SIST EN 60068-3-8:2004
(Main)Environmental testing -- Part 3-8: Supporting documentation and guidance - Selecting amongst vibration tests
Environmental testing -- Part 3-8: Supporting documentation and guidance - Selecting amongst vibration tests
Provides guidance for selecting amongst the EN 60068-2 stationary vibration test methods Fc sinusoidal, Fh random and F(x) Mixed mode vibration. The different steady-state test methods and their aims are briefly described in Clause 4. Transient test methods are not included. For vibration testing, the environmental conditions, especially the dynamic conditions for the specimen, should be known. This standard helps to collect information about the environmental conditions (Clause 5), to estimate or measure the dynamic conditions (Clause 6) and gives examples to enable decisions to be made on the most applicable environmental vibration test method. Starting from the condition, the method of selecting the appropriate test is given. Since real life vibration conditions are dominated by vibration of a random nature, random testing should be the commonly used method, see Table 1, Clause 7. The methods included hereafter may be used to examine the vibration response of a specimen under test before, during and after vibration testing. The selection for the appropriate excitation method is described in Clause 8 and tabulated in Table 2. In this standard specification, writers will find information concerning vibration test methods and guidance for their selection. For guidance on test parameters, or severities of one of the test methods, reference should be made to the normative references. Has the status of a basic safety publication in accordance with IEC Guide 104.
Umweltprüfungen -- Teil 3-8: Unterstützende Dokumentation und Leitfaden - Auswahl zwischen verschiedenen Schwingprüfverfahren
Essais d'environnement -- Partie 3-8: Documentation d'accompagnement et lignes directrices - Sélection d'essais de vibrations
Fournit les lignes directrices pour la sélection parmi les méthodes d'essais Fc de vibrations stationnaires sinusoïdales, Fh aléatoires et Fx composites de la série 60068-2. Ces différentes méthodes d'essais quasi stationnaires ainsi que leur objet sont brièvement décrites à l'Article 4. Les méthodes d'essais en transitoire ne sont pas incluses. Lors de la réalisation d'essais en vibration, il convient de connaître les conditions d'environnement, et spécialement les conditions dynamiques du spécimen en essai. La présente norme aide à réunir l'information relative aux conditions d'environnement (Article 5), à estimer ou à mesurer les conditions dynamiques (Article 6) et donne des exemples afin d'illustrer les choix à réaliser pour la plupart des méthodes d'essais applicables en environnement vibratoire. A partir des conditions d'environnement, la méthodologie de choix de l'essai approprié est fournie. Puisque les conditions d'environnement vibratoire naturelles sont de nature aléatoire, il est recommandé que les essais en vibrations aléatoires soient généralement, les méthodes retenues (voir Tableau 1, Article 7). Les méthodes décrites ci-après peuvent être utilisées pour examiner la réponse vibratoire du spécimen en essai avant, pendant et après un essai de vibrations. Le choix de la méthode appropriée est décrit à l'Article 8 et présenté au Tableau 2. Les spécificateurs trouveront dans la présente norme les informations relatives aux méthodes d'essais vibratoires et les lignes directrices pour choisir parmi elles la méthode appropriée. Pour choisir les paramètres ou les sévérités relatives à l'une de ces méthodes, il y a lieu de se reporter aux références normatives. A le statut d'une publication fondamentale de sécurité conformément au Guide 104 de la CEI.
Environmental testing - Part 3-8: Supporting documentation and guidance - Selecting amongst vibration tests (IEC 60068-3-8:2003)
General Information
Standards Content (Sample)
SLOVENSKI SIST EN 60068-3-8:2004
STANDARD
februar 2004
Environmental testing - Part 3-8: Supporting documentation and guidance -
Selecting amongst vibration tests (IEC 60068-3-8:2003)
ICS 19.040; 29.020 Referenčna številka
SIST EN 60068-3-8:2004(en)
© Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno
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EUROPEAN STANDARD EN 60068-3-8
NORME EUROPÉENNE
EUROPÄISCHE NORM November 2003
ICS 19.040; 29.020
English version
Environmental testing
Part 3-8: Supporting documentation and guidance –
Selecting amongst vibration tests
(IEC 60068-3-8:2003)
Essais d'environnement Umweltprüfungen
Partie 3-8: Documentation Teil 3-8: Unterstützende Dokumentation
d'accompagnement et lignes directrices - und Leitfaden –
Sélection d'essais de vibrations Auswahl zwischen verschiedenen
(CEI 60068-3-8:2003) Schwingprüfverfahren
(IEC 60068-3-8:2003)
This European Standard was approved by CENELEC on 2003-11-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2003 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60068-3-8:2003 E
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EN 60068-3-8:2003 - 2 -
Foreword
The text of document 104/308/FDIS, future edition 1 of IEC 60068-3-8, prepared by IEC TC 104,
Environmental conditions, classification and methods of test, was submitted to the IEC-CENELEC
parallel vote and was approved by CENELEC as EN 60068-3-8 on 2003-11-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2004-08-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2006-11-01
Annexes designated "normative" are part of the body of the standard.
In this standard, annex ZA is normative.
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60068-3-8:2003 was approved by CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 60721-3-0 NOTE Harmonized as HD 478.3.0 S1:1987 (not modified).
__________
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- 3 - EN 60068-3-8:2003
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of any
of these publications apply to this European Standard only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies (including
amendments).
NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
1) 2)
IEC 60068-1 - Environmental testing EN 60068-1 1994
Part 1: General and guidance
1) 2)
IEC 60068-2-6 - Part 2-6: Tests - Test Fc: Vibration EN 60068-2-6 1995
(sinusoidal)
1) 2)
IEC 60068-2-64 - Part 2-64: Test methods - Test Fh: EN 60068-2-64 1994
Vibration, broad-band random (digital
control) and guidance
3)
IEC 60068-2-80 - Part 2-80: Tests - Test Fi: Mixed mode - -
IEC 60721-3 Series Classification of environmental EN 60721-3 Series
conditions
Part 3: Classification of groups of
environmental parameters and their
severities
IEC 60721-4 Series Part 4: Guidance for the correlation and - -
transformation of environmental
condition classes of IEC 60721-3 to the
environmental tests of IEC 60068
IEC Guide 104 1997 The preparation of safety publications - -
and the use of basic safety publications
and group safety publications
1)
ISO 2041 - Vibration and shock - Vocabulary - -
1)
ISO 5348 - Mechanical vibration and shock - - -
Mechanical mounting of accelerometers
1)
Undated reference.
2)
Valid edition at date of issue.
3)
At draft stage.
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NORME CEI
INTERNATIONALE IEC
60068-3-8
INTERNATIONAL
Première édition
STANDARD
First edition
2003-08
PUBLICATION FONDAMENTALE DE SÉCURITÉ
BASIC SAFETY PUBLICATION
Essais d'environnement –
Partie 3-8:
Documentation d'accompagnement
et lignes directrices –
Sélection d'essais de vibrations
Environmental testing –
Part 3-8:
Supporting documentation and guidance –
Selecting amongst vibration tests
IEC 2003 Droits de reproduction réservés Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
y compris la photo-copie et les photocopying and microfilm, without permission in writing from
électronique ou mécanique,
microfilms, sans l'accord écrit de l'éditeur. the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
CODE PRIX
S
Commission Electrotechnique Internationale
PRICE CODE
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue
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60068-3-8 IEC:2003 – 3 –
CONTENTS
FOREWORD.5
INTRODUCTION.9
1 Scope.11
2 Normative references .11
3 Terms and definitions .13
4 Description of vibration test methods .15
4.1 General .15
4.2 Test methods .15
4.3 Accelerated testing.19
5 Vibration environment of a specimen .19
5.1 General .19
5.2 Collecting information, preparing a decision .19
5.3 Definition of dynamic conditions .21
6 Estimation of ‘real life’ dynamic conditions for the specimen.21
6.1 General .21
6.2 Measurement of dynamic conditions.21
6.3 Data analysis .23
7 Selection of test method .31
7.1 General .31
7.2 Sine testing .33
7.3 Random testing .33
7.4 Mixed mode testing .35
8 Vibration response investigation of the specimen .35
8.1 General .35
8.2 Aims, purposes .37
8.3 Sinusoidal excitation .37
8.4 Random excitation.39
8.5 Problem investigation (troubleshooting).39
8.6 Survival pass/fail criterion .39
8.7 Information to be given in the relevant specification .43
Bibliography.45
Figure 1 – Probability density of a single frequency sinusoidal signal.27
Figure 2 – Probability density of a mixture of sine and random signals.27
Figure 3 – Autocorrelation functions for various signals .29
Table 1 – Examples of vibration environment and recommended test method .31
Table 2 – Recommended method for response investigation.43
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60068-3-8 IEC:2003 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 3-8: Supporting documentation and guidance –
Selecting amongst vibration tests
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, and Guides (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted to
technical committees; any IEC National Committee interested in the subject dealt with may participate in this
preparatory work. International, governmental and non-governmental organizations liaising with the IEC also
participate in this preparation. IEC collaborates closely with the International Organization for Standardization
(ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60068-3-8 has been prepared by IEC technical committee 104:
Environmental conditions, classification and methods of test.
The text of this standard is based on the following documents:
FDIS Report on voting
104/308/FDIS 104/324/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
It has the status of a basic safety publication in accordance with IEC Guide 104.
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60068-3-8 IEC:2003 – 7 –
The committee has decided that the contents of this publication will remain unchanged until
2007. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
IEC 60068 consists of the following parts, under the general title Environmental testing:
Part 1: General and guidance
Part 2: Tests
Part 3: Supporting documentation and guidance
Part 4: Information for specification writers – Test summaries
Part 5: Guide to drafting of test methods
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60068-3-8 IEC:2003 – 9 –
INTRODUCTION
Components, equipment and other electrotechnical products, hereinafter called specimens,
can be subjected to different kinds of vibration during manufacture, transportation or in
service. In the IEC 60721-3 standards, those different vibration environments are tabulated
into classes characterizing stationary and transient vibration conditions. The standards in the
IEC 60068-2 series describe methods for testing with stationary or transient vibration. There
will be three standards in the IEC 60068-2 series for environmental testing that specify test
methods employing stationary vibration:
Part 2-6 Test Fc: Vibration (sinusoidal),
Part 2-64 Test Fh: Vibration, broad-band random (digital control) and guidance, and
1
Part 2-80 Test F-: Mixed mode testing
___________
1
Under consideration.
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60068-3-8 IEC:2003 – 11 –
ENVIRONMENTAL TESTING –
Part 3-8: Supporting documentation and guidance –
Selecting amongst vibration tests
1 Scope
This part of IEC 60068 provides guidance for selecting amongst the IEC 60068-2 stationary
vibration test methods Fc sinusoidal, Fh random and F(x) Mixed mode vibration. The different
steady-state test methods and their aims are briefly described in Clause 4. Transient test
methods are not included.
For vibration testing, the environmental conditions, especially the dynamic conditions for
the specimen, should be known. This standard helps to collect information about the
environmental conditions (Clause 5), to estimate or measure the dynamic conditions
(Clause 6) and gives examples to enable decisions to be made on the most applicable
environmental vibration test method. Starting from the condition, the method of selecting the
appropriate test is given. Since real life vibration conditions are dominated by vibration of a
random nature, random testing should be the commonly used method, see Table 1, Clause 7.
The methods included hereafter may be used to examine the vibration response of a
specimen under test before, during and after vibration testing. The selection for the
appropriate excitation method is described in Clause 8 and tabulated in Table 2.
In this standard specification, writers will find information concerning vibration test methods
and guidance for their selection. For guidance on test parameters, or severities of one of the
test methods, reference should be made to the normative references.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60068-1, Environmental testing – Part 1: General and guidance
IEC 60068-2-6, Environmental testing – Part 2-6: Tests – Test Fc: Vibration (sinusoidal)
IEC 60068-2-64, Environmental testing – Part 2-64: Test methods – Test Fh: Vibration, broad-
band random (digital control) and guidance
2
IEC 60068-2-80, Environmental testing – Part 2-80: Tests – Test F-: Mixed mode testing
IEC 60721-3 (all parts), Classification of environmental conditions – Part 3: Classification of
groups of environmental parameters and their severities
IEC 60721-4 (all parts), Classification of environmental conditions – Part 4: Guidance for
the correlation and transformation of environmental condition classes of IEC 60721-3 to the
environmental tests of IEC 60068-2
___________
2
Under consideration.
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60068-3-8 IEC:2003 – 13 –
IEC Guide 104:1997, The preparation of safety publications and the use of basic safety
publications and group safety publications
ISO 2041, Vibration and shock – Vocabulary
ISO 5348, Mechanical vibration and shock – Mechanical mounting of accelerometers
3 Terms and definitions
For the purposes of this document, terms and definitions used are generally defined in
ISO 2041, in IEC 60068-1, IEC 60068-2-6 or IEC 60068-2-64. Where, for the convenience of
the reader, a definition from one of those sources is included here, the derivation is indicated
and departures from the definitions in those sources are also indicated.
3.1
dynamic conditions
all parameters that describe the vibration environment for a specimen
3.2
stationary vibration
type of vibration with all the vibration-related parameters (statistical and spectral) constant
over time
3.3
frequency sweep
change of exciting frequency during sine testing
NOTE For further definitions for sine testing, see IEC 60068-2-6.
3.4
linear spectrum
type of spectrum used for periodic signals, usually calculated with fast Fourier transformation
(FFT) algorithms, units being, for example, m/s² × s or g/Hz or g × s.
[IES-RP-DET 012.1]
3.5
acceleration spectral density
ASD
type of spectrum used for stationary random signals, usually calculated using squared
discrete Fourier transformations (DFT): mean-square value of that part of an acceleration
signal passed by a narrow-band filter of a centre frequency, per unit bandwidth, in the limit as
the bandwidth approaches zero and the averaging time approaches infinity, sometimes called
2 2 2
autospectrum, the unit being (m/s ) /Hz or g /Hz
n
[ISO 2041, modified]
3.6
autocorrelation
statistical measure of the degree of which one part of a signal is related to another part (offset
by a given time) of the same signal
NOTE The Fourier transform of the autocorrelation function gives the autospectrum or ASD, the unit being a ratio
from –1 to +1.
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60068-3-8 IEC:2003 – 15 –
3.7
statistical degrees of freedom
DOF
for the estimation of the acceleration spectral density of random data with a time-averaging
technique, effective number of statistical degrees of freedom derived from the frequency
resolution and the effective averaging time
[IEC 60068-2-64, 4.3.5, ISO 2041, modified]
3.8
critical frequency
frequencies at which
– malfunctioning and/or deterioration of performance of the specimen, which are dependent
on vibration are exhibited, and/or
– mechanical resonances and/or other response effects occur, for example chatter
4 Description of vibration test methods
4.1 General
Environmental testing is used to simulate in a laboratory the effects of a real life vibration
environment. Vibration testing uses different input signals to excite the specimen, for example
on a vibration table. The test methods are characterized by those input signals.
4.2 Test methods
Sine and random vibration are different physical processes and produce different effects on
the specimen. The specification writer should be aware that, due to the physically different
processes there is no precise equivalence between sine and random vibration testing. It is
strongly recommended not to attempt to transfer severities from sine to random or vice versa.
A brief description of the various vibration test methods is given.
4.2.1 Sine testing
Sine testing (IEC 60068-2-6) uses a sinusoidal signal with constant or changing frequency
and amplitude. Only one frequency is applied at any instant in time. The test conditions
include frequency range (bands) or fixed frequencies, vibration amplitudes and test duration.
Sinusoidal vibration rarely, if ever, occurs as a single frequency vibration in isolation in a real
life environment. This can be the case even when measuring the acceleration directly on
rotating machinery. Practical tolerances and clearances, e.g. in gears and bearings, generally
result in a small change in frequency. Some form of random vibration is also produced by
random properties of the rotating machinery.
Sinusoidal vibration may be described as deterministic. It follows an established pattern so
that the value of the vibration at any designated future time is completely predictable from
the past history.
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60068-3-8 IEC:2003 – 17 –
An area where this type of testing can be advantageous is in the timing of a failure during a
frequency sweep, where it may be possible to associate it with a particular frequency that,
otherwise, may not be readily obvious if applying a random test. However, compared to
random vibration, it tends to take longer to produce failures because it excites each
resonance only briefly during a sweep. Although only one frequency is applied at any one
instant, it does allow a particular resonance of the specimen to potentially build to its full
amplitude, if the sweep-rate is low enough. It can also be used for establishing possible
damaging resonances particularly during design/development testing.
An additional use of sinusoidal vibration testing may be the frequency ‘dwell test’ either at
a) a known forcing frequency, or
b) at the resonance frequencies of the specimen.
4.2.2 Random testing
Random excitation uses a stochastic, random input signal, which includes all frequencies in a
specified frequency range (bandwidth) at all times (IEC 60068-2-64). The instantaneous values
are distributed normally (Gaussian). The distribution over the frequency range is specified by
an acceleration spectral density (ASD) curve.
Random vibration is the most commonly occurring type of excitation seen in a real life
environment. Its future instantaneous values are unpredictable from past time history and can,
therefore, only be predicted on the basis of probability. In fact, this property is applicable to
most calculations associated with random vibration, for example, fatigue, stress reversals and
so on.
In contrast to sinusoidal testing, random vibration excites a resonance continuously through-
out the test duration, although not to maximum value. Most random vibration signals in the
test laboratory contain three sigma levels which means that the instantaneous value of
excitation in the test frequency range could range between zero and three times the overall
r.m.s. value of the signal. A further difference to consider with random excitation is that there
are a number of stress reversals that can occur, in either the positive or negative direction, in
between a zero crossing. This property can influence the fatigue damage accumulation and
hence the life expectancy to failure.
4.2.3 Mixed mode testing
Mixed mode testing (IEC 60068-2-80) combines sinusoidal and random signals. Environments
with more than one vibration source can be simulated. Depending on the type of combined
vibration sources, the tests are called:
− sine on random (SoR);
− random on random (RoR);
− sine on random on random (SoRoR).
NOTE Shock on random (transient on stochastic vibration like gunfire test) is not included in this standard.
Mixed mode testing combines the advantages of both sine and random testing, permitting a
closer approximation to a real life environment. Furthermore, it does permit a greater degree
of test tailoring to be performed and it is equally important to minimize the degree of under- or
over-testing since either can have catastrophic consequences. Its major disadvantage is the
increase in complexity in understanding specifying, controlling and verifying the test.
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60068-3-8 IEC:2003 – 19 –
4.3 Accelerated testing
It may be necessary, for example, to limit test time, to raise the test severity above the actual
dynamic conditions. By increasing the vibration levels, the mechanical stresses in the
specimen increase and the lifetime for fatigue damage decreases. In general, accelerated
testing is possible with all the test methods described above.
Accelerated testing demands a high degree of engineering judgement in the choice of
acceleration factors. They are very different for diverse failure modes and depend on the
structure of the specimen itself (for example rattle due to slackness, non-linearities), the
materials (notch effects, welds, heat treatment), loading and other environmental conditions.
When high acceleration factors are used, other unrealistic failure modes or locations of
damage can occur on the specimen (IEC 60068-1) or important failure modes may be
removed. For example, fretting due to looseness between parts may be removed/inhibited by
unrealistic high test levels.
Example of an acceleration factor for mild steel:
For fatigue failure modes of mild steel, acceleration factors not greater than 2 are
recommended. The test acceleration levels a should be increased by not more than a
test
factor of 2 above the real life levels a . For a sine test, this means that the test amplitude
real life
a should be less than twice the real life amplitude a . The r.m.s. value of the
peak peak, real life
test excitation a during an accelerated random test should be limited to twice the real life
rms
r.m.s. value a .
rms, real life
Sine: a ≤ 2 × a
peak peak, real life
Random: a ≤ 2 × a
rms rms, real life
NOTE For mild steel and fatigue failure, an acceleration factor of 2 reduces the test time by a factor of between 8
and 32.
A higher acceleration factor may be appropriate if there is detailed knowledge about the
specimen, the failure mode, the location of damage, the stresses at this location, the
material and its fatigue characteristics (S/N-curve). Looking at the appropriate stress-
cycles-to-failure curves of the material considered, the acceleration factor can be chosen by
considering a reduced number of cycles-to-failure with respect to the actual one, and the
corresponding increased stress level. For accelerated fatigue testing, it is recommended to
use sine excitation at fixed or resonance frequencies.
5 Vibration environment of a specimen
5.1 General
Environmental testing is used to simulate in a laboratory the effects of a real life vibration
environment. In the following, a proposal to estimate this vibration environment is given.
5.2 Collecting information, preparing a decision
Define a life cycle of the specimen as defined in IEC 60721-4.
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