GB/T 2423.56-2023 Environmental testing - Part 2: Test methods - Test Fh: Vibration, broadband random and guidance
1 Scope
This document provides test methods for random vibration standard to demonstrate the adequacy of specimens to resist dynamic loads without unacceptable degradation of its functional and/or structural integrity when subjected to the specified random vibration test requirements.
Broadband random vibration may be used to identify accumulated stress effects and degradation in the specified performance. This information, in conjunction with the relevant specification, may be used to assess the acceptability of specimens.
This document is applicable to specimens which may be subjected to vibration of a stochastic nature resulting from transportation or operational environments, for example in aircraft, space vehicles and land vehicles. It is primarily intended for unpackaged specimens, and for items in their transportation container when the latter may be considered as part of the specimen itself. 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. This document may be used in conjunction with GB/T 2423.43-2008, for testing packaged products.
If the specimens are subjected to vibration of a combination of random and deterministic nature resulting from transportation or real life environments, for example in aircraft, space vehicles and for items in their transportation container, testing with pure random may not be sufficient. See GB/T 2424.26-2008 for estimating the dynamic vibration environment of the specimen and based on that, selecting the appropriate test method.
Although primarily intended for electrotechnical specimens, this document is not restricted to them and may be used in other fields where desired (see Annex A).
2 Normative references
The following documents contain requirements which, through reference in this text, constitute provisions 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.
ISO 2041 Vibration and shock – Vocabulary
Note: GB/T 2298-2010 Mechanical vibration, shock and condition monitoring - Vocabulary (ISO 2041: 2009, IDT)
IEC 60050-300 International Electrotechnical Vocabulary - Electrical and electronic measurements and measuring instruments - Part 311: General terms relating to measurements - Part 312: General terms relating to electrical measurements - Part 313: Types of electrical measuring instruments - Part 314: Specific terms according to the type of instrument
IEC 60068-1 Environmental testing - Part 1: General and guidance
Note: GB/T 2421-2020 Environmental testing - General and guidance (IEC 60068-1: 2013, IDT)
IEC 60068-2-6 Environmental testing - Part 2-6: Tests - Test Fc: Vibration (sinusoidal)
Note: GB/T 2423.10-2019 Environmental testing - Part 2: Tests methods - Test Fc: Vibration (sinusoidal) (IEC 60068-2-6: 2007, IDT)
IEC 60068-2-47 Environmental testing - Part 2-47: Tests - Mounting of specimens for vibration, impact and similar dynamic tests
Note: GB/T 2423.43-2008 Environmental testing for electric and electronic products - Part 2: Test methods - Mounting of specimens for vibration, impact and similar dynamic tests (IEC 60068-2-47: 2005, IDT)
IEC 60068-3-8 Environmental testing - Part 3-8: Supporting documentation and guidance - Selecting amongst vibration tests
Note: GB/T 2424.26-2008 Environmental testing for electric and electronic products - Part 3: Supporting documentation and guidance - Selecting amongst vibration tests (IEC 60068-3-8: 2003, IDT)
IEC 60068-5-2 Environmental testing - Part 5-2: Guide to drafting of test methods - Terms and definitions
Note: GB/T 2422-2012 Environmental testing - Guide to drafting of test methods - Terms and definitions (IEC 60068-5-2: 1990, IDT)
IEC 60721-3
(all parts) Classification of environmental conditions - Part 3: Classification of groups of environmental parameters and their severities
Note: GB/T 4798 (all parts) Classification of environmental conditions - Classification of groups of environmental parameters and their severities [IEC 60721-3(all parts)]
IEC Guide 104 The preparation of safety publications and the use of basic safety publications and group safety publications
Note: GB/T 16499-2017 Guide for the preparation of electrical and electronic safety publications and the use of basic safety publications and group safety publications (IEC Guide 104: 2010, NEQ)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-300, IEC 60068-1, IEC 60068-2-6, IEC 60068-5-2 and ISO 2041 as well as the following apply.
3.1
cross-axis motion
motion not in the direction of the stimulus; generally specified in the two axes orthogonal to the direction of the stimulus
Note: The cross-axis motion shall be measured close to the fixing points.
3.2
actual motion
motion represented by the wideband signal returned from the reference point transducer
3.3
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: 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.
3.4
control methods
3.4.1
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
3.4.2
multipoint control
control method using the signals from each of the transducers at the checkpoints
Note: The signals are either continuously averaged arithmetically or processed by using comparison techniques, depending upon the relevant specification. See 3.13.
3.5
gn
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 gn is rounded up to the nearest whole number, that is 10 m/s2.
Contents
Foreword i
Introduction ii
1 Scope
2 Normative references
3 Terms and definitions
4 Test requirements
4.1 General
4.2 Basic motion
4.3 Cross-axis motion
4.4 Mounting
4.5 Measurement systems
4.6 Vibration tolerances
4.7 Control strategy
4.8 Vibration response investigation
5 Severities
5.1 Test frequency range
5.2 RMS value of acceleration
5.3 Shape of acceleration spectral density curve
5.4 Test duration
6 Preconditioning
7 Initial measurements and functional performance test
8 Test
8.1 General
8.2 Initial vibration response investigation
8.3 Low-level excitation for equalization prior to testing
8.4 Random test
8.5 Final vibration response investigation
9 Recovery
10 Final measurements and functional performance
11 Information to be given in the relevant specification
12 Information to be given in the test report
Annex A (Informative) Standardized test spectra
A.1 Transportation
A.2 Stationary installation
A.3 Equipment in wheeled vehicles
A.4 Equipment installed in airplanes and helicopters
Annex B (Informative) Guidance
B.1 General introduction
B.2 Requirements for the test
B.3 Test procedures
B.4 Equipment normally used with vibration isolators
B.5 Test severities
B.6 Equipment performance
B.7 Initial and final measurements
Annex C (Informative) Guidance on non-Gaussian distribution/high kurtosis tests
C.1 Non-Gaussian random vibration
C.2 Methods to generate non-Gaussian random vibration
C.3 Additional analysis
C.4 Frequency range
Annex NA (Informative) Components of GB/T 2423
Bibliography
Figure 4 Examples of the beta distribution with different α and β values
Figure 1 Tolerance bands for acceleration spectral density, initial and final slope (see B.2.3)
Figure 2 Time history of stochastically excitation——probability density function with Gaussian (normal) distribution (example with crest factor = 3, see also 3.14 and 4.6.2)
Figure 3 Statistical accuracy of acceleration spectral density versus degrees of freedom for different confidence levels (see also 4.6.3)
Figure 5 Time history of non-Gaussian excitation – Probability density function compared with Gaussian (normal) distribution
Figure A.1 Frequency/amplitude break points – Transportation
Figure A.2 Stationary installation spectrum – Frequency/amplitude break points
Figure A.3 Equipment in wheeled vehicles – Frequency/amplitude break points
Figure A.4 Equipment installed in airplanes and helicopters
Table A.1 Categories for spectrum – Transportation
Table A.2 Break points for spectrum – Transportation
Table A.3 Categories for spectrum – Stationary installation
Table A.4 Break points for spectrum – Stationary installation
Table A.5 Categories for spectrum – Equipment in wheeled vehicles
Table A.6 Break points for spectrum – Equipment in wheeled vehicles
Table A.7 Categories for spectrum – Equipment in airplanes and helicopters
Table A.8 Break points for spectrum – Equipment in airplanes and helicopters
