairements? AUTHOR: Following these experiences, the pneumatic tool used by the workers who re-finished the statues of the Milan Cathedral was compared with a new model of penumatic tool built also according to the suggestions of the workers themselves. The comparison took into consideration a number of physiological and psychomotor parameters. The results are about to be published.

G. BIANCHI: The workers had the subjective impression that the damage was produced by the cold temperature of the outlet air. Could you ascertain if, and in what measure, this was true? AUTHOR: In fact, the workers felt that the cold temperature both outside o r inside the factory, or caused by the outlet air of the tool, was the main cause of their d isturbances

.

The cold temperature certainly plays an important role in the Raynaud phenomenon, but much less in the peripheral neuropathies that are due to compression by bone tissue or to a direct toxic action on the nerve fibre.

A. O 4 D Z K I : I would like to put one queetion and to make one remark. In the list of dangerous tools you mentioned I could not find impact wrenches. Have you heard about such tools? If not, I would like to add impact wrenches (Atlas Copco, e,g.).

which we (experimentally) found dangerous, t o

your list. They a r e widely used i n automotive induotry. AS f o r your i n t e r e s t i n g r e p o r t on t h e use of FPG method

f o r i n v e s t i g a t i n g t h e p e r i p h e r a l c i r c u l a t i o n I would l i k e t o mention t h a t about t e n y e a r s ago an o r i g i n a l device was invented i n Poland ( C e n t r a l I n s t i t u t e f o r Occupational S a f e t y , Warsaw) f o r t h e same purpose. More d e t a i l s can b e obtained from D r . Koradecka working a t that I n s t i t u t e . AUTHOR: Unfortunately, I have not heard about the t o o l

you mention1 being a n e u r o l o g i s t my t e c h n o l o g i c a l knowledge is limited. However, I presume t h a t , i f t h e v i b r a t i o n

f r e q u e n c i e s f a l l w i t h i n t h e dangerous range (50-150 c / s ) , t h e problem would be t h e same. A s t o your r e m a r k , I must say t h a t 2°C is one of t h e

methods used t h a t , though having advanteges and drawbacks, y i e l d s f a i r l y r e l i a b l e r e s u l t s 4 of course, o t h e r methods could be used, f o r i n s t a n c e cutaneous thermometry. I would b e very i n t e r e s t e d t o hear about D r . Koradecka's experience.

E. SHEMYAKIN: What temperature you c a l l f t c o l a l f ? (Siberian question)

AUTHOR:

...

Living i n Southern Europe, 1 0 '

C a r e accepted

as being "cold'f. PAPER: SESSION II/1 (Paper Presented bY

D.P.

v.

ZataiOmky)

GARG: Could you Zlease comment on the number of

s u b j e c t s used, and how a r e your r e s u l t s l i k e l y t o change i f female s u b j e c t s were used i n the study. AUTHOR: Seven f i t men took p a r t i n t h e experiments. We d i d n o t make any experiment with female s u b j e c t s .

H. UUP'JIS: Xay I ask you, which kind of body posture was w e d ? The body posture, straight errected or more comfortable,

csn influence the results very much. AUTHOZ: During our experiments the subjects were standing

on tiptoe8 and straight strained legs the angle in the ankle joint being about )'01

.

B.M. NICG: Would it be possible to describe with a more sophisticated model different body pos tions at the same time?

AUTHOR: Yes. If the position of the subject is changed, the moael of the human body represented by the system with a single degree of freedom may be not satisfactory. But in our experiments amplitude/frequency characteristics with a single clearly manifested resonance (the same for all parts of the body) have been recorded, This testifies the validity of the used model for the human body. PAPER: SESSION II/2 (paper presented by D. Y. Gwg)

M. KSI@EK:

In your accurate and very interesting paper

you considered the structure of the human body assumed on anthropometric data. Did you consider the possibility of obtaining a dynamical model of the human body by other methods in which a priori-assumed structure is not necessary? The second question: You considered the human body as a linear system. Did you take into account the non-linear effects?

AUTHOR: Thank you for your questions. To be of utmost use and to maintain the proximity of reality, the objectives of

425

o u r study were twofold: One was t o develop a model t h a t would resemble human anatomy, and the o t h e r was t o o b t a i n t h e response from t h i s model t h a t would c l o s e l y rcsemble t h e resemble obtained experimentally. Thus, a p r i o r i assumption of human body s t r u c t u r e was necessary. The model obtained

was a linear-lumped-parameter

model, and while i t i s

recognized by u s t h a t i n t h e r e a l human body t h e parameters e x h i b i t n o n l i n e a r c h a r a c t e r i s t i c s , a comparison of t h e response from t h e l i n e a r model and t h a t experimentally obtained shows t h a t i n t h e present case a l i n e a r model i s adequate f o r preliminary v i b r a t i o n s t u d i e s .

H. DUPUIS: Your f i n d i n g s on t h e human t r a n s m i s s i b i l i t y a r e q u i t e d i f f e r e n t from t h e r e s u l t s of t h e l a s t paper ( D r . Zatsiorsky, Moscow) r e f e r r i n g t o t h e main resonances. Do you have any i d e a what t h e reason f o r t h a t may be? AUTHOR: Thank you f o r your question. The r e s u l t s r e p o r t e d

i n "The Determination of t h e Equivalent Biomechanical C h a r a c t e r i s t i c s of t h e Ankle J o i n t Muscles by V i b r a t i o n Tests" coauthored by Dr.

Zatsiorsky

e t al. of t h e S t a t e C e n t r a l

I n s t i t u t e of Physical Education, filoscow, U.S.S.R.,

which i s

r e f e r r e d t o i n your question, were obtained from s u b j e c t s who stood on t h e v i b r a t o r p l a t f o r m on t h e i r t i p t o e s a n d s t r a i g h 4 s t r a i n e d l e g s w i t h t h e angle i n t h e ankle j o i n t s being approximately l l O o .

Also, i n s e v e r a l c a s e s a d d i t i o n a l weights

were a t t a c h e d t o the s u b j e c t s ' l o i n s . In our experiments t h e s u b j e c t s s t o o d u p r i g h t w i t h a normal stance. Thus t h e p o s t u r e and some of t h e parameters i n two c a s e s were d i s s i m i l a r . This

fact accounts for the d i f f e r e n c e i n human t r a n s m i s s i b i l i t y

426

r e s u l t s obtained i n t h e two s e t s of experiments. A. PEDOTTI: Did you perform i n v e s t i g a t i o n s on t h e

s e n s i t i v i t y of t h e model t o the p a r a x e t e r values? Did you i n v e s t i g a t e t h e range of l i n e a r i t y ? AUTHOR: Your q u e s t i o n s a r e indeed very i n t e r e s t i n g and

p e r t i n e n t . Yes, we d i d conduct a s e r i e s of s t u d i e s d e a l i n g w i t h t h e s e n s i t i v i t y of model w i t h v a r i a t i o n i n parameters.

R e s u l t s of parametric s e n s i t i v i t y t e s t s i n d i c a t e d t h a t a v a r i a t i o n i n s p i n e damping had a major e f f e c t on t h e 6-Hz resonance. A v a r i a t i o n i n i n t e r n a l organ damping had an e f f e c t only on t h e 2-Hz resonance. S i m i l a r l y , a modulation i n damping a s s o c i a t e d w i t h lower e x t r e m e t i e s y i e l d e d s i g n i f i c a n t v a r i a t i o n s i n 2 0 Hz resonance frequency range. bamping parameter was found t o be of most s i g n i f i c a n c e out of t h e v a r i o u s parameters r e p r e s e n t e d i n t h e model. With r e s p e c t t o your second question on t h e range of

l i n e a r i t y , I would' wish t o comment that t h e parameters s e l e c t ed f o r our model were based on information a v a i l a b l e i n t h e medical l i t e r a t u r e , and t h e s e v a l u e s r e p r e s e n t the average i n l i n e a r range of parameters wherever possible.

PAPER: SESSION II/4 (paper presented by M. B i q z e k )

K.V.

FROLOV: Do you know t h a t s i m i l a r r e s u l t s were

obtained and published by B.A.

Potemkin ( U S S R ) ?

AUTHOR: Yes, I know t h i s p u b l i c a t i o n . I have obtained my

r e s u l t s i n a l i t t l e d i f f e r e n t way and t h e models presented i n my paper have a d i f f e r e n t s t r u c t u r e .

E. SHEWAKIN: 1) It is v e r y d i f f i c u l t t o c o n s t r u c t a

427

mathematical model of t h e human body without an adequate mechanical model. Could it be t h a t t h e n a t u r a l way i s t h e r e v e r s e of yours? What is your opinion? 2) I n t h i s way, i.e. t o c o n s t r u c t t h e mathematical model without t h e mechanical d e s c r i p t i o n , you can meet d i f f i c u l t problems

- interpolation

problems.

AUTHOR: 1) I would l i k e t o maintain t h e assumption t h a t we hsve two ways f o r c o n s t r u c t i n g t h e mechanical models of t h e human body. Both of t h e s e ways a r e based on t h e d a t a obt a i n e d from t h e experimental i n v e s t i g a t i o n s . F i r s t way: t o assume t h e dynamical s t r u c t u r e of t h e humn body and t o c a l c u l a t e i t s parameters i n such a way t h a t t h e driving-point impedances 2

(8)

measured and c a l c u l a t e d be ( w i t h minimal

e r r o r ) t h e same. Second way: t o approximate t h e driving-point impedance, obtained from experimental i n v e s t i g a t i o n s , a8 a f u n c t i o n of frequency by t h e f u n c t i o n 2 ( s ) ( w h i c h f u l f i l l s a l l necessary c o n d i t i o n s ) and t o apply t h e methods of syn-

t h e s i s , e x i s t i n g f o r e l e c t r i c a l networks, t o b u i l d up some mechanical models. In my opinion, t h e second way has not s o many r e s t r i c t i o n s . We do n o t assume a p r i o r i t h e s t r u c t u r e of t h e human body, which i s s o complex t h a t such an assumption c o n s t i t u t e s i t s e l f a g r e a t r e s t r i c t i o n . Besides, t h e second way g i v e s us t h e p o s s i b i l i t y of o b t a i n i n g v a r i o u s models of t h e human body. It allows u s , i n some c a s e s , t o e x p l a i n some phenomena (complex and u n l i k e l y t o be understood) which i n t h e first method may be l o s t . 2) It i s d i f f i c u l t t o approximate t h e curve of t h e driving-point impedance ( i n o u r case t h e a b s o l u t e v a l u e of t h e impedance) obtained from

428

investigations. We must consider all the realixability conditions of 2

(9)

and therefore the algorithm of the numerical

calculations is complicated. In this paper the procedure of Hosenbrook with additional restrictions was applied.

D.P.

GARG: Would it be possible to use the technique you

propose for higher-order models, and if so, would the components you may get for high-order systems be truly representative of the human body components? AUTHOR:

I think that it would be possible to use the

technique I propose for higher-order models. It is connected, however, with more complicated numerical calculations. What

- to some extent - on which of

shall we obtain? It,depends

the mathematical methods of synthesis will be considered. If the expression for 2 ( s ) is chosen in the proper way and if the approximation is exactly done, it is possible to obtain high-order modelo which ohould be (in my opinion) representative of the human body dynamical properties. PAPER: SESSION 11/7(paper D.P.

presented by K. V. Frolov)

GARG: The jump phenomenon is typically analysed by

dual-input describing function technique for nonlinear systems. Could you please comment on the methods of analysis for nonlinear models presented in your paper?

AUTHOR: As usual, the method of analysis used, as main limitation, the presence of small nonlinearitiss; but real physical systems have real nonlinearitiea, which are not necessarily small. The assumption of small nonlinearities is only the first step. In our investigations we used

429

e l e c t r o n i c d i g i t a l and a n a l o g computers which allowed r a t h e r t o r a t e n o n l i n e a r i t y as a parameter of our system. It i s poss i b l e t h a t t h e c o n v e n t i o n a l l y s t a b l e p a r t of t h e jump curve may be u n s t a b l e , o r t h e u n s t a b l e p a r t of t h e cu rv e may be s t ti b l e. It depends on t h e so u rc e of e x c i t a t i o n . Bes i d es , r e a l n o n l i n e a r systems have time-varying p aramet ers which we have s t u d i e d f o r jumping e f f e c t and have o b t a i n e d h e r e some r e s u l t s . F o r example, t h e peak of t h e re sp o n s e cu rv e may be u n s t a b l e

i n an

& - r e g i o n which would depend on t h e v a r i a t i o n i n range

of parameters which d e t e rm i n e t h e n a t u r a l freq u en cy of t h e

system. Some of' t k e s e r e s u l t s have been p u b l i s h ed i n o u r book ttNonlinear V i b r a t i o n s of Mechanical Systemst1, p u b l i s h e d by Nauka, Moscow, 1967. 2.

CHERNEVA-POPOVA:

What about t h e d i s s i p a t i v e f o r c e s i n

t h e human body? Have t h e y a n o n l i n e a r e f f e c t ? AUTHOR: The d i s s i p a t i v e f o r c e s a r e r a t h e r l a r g e indeed.

For t h e main p a r a m e t r i c re so n a n c e s t h e y a r e n o t r e l e v a n t , b u t f o r t h e s u b l i a n o n i c and u l t ra su b h a rmo n i c ones t h e y have a s e r i o u s e f f e c t a n d re so n a n c e s w i l l be avoided. PAPER: SESSION I I I / 1 (paper p re se n ted by E. 1. Shemyakin)

H.DUPUIS:

In Table 1 v a l u e s between 6p an d90 Hz f o r t h e

resonance o f t h e e y e b a l l a r e given. Have t h e s e d a t a been worked o u t from biodynanic experiments o r o n l y r e p o r t e d from l i t e r a t u r e r e s u l t s ? This q u e s t i o n a r i s e s , because by ex p eri ments w i t h monkeys and human b e i n gs we found res o n an ces for t h e b u l b u s between 20 and 30 Hz. LECTURER: S o r r y I cannot answer t h i s q u es t i o n . S i n c e I

have j u s t r e p o r t e d t h e r e s u l t s g i v e n b y Prof. Kluev and h i s c o l l e a g u e s i n t h e i r t e x t , I do n o t know some d e t a i l s .

PAPER: S E S S I O N ILI/3 (paper p r e s e n t e d by A . Olqdzki) E. SHEMAYKIN: What can you s a y about low f r e q u e n c y range f o r the f i r s t type transducer?

AUTHOR: We d i d n o t t e s t it. But t h e e l e c t r o - k i n e t i c gauges a r e r a t h e r u s e l e s s f o r f r e q u e n c i e s below 1 Hz. D.P.

CARG: Have you done any dynamic t e s t i n g w i t h t h e

m e t a l bands shown i n t h e l a s t s e t of f i g u r e s of your p a p e r ? If s o , w i t h what r e s u l t s ? and what t y p e of c o m p l e x i t i e s a n d

c o n s t r a i n t s y o u f o r e s e e i n such measurements? AUTHOR:

m e t a l bands.

Up t o now I have made o n l y s t a t i c t e s t s w i t h But I do t h i n k t h a t , i n c a s e of s t e a d y s t a t e

v i b r a t i o n s , we can u s e t h e same method w i t h a moderate speed of t h e bands ( p u l l i n g ) . Only t h e change of t h e v a l u e of t h e

f r i c t i o n c o e f f i c i e n t should be t a k e n i n t o account.

PAPER:

H.

SESSION IV/2(paper p r e s e n t e d by K. V. Frolov) DUPUIS:

Are t h e r e s u l t s of your p a p e r worked o u t o n l y

on a t h e o r c t i c a l b a s i s o r have you some p r a c t i c a l e x p e r i e n c e w i t h a c t i v e s e a t systemo? AUTHOR: Yes. We have e x p e r i m e n t a l l y v e r i f i e d t h i s t h e o r y

and o b t a i n e d v e r y good c o i n c i d e n c e s of t h e o r e t i c a l and exp e r irnent a1 r*ee u l t 8 . D.P.

GARG: V i b r a t i o n i s o l a t i o n d e v i c e s a r e i n h e r e n t l y

s e n s i t i v e and a c c u r a t e , b u t a l s o expensive. Under what

-

s i t u a t i o n s do you f e e l t h a t a c t i v e c o n t r o l must be used; and

43 1

a r e t h e r e any f i g u r e s a v a i l a b l e on c o s t comparison f o r a c t i v e VG.

passive i o o l a t i o n devices? AUTHOR:

I believe t h a t a c t i v e vibro-isolation devicee

muot be of a l l i n t r a c t o r s and r o a d - b u i l d i n g machines. Active vibro-isolation-systems

a r e expensive t o d a y , b u t t h e i r c o s t

mainly depends on t h e i r l e v e l of p r o d u c t i o n . H. DUPUIS: From some e x p e r i e n c e s w i t h a c t i v e s e a t s we

know t h a t some p r a c t i c a l problems s t i l l e x i s t : 1. The r e q u i r e m e n t s p u t t o t h e h y d r a u l i c power Eystem o f the v e h i c l e a r e v e r y high. This r e f e r s t o t h e h y d r a u l i c p r e s s u r e and t o t h e h y d r a u l i c flow r a t e . 2. Up t o now a c t i v e s e a t systems a r e complicated and s e n s i t i v e . T h i s i s t h e r e a s o n why v e h i c l e m a n u f a c t u r e r s s t i l l n o t u s e them. 3. The high p r i c e of such a system ( a t l e a s t 500 d o l l a r s ) i s a n o t h e r r e a s o n for t h a t .

4. When s t u d y i n g t h e s t a b i l i z a t i o n of a d r i v e r ’ s s e a t , a150 t h e o p e r a t i o n a l f u n c t i o n s have t o be considered.

In f a c t , t h e y

become more d i f f i c u l t , if t h e r e l a t i v e movements between s e a t and c o n t r o l d e v i c e s exceed 150 mm. PAPER: SESSION IV/6 (paper presented bY E e I. S h w a k i n )

D.P.

GARG: Your approach a p p e a r s t o be q u i t e g e n e r a l .

Could you, p l e a s e , comment on how t h e r e s u l t s c o u l d be t r a n s l a t e d and a p p l i e d t o s e t t i n g up mining o p e r a t i o n s a t a n o t h e r l o c a t i o n o t h e r t h a n S i b e r i a ( f o r which your r e s u l t s were derived )? AUTHOR: Yes, of course. The same r e s u l t s you have s e e n on t h e s e p i c t u r e s can b e a p p l i e d t o t y p i c a l underground condit i o n s i n o t h e r c o u n t r i e s . R e g i s t r a t i o n s of v i b r a t i o n s in

underground mining can be e a s i l y o b t a i n e d w i t h remote c o n t r o l systems. Summary of t h e r e p o r t by

E. NOVOSELOV, Higher School f o r t h e Trade-Union Movement of t h e C e n t r a l Co u n c il of t h e USSR Trade-Unions The s o c i a l i m p l i c a t i o n s of t h e problems d i s c u s s e d at t h e Symposium a r e p o i n t e d out. As w e l l known, v i b r a t i o n o f t e n g i v e s r i s e t o v e r y s e r i o u s diseases among t h e workers4 t h e r e f o r e t h i s problem i s s t e a d i l y drawing t h e a t t e n t i o n n o t o n l y

of t h e s c i e n t i s t s and r e s e a r c h workers, b u t a l s o of t h e l a b o u r o r g a n i z a t i o n s , f i r s t of a l l of t h e trade-unions.

I n t h e S o v i e t Union t h e I n s t i t u t e f o r Occupational S a f e t y i s a n organ d i r e c t e d by t h e C e n t r a l Council of t h e USSR TradeUnions. In t h e S o v i e t Union, as i n o t h e r c o u n t r i e s , e.g. I t a l y , t h e Trade-Unions c a r r y o u t an a c t i v i t y aiming a t t h e improvement o f t h e l a b o u r c o n d i t i o n s a n d , i n p a r t i c u l e - ,

at

t h e r e d u c t i o n of t h e dangerous e f f e c t s of v i b r a t i o n . T h i s a c t i v i t y i s b e i n g developed i n s t r i c t c o o p e r a t i o n w i t h s c i e n t i s t s , because n o t h i n g can be done i n t h i s f i e l d w i t h o u t t h e h e l p of s c i e n c e . If c o n s t r u c t e d on i n t e r n a t i o n a l s c a l e , t h i s c o o p e r a t i o n could however become more f r u i t f u l and subs t a n t i a l . Three European meetings on o c c u p a t i o n a l s a f e t y have a l r e a d y been o rg a n i z e d a n d t h i s i n i t i a t i v e w i l l doubt

-

- wi t h o u t

continue i n t h e future.

The p a r t i c i p a t i o n of t h e s p e c i a l i s t s can and must b e more

433

numerous and e f f i c i e n t and CISM can c o n t r i b u t e t o t h i s i n i t i a t i v e g i v i n g t h e trade-unions t h e p o s s i b i l i t y of t a k i w advantage of t h e e x p e ri e n c e s and s c i e n t i f i c r e s e a r c h i n t h e f i e l d of v i b r a t i o n . I n t h e f u t u r e CISM could o rg an i ze t o g e t h e r w i t h t h e i n t e r e s t e d trade-unions,

e.g.

w i th t h e European F e d e r a t i o n

of t h e M e t a l l u r g i c a l a n d Mechanical Trade-3nions

-

PEM, o r

w i t h t h e I n t e r n a t i o n a l Union of t h e M e t a l l u r g i c a l and Mechan i c a l Trade-Unions,

a Symposium on t h e t h e o r e t i c a l and prac-

t i c a l problems of v i b r a t i o n . S p e c i a l i s t s a n d trade-union r e p r e s e n t a t i v e s should be i n v i t e d t o t a k e p a r t i n t h e mee t i n g s i n such a way t h e l i n k between s c i e n c e and occupation a l s a f e t y , which i s becoming more and more u r g e n t and n e c e s s a r y , c o u l d be st re n g t h e n e d , It i s s u r e t h a t whatever p ro p o s al CISM should p u t forward

i n t h i s co n n e c t i o n , i t w i l l a ro u s e g r e a t i n t e r e z t and f i n d t h e t r a d e u n i o n s w i l l i n g t o cooperate.

434

LIST OF PARTICIPANTS

ABRAMI Bruno, E n g i n e e r , San F e l i c e d i S e g r a t e , 20090 T o r r e I X , MILANO, I t a l y B I A N C H I Giovanni, P r o f e s s o r , S e c r e t a r y General of CISM, I s t i t u t o d i Meccanica k p p l i c a t a a l l e Macchine, P o l i t e c n i c o d i Milano, P i a z z a L. d a V i n c i 32, 20133 MILANO, I t a l y

BOVEKZI Massimo, Medical Doctor, I s t i t u t o d i Medicina d e l Lavoro, c / o Ospedale Maggiore, TRIFSTE, I t a l y DALE A l a n , Higher S c i e n t i f i c O f f i c e r , N.I.A.E., S i l s o e , BEDFORD, Great B r i t a i n

Wrest Park,

D I G I U L I O Augusto, Research Worker, I s t i t u t o d i E r g o t e c n i c a , P o l i t e c n i c o d i Milano, P i a z z a L. d a V i n c i 32, 20133 MILANO, I t a l y D I MARINO F u l v i o , A s s i s t a n t P r o f e s s o r , I s t i t u t o d i Meccanica A p p l i c a t a , U n i v e r s i t h d i T r i k s t e , TRIESTE, I t a l y

DUPUIS H e i n r i c h , P r o f e s s o r , I n s t . f o r Occupational H e a l t h and S o c i a l Medicine, Johannes Gutenberg U n i v e r s i t y , MAINZ, F.R. G.

FROLOV C o n s t a n t i n , D i r e c t o r of I n s t i t u t e , Mech. Eng. Research I n s t i t u t e , Griboedov S t r e e t 4 , MOSCOW C e n t r e 101000, U.S. S.R. GARG D.P., P r o f e s s o r , Department of Mechanical E n g i n e e r i n g and M a t e r i a l s S c i e n c e , Duke U n i v e r s i t y , DURHUT, NC 27706, U e S. A.

435

GILIOLI Renato, Neurologist, C l i n i c a d e l Lavoro, v i a San Barnaba 8, MILANO, I t a l y

GOLDSHTEIN Boris, Deputy General Manager f o r Researches, Ministry of C o n s t r u c t i o n a l , Road-Building and Communal Machinery, Leningradakaya S t r e e t 1 , MOSCOW, Distr. Khimki, U. So S o Re KSIAZEK Marek, Doctor (Ph. D ) , Tfie Technical U n i v e r s i t y of Krakow, I n s t i t u t e M 1 , ul. Warszawska 24, KRAKOW, Poland

-

MENSHOV Alexandre, Chief of Lab. V i b r . and Noise, I n s t . Labour Hyg. and Prof. Deseases, Sacsagansky 75, K I E V 252033, UeSoSoR. MF,STURIMO Claudio, Engineer, F. I.A.T. Auto S.p.A., D. I.P. S i s t e m i dell’Autom., Corso A g n e l l i 200, TORINO, I t a l y MUFTIC Osman., P r o f e s e o r , Cazmanska bb/B, Yugoslavia

ZAGREB 41000,

N I G G Benno M,, D i r e c t o r Biomechanics Laboratory, Laboratorium f t l r Biomechanik ETH Ztlrich, Weinberg S t r a s s e 98, ZURICH 8092, Switzerland

NOVOCELOV Evgeni, Research O f f i c e r , High Trade Union College of C e n t r a l Council of Trade Unions, Solianka 14/2, MOSCOW, U. S o S.R.

O U D Z K I Andrzej, Professor, Gorska 7 m 44. WARSAW 00-740, Poland PASCOLO Paolo, A s s i s t a n t P r o f e s s o r , I s t i t u t o d i Meccanica Applicata a l l e Macchine, U n i v e r s i t h d i T r l e s t e , TRIESTE, Italy *DOTTI Antonio, Ass. P r o f e s s o r , I s t i t u t o d i E l e t t r o n i c a , P o l i t e c n i c o d i Milano, MILANO, I t a l y PETRONIO Lucio, Medical Doctor, I s t i t u t o d i Yedicina d e l Lavoro, c/o Oepedale Maggiore, TRIESTE, I t a l y PETTERNELLA Massimiliano, D i r e c t o r , I s t i t u t o d i Automatice, UniversitA d i Roma, v i a Eudossiana 18, ROMA 00184, I t a l y

436

POPOVA Zdravka, Assistant Professor, Higher Inst. of Elect. and Mech. Engineer. YLenin I), "H. Bot ev", SOFIA 1156, Bulgaria PRAVOTOROVA Elene, Dr. Sc., Machinery Research Insitute, Griboedova Street; 4, MOSCOW, U.S.S.R. REPACI Antonino, Assistant Professor, Istituto di Meccanica Razionale, Polijecnico di Torino, Corso Duca degli Abruzzi 24, TORINO, Italy Giancarlo, Engineer, Pittini Impianti Industriali, Rivoli di Osoppo, UDINE, Italy

SARO

SCHNAUBER Herbert, Professor, Gesamthochschule Fachbereich Maschinentechnik I, SIEGEN 5900, F.R.G. SHEMJAKIN Evgeni, Professor Mechanics of Solids, Syberian Branch of Acad. of Sc., Pravda Street 1, NOVOSIBIRSK U. So S.R. SOLOVIEV Vsevolod, Dr. Sc., Machinery Research Institute, Griboedov Street 4, MOSCOW, U.S.S.R. TIRINDA Peter, Researcher, Slovak Academy of Sciences, Inst. of Machine Mech., Dubravska Cesta, BRATISLAVA 80900, Czechoslovakia TISCHKOV Anatole, Professor, Institute of Mining, Academy of Sciences, NOVOSIBIRSK, U.S.S.R. VAN CAMPEN Dick, Reader Eng. Mech., Department of Mechanical Engineering, Twente University of Technology, P.O. Box 217, ENSCHEDE, The Netherlands VASSILIEV Youri, Chief of Labour Inst. of Labour Protection, Central Council of Trade Unions, Obolenski 10, MOSCOW, U. S o So R. WEISS Franz, Engineer, Messerschmitt-BUlkow-Blohm, Postfach 8000

MUNCHEN 80, F.R.G.

ZAlWORSKI Vladimir, Professor, Department of Biomechanics, Central Institute of Physical Education, Sirenevy B1. 4, MOSCOW 115184, U.S.S.R.

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