Disclosure to Promote the Right To Information

Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public.

इंटरनेट मानक

“!ान $ एक न' भारत का +नम-ण”Satyanarayan Gangaram Pitroda

“Invent a New India Using Knowledge”

“प0रा1 को छोड न' 5 तरफ”Jawaharlal Nehru

“Step Out From the Old to the New”

“जान1 का अ+धकार, जी1 का अ+धकार”Mazdoor Kisan Shakti Sangathan

“The Right to Information, The Right to Live”

“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता है”Bhartṛhari—Nītiśatakam

“Knowledge is such a treasure which cannot be stolen”

“Invent a New India Using Knowledge”

है”ह”ह

IS 14917-1 (2001): Mechanical Vibration - Laboratory Methodfor Evaluating Vehicle Seat Vibration, Part 1: BasicRequirements [MED 28: Mechanical Vibration and Shock]

IS 14917 (Part 1): 2001ISO 10326-1:1992

Indian Standard

MECHANICAL VIBRATION — LABORATORYMETHOD FOR EVALUATING VEHICLE

SEAT VIBRATIONPART 1 BASIC REQUIREMENTS

ICS 13.160

@ BIS 2001

BUREAU OF IN DI AN STAN DARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

January 2001Price Group 4

Mechanical Vibration and Shock Sectional Committee, ME 28

NATIONAL FOREWORD

This Indian Standard (Part 1) which is identical with ISO 10326-1 : 1992 ‘Mechanical vibration —Laboratory method for evaluating vehicle seat vibration — Patt 1: Basic requirements’ issued by theInternational Organization for Standardization (ISO) was adopted by the Bureau of Indian Standardson the recommendations of the Mechanical Vibration and Shock Sectional Committee and approval ofthe Mechanical Engineering Division Council.

The text of ISO Standard has been approved as suitable for publication as Indian Standard withoutdeviations. In the adopted standard, certain conventions are not identical to thos,e used in IndianStandards. Attention is especially drawn to the following:

a)

b)

In this

Wherever the words ‘International Standard’ appear referring to this standard, they should beread as ‘Indian Standard’.

Comma (,) has been used as a decimal marker while in Indian Standards, the current practiceis to use a full point (.) as the decimal marker.

adopted standard, reference appears to certain International Standards for which IndianStandards also exist. The corresponding” Indian Standards which are to be substituted in their placeare listed below along with their degree of equivalence for the editions indicated:

/ntemafiona/ Corresponding Degree ofStandard Indian Standard Equivalence

ISO 263

ISO 804

-1:1997 IS 13276 (Part 1) :2000 Evaluation of human Identicalexposure to whole body vibration: Part 1General requirements

:1990 Is 14737 : 1999 Human res~onse to dovibration — Measuring instrumenta~ion

For the purpose of deciding whether a particular requirement of this standard is complied with, thefinal value, observed or calculated, expressing the result of test or analysis shall be rounded off inaccordance with IS 2 : 1960, ‘Rules for rounding off numerical values ( reviseo)’. The (number ofsignificant places retained in the rounded off value should be the same as that of the specified value inthis standard.

IS 14917 (Partl ):2001ISO 10326-1 :1992

Indian Standard

MECHANICAL VIBRATION — LABORATORYMETHOD FOR EVALUATING VEHICLE

SEAT VIBRATIONPART 1 BASIC REQUIREMENTS

1 Scope

This part of ISO 10326 specifies basic requirementsfor the laboratory testing of vibration transmissionthrough a vehicle seat to the’ occupant. Thesemethods for measurement and analysis make itpossible to compare test results from different lab-oratories.

It specifies the test method, the instrumentation re-quirements, the measuring assessment method andthe way to report the test result.

This part of ISO 10326 applies to specific laboratoryseat tests which evaluate vibration transmission tothe occupants of any type of seat used in vehiclesand mobile off-road machinery.

Application standards for specific vehicles shouldrefer to this part of ISO 10326 when defining the testinput vibration that is typical for the vibrationcharacteristics of the type or class of vehicle ormachinery in which the seat is to be fitted.

2 Normative references

The following standards contain provisions which,through reference in this text, constitute provisionsof this part of ISO 10326. At the time of publication,the editions indicated were valid. All standards aresubject to revision, and parties to agreements basedon this part of ISO 10326 are encouraged to investi-gate the possibility of applying the most recent edi-tions of the standards indicated below. Members ofIEC and ISO maintain registers of currently valid in-ternational Standards.

ISO 2631-1:1985, Evaluation of human exposure towhole-body vibration — Part 1: General require-ments.

ISO 5347-0 :1987,. Methods for the calibration of vi-bration and shock pick-ups – Part O: Basicconcepts.

ISO 8041:1990, Human response to vibration –Measuring instrumentation.

3 General

The measurement and assessment methods givenin this part of ISO 10326 comply with the presentpractice standardized in ISO 2631-1. The measuringequipment and the frequency weighings shall be inaccordance with ISO 8041.

The primary test for the vibration characteristics ofthe seat involves measurements under conditionswhich simulate the range of actual uses of a vehicleor machine. For some applications, a secondary testis used to ensure that the seat responds acceptablyto occasional severe shocks or transient vibraiion.Given the present state of knowledge, a test toevaluate the damping of the seat suspension is pro-posed for this purpose. The seat to be tested shallbe mounted on a horizontal platform of a vibrationsimulator, which shall have movements in the verti-cal and/or one of the horizontal directions, asspecified in application standards.

NOTE 1 In order to make tests in both horizontal di-rections, x and y, the seat may be turned 90° on the plat-form.

1

IS 14917 ( Part 1 ) :2001ISO 10326-1 :1992

4 Instrumentation Dimensions in millimetres

4.1 Acceleration transducers

The measuring systems selected for the evaluationof vibration at the seat mounting base or platformof tbe vibration simulator and that selected for theevaluation of vibration transmitted to the seat occu-pant, or to an inert mass when used, shall havesimilar characteristics.

The characteristics of the vibration measuring sys-tem, accelerometers, signal conditioning and dataacquisition equipment, including recording devices,shall be specified in the relevant application stan-dard, especially the dynamic range, sensitivity, ac-curacy, linearity and overload capacity.

4.2 Transducer mounting

One accelerometer shall be located on the platform(P) at the place of the vibration transmission to theseat. The other accelerometer(s) shall be located atthe interface between the human body and the seat,at either the seat pan (S) and/or the backrest (B)(see figure 1).

4.2.1 Transducer mounting on the platform

The accelerometer on the platform shall be locatedwithin a circle with a diameter of 200 mm centreddirectly below the seat accelerometer. The measur-ing directions shall be aligned parallel to the move-ment of the platform,

4,2,2 Transducer mounting on the seat pan andlorbackrest

The accelerometers on the seat pan shall be at-tached in the centre of a mounting disc with a totaldiameter of 250 mm + 50 mm. The disc shall be asthin as possible (see figure 2). The height shall notbe more than 12 mm. This semi-rigid mounting discof approximately 80 to 90 durometer units (A-scale)moulded rubber or plastics material shall have acentre cavity in which to place the accelerometers.The accelerometers shall be attached to a thin metaldisc with a thickness of 1,5 mm t 0,2 mm and a di-ameter of 75 mm + 5 mm.

The mounting disc shall be placed on the surface ofthe seat pan and taped to the cushion in such a waythat the accelerometers are located midway be-tween the ischial tuberosities of the seat occupantwith a tolerance to be defined in the relevant appli-cation standards. Alternative positioning of the discmay be recommended for certain applications. Anyvariation from the position here defined shall bespecified in application standards.

Figure 1 – Location of the accelerometers on thepiatform (P), on the seat pan (S) and on the backrest

(B)

When tests are performed without a person sittingon the seat, e.g. during damping tests, the disc shallbe placed in the same position as if a per%on wereseated in the seat.

If measurements are made on the backrest, the ac-celerometers shall be (horizontally) located in thevertical longitudinal plane through the centre-line ofthe seat. The relevant application standards shallspecify the vertical position of the accelerometers.The measurement axes shall be aligned parallel tothe basicentric coordinate system.

NOTES

2 Besides the semi-rigid mounting disc recommendedfor soft or highly contoured cushions, a rigid disc with agenerally flat surface or an individual-form design may beused. Such discs may be, for instance, required for testingrail vehicle passenger seats. The transducer mountingshould be made of low-mass materials, so that the res-onant frequency of the mounting is at least four times thehighest frequency specified for the test.

3 For practical reasons, it is usually not possible to alignperfectly the accelerometers in the disc with the axes ofmotion of the platform. In a tolerance range within 15° ofthe appropriate axes, the accelerometers may be con-sidered as aligned parallel to the axes of interest. Fordeviations greater than 15“, acceleration should bemeasured along two axes and the acceleration vector sumalong the axis of interest should be calculated.

2

Is 14s17(F%wt 1 ] :2001ISO 10326-1:1992

Dimensions in mllllmetres

Thin metal disc for accelerometer Appropriate cavitymountandaddedmntre rlgldlty

\ rtar accelerometer(s)

Figure 2 – A semi-rigid mounting disc

4.3 Frequency weighting

Frequency weighting shall be in accordance withISO 8041.

4.4 Calibration

The instrumentation shall be calibrated in accord-ance with ISO 5347-O and, depending on the type ofmeasuring system used, to the relevant part of1s0 53471).

It is recommended to check the whole measuringchain following the specifications given in ISO 8041.

Calibration shall be made before and afler each test

series.

Where necessary, the output from each acceler-ometer amplifier shall be zeroed after mounting theaccelerometers in the test position.

5 Vibration equipment

5.1 Physical characteristics

The minimum equipment required is a vibrator ca-pable of driving the platform in the vertical and/or

horizontal directions. The dynamic response of theexciter’ shall be capable of exciting the seat with the

seated test person and additional equipment, in ac-cordance with the specified test input vibration.

Attributes of performance to be specified includefrequel}cy range and displacement capability ineach of the required directions.

Application standards shall specify the lowest ac-ceptable resonance frequency of the platform, theacceptable cross-axis motion of the platform and thefrequency range for which this applies,

1) Parts 1 to 20 are to be published.

Application standards shall specl~ requirements fortest stand dimensions and equipment to ensure thatthese are adequate for each particular application.

NOTE 4 It has been observed that the use of certainequipment (e.g. a steering wheel, pedals, etc.) may lowerthe repeatability of the results.

5.2 Control system

The frequency response characteristics of the vi-bration test system shall be compensated for to en-sure that the power spectral density (PSD) and theprobability density function (PDF) of the accelerationamplitudes of the vibration at the seat mountingbase comply with the requirements of the specifiedtest input vibration.

6 Safety requirements

Safety requirements with regard to tests in whichpeople are exposed to mechanical vibration and re-peated shock will be the subject of a future inter-national Standard.

Specific safety requirements shall be consideredwhen the relevant application standard is being de-veloped.

7 Test conditions

7.1 Test seat

7,1,1 General

The seat to be tested shall be representative of ac-tual or intended production models with regard todesign, construction, mechanical and geometricalcharacteristics, and any other factors which may af-fect the vibration test results.

IS 14917 ( Part 1 ) :2001ISO 10326-1 :1992

NOTE 5 The performance may vary between seats ofthe same type. Therefore, it i-srecommended to test morethan one seat.

7.1.2 Run-in periods for suspension seats

Suspension seats require a run-in period prior toexposure to vibration in order to free the movingparts of the suspension. This period shall be longenough for the seat performance to stabilize.

Any required air, hydraulic or electric power shallbe supplied to the seat at the pressure and flow rate,or voltage, recommended by the seat manufacturerand shall be connected to the seat in the mannerrecommended by the seat manufacturer. The testseat shall be loaded with an inert mass of75 kg ~ 1 % placed 6n the seat cushion, and theseat sh@l be adjusted according to the’ manufac-turer’s hwtructions for a nominal value of 100 kgoperator mass.

NOTE 6 A suitable inert mass consists of lead shot. Thelead shot can be contained within thin cushions which aresewn so as to form a quilt. About ten such cushions aresufficient to obtain a 75 kg mass.

During the run-in period, the test seat sha[l be ex-cited by a sinusoidal input vibration at approxi-mately the natural frequency of the suspension. Theamplitude of the applied sinusoidal vibration shallbe 75 O/. of the full amplitude of the seat suspension.

The dampef may over-heat during the run-in period.Therefore, use an automatic shut-down and monitorthe temperature of the damper.

If additional vibration tests in the horizontal directionare planned, the run-in procedure shall be followedunder the same conditions separately for each di-rection.

NOTE 7 Deviations from this run-in method for the seatsuspension may be specified in relevant application stan-dards for individual seat tests.

7.2 Test persons

Application standards shall specify the masses oftwo test persons to be used for the test. Thesemasses will normally be based on the 5th and the95th percentile masses of the population of vehicleor machinary users for which the seat is intended.The tolerance shall be low, preferably _~ % of therequired mass for the low-mass test person. For theheavy test person, a greater tolerance is permiss-ible, up to ‘~ 0/0 of the required mass.

NOTE 8 To meet the required mass of the test persons,added masses may be used. The use of added massesand other optional possibilities (such as carrying out thetest with only one test person) should be dealt with inapplication standards.

The application standards shall also define a pos-

ture appropriate to the application. This could in-clude some relationship between seat height andlongitudinal footrest position, absence or presenceof a steering wheel (and its position), and someguidance as to how the correct posture can be as-sured, e.g. by measurement of certain limb or jointangles.

The test persons shall be trained in preliminary testsuntil they have become accustomed to maintaininga normal, inactive behaviour and posture with re-spect to the seat throughout the test.

7.3 Other possibilities

In order to avoid the exposure of human beings to

testing, it may in future application standards bepossible to recommend other solutions.

8 Test input vibration

The application standards shall specify one or moredynamic tests, designed to ensure that a seat issuitable for the intended purpose. As a minimum,there shall be a test using an input representativeof severe but not abnormal use, in the course ofwhich the vibration transmitted to the interface be-tween the seat and the operator is measured, as thebasic performance parameter of the seat.

In order to specify the transmission characteristicsof seats with regard to different input frequencies(e.g. for tuning the vibration response of seats ondifferent types of vehicle, such as foam seats inpassenger cars), an alternative method is rec-ommended in 8.2 for the determination of the trans-fer function for the relevant frequency range with asinusoidal vibration input.

For seats with suspension systems used in off-roadmachinery, there should be a test of the effective-ness of the suspension damper in controlling oc-casional large-amplitude vibrations or shocks. Thiscan take the form of a sinusoidal test to determinethe maximum response of the seat at a frequencyclose to its resonant frequency when carrying asimple load equivalent to an average operator (e.g.the inert mass as specified in 7.1.2).

NOTE 9 In some case, a further or alternative test maybe needed to ensure that, under conditions of excessivesuspension travel, the suspension end stops are so con-structed as to keep the resulting shock acceleration at anacceptable level. Application standards should specify thisadditional test if needed.

8.1 Simuiated input vibration test

The simulated input test vibration shall be specifiedin accordance with the vehicle or machinery groupsdefined either by the acceleration power spectral

4

IS 14917 (Partl ):2001

ISO 10326-1 :1992

density function or by the time history of an actual available. All measurements shall be made with anand representative signal. inert mass of 75 kg + 1 0/0 on the seat, adjusted in

accordance with 7.1.2.When the input vibration is defined by PSD, the rel-evant application standard should give the equationdescribing the PSD and its tolerance. The equationfor the PSD may be in the form of filter equations,

8.3.2 Other seats

which should be those of a low-pass filte”r and ahigh-pass filter (the pair constituting a band-pass

Application standards may specify damping tests for

filter), both of the Butterworth type. The cut-off fre-non-suspension seats in a manner similar to that

quencies and the slopes of the filters shall be clearlydescribed above, with appropriate modifications.

defined.

When the input vibration is defined by a time history,the application standard shall specify the number ofmeasured (calculated) points, frequency and ampli-tude spacing and the sampling rate.

A tolerance on this level shall also be specifiedwhen the input vibration is defined by a time history.

The probability density function of the random vi-bration at the mqunting base of the seat during thetest may be required in application standards.

9 Test procedure

Mount the seat to be tested on the platform of thevibration simulator, in accordance with the specifiedtest seat arrangement. Check the safety require-ments and calibrate the instruments. Prior to thedamping test and simulated input vibration test,carry out the run-in procedure on the test seat (see7.1.2).

For both types of input vibration, the required rootmean square (r. m.s.) acceleration on the platform,CQ, shall be specified in application standards. 9.1 Simulated input vibration test

8.2 Transfer function with sinusoidal vibrationinput

The vibration transfer function test shall be carriedout with two persons, as specified in 7.2. Input vi-bration magnitude and phase versus frequency, fre-quency spacing, transient time and duration ofvibration input per frequency step shall be specifiedin application standards.

8.3 Damping test

8.3.1 Suspension seats

9.1.1 Position a test person in the seat. Operate thevibration simulator to produce the appropriate testinput vibration.

The test input vibration, during each test run, shallbe continuous to provide an analysing time sufficientto be specified in application standards.

Repeat the test to obtain three consecutive test runsin which the frequency-weighted r.m.s. accelerationvalues, ~, measured at the seat are within & 5 0/0of their arithmetic mean. Record this arithmeticmean as the fequency-weighted r.m.s. accelerationat the seat, ~s.

For the tests described above, the vibration at’theplatform during each test shall be within the PSDtolerances mentioned in 8.1. The arithmetic meanof the three test values measured at the platformshall be recorded as the frequency-weighted r.m.s.acceleration values at the platform, ~p.

Application standards shall specify the charac-teristics of either a sinusoidal vibration or a random 9,1.2 If the purpose of the simulated input vibrationvibration to be used to assess the damping of sus-pension seats. The sine-wave test shall be con-

test of the relevant application standard is to obtain

ducted at the resonance frequency of the seatthe seat effective amplitude transmissibility factor(SEAT) of the seat, calculate the ratio of the re-

suspension. This resonance frequency shall be de-termined by exciting the seat in the frequency range

corded values as follows:

from 0,5 to 2,0 times the expected resonance fre-quency. This displacement amplitude for both the

SEAT =%

damping test and the determi.nation of the reson-ance frequency shall be (75 + 5) 0/0 of the full travel where Q and cqP are as defined in 9.1.1.

5

IS 14917 ( Part 1 ) :2001

ISO 10326-1 :1992

9.1.3 If the purpose of the simulated input vibrationtest is to obtain the absolute magnitude for vibrationto be transmitted to a person in a vehicle or ma-chinery, the magnitude on the seat, ~s, shall becorrected according to the ratio between the meas-ured test input magnitude, ~p, and the intended in-put value &. The corrected magnitude on the seat,&$, is given by

%s’f&P4s = qp

The acceptance value for the simulated input vi-bration test shall be given either as the maximumvalue of the SEAT or the maximum corrected m.a9-nitude on the seat, u&. To pass the test, lower val-ues than this maximum shall be obtained for eachtest person.

The acceptance value for the damping testdefined as transmissibility at resonance.

or

~s = SEAT.&p

11 Test report

where SEAT is as defined in 9.1.2.

9.2 Damping test

Load the seat with an inert mass of 75 kg & 1 V.(see 7.1.2).

Apply the required peak-to-peak displacement am-plitude to the base of the seat at the resonance fre-quency. ~, of the suspension.

Repeat the test to obtain three consecutive test runsin which the r.m.s. acceleration values, u&), meas-ured at the disc are within + 5 0/0 of their arithmeticmean. Record this arithmetic mean, u.#J.

Note the arithmetical mean of the three values of ther.m. s. acceleration values, +~r), measured on theplatform.

Calculate the transmissibility, T, at resonance of theseat as the ratio of the registered values, as follows:

10 Acceptance

Under the test procedures of this part of ISO 10326,acceptance values from the simulated input vi-bration test ardior damping test can be defined.Application standards shall state the acceptancevalues relevant to the specific seat test.

The test report should contain the following:

shall be

a)

b)

c)

d)

e)

9

9)

h)

i)

j)

name and address of seat manufacture~

model of seat, product and serial numbec

date of test;

duration of run-in period, in hours;

type of measurement equipment and mountingdisc used (semi-rigid or rigid);

characteristics of the simulated input vibrationtest;

vibration transmission to the test persons duringthe simulated input vibration test

— mass of test persons, in kilograms,

– SEAT-factor, andlor

— corrected magnitude on the seat surface;

transmissibility at resonance during the dampingtest and the resonance frequency (alternatively,the transfer function with sinusoidal-vibration in-put) ;

name of person responsible for the test;

identification of test laboratory.

6

IS 14917 (Partl ):2001

ISO 10326-1 :1992

Annex A(informative)

Bibliography

[1] 1S02041:1990, Vibration andshock– Vocabu- [2] ISO 5805:– 2), Mechanjca/ vibration and shock

Iary. affecting man — Human exposure –Vocabulary.

2) To be published. (Revision, of ISO 5805:1981)

7

Bureau of Indian Standards

BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promoteharmonious development of the activities of standardization, marking and quality certification of goodsand attending to connected matters in the country.

Copyright

BIS has the copyright of all its publications. No part of these publications may be reproduced in any formwithout the prior permission in writing of BIS. This does not preclude the free use, in the course ofimplement ing the standard, of necessary details, such as symbols and sizes, type or grade designations.Enquiries relating to copyright be addressed to the Direetor (publications), BIS.

Review of Indian Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewedperiodically; a standard along with amendments is reaffied when such review indicates that no changes areneeded; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standardsshould ascertain that they are in possession of the latest amendments or edition by m,ferring to the latest issue of‘BIS Catalogue’ and ‘Standards: Monthly Additions’.

This Indian Standard has been developed from Doc : No. ME 28 (0543).

Amendments Issued Since Publication

Amend No. Date of Issue Text Affeeted

BUREAU OF INDIAN STANDARDS

Headquarters :

Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002 Telegrams : ManaksansthaTelephones :3230131,3233375,3239402 (Common to all oflices)

Regional Offices : Telephone

Central : Manak Bhavan, 9 Bahadur Shah Zafiir Marg

{

3237617NEW DELHI 110002 3233841

Eastern : 1/14 C. I. T. Scheme VII M, V. I. P. Road, Kankurgachi

{

3378499,3378561CALCUTTA 700054 3378626,3379120

Northern : SCO 335-336, Sector 34-A, CWIGARH 160022

{

603843602025

Southern : C. L T. Campus, IV Cross Road, CHENNAI 600113

{

2350216,23504422351519>2352315

Western : Manakalaya, E9 MIDC, Marol, Andheri (East)

{

8329295,8327858MUMBAI 400093 8327891,8327892

Branches : AHMADABAD. BANGALORE. BHOPAL. BHUBANESHWAR. COIMBATORE.FARIDABAD. GHAZIABAD. GUWAHATI. HYDERABAD. JAIPUR. KANPUR.LUCICNOW. NAGPUR. PATNA. PUNE. RAJKOT. THIRUVANANTHAPURAM.

priuted w PR lNTO~RAPH. New Delhi