IEC 60068-2-6:2007
(Main)Environmental testing - Part 2-6: Tests - Test Fc: Vibration (sinusoidal)
Environmental testing - Part 2-6: Tests - Test Fc: Vibration (sinusoidal)
Gives a method of test which provides a standard procedure to determine the ability of components, equipment and other articles, hereinafter referred to as specimens, to withstand specified severities of sinusoidal vibration. If an item is to be tested in an unpackaged form, that is without its packaging, it is referred to as a test specimen. However, if the item is packaged then the item itself is referred to as a product and the item and its packaging together are referred to as a test specimen. The purpose of this test is to determine any mechanical weakness and/or degradation in the specified performance of specimens and to use this information, in conjunction with the relevant specification, to decide upon the acceptability of the specimens. In some cases, the test method may also be used to demonstrate the mechanical robustness of specimens and/or to study their dynamic behaviour. Categorization of components can also be made on the basis of a selection from within the severities quoted in the test. The major changes with regard to the previous edition concern: - Reference to the latest version of IEC 60068-2-47:Mounting - Simplification of the layout of the standard by replacing some tables with text. - Addition of the test report requirements (see Clause 13).
Essais d'environnement - Partie 2-6: Essais - Essai Fc: Vibrations (sinusoïdales)
Fournit une méthode d'essai qui donne des règles d'exécution normalisées pour déterminer l'aptitude des composants, matériels et autres articles ci-après désignés "spécimens", à résister à des sévérités spécifiées de vibrations sinusoïdales. S'il est prevu de soumettre un objet aux essais en étant non emballé, sans son emballage, il est désigné comme un spécimen d'essai. Cependant, si l'objet est emballé, alors l'objet lui-même est désigné comme produit et l'objet ainsi que son emballage sont désignés comme spécimen d'essai. L'objet de cet essai est de déterminer les faiblesses mécaniques et/ou les dégradations des performances spécifiées des spécimens, et d'utiliser ces renseignements conjointement avec la spécification particulière pour décider si un spécimen est acceptable ou non. Dans certains cas, la méthode d'essai peut également être utilisée pour démontrer la robustesse mécanique d'un spécimen et/ou pour étudier son comportement dynamique. La classification des composants en catégories peut également se faire sur la base d'une sélection faite à partir des sévérités données dans l'essai. Les modifications principales par rapport à l'édition précédente sont les suivantes: - Référence à la dernière version de la CEI 60068 2 47: Fixation. - Simplification de la mise en page de la norme en remplaçant quelques tableaux par du texte. - Ajout d'exigences sur le rapport d'essai (voir Article 13).
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Standards Content (Sample)
IEC 60068-2-6
Edition 7.0 2007-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing –
Part 2-6: Tests – Test Fc: Vibration (sinusoidal)
Essais d'environnement –
Partie 2-6: Essais – Essai Fc: Vibrations (sinusoïdales)
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IEC 60068-2-6
Edition 7.0 2007-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Environmental testing –
Part 2-6: Tests – Test Fc: Vibration (sinusoidal)
Essais d'environnement –
Partie 2-6: Essais – Essai Fc: Vibrations (sinusoïdales)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
X
CODE PRIX
ICS 19.040 ISBN 2-8318-9490-5
– 2 – 60068-2-6 © IEC:2007
CONTENTS
FOREWORD.4
INTRODUCTION.6
1 Scope.7
2 Normative references.7
3 Terms and definitions .7
4 Requirements for testing.10
4.1 Required characteristics .10
4.1.1 Basic motion.10
4.1.2 Spurious motion.10
4.1.3 Signal tolerance.11
4.1.4 Vibration amplitude tolerances .11
4.1.5 Frequency tolerances.11
4.1.6 Sweep .12
4.2 Control strategy .12
4.2.1 Single/multipoint control.12
4.2.2 Multi-reference control .13
4.3 Mounting .13
5 Severities .13
5.1 Frequency range.14
5.1.1 Lower frequency f Hz .14
5.1.2 Upper frequency f Hz .14
5.2 Vibration amplitude.14
5.3 Duration of endurance .17
5.3.1 Endurance by sweeping .17
5.3.2 Endurance at fixed frequencies .18
6 Preconditioning.18
7 Initial measurements.18
8 Testing .18
8.1 General .18
8.2 Vibration response investigation.19
8.3 Endurance procedures.19
8.3.1 Endurance by sweeping .19
8.3.2 Endurance at fixed frequencies .19
9 Intermediate measurements.20
10 Recovery .20
11 Final measurements .20
12 Information to be given in the relevant specification.20
13 Information to be given in the test report .21
Annex A (informative) Guide to test Fc .
Annex B (informative) Examples of severities primarily intended for components .36
Annex C (informative) Examples of severities primarily intended for equipment.37
Bibliography .39
60068-2-6 © IEC:2007 – 3 –
Figure 1 – Nomogram relating vibration amplitude to frequency with lower cross-over
frequency (8 Hz to 10 Hz).15
Figure 2 – Nomogram relating vibration amplitude to frequency with higher cross-over
frequency (58 Hz to 62 Hz).
Figure 3 – Nomogram relating vibration displacement amplitude to frequency (only
applicable for frequency ranges with an upper frequency of 10 Hz) .17
Figure A.1 – Generalized transmissibility factors for vibration isolators.33
Table A.1 – Number of sweep cycles and associated endurance times per axis .30
Table A.2 – CB response time .31
Table A.3 – CPB response time.32
Table B.1 – Endurance by sweeping – Examples with higher cross-over frequency .36
Table C.1 – Endurance by sweeping – Examples with lower cross-over frequency .37
Table C.2 – Endurance by sweeping – Examples with higher cross-over frequency .38
– 4 – 60068-2-6 © IEC:2007
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ENVIRONMENTAL TESTING –
Part 2: Tests – Test Fc: Vibration (sinusoidal)
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
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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 60068-2-6 has been prepared by IEC technical committee 104:
Environmental conditions, classification and methods of test.
This seventh edition cancels and replaces the sixth edition, published in 1995. It consitutes a
technical revision.
The major changes with regard to the previous edition concern:
⎯ The agreed wording from IEC technical committee 104 meeting held in Stockholm:2000
on the testing of soft packages.
⎯ Reference to the latest version of IEC 60068-2-47:Mounting
⎯ Simplification of the layout of the standard by replacing some tables with text.
⎯ Addition of the test report requirements (see Clause 13).
60068-2-6 © IEC:2007 – 5 –
The text of this standard is based on the following documents:
FDIS Report on voting
104/439/FDIS 104/449/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.
A list of all the parts in the IEC 60068 series, under the general title Environmental testing, can
be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until the
maintenance result 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 – 60068-2-6 © IEC:2007
INTRODUCTION
This part of IEC 60068 gives a method of test applicable to components, equipment and other
articles which, during transportation or in service, may be subjected to conditions involving
vibration of a harmonic pattern, generated primarily by rotating, pulsating or oscillating forces,
such as occur in ships, aircraft, land vehicles, rotorcraft and space applications or are caused
by machinery and seismic phenomena.
This standard consists basically of subjecting a specimen to sinusoidal vibration over a given
frequency range or at discrete frequencies, for a given period of time. A vibration response
investigation may be specified which aims at determining critical frequencies of the specimen.
The relevant specification shall indicate whether the specimen shall function during vibration or
whether it suffices that it still works after having been submitted to vibration.
It is emphasized that vibration testing always demands a certain degree of engineering
judgement, and both the supplier and purchaser should be fully aware of this fact. However,
sinusoidal testing is deterministic and, therefore, relatively simple to perform. Thus it is readily
applicable to both diagnostic and service life testing.
The main part of this standard deals primarily with the methods of controlling the test at
specified points using either analogue or digital techniques, and gives, in detail, the testing
procedure. The requirements for the vibration motion, choice of severities including frequency
ranges, amplitudes and endurance times are also specified, these severities representing a
rationalized series of parameters. The relevant specification writer is expected to choose the
testing procedure and values appropriate to the specimen and its use.
Certain terms have been defined to facilitate a proper understanding of the text. These
definitions are given in Clause 3.
Annex A gives general guidance for the test and Annexes B and C provide guidance on the
selection of severities for components and equipment.
60068-2-6 © IEC:2007 – 7 –
ENVIRONMENTAL TESTING –
Part 2: Tests – Test Fc: Vibration (sinusoidal)
1 Scope
This part of IEC 60068 gives a method of test which provides a standard procedure to
determine the ability of components, equipment and other articles, hereinafter referred to as
specimens, to withstand specified severities of sinusoidal vibration. If an item is to be tested in
an unpackaged form, that is without its packaging, it is referred to as a test specimen.
However, if the item is packaged then the item itself is referred to as a product and the item
and its packaging together are referred to as a test specimen.
The purpose of this test is to determine any mechanical weakness and/or degradation in the
specified performance of specimens and to use this information, in conjunction with the
relevant specification, to decide upon the acceptability of the specimens. In some cases, the
test method may also be used to demonstrate the mechanical robustness of specimens and/or
to study their dynamic behaviour. Categorization of components can also be made on the basis
of a selection from within the severities quoted in the test.
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 60068-2-47, Environmental testing – Part 2-47: Tests – Mounting of specimens for
vibration, impact and similar dynamic tests
IEC 60721-3 (all parts), Classification of environmental conditions – Part 3: Classification of
groups of environmental parameters and their severities
ISO 2041, Vibration and shock – Vocabulary
ISO/IEC 17025:2005, General requirements for the competence of testing and calibration
laboratories
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
NOTE 1 The terms used are generally taken from ISO 2041 and IEC 60068-1. However, “sweep cycle” (3.4) and
“signal tolerance” (3.5) have specific meanings in this standard.
Definitions in alphabetical order:
Actual motion 3.7
Basic motion 3.6
Centred resonance frequency 3.10
Check point 3.2.1
– 8 – 60068-2-6 © IEC:2007
Critical frequencies 3.9
Damping 3.8
Fictitious reference point 3.2.3
Fixing point 3.1
g 3.12
n
Measuring points 3.2
Multipoint control 3.3.2
Reference point 3.2.2
Restricted frequency sweeping 3.11
Signal tolerance 3.5
Single point control 3.3.1
Sweep cycle 3.4
NOTE 2 Terms described below are either not identical to, or not defined in ISO 2041 or in IEC 60068-1.
3.1
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 If a part of the real mounting structure is used as the fixture, the fixing points are those of the mounting
structure and not of the specimen.
NOTE 2 Where the specimen consists of a packaged product, fixing point may be interpreted as the surface of the
specimen which is in contact with the vibration table.
3.2
measuring points
specific points at which data are gathered conducting the test
NOTE 1 These are of two main types, the definitions of which are given below.
NOTE 2 Measurements may be made at points within the specimen in order to assess its behaviour, but these are
not considered as measuring points in the sense of this standard. For further details, see A.2.1.
3.2.1
check point
point located on the fixture, 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 A number of check points are used as a means of ensuring that the test requirements are satisfied.
NOTE 2 If four or fewer fixing points exist, each is used as a check point. For packaged products, where a fixing
point may be interpreted as the packaging surface in contact with the vibration table, one check point may be used,
provided that there are no effects due to resonances of the vibration table or the mounting structure in the
frequency range specified for the test. If this is the case, multipoint control may be necessary, but see also Note 3.
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 In special cases, for example for large or complex specimens, the check points will be prescribed in the
relevant specification if not close to the fixing points.
NOTE 4 Where a large number of small specimens are mounted on one fixture, or in the case of a small specimen
where there are several fixing points, a single check point (i.e. 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 is only valid when the lowest resonance frequency of the loaded fixture is well above the upper
frequency of the test.
60068-2-6 © IEC:2007 – 9 –
3.2.2
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
3.2.3
fictitious reference point
point, derived from multiple check points, either manually or automatically, the result of which
is used to control the test, so that the requirements of this standard are satisfied
3.3
control methods
3.3.1
single point control
control method using the signal from the transducer at the reference point in order to maintain
this point at the specified vibration level (see 4.1.4.1)
3.3.2
multipoint control
control method achieved by using the signals from each of the transducers at the check points
NOTE The signals are either continuously averaged arithmetically or processed by using comparison techniques,
depending upon the relevant specification (see 4.1.4.1)
3.4
sweep cycle
traverse of the specified frequency range once in each direction, for example 10 Hz to 150 Hz
to 10 Hz
NOTE Manufacturers' handbooks for digital sine control systems often refer to a sweep cycle as f to f , and not f
1 2 1
to f to f .
2 1
3.5
signal tolerance
NF
⎛ ⎞
signal tolerance T = −1 × 100 %
⎜ ⎟
⎝ ⎠
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 This parameter applies to whichever signal, i.e. acceleration, velocity or displacement, is being used to
control the test (see A.2.2).
3.6
basic motion
motion at the driving frequency of vibration at the reference point (see also 4.1.1)
3.7
actual motion
motion represented by the wideband signal returned from the reference point transducer
3.8
damping
generic term ascribed to the numerous energy dissipation mechanisms in a system
NOTE In practice, damping depends on many parameters, such as the structural system, mode of vibration,
strain, applied forces, velocity, materials, joint slippage, etc.
– 10 – 60068-2-6 © IEC:2007
3.9
critical frequencies
frequencies at which
– malfunctioning and/or deterioration of performance of the specimen are exhibited which
are dependent on vibration, and/or
– mechanical resonances and/or other response effects occur, for example, chatter
3.10
centred resonance frequency
frequency automatically centred on the actual resonance frequency derived from the vibration
response investigation
3.11
restricted frequency sweeping
sweeping over a restricted frequency range between 0,8 and 1,2 times the critical frequency
3.12
g
n
standard acceleration due to the earth's gravity, which itself varies with altitude and
geographical latitude
NOTE For the purposes of this standard, the value of g is rounded up to the nearest whole number, that is
n
10 m/s .
4 Requirements for testing
4.1 Required characteristics
The required characteristics apply to the complete vibration system, which includes the power
amplifier, vibrator, test fixture, specimen and control system when loaded for testing.
4.1.1 Basic motion
The basic motion shall be a sinusoidal function of time and such that the fixing points of the
specimen move substantially in phase and in straight parallel lines, subject to the limitations of
4.1.2 and 4.1.3.
4.1.2 Spurious motion
4.1.2.1 Cross-axis motion
The maximum vibration amplitude at the check points in any axis perpendicular to the specified
axis shall not exceed 50 % of the specified amplitude up to 500 Hz or 100 % for frequencies in
excess of 500 Hz. The measurements need only cover the specified frequency range. In
special cases, e.g. small specimens, the amplitude of the permissible cross axis motion may
be limited to 25 %, if required by the relevant specification.
In some cases, for example for large size or high mass specimens or at some frequencies, it
may be difficult to achieve the figures quoted above. In such cases, the relevant specification
shall state which of the following requirements apply:
a) any cross-axis motion in excess of that stated above shall be noted and stated in the test
report; or
b) cross-axis motion which is known to offer no hazard to the specimen need not be
monitored.
60068-2-6 © IEC:2007 – 11 –
4.1.2.2 Rotational motion
In the case of large size or high mass specimens, the occurrence of spurious rotational motion
of the vibration table may be important. If so, the relevant specification shall prescribe a
tolerable level. The achieved level shall be stated in the test report (see also A.2.4).
4.1.3 Signal tolerance
Acceleration signal tolerance measurements shall be performed if stated in the relevant
specification. They shall be carried out at the reference point and shall cover the frequencies
up to 5 000 Hz or five times the driving frequency whichever is the lesser. However, this
maximum analysing frequency may be extended to the upper test frequency for the sweep, or
beyond, if specified in the relevant specification. Unless otherwise stated in the relevant
specification, the signal tolerance shall not exceed 5 % (see 3.5).
If stated in the relevant specification, the acceleration amplitude of the control signal at the
fundamental driving frequency shall be restored to the specified value by use of a tracking filter
(see A.4.4).
In the case of large or complex specimens, where the specified signal tolerance values 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, but the signal tolerance shall be stated in the
test report (see A.2.2).
NOTE If a tracking filter is not used and the signal tolerance is in excess of 5 %, the reproducibility may be
significantly affected by the choice of either a digital or analogue control system (see A.4.5).
The relevant specification may require that the signal tolerance, together with the frequency
range affected, is stated in the test report whether or not a tracking filter has been used
(see A.2.2).
4.1.4 Vibration amplitude tolerances
The basic motion amplitude in the required axis at the check and reference points shall be
equal to the specified value, within the following tolerances. These tolerances include
instrumentation errors. The relevant specification may require that the confidence level used in
the assessment of measurement uncertainty is stated in the test report.
At low frequencies or with large size or high mass specimens it may be difficult to achieve the
required tolerances. In these cases, it is expected that a wider tolerance or the use of an
alternative method of assessment shall be prescribed in the relevant specification and stated in
the test report.
4.1.4.1 Reference point
Tolerance on the control signal at the reference point shall be ±15 % (see A.2.3).
4.1.4.2 Check points
Tolerance on the control signal at each check point:
±25 % up to 500 Hz;
±50 % above 500 Hz.
(See A.2.3.)
4.1.5 Frequency tolerances
The following frequency tolerances apply.
– 12 – 60068-2-6 © IEC:2007
4.1.5.1 Endurance by sweeping
±0,05 Hz up to 0,25 Hz;
±20 % from 0,25 Hz to 5 Hz;
±1 Hz from 5 Hz to 50 Hz;
±2 % above 50 Hz.
4.1.5.2 Endurance at fixed frequency
a) Fixed frequency:
±2 %.
b) Almost fixed frequency:
±0,05 Hz up to 0,25 Hz;
±20 % from 0,25 Hz to 5 Hz;
±1 Hz from 5 Hz to 50 Hz;
±2 % above 50 Hz.
4.1.5.3 Measurement of critical frequency
When the critical frequencies (see 8.2) before and after endurance have to be compared, i.e.
during vibration response investigations, the following tolerances shall apply:
±0,05 Hz up to 0,5 Hz;
±10 % from 0,5 Hz to 5 Hz;
±0,5 Hz from 5 Hz to 100 Hz;
±0,5 % above 100 Hz.
4.1.6 Sweep
The sweeping shall be continuous and the frequency shall change exponentially with time
(see A.4.3). The sweep rate shall be one octave per minute with a tolerance of ±10 %. This
may be varied for a vibration response investigation (see 8.2).
NOTE With a digital control system, it is not strictly correct to refer to the sweeping being “continuous”, but the
difference is of no practical significance.
4.2 Control strategy
4.2.1 Single/multipoint control
When multipoint control is specified or necessary, the control strategy has to be specified.
The relevant specification shall state whether single point or multipoint control shall be used. If
multipoint control is prescribed, the relevant specification shall state whether the average
amplitude of the signals at the check points or the amplitude of the signal at a selected point
(for example, that with the largest amplitude) shall be controlled to the specified level, see also
A.2.3.
If it is not possible to achieve single point control, as required by the relevant specification,
then multipoint control shall be used by controlling the average or extreme value of the signals
at the check points. In either of these cases of multipoint control, the reference point is a
fictitious reference point. The method used shall be stated in the test report.
Use of multipoint control does not assure that the tolerances of each checkpoint are met. In
general it reduces the deviation from the nominal values, when compared with single-point
control, at the fictitious reference point.
The following strategies are available.
60068-2-6 © IEC:2007 – 13 –
4.2.1.1 Averaging strategy
In this method, the control amplitude is computed from the signal from each check point. A
composite control amplitude is formed by arithmetically averaging the signal amplitudes from
the check points. This arithmetically averaged control amplitude is then compared with the
specified amplitude.
4.2.1.2 Weighted averaging strategy
The control amplitude a is formed by averaging the signal amplitude from the check points a
C 1
to a according to their weighting w to w :
n 1
n
a = (w x a + w x a +….+ w x a ) / (w + w +…+ w )
C 1 1 2 2 n n 1 2 n
This control strategy offers the possibility that different check point signals contribute a
different portion to the control.
4.2.1.3 Extremal strategy
In this method, a composite control amplitude is computed from the maximum (MAX) or the
minimum (MIN) extreme amplitudes of the signal amplitude measured at each check point.
This strategy will produce a control amplitude that represents the envelope of the signal
amplitudes from each check point (MAX) or a lower limit of the signal amplitudes from each
check point (MIN).
4.2.2 Multi-reference control
If specified by the relevant specification, multiple reference spectra may be defined for different
check points or measuring points or different types of controlled variables, for example, for
force limited vibration testing.
When multi-reference control is specified, the control strategy shall be prescribed as follows:
Limiting: All control signals shall be beneath their appropriate reference;
Superseding: All control signals shall be above their appropriate reference.
4.3 Mounting
Unless otherwise stated in the relevant specification, the specimens shall be mounted on the
test apparatus in accordance with the requirements in IEC 60068-2-47. For specimens
normally mounted on vibration isolators, see the note in 8.3.2 as well as A.3.1, A.3.2 and
Clause A.5.
5 Severities
A vibration severity is defined by the combination of the three parameters: frequency range,
vibration amplitude and duration of endurance (in sweep cycles or time).
Each parameter shall be prescribed by the relevant specification. They may be:
a) chosen from the values in 5.1 to 5.3;
b) chosen from examples in Annex A or Annex C;
c) derived from the known environment;
d) derived from other known sources of relevant data, for example, the IEC 60721-3 series.
To permit some flexibility in situations where the real environment is known, it may be
appropriate to specify a shaped acceleration versus frequency curve and, in these cases, the
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relevant specification shall prescribe the shape as a function of frequency. The different levels
and their corresponding frequency ranges, i.e. the break points, shall be selected, wherever
possible, from the values given in this standard.
Examples of severities for components are given in Annex B, and for equipment in Annex C
(see also A.4.1 and A.4.2).
5.1 Frequency range
If test frequency range option a) is adopted, then a lower frequency may be chosen from 5.1.1
and an upper frequency from 5.1.2.
5.1.1 Lower frequency f Hz
0,1; 1; 5; 10; 55; 100
5.1.2 Upper frequency f Hz
10; 20; 35; 55; 100; 150; 200; 300; 500; 1 000; 2 000; 5 000
Examples of ranges for particular applications are given in Tables B.1, C.1 and C.2.
5.2 Vibration amplitude
The amplitude of displacement, velocity or acceleration or combinations of those, shall be
stated in the relevant specification.
Below a certain frequency known as the cross-over frequency, all amplitudes are specified as
constant displacement, whilst above this frequency, amplitudes are given as constant velocity
or constant acceleration. Example values are given in Figures 1 and 2 for the two different
cross-over frequencies.
Each value of displacement amplitude is associated with a corresponding value of acceleration
amplitude so that the amplitude of vibration is the same at the cross-over frequency (see
A.4.1).
Where it is not technically appropriate to adopt the cross-over frequencies stated in this
subclause, the relevant specification may couple displacement and acceleration amplitudes
giving a different value of cross-over frequency. In some circumstances, more than one cross-
over frequency may also be specified.
NOTE Nomograms relating vibration amplitude to frequency are given in Figures 1, 2 and 3, but before their use in
the low-frequency region, consideration should be given to the guidance in A.4.1.
Up to an upper frequency of 10 Hz, it is normally appropriate to specify a displacement
amplitude over the whole frequency range. Therefore, in Figure 3 only displacement amplitudes
are specified.
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Figure 1 – Nomogram relating vibration amplitude to frequency with lower
cross-over frequency (8 Hz to 10 Hz)
NOTE This nomogram should not be taken as being a precise graphical representation of the severities.
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Figure 2 – Nomogram relating vibration amplitude to frequency with higher cross-over
frequency (58 Hz to 62 Hz)
NOTE This nomogram should not be taken as being a precise graphical representation of the severities.
60068-2-6 © IEC:2007 – 17 –
NOTE This nomogram should not be taken as being a precise graphical representation of the severities.
Figure 3 – Nomogram relating vibration displacement amplitude to frequency
(only applicable for frequency ranges with an upper frequency of 10 Hz)
5.3 Duration of endurance
The relevant specification shall select the duration(s) from the recommended values given
below. If the specified duration leads to an endurance time of 10 h or more per axis or
frequency, this time may be split into separate testing periods, provided that stresses in the
specimen are not thereby reduced (see Clause A.1 and A.6.2).
5.3.1 Endurance by sweeping
The duration of the endurance in each axis shall be given as a number of sweep cycles
(see 3.4) in the relevant specification or may be chosen from the following values:
1, 2, 5, 10, 20, 50, 100.
When a higher number of sweep cycles is required, the same series should be applied
(see A.4.3).
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5.3.2 Endurance at fixed frequencies
5.3.2.1 Endurance at critical frequencies
The duration of the endurance in each appropriate axis at each frequency found during the
vibration response investigation (see 8.2) shall be given in the relevant specification or may be
+5
chosen from the values given below with a tolerance of % (see Clause A.1 and A.6.2):
10 min; 30 min; 90 min; 10 h.
For almost fixed frequencies, see Clause A.1.
5.3.2.2 Endurance at predetermined frequencies
The duration stated in the relevant specification shall take into account the total time the
specimen is expected to be submitted to such vibration during its operational life. An upper
limit of 10 stress cycles shall apply for each stated combination of frequency and axis (see
Clause A.1 and A.6.2).
6 Preconditioning
The relevant specification may call for preconditioning and shall then prescribe the conditions
(see IEC 60068-1).
7 Initial measurements
The specimen shall be submitted to the visual, dimensional and functional checks prescribed
by the relevant specification (see Clause A.9).
8 Testing
8.1 General
The relevant specification shall state the number of axes in which the specimen shall be
vibrated and their relative positions. If not stated in the relevant specification, the specimen
shall be vibrated in three mutually perpendicular axes, in turn, which should be so chosen that
faults are most likely to be revealed.
The control signal at the reference point shall be derived from the signals at the check points
and shall be used for single point or multipoint control (see A.4.5).
The test procedure to be applied shall be chosen, by the relevant specification, from the stages
given below. Guidance is given in Annex A. In general, the test stages shall be performed in
sequence in the same axis and then repeated for the other axes (see Clause A.3).
Special action is necessary when a specimen, normally intended for use with vibration
isolators, needs to be tested without them (see Clause A.5). Special action is also necessary
when a product, normally intended for transportation in packaging, needs to be tested without
the packaging (see IEC 60068-2-47).
When called for by the relevant specification, control of the specified vibration amplitude shall
be supplemented by a maximum limit of the driving force applied to the vibrating system. The
method of force limitation shall be stated in the relevant specification (see Clause A.7).
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8.2 Vibration response investigation
When called for in the relevant specification, the response of the specimen in the defined
frequency range shall be investigated in order to study the behaviour of the specimen under
vibration. Normally, the vibration response investigation shall be carried out over a sweep cycle
under the same conditions as for the endurance (see 8.3), but the vibration amplitude may be
diminished and the sweep rate decreased below the specified value if, thereby, more precise
determination of the response characteristics can be obtained. Undue dwell time and
overstressing of the specimen shall be avoided (see A.3.1). For vibration response
investigation of packaged products, for the case where it is not possible to instrument the
product within the packaging, then measurement of the force excitation of the specimen may
be used to detect the resonant frequencies of the product within the packaging. This is not a
trivial procedure to adopt and a suitable balance between making such measurements or not
having knowledge of the resonance frequencies of the packaged specimens must be made.
For the vibration response investigations of an ‘undefined type’ specimen or package it may be
necessary to measure different signals such as driving force or vibration velocity. If specified
by the relevant specification, for example the spectra of the mechanical impedance of the
specimen before and after the test may be calculated.
The specimen shall function during this vibration response investigation if required by the
relevant specification. Where the mechanical vibration characteristics cannot be assessed
because the specimen is functioning, an additional vibration response investigation with the
specimen not functioning shall be carried out.
During the vibration response investigation, the specimen and the vibration response data shall
be examined in order to determine critical frequencies. These frequencies, applied amplitudes
and
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