Environmental testing for electric and electronic products - Part 2: Test methods - Test Fh: Vibration, broad-band random (digital control) and guidance
1 Scope
This part provides two standard test methods (method 1 and method 2) for determining the ability of a specimen to withstand specified severities of broad-band random vibration. Neither test method can be considered more severe than the other, the difference being primarily that method 2 provides more information to quantify the applied test, and is therefore more reproducible.
It is also to reveal the accumulated effects of stress induced by random vibration and degradation in specified performance and to use this information, in conjunction with the relevant specification, to assess the acceptability of specimens. In some cases, this part may also be used to demonstrate the mechanical robustness of specimens and/or to study their dynamic behaviour.
This part 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.
Although primarily intended for electrotechnical products, this part is not restricted to them and may be used in other fields where desired.
2 Normative References
The following normative documents contain provisions which, through reference in this part, constitute provisions of this part. For dated reference, subsequent amendments (excluding corrections), or revisions of, any of these publications do not apply. However, all parties coming to an agreement according to this part are encouraged to study whether the latest editions of these documents are applicable. For undated references, the latest edition of the normative document referred to applies.
GB/T 2298-1991 Mechanical Vibration and Shock – Terminology (idt ISO2041:1990)
GB/T 2421-1999 Environmental Testing for Electric and Electronic Products - Part 1: General and Guidance (idt IEC 60068-1:1988)
GB/T 2423.10-1995 Environmental Testing for Electric and Electronic Products - Part 2: Test Methods - Test Fc and Guidance: Vibration (Sinusoidal) (idt IEC 60068-2-6:1982)
GB/T 2423.43-1995 Environmental Testing for Electric and Electronic Products - Part 2: Test Methods - Mounting of Components, Equipment and other Articles for Dynamic Tests including Shock (Ea), Bump (Eb), Vibration (Fc and Fd) and Steady-state Acceleration (Ga) and Guidance (idt IEC 60068-2-47:1982)
GB/T 4796 Classification of Environmental Parameters and their Severities of Electric and Electronic Products (GB/T 4796-2001, idt IEC 600721-1:1991)
IEC 60050-301:1983 International Electrotechnical Vocabulary (IEV) - Chapter 301: General terms on measurements in electricity
IEC 60050-302:1983 International Electrotechnical Vocabulary (IEV) - Chapter 302: Electrical measuring instruments
IEC 60050-303:1983 International Electrotechnical Vocabulary (IEV) - Chapter 303: Electronic measuring instruments (Advance edition)
IEC 60068 Environmental testing
IEC 60068-2 Environmental testing - Part 2: Tests.
3 Terms and Definitions
The terms used are generally defined in GB/T 2298-1991 or IEC 60050 (301, 302, 303):1983 and in GB/T 2421-1999 or GB/T 2423.10-1995. 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.
The additional terms and definitions that follow are also applicable for the purposes of this part.
3.1
-3dB bandwidth Br
frequency bandwidth between two points in a frequency response function which is 0.707 of the maximum response when associated with a single resonance peak (see 4.3.6.2)
[GB/T 2298-1991, modified]
3.2
acceleration spectral density
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 (see 4.3.4)
Foreword i
Introduction ii
1 Scope
2 Normative References
3 Terms and Definitions
4 Requirements for Testing
5 Severities
6 Pre-conditioning
7 Initial Measurements
8 Testing
9 Recovery
10 Final Measurements
11 Information to be Given in the Relevant Specification
Annex A (Normative) Vibration Response Investigation
Annex B (Informative) Guidance
Annex C (Informative) Conversion between Percentage Values and dB
Figure 1 Tolerance Band for Distribution of Instantaneous Acceleration Values
Figure 2 Tolerance Boundaries for Acceleration Spectral Density
Figure 3 Gaussian (Normal) Probability Density Function
Figure 4 Schematic Diagram of Signal Clipping
Figure 5 Non-Gaussian Probability Density Function
Figure 6 Statistical Accuracy of Acceleration Spectral Density Versus Degrees of Freedom for Different Confidence Levels
Figure 7 Relationship between Acceleration Spectral Density and Frequency
Figure 8 Flow Chart for Vibration, Broad-band Random Test
Figure 9 Generalized Transmissibility Factors for Isolators
