IEC 60068-2-64:2008/AMD1:2019

IEC 60068-2-64 ®
Edition 2.0 2019-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
A MENDMENT 1
AM ENDEMENT 1
Environmental testing –
Part 2-64: Tests – Test Fh: Vibration, broadband random and guidance

Essais d’environnement –
Partie 2-64: Essais – Essai Fh: Vibrations aléatoires à large bande et guide

IEC 60068-2-64:2008-04/AMD1:2019-10(en-fr)

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IEC 60068-2-64 ®
Edition 2.0 2019-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
A MENDMENT 1
AM ENDEMENT 1
Environmental testing –
Part 2-64: Tests – Test Fh: Vibration, broadband random and guidance

Essais d’environnement –
Partie 2-64: Essais – Essai Fh: Vibrations aléatoires à large bande et guide

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 19.040 ISBN 978-2-8322-7458-3

– 2 – IEC 60068-2-64:2008/AMD1:2019
© IEC 2019
FOREWORD
This amendment has been prepared by IEC technical committee 104: Environmental
conditions, classification and methods of test.
The text of this amendment is based on the following documents:
FDIS Report on voting
104/848/FDIS 104/855/RVD
Full information on the voting for the approval of this amendment can be found in the report
on voting indicated in the above table.
The committee has decided that the contents of this amendment and the base publication will
remain unchanged until the stability date indicated on the IEC website 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• withdrawn,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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
___________
INTRODUCTION
Add, after the fourth paragraph, the following new paragraph:
The traditional general purpose broad-band random vibration test utilizes waveforms with a
Gaussian distribution of amplitudes. However, when so specified, this test procedure can also
be utilized with random vibration tests with a non-Gaussian distribution of amplitudes. Such
tests are sometimes alternatively known as high kurtosis tests.
Add, after the last paragraph, the following new paragraph:
Annex C is an informative annex giving information on non-Gaussian distribution/high kurtosis
tests.
© IEC 2019
3 Definitions
Add the following new terminological entries:
3.39
kurtosis
th
4 statistical moment, which provides a measure of the shape of an amplitude distribution
Note 1 to entry: Typically a waveform with Gaussian distribution will have a kurtosis of 3, if considered over an
infinite period.
Note 2 to entry: Kurtosis is given by:
N
kurtosis xx−.
( )
∑ i
N σ
i=1
where:
σ is the standard deviation of the N values which describe the waveform;
x are individual values representing the waveform described by N such values;
i
𝑥𝑥̅ is the mean value of the N values which describe the waveform.
3.40
skewness
rd
3 statistical moment, which provides a measure of non-symmetry of an amplitude
distribution
Note 1 to entry: Typically a waveform with Gaussian distribution will have a skewness of 0, if considered over an
infinite period.
Note 2 to entry: Skewness is given by:
N
skewness xx−.
( )
∑ i
N σ
i=1
where:
σ is the standard deviation of the N values which describe the waveform;
x are individual values representing the waveform described by N such values;
i
𝑥𝑥̅ is the mean value of the N values which describe the waveform.
3.41
beta distribution
family of continuous probability distributions defined on the interval [0, 1] parametrized by two
positive shape parameters, denoted by α and β, that appear as exponents of the random
variable and control the shape of the distribution
SEE: Figure 4.
=
=
– 4 – IEC 60068-2-64:2008/AMD1:2019
© IEC 2019
Figure 4 – Examples of the beta distribution with different α and β values
4 Requirements for test apparatus
4.1 General
Add, at the end of 4.1, the following new paragraph:
For non-Gaussian testing, the test apparatus shall be able to produce a signal with a specified
probability distribution and crest factor. Generally, non-Gaussian random vibration testing
requires shaker and amplifier systems that are designed for Gaussian random vibrations but
with increased crest factor capabilities.
4.6.2 Distribution
Add, after Figure 2, the following new paragraph:
For non-Gaussian tests, the time history shall be recorded and the statistical characteristics of
crest factor, skewness, kurtosis and amplitude probability distribution established, see
Clause C.3. If required by the test specification, additional analysis of the time history shall be
undertaken. The measurement time for kurtosis, skewness and amplitude probability
distribution should be long enough to obtain statistically acceptable results.
5 Severities
Replace, in the second paragraph, the first two sentences with the following:
Each parameter shall be specified by the relevant specification. They shall be:
Add, at the end of the second paragraph, after list item d), the following new text:
For non-Gaussian vibration testing the test severity is determined by the same parameters as
for broad-band Gaussian vibration testing but with the addition of:
– the type of non-Gaussian testing to be undertaken (see Annex C),
– the required probability distribution or kurtosis (and skewness if applicable),

© IEC 2019
– the required crest factor.
8.4.1 General
Add, at the end of 8.4.1, the following new text and Figure 5:
For non-Gaussian vibration testing, the time history shall be recorded and the kurtosis,
skewness (if applicable) and amplitude probability density shall be established as required by
the relevant specification (see also Figure 5).

Key
Kurtosis = 4,5 (see 3.39)
Skewness = 0 (see 3.40)
Figure 5 – Time history of non-Gaussian excitation –
Probability density function compared with Gaussian (normal) distribution
11 Information to be given in the relevant specification
Replace the existing list item h) with the following new list item h):
h) Crest factor* / amplitude distribution, kurtosis and skewness (if applicable)/drive signal
clipping amplitude
– 6 – IEC 60068-2-64:2008/AMD1:2019
© IEC 2019
Replace, in list item h) the clause number with "4.6.2 and 5.3"
Add, at the end of Annex B, the following new Annex C:

© IEC 2019
Annex C
(informative)
Guidance on non-Gaussian distribution/high kurtosis tests
C.1 Non-Gaussian random vibration
Random vibration testing has traditionally utilized a nominally Gaussian distribution of
amplitudes, but with the crest factor of the waveform set so as to truncate the amplitude
distribution at around three standard deviations. In recent years, several different techniques
have become available, which allow the required acceleration spectral density to be achieved,
but with a waveform distribution typically modified to permit higher amplitudes to occur with a
th
greater probability. This commonly results in a distribution with a 4 moment of statistics
(kurtosis), which is greater than that of a normal or Gaussian distribution. Hence, the
approach is sometimes referred to as high kurtosis or non-Gaussian vibration testing. With
some available techniques it may also be possible to use a waveform with a kurtosis less than
that of a Gaussian distribution and/or with a non-zero skewness.
High kurtosis or non-Gaussian vibration testing can be advantageous in a number of
circumstances. A typical application arises when both vibration and shock conditions occur
together. Such conditions commonly occur when equipment is transported on or installed in
land vehicles. In such cases it may be required to incorporate moderately higher amplitude
components to the waveform either randomly or pseudo-periodically. High kurtosis or non-
Gaussian vibration testing may also be used to replicate the effects of repeated impacts of
moderate amplitude such as occurs when equipment is loose or experiences “rattling”. In this
case a waveform with a high kurtosis and non-zero skewness could be used.
The traditional general purpose broad-band random vibration test procedure of this document
can also be used with high kurtosis or non-Gaussian vibration testing with only minor
modifications.
High kurtosis or non-Gaussian vibration testing should not be used in place of a traditional
broad-band Gaussian vibration test, except were explicitly specified in the relevant
specification.
C.2 Methods to generate non-Gaussian random vibration
C.2.1 General
High kurtosis or non-Gaussian vibration testing mostly utilizes the same control strategy as
used with traditional broad-band Gaussian vibration tests. Moreover, the underlying
techniques used by vibration controllers to establish a non-Gaussian waveform, are
essentially the same as for Gaussian vibration testing, but typically with an addition
...