IEC 60068-2-57:2013

IEC 60068-2-57 ®
Edition 3.0 2013-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing –
Part 2-57: Tests – Test Ff: Vibration – Time-history and sine-beat method

Essais d'environnement –
Partie 2-57: Essais – Essai Ff: Vibrations – Méthode par accélérogrammes et
sinusoïdes modulées
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IEC 60068-2-57 ®
Edition 3.0 2013-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing –
Part 2-57: Tests – Test Ff: Vibration – Time-history and sine-beat method

Essais d'environnement –
Partie 2-57: Essais – Essai Ff: Vibrations – Méthode par accélérogrammes et

sinusoïdes modulées
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX X
ICS 19.040 ISBN 978-2-83220-745-1

– 2 – 60068-2-57 © IEC:2013
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 Test requirements and associated parameters . 15
4.1 General . 15
4.2 Requirements for testing . 15
4.3 Vibration response investigation . 16
4.3.1 General . 16
4.3.2 Basic motion . 16
4.3.3 Transverse motion . 16
4.3.4 Rotational motion . 16
4.3.5 Measuring points . 16
4.3.6 Vibration amplitude tolerances . 17
4.3.7 Frequency tolerances . 17
4.3.8 Sweeping . 17
4.3.9 Damping ratio . 17
4.4 Time-history testing . 18
4.4.1 Basic motion . 18
4.4.2 Transverse motion . 18
4.4.3 Rotational motion . 18
4.4.4 Tolerance zone for the required response spectrum . 18
4.4.5 Frequency range . 19
4.5 Sine-beat testing . 19
4.5.1 General description . 19
4.5.2 Vibration amplitude tolerances . 19
4.5.3 Test frequency tolerances . 19
4.5.4 Transverse motion . 19
4.6 Mounting . 20
5 Severities . 20
5.1 General . 20
5.2 Time history . 20
5.3 Test frequency range. 21
5.4 Required response spectrum . 21
5.5 Number and duration of time-histories . 21
5.5.1 Number of time histories . 21
5.5.2 Time-history duration . 21
5.5.3 Duration of the strong part of the time history . 22
5.5.4 Number of high stress cycles . 22
5.6 Sine-beat test level . 23
5.6.1 General . 23
5.6.2 Test frequency determination . 29
5.6.3 Sine-beat test wave . 29
5.6.4 Number of cycles in the sine beat . 29
5.6.5 Modulating frequency . 30

60068-2-57 © IEC:2013 – 3 –
5.6.6 Number of sine beats. 31
5.6.7 High-stress low-cycle fatigue effects . 31
6 Preconditioning . 31
7 Initial measurements . 31
8 Testing . 31
8.1 General . 31
8.2 Vibration response investigation . 31
8.3 Time-history testing . 32
8.4 Sine-beat testing . 32
8.5 Multi-axis testing . 32
8.5.1 General . 32
8.5.2 Single axis testing . 32
8.5.3 Biaxial testing . 32
8.5.4 Triaxial testing . 32
9 Intermediate measurements . 33
10 Recovery . 33
11 Final measurements . 33
12 Information to be given in the relevant specification. 33
13 Information to be given in the test report . 34
Annex A (informative) Guidance for time-history and sine-beat methods . 35
Bibliography . 41

Figure 1 – Sequence of five sine beats with five cycles . 7
Figure 2 – Number of cycles per sine beat . 13
Figure 3 – Typical time history . 14
Figure 4 – Typical logarithmic plot of a required response spectrum, test response
spectrum and tolerance zone . 14
Figure 5 – Typical response of an oscillator excited by a specific time history during a
test . 22
Figure 6 – Recommended test level with crossover frequency at 0,8 Hz . 24
Figure 7 – Recommended test level with crossover frequency at 1,6 Hz . 26
Figure 8 – Recommended test level with crossover frequency at 8 Hz . 28
Figure 9 – Amplification factors of different sine beats, continuous sine and a typical
natural time-history . 30
Figure A.1 – Recommended shape of a required response spectrum in generalized
form . 37
Figure A.2 – Standardized presentation of matched sine beats of acceleration, velocity
and displacement (five cycles within the sine beat of acceleration) . 40

Table 1 – Comparison of tolerances . 15
Table 2 – Recommended test frequency ranges . 21
Table 3 – Recommended test levels with a crossover frequency of 0,8 Hz (see Figure 6) . 23
Table 4 – Recommended test levels with a crossover frequency of 1,6 Hz (see Figure 7) . 25
Table 5 – Recommended test levels with a crossover frequency of 8 Hz (see Figure 8) . 27

– 4 – 60068-2-57 © IEC:2013
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
ENVIRONMENTAL TESTING –
Part 2-57: Tests – Test Ff: Vibration –
Time-history and sine-beat method

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,
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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-
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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
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
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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 60068-2-57 has been prepared by IEC technical committee 104:
Environmental conditions, classification and methods of test.
This third edition cancels and replaces the second edition, published in 1999. It also replaces
IEC 60068-2-59:1990, which will be withdrawn.
This edition includes only minor technical changes with respect to the previous edition:
– editorially combines IEC 60068-2-57 and IEC 60068-2-59;
– the title has been modified to include a sine beat method.
The text of this standard is based on the following documents:
FDIS Report on voting
104/595/FDIS 104/612/RVD
60068-2-57 © IEC:2013 – 5 –
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.
A list of all the parts in the IEC 60068 series, published under the general title Environmental
testing, can be found on the IEC website.
This standard is to be used in conjunction with IEC 60068-1.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – 60068-2-57 © IEC:2013
INTRODUCTION
This part of IEC 60068 details methods for testing components, equipment and other
electrotechnical products (hereinafter referred to as “specimens”) which in service can be
subjected to random or oscillating type dynamic forces of short duration, typical examples of
which are the stresses induced in equipment as a result of earthquakes, explosions and
certain phases of transportation, or by transient, short time vibration in machinery.
The characteristics of these forces and the damping of the specimen may be such that the
vibration response of the specimen will not reach a steady-state condition.
The time-history test consists, after any preliminary vibration response investigation with
sinusoidal or random vibration, in subjecting the specimen to a vibration (acceleration,
velocity or displacement) the time history being specified by a response spectrum with
characteristics simulating the effects of the dynamic forces.
A time history may be developed or obtained from
– a natural event (natural time history),
– a random sample


artificial time history.
– a synthesized signal 
In general, to adapt to the required testing severity, some modification is necessary.
The use of a time history allows a single test wave to envelop a broadband response
spectrum.
It is possible for all the modes of the structure in the excitation axis (or axes) to be excited at
the same time and consequently the stresses derived from the combined effects of the
coupled modes are generally taken into account.
In the sine beat test, the specimen is excited at fixed frequencies with a preset number of sine
beats (see Figure 1). These fixed test frequencies are predetermined test frequencies, or
critical frequencies identified by means of a sinusoidal vibration test (IEC 60068-2-6), or both.
Pauses are provided between the individual sine beats in order to allow decay of the free
response of the specimen.
In Clause 12 specification writers will find a list of details to be considered for inclusion in
specifications and, in Annex A, guidance giving necessary extra information.

60068-2-57 © IEC:2013             – 7 –

st nd rd th th
1 sine beat Pause 2 sine beat Pause 3 sine beat Pause 4 sine beat Pause 5 sine beat
f
Test frequency
f
Modulating frequency Time
Five cycles
IEC  907/13
Figure 1 – Sequence of five sine beats with five cycles

Vibration amplitude
– 8 – 60068-2-57 © IEC:2013
ENVIRONMENTAL TESTING –
Part 2-57: Tests – Test Ff: Vibration –
Time-history and sine-beat method

1 Scope
This part of IEC 60068 provides a standard procedure for determining, by the time-history and
sine-beat methods, the ability of a specimen to withstand specified severities of transient
vibration.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60068 (all parts), Environmental testing
IEC 60068-1, Environmental testing – Part 1: General and guidance
IEC 60068-2-6:2007, Environmental testing – Part 2-6: Tests – Test Fc: Vibration (sinusoidal)
IEC 60068-2-47:2005, Environmental testing – Part 2-47: Tests – Mounting of specimens for
vibration, impact and similar dynamic tests
IEC 60068-2-64:2008, Environmental testing – Part 2-64: Tests –Vibration, broadband random
and guidance
IEC 60068-3-3:1991, Environmental testing – Part 3: Guidance – Seismic test methods for
equipments
IEC 60068-3-8, Environmental testing – Part 3-8: Supporting documentation and guidance –
Selecting amongst vibration tests
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
NOTE Some of the following terms can be found in ISO 2041, IEC 60068-1 or in IEC 60068-2-6. Where, for the
convenience of the reader, a definition from one of those sources is included here, it is indicated.
3.1
critical frequency
frequency 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
[SOURCE: IEC 60068-2-6:2007, definition 3.9]

60068-2-57 © IEC:2013 – 9 –
3.2
crossover frequency
frequency at which the characteristic of a vibration changes from one relationship to another
Note 1 to entry: For example, a crossover frequency may be that frequency at which the test vibration amplitude
changes from a constant displacement value versus frequency to a constant acceleration value versus frequency.
[SOURCE: ISO 2041:2007, definition 2.118]
3.3
damping
progressive reduction of the amplitude with time due to the dissipation of energy in a system
Note 1 to entry: In practice, damping depends on many parameters, such as the structural system, mode of
vibration, strain, applied forces, velocity, materials, joint slippage, etc.
[SOURCE: IEC 60068-2-6:2007, definition 3.8, modified – original text reads "generic term
ascribed to the numerous energy dissipation mechanisms in a system"; Note remains same]
3.4
viscous damping
damping that occurs when an element or a part of a vibration system is resisted by a force the
magnitude of which is proportional to the velocity of the element and the direction of which is
opposite to the direction of the velocity
3.5
critical damping
C
c
minimum viscous damping that will allow a displaced system to return to its initial position
without oscillation
3.6
damping ratio
ratio of actual viscous damping to critical damping in a system with viscous damping
Note 1 to entry: The damping ratio (DR) can be calculated using the formula DR = C/C where C is actual viscous
C
damping value and C is the critical damping.
C
Note 2 to entry: This parameter is normally expressed as a percentage value.
3.7
signal tolerance
 NF 
signal tolerance T = × 100 (per cent)
 −1
F
 
where
NF is the r.m.s value of the unfiltered signal;
F is the r.m.s value of the filtered signal.
Note 1 to entry: This parameter applies to whichever signal, i.e. acceleration, velocity or displacement, is being
used to control the test (see A.2.2 of IEC 60068-2-6:2007)
3.8
fixing point
part of the specimen in contact with the fixture or vibration table at a point where the
specimen is normally fastened in service
Note 1 to entry: If a part of the real mounting structure is used as the fixture, the fixing points are taken as those
of the mounting structure and not of the specimen.
[SOURCE: IEC 60068-2-6:2007, definition 3.1, modified – omission of the second NOTE]

– 10 – 60068-2-57 © IEC:2013
3.9
standard acceleration
g
n
standard acceleration due to the earth's gravity, which itself varies with altitude and
geographical latitude
Note 1 to entry: For the purposes of this standard, the value of g is rounded up to the nearest whole number, that
n
is 10 m/s .
3.10
high stress cycles
response cycles giving rise to values of stress which may cause degradation, deformation or
low cycle fatigue in the specimen
Note 1 to entry: Stresses in the specimen are normally not measured or controlled. High stress is used here as a
circumscription for high excitation, see A.1.4.
3.11
measuring points
specific points at which data are gathered for conducting the test
Note 1 to entry: These points are of two main types, as defined below
Note 2 to entry: Measurements may be made at points within the specimen in order to assess its behaviour; these
are not considered as measuring points in the sense of this standard.
[SOURCE: IEC 60068-2-6:2007, definition 3.2]
3.11.1
check point
point located on the fixture, the real mounting structure, on the vibration table or on the
specimen as close as possible to one of its fixing points and in any case rigidly connected to it
Note 1 to entry: A number of check points are used as a means of ensuring that the test requirements are
satisfied.
Note 2 to entry: If four or fewer fixing points exist, each is used as a check point. If more than four fixing points
exist, four representative fixing points will be defined in the relevant specification to be used as check points.
Note 3 to entry: In special cases, for example for large or complex specimens, the check points will be prescribed
by the relevant specification if not close to the fixing points.
Note 4 to entry: Where a large number of small specimens are mounted on one fixture, or in the case of a small
specimen where there are a number of fixing points, a single check point (that is the reference point) may be
selected for the derivation of the control signal. This signal is then related to the fixture rather than to the fixing
points of the specimen(s). This procedure is only valid when the lowest resonance frequency of the loaded fixture
is well above the upper frequency of the test.
3.11.2
reference point
point, chosen from the check points, whose signal is used to control the test, so that the
requirements of this standard are satisfied
[SOURCE: IEC 60068-2-6:2007, definition 3.2.2]
3.12
modulating frequency
frequency with which the test frequency is modulated
Note 1 to entry: See A.2.2 and Figure 1.

60068-2-57 © IEC:2013 – 11 –
3.13
natural time history
recording, as a function of time, of the acceleration, velocity or displacement, etc., resulting
from a given event
3.14
oscillator
single degree of freedom system intended to produce or be capable of maintaining
mechanical oscillations
3.15
pause
interval between two consecutive time histories or sine beats
Note 1 to entry: A pause should be such as to result in no significant superposition of the response motion of the
specimen.
For sine beats, this is:
1 100
T > ⋅
f C
c
where
T is the duration (s);
f is the sine beat test frequency (Hz);
C is the critical damping at the test frequency (in per cent).
c
3.16
preferred testing axes
three orthogonal axes which correspond to the most vulnerable axes of the specimen
3.17
required response spectrum
response spectrum specified by the user (customer)
3.18
response spectrum
plot of the maximum response to a defined input motion of a family of single-degree-of-
freedom bodies as a function of their natural frequencies and at a specified damping ratio
3.19
sine beat
continuous sinusoidal wave of one frequency which is modulated by a sinusoidal wave of a
lower frequency
Note 1 to entry: The duration of one sine beat is half the period of the modulating frequency (see Figure 2).
Note 2 to entry: See A.2.2.1 for a mathematical explanation of the sine-beat signal.
3.20
strong part of the time history
part of time history from the time when the plot first reaches 25 % of the maximum value to
the time when it falls for the last time to the 25 % level (see Figure 3)
3.21
sweep cycle
traverse of the specified frequency range once in each direction, for example 1 Hz to 35 Hz to
1 Hz
– 12 – 60068-2-57 © IEC:2013
[SOURCE: IEC 60068-2-6:2007, definition 3.4, modified – values changed, were "10 Hz to
150 Hz to 10 Hz"]
3.22
synthesized time history
artificially generated time history such that its response spectrum envelops the required
response spectrum
3.23
test frequency
frequency at which the specimen is to be excited with sine beats during a test
Note 1 to entry: A test frequency is one of two types which are defined below.
3.23.1
predetermined test frequency
frequency prescribed by the relevant specification.
3.23.2
investigated test frequency
frequency obtained by a vibration response investigation
3.24
test level
largest peak value within a test wave
Note 1 to entry: This definition is not applicable to time-history testing.
Note 2 to entry: For the sine beat method, this is equal to or a negligibly smaller value than the peak value of the
modulating half-wave for sine beats.
3.25
test response spectrum
response spectrum derived from the real motion of the vibration table either analytically or by
using spectrum analysis equipment
3.26
time history
recording, as a function of time, of acceleration, velocity or displacement
Note 1 to entry: A definition of a mathematical term “time-history” is given in ISO 2041 and relates to the
magnitude of a quantity expressed as a function of time.
3.27
zero period acceleration
high frequency asymptotic value of acceleration of the response spectrum
Note 1 to entry: The zero period acceleration is of practical significance as it represents the largest peak value of
acceleration, for example in a time history. This is not to be confused with the peak value of acceleration in the
response spectrum. For an example see Figure 4.

60068-2-57 © IEC:2013 – 13 –
a) Sine beat of 3 cycles
b) Sine beat of 5 cycles
c) Sine beat of 10 cycles
d) Sine beat of 20 cycles
IEC  908/13
Figure 2 – Number of cycles per sine beat

– 14 – 60068-2-57 © IEC:2013
+100
+50
+25
Time
–25
–50
–100
Strong part
IEC  909/13
Figure 3 – Typical time history

Test response spectrum
points located outside
the tolerance zone
Required response spectrum
+ 50 %
Test response spectrum
Tolerance zone
Zero period acceleration
Frequency
IEC  910/13
Figure 4 – Typical logarithmic plot of a required response spectrum,
test response spectrum and tolerance zone
Acceleration  (%)
Acceleration
60068-2-57 © IEC:2013 – 15 –
4 Test requirements and associated parameters
4.1 General
The purpose of this test is to determine mechanical weakness and/or degradation in specified
performance and to use this information, in conjunction with the relevant specification, to
decide whether a specimen is acceptable or not. It may also be used, in some cases, to
demonstrate the mechanical robustness of specimens and/or to study their dynamic
behaviour.
The extent to which a specimen has to function during vibration or merely to survive
conditions of vibration shall be stated in the relevant specification.
Procedures are described for conducting the test and for the measurement of the vibration at
given points. The requirements for the vibration motion and for the choice of severities
(including frequency range, required response spectrum, number of high-stress cycles and
number of time-histories, sine-beat cycles and number of sine beats) are also detailed.
It is emphasized that vibration testing always demands a certain degree of engineering
judgement and both supplier and purchaser should be fully aware of this fact. The writer of
the relevant specification is expected to select the testing procedure and the values of
severity appropriate to the specimen and its use.
For the purpose of this test, the specimen is always fastened directly to the vibration table
with its real mounting or a fixture.
In order to facilitate the use of this standard, references are given in the main body of the
standard where the reader is invited to refer to Annex A; at the same time, clause numbers in
the main body of the standard are also referred to in Annex A. These clauses provide specific
information on the correlation between sine beats of displacement, velocity and acceleration.
4.2 Requirements for testing
The requirements for a vibration response investigation are given in 4.3, those for time-history
testing in 4.4, those for sine-beat testing in 4.5 while 4.6 deals with mounting for testing. The
tolerances applicable to the vibration response investigation and to sine-beat and time history
testing are compared in Table 1.
Table 1 – Comparison of tolerances
Parameter Tolerance
Vibration response investigation Sine-beat and time-history testing
Signal tolerance 5 % (see 4.3.5.3) of basic motion Not applicable
Vibration at reference
±15 % (see 4.3.6 a)) of basic motion
point
Vibration at check points
±25 % up to 500 Hz (see 4.3.6 b)) of acceleration
±50 % above 500 Hz (see 4.3.6 b)) of acceleration
Transverse motion 50 % or 25 %
25 % (see 4.4.2)
(for special cases see 4.3.3)
Test frequency (for alternatives see 4.3.7) a) Predetermined (see 4.5.3.2)
±0,05 Hz up to 0,5 Hz ±0,05 Hz up to 0,5 Hz
±10 % from 0,5 Hz to 5 Hz ±10 % from 0,5 Hz to 5 Hz
±0,5 Hz from 5 Hz to 100 Hz ±0,5 Hz from 5 Hz to 100 Hz
±0,5 % above 100 Hz ±0,5 % above 100 Hz
b) Investigated (see 4.5.3.3): ±2 %

– 16 – 60068-2-57 © IEC:2013
4.3 Vibration response investigation
4.3.1 General
When prescribed by the relevant specification, the vibration response investigation shall (see
8.2) be carried out with single axis excitation in a manner based on that of IEC 60068-2-6
particularly taking account of 4.3.2 to 4.3.9 below in order to determine the critical frequencies
and, where required, the damping ratio. If considered appropriate, or if specified by the
relevant specification, the vibration response investigation may be performed using random
vibration in a manner based upon that of IEC 60068-2-64.
4.3.2 Basic motion
The basic motion shall be a sinusoidal function of time and such that the fixing points of the
specimen on the vibration table, which shall be prescribed by the relevant specification, move
substantially in phase and in straight parallel lines, subject to the limitations imposed in 4.3.3,
4.3.4 and 4.3.6.
4.3.3 Transverse motion
The maximum vibration amplitude at the check points in any axis perpendicular to the
specified axis shall not exceed 50 % of the basic motion amplitude. In special cases, for
example a small specimen, the peak value of the permissible transverse motion may be
limited to 25 % if required by the relevant specification.
At some frequencies, or with large size or high mass specimens, it may be difficult to achieve
these values (see also A.1.1). In such cases, the relevant specification shall state which of
the following applies:
a) transverse motion in excess of that stated above shall be reported in the test report;
b) transverse motion need not be monitored.
4.3.4 Rotational motion
Where spurious rotational motion of the vibration table is likely to be important, a tolerable
level, which shall then be reported in the test report, may be prescribed in the relevant
specification.
4.3.5 Measuring points
4.3.5.1 Reference point
The relevant specification shall state whether single point or multipoint control is to be used.
Where multipoint control is prescribed by the relevant specification, it shall specify whether
the average value of the signal at the check points or the value of the signal at a selected
point is to be controlled at the specified level.
4.3.5.2 Check points
At some frequencies, or with large size or high mass specimens, it may be difficult to achieve
the required tolerances in 4.3.6 b) (see also A.1.1). In these cases, it is expected that a wider
tolerance will be prescribed by the relevant specification or that the use of an alternative
method of assessment will be reported in the test report.
4.3.5.3 Signal tolerance
The signal tolerance measurement shall be carried out at the reference point at frequencies
up to five times the test frequency.
The signal tolerance as defined in 3.7 shall not exceed 5 % of the basic motion.

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NOTE In some instances it may not be possible to achieve this, in which case a value of signal tolerance greater
than 5 % is acceptable if the test amplitude of the control signal at the fundamental frequency is restored to the
specified value, for example by the use of a tracking filter.
In the case of large or complex specimens, where the specified values of signal tolerance
cannot be satisfied at some parts of the frequency range and it is impracticable to use a
tracking filter, the acceleration amplitude need not be restored and the signal tolerance shall
then be reported in the test report (see A.1.1).
The relevant specification may require that the signal tolerance, together with the frequency
range affected, is stated in the test report (see Clause 13), and whether or not a tracking filter
has been used.
4.3.6 Vibration amplitude tolerances
The basic motion along the required axis at the check and reference points shall be equal to
the specified values within the following tolerances. These tolerances include instrument
errors:
a) Reference point
Tolerance on the control signal at the reference point shall be ±15 % of basic motion.
b) Check points
Tolerance at each check point: up to 500 Hz shall be ±25 % of acceleration; above 500 Hz:
±50 % of acceleration (see also 4.3.5.2).
4.3.7 Frequency tolerances
The tolerances on the critical frequencies shall be as follows:
− up to 0,25 Hz:  ±0,05 Hz;
− from 0,25 Hz to 5 Hz: ±20 %;
− from 5 Hz to 50 Hz: ±1 Hz;
− above 50 Hz: ±2 %.
When the critical frequencies (see 8.2) are to be compared before and after testing, the
relevant specification should specify the comparison criteria; for determination of the critical
frequencies, the following frequency tolerances apply:
− up to 0,5 Hz: ±0,05 Hz;
− from 0,5 Hz to 5 Hz: ±10 %;
− from 5 Hz to 100 Hz: ±0,5 Hz;
− above 100 Hz: ±0,5 %.
4.3.8 Sweeping
Sweeping shall be continuous with the frequency changing exponentially with time at a rate
not exceeding one octave per minute (see 3.20).
NOTE With a digital control system, it is not strictly correct to refer to the sweeping as being “continuous” but the
difference is of no practical significance.
4.3.9 Damping ratio
The damping ratio of the specimen is normally determined from the vibration response
investigation. This determination depends on the test apparatus used and demands
engineering judgement. Other methods may be employed if justified in the test report.

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4.4 Time-history testing
4.4.1 Basic motion
The time history used can be obtained from either:
a) a natural time history;
b) a synthesized time history by composition of frequencies included within the specified
range. In this case, the synthesized time history shall be generated with the appropriate
resolution, as follows:
– not more than 1/12 octave bands when the specimen damping (= damping ratio) is
lower than or equal to 2 %;
– not more than 1/6 octave bands when the specimen damping lies between 2 % and
10 % (general case);
– not more than 1/3 octave bands when the specimen damping is higher than or equal to
10 %.
The value of the damping ratio (see 3.6) may be defined by the relevant specification or
otherwise obtained (see 4.3.9). A value of 5 % is normally taken.
4.4.2 Transverse motion
The maximum peak value of acceleration or displacement at the check points on any axis
perpendicular to the specified axis (basic motion) shall not exceed 25 % of the specified peak
value in the time
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