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GB/T 2423.5-1995 English PDF (GBT2423.5-1995)

GB/T 2423.5-1995 English PDF (GBT2423.5-1995)

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GB/T 2423.5-1995: Environmental testing for electric and electronic products - Part 2: Test methods - Test Ea and guidance: Shock

To provide a standard procedure for determining the ability of a specimen to withstand specified severities of bump.
GB/T 2423.5-1995
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
GB/T 2423.5-1995 / IDT IEC 68-2-27:1987
Replacing GB 2423.5-81
GB 2424.3-81
Environmental Testing for Electric and Electronic
Products - Part 2: Test Methods - Test Ea and
Guidance: Shock
APPROVED ON: AUGUST 29, 1995
IMPLEMENTED ON: AUGUST 01, 1996
Approved by: State Bureau of Technical Supervision
Table of Contents
Foreword ... 3
IEC Foreword ... 4
1 Objective ... 5
2 General Description ... 5
3. Definitions ... 6
4. Description of Test Apparatus ... 7
5. Severities ... 8
6 Pre-Conditioning ... 9
7 Initial Inspection ... 9
8 Conditional Test ... 9
9 Recovery ... 10
10 Final Inspection ... 10
11 Information to be Given in the Relevant Specification ... 10
Appendix A (Normative) Guidance ... 14
Appendix B (Normative) Shock Response Spectrum and Other
Characteristics of Pulse Waveform ... 21
Appendix C (Normative) Comparison among Collision Tests ... 31
Foreword
This Standard equivalently adopts the International Electrotechnical Commission standard 3rd edition (1987) of IEC 68-2-27 ?€?Environmental Testing ?€? Part 2: Test Methods ?€? Test Ea and Guidance: Shock?€?.
This Standard replaced GB 2423.5-81 ?€?Electric and Electronic Products - Basic Environmental Test Regulations for Electricians - Test Ea: The Impact Method?€? and GB 2424.3-81 ?€?Electric and Electronic Products - Basic Environmental Test Regulations for Electricians ?€? Guidelines for Impact Tests?€?.
GB 2423.5-81 and GB 2424.3-81 were drafted by reference of the International Electrotechnical Commission standard 2rd edition (1972) of IEC 68-2-27 ?€?Basic Environmental Test Regulations ?€? Part 2: Test Methods ?€? Test Ea and Guidance: Shock?€?; divided one standard of the International Electrotechnical Commission into two standards; its text became the shock test methods in GB 2423.5; while its appendix became the shock test guidance in GB 2424.3. This revision incorporates the test methods and guidance; like the 3rd edition of IEC 68-2-27, add Clause 3 Definitions. Increase the appendix from 1 to 3; namely, Appendix A: Guidance; Appendix B: Shock Response Spectrum and Other Characteristics of the Pulse Waveform; Appendix C: Comparison of Shock Test Methods. Relax restrictions for tolerance requirements of pulse waveforms.
This Standard was first-time published in 1981; first-time revised in August, 1995. It is implemented since the August 01, 1996.
The original China?€?s national standards of GB 2423.5-81 and GB 2424.3-81 were abolished at the same time since the date of implementation.
This Standard?€?s Appendixes A, B and C are standard ones.
This Standard was proposed by the Ministry of Electronics Industry of the PEOPLE Republic of China.
This Standard shall be under the jurisdiction of National Technical Committee on Environmental Conditions of Electric and Electronic Products and Environmental Test of Standardization of China.
Drafting organization of this Standard: No. 5 Institute of Ministry of Electronics Industry. Chief drafting staffs of this Standard: Xu Yongmei, and Wang Shurong.
Environmental Testing for Electric and Electronic
Products - Part 2: Test Methods - Test Ea and
Guidance: Shock
1 Objective
To provide a standard procedure for determining the ability of a specimen to withstand specified severities of bump.
2 General Description
This Standard was drafted according to the pulse waveforms; refer to Appendix A for guidance on selecting and using these pulse waveforms. The characteristics of various pulse waveforms shall be discussed in Appendix B. This Standard includes three pulse waveforms, namely, semi-sine pulse, post-peak zigzag pulse and trapezoidal pulse. The selection of pulse waveform depends on many factors, and the selection itself is difficult, therefore, this Standard does not give priority sequence of the waveforms (see Clause A3).
The purpose of the test is to reveal mechanical weakness and/or performance degradation; use these materials, and combine with relevant regulations to determine whether a specimen is acceptable or not. It may also be used, in some cases, to determine the structural integrity of specimens or as a means of quality control (see Clause A2).
This test is primarily intended for unpackaged specimens and for items in their transport case when the latter may be considered as part of the specimen itself. The bumps are not intended to reproduce those encountered in practice. Wherever possible, the test severity applied to the specimen and shock pulse waveforms should be such as to reproduce the effects of the actual transport or operational environment to which the specimen will be subjected to or to satisfy the design requirements if the object of the test is to assess structural integrity (see Clauses A2 and A4). For the purpose of this test the specimen is always fastened to the fixture or the table of the bump tester during conditioning.
In order to facilitate the use of this Standard, the text of this Standard also listed the geographical latitude. For the purposes of this Standard, the value of gn, is rounded up to the integer of 10 m/s2.
4. Description of Test Apparatus
4.1 Characteristic requirements
When the bump tester and/or fixture are loaded with the specimen, the shock pulse applied at the check point shall be approximate to the one of the nominal curves about acceleration versus time shown in virtual line.
4.1.1 Basic pulse shape
The true value of the pulse shall be within the tolerance limit in the relevant Figures shown in solid line.
NOTE - Where it is not practicable to achieve a pulse waveform falling within the specified tolerance. The relevant specification should state the alternative procedure to be applied (see Clause A5).
All specified pulse waveforms are as follows, and their order of arrangement does not indicate that the front pulse is prioritized.
Post-peak zigzag pulse: an asymmetrical triangle with a short fall time, as shown in Figure1.
Half-sine pulse: half cycle of a sine wave, as shown in Figure 2.
Trapezoidal pulse: a symmetrical quadrilateral with short rise and fall time, as shown in Figure 3.
4.1.2 Speed variation tolerance
For all pulse waveforms, the actual speed variation shall be within ??15% of its corresponding nominal pulse value.
When the speed variation is determined by the integral of the actual pulse, it shall be begun from pre-pulse 0.4D integral to post-pulse 0.1D, where D is the duration of the nominal pulse.
NOTE: If the speed variation tolerance is not available due to lack of an accurate integration device, the relevant specification should state the alternative procedure to be applied. 4.1.3 Transverse motion
The positive or negative peak acceleration at the check point, perpendicular to the intended bump direction, shall not exceed 30% of the value of the peak acceleration of the nominal pulse in the intended direction, when determined with a measuring system in accordance with Sub-clause 4.2 (see Clause A5).
NOTE ?€? If the transverse motion tolerance cannot be achieved, the relevant specification should state the alternative procedure to be adopted (see Clause A5).
4.2 Measuring system
The frequency characteristics of the measuring system shall be such that it can be determined that the true value of the actual pulse as measured in the intended direction at the check point is within the tolerance range in the Figure prescribed by Sub-clause 4.1.1.
The frequency characteristics of the overall measuring system, which includes the accelerometer, can have a significant effect on the measuring accuracy and shall be within the tolerance limits shown in Figure 4 (see Clause A5).
4.3 Mounting
During the conditional test, the specimen shall be mounted to the fixture or the table of the bump tester by its normal mounting means. Mounting method shall be as specified in GB/T 2423.43-1995 Environmental Testing for Electric and Electronic Products - Part 2: Test Methods - Mounting Requirements and Guidance of Components, Equipment and Other Products for Shock (Ea), Collision (Eb), Vibration (Fc and Fd), Stable Acceleration (Ga) and Similar Dynamic Tests.
5. Severities
The relevant specification shall give both the pulse waveform and the test severity level. A pulse waveform given in 4.1.1 and a severity level specified in Table 1 shall be selected.
Unless otherwise specified, a set of data on the same line in Table 1 shall be used. The data of each line with * shall be preferred. The specified corresponding speed variation is listed in Table 1 (see Clause A4).
NOTE: If the severity level in the Table 1 can?€?t simulate the effect of a known environment on the sample, the relevant specification can use one of three standard pulse waveforms shown in Figure 1, Figure 2 and Figure 3 (see Clause A4) to specify other suitable test severity level. The relevant specifications state:
a) Whether the specimen is to be operated during the shock test and whether it is to be monitored for its function; and/or
b) The specimen shall be able to subjected to the applied shock.
For both cases, the relevant specification shall give criteria for receipt or rejection. 9 Recovery
The relevant specification can propose recovery requirements.
10 Final Inspection
The specimen shall be submitted to the appearance, dimensional and functional checks prescribed by the relevant specification.
The relevant specification shall give the criteria for receipt or rejection. 11 Information to be Given in the Relevant Specification
When relevant specification adopts this test, it shall give the following information: a) Pulse waveforms (A3) (4.1.1);
b) Tolerance under special conditions (A5) (4.1.1);
c) Speed variation under special conditions (A6) (4.1.2);
d) Transvers motion under special conditions (4.1.3);
e) Mounting mode (4.3);
f) Severity level (A4) (Clause 5);
g) Pre-conditioning (Clause 6);
h) Initial inspection (Clause 7);
i) The direction and number of shocks only under special conditions (A7) (8.1); j) Operating mode and functional monitoring (8.2);
Appendix A
(Normative)
Guidance
A1 Introduction
The test provides a method by which effects on a specimen comparable with those likely to be experienced in practice in the environment to which the specimen will be subjected during either transportation or operation can be reproduced in the test laboratory. The basic intention of the test is not to simulate the real environment. The parameters given are standardized and suitable tolerances are chosen in order to obtain similar results when a test is carried out at different locations by different people. The standardization of values also enables components to be grouped into categories corresponding to their ability to withstand certain severities given in this Standard. In order to facilitate the use of this Appendix the related clause numbers of the text are referred to herein.
A2 Applicability range of shock test
Many specimens are susceptible to shock during use, loading/unloading,
transportation processes. The magnitude of these shock varies widely and has complex properties. This Test provides a very convenient method for determining the ability of a sample to withstand these non-repetitive shock conditions. For the repetitive shock, it shall use GB/T 2423.6-1995 Environmental Testing for Electric and Electronic Products - Part 2: Test Methods???Test Eb and Guidance: Bump (Appendix C). The shock test is also applicable to structural integrity tests performed on the component specimens for identification or quality management. In these cases, high accelerations hocks are usually applied, the main purpose is to apply a known shock to the internal structure of the specimen (especially for the specimens with cavities) (Clause 2).
The specification writer intending to adopt this test should refer to Clause 11 ?€?Information to be given in the relevant specification?€? in order to ensure that all such information is so provided.
A3 Pulse waveform (Clause 2)
This Standard specifies three commonly used shock pulse waveforms. Any one of them can be selected according to the purpose of the test (see also 4.1.1 and Table 1 of this Standard).
A5 Tolerance
The test method described in this standard is capable of a high degree of reproducibility when the tolerance requirements relating to the pulse waveform, velocity variation, and transverse motion are complied with.
However, there are certain exceptions to these tolerance requirements and these are primarily applicable to specimens which provide a highly reactive load, that is with mass and dynamic responses which would influence the characteristics of the bump tester. In these cases, it is expected that the relevant specification will specify relaxed tolerances or state that the values obtained will be recorded in the test report (see Sub- clauses 4.1. 1, 4.1.2 and 4.1.3).
When testing highly reactive specimens it may be necessary to carry out preliminary bump conditioning to check the characteristics of the loaded bump tester. With complex specimens, where only one or a limited number is provided for test, the repeated application of bumps prior to the definitive test, particularly for the lower number of bumps, could result in an over-test and possibly unrepresentative cumulative damage. In such instances it is recommended that, whenever possible, the preliminary checking should be carried out using a representative specimen (such as rejected equipment), or, when this is not available, it may be necessary to use model having the correct mass and center of gravity position to carry out shock pre-conditioning. However, it needs to be noted that the above model is unlikely to have the same dynamic response as the real specimen.
For the frequency response of the entire measurement system including the accelerometer, it is an important factor to reach the required pulse waveform and severity level, which shall be within the tolerance range shown in Figure 4. If a low- pass filter is used to reduce the high-frequency resonance effects inherent in the accelerometer, then the amplitude-frequency characteristics and phase-frequency characteristics of the measurement system must be considered to avoid the distortion in the measurement system itself (see 4.2).
For the shock with pulse duration equal to or less than 0.5ms, the f3 and f4 shown in Figure 4 may be too high; in this case, the relevant specification may be specified otherwise (see 4.2).
A6 Speed variation (see 4.1.2)
For all pulse waveforms, it is necessary to determine the actual velocity variation. This can be done in a number of ways., amongst which are:
- the shock pulses not involving rebound motion, which shall be determined by the collision speed.
- the free-fall testers shall be determined by the height of falling and rebounding. Appendix B
(Normative)
Shock Response Spectrum and Other Characteristics of Pulse
Waveform
Introduction
In order to utilize the improved technology in the shock test and to further develop the impact tester, Test Ea requires one of three pulse waveforms with a specified severity level to be applied to the fixed point of the specimen without limiting the used shock tester. The selection of the pulse waveforms and severity levels shall be based on the technical consideration applicable to the design and type of the specimen. From the point of view for specifying the reproducibility of the test conditions and reproducibility of influence on the actual shock environmental conditions, all methods are feasible. In order to make the test both reproducible and practical, some basic concepts must be considered when developing the test procedures and described as follows:
B1 Concept of shock response spectrum
When developing the shock test procedures, the acceleration shock response spectrum of various pulse waveforms has been considered; because under many important practical situations, they provide useful magnitudes for potential damage to the shock. However, it must be acknowledged that, from certain aspects, their application has limitations.
The acceleration shock response spectrum can be considered to be the maximum acceleration response as a function of the resonant frequency of the system for a given undamped mass-elastic system under specified shock excitation. In most cases, the maximum acceleration of the vibrations systems determines the maximum mechanical stress of the joint and the maximum relative displacement of the elastic member. Let the frame shown in Figure B1 withstand a shock excitation with a specified pulse waveform, namely, the time period of the acceleration is d2Xf/dt2 = a(t). Since the mass, m, determines the resonant frequencies (f1, f2, f3, etc.), the system response is an oscillation with different acceleration time period.
Figure B2a is an example of pulse waveform with a peak acceleration of A and a duration of D; its response acceleration d2X1/dt2 = a(t), etc. can refer to Figure B2b. The shock response spectrum (see Figure B2c) is caused by an infinite number of given in this Appendix has two coordinates, namely, amax/A as fD function, and amax as f function shall be the special case of pulse duration and peak acceleration. B2 Application of Level-I shock response spectrum in actual conditions
In components and equipment, their internal components typically form a more complex system than an undamped system. For instance, the damped series multi- degree-of-freedom system shown in Figure B3. In this case, when the external system excites the oscillation due to the shock, the internal system may be damaged due to the coupling resonance effect. Such effect can be illustrated by a series of effective high-order shock spectra that give the mass-elastic separation system combined resonant frequency.
If the resonant frequencies of the series system can be completely separated, then the Level-I shock spectrum can give a reasonable magnitude of the potential damage caused by comparing different pulse waveforms.
If the resonance is excited during the pulse period, then various masses in the system shall reach the highest acceleration. In this case, the oscillation acceleration overlaps with the pulse itself. Therefore, when suing a pulse with a short rise time, it is obvious form Claus B3 that the damage is mostly likely to occur.
Generally, the damping can reduce the response of the mid-frequency-band during the pulse duration and reduce the response of the mid-and-high-frequency-band after the pulse. Meanwhile, damping can also reduce the amplitude of the oscillation and the duration of oscillation; thus, attenuate the response of the internal system. So the damage from the damping system may be lower than from the undamped system, especially for the multi-degree-of-freedom system. Therefore, the shock response spectrum of the undamped system represents the worst possible damage.
It can be seen from the above that the acceleration shock spectrum can?€?t fully explain the damage capability of the shock. Nevertheless, this simplified method of expression is sufficient to select a suitable shock pulse for the actual structure. Before comparing the shock spectrum, the accurate shock test shall compare the long- term response oscillation exhibited by the residual shock spectrum with the importance of the short response oscillation exhibited by the initial response spectrum, and make a judgment. Such j...

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