GB/T 2423.48-1997 Environmental testing for electric and electronic products Part 2: Test methods Test Ff: Vibration - Time history method
Some standard content:
GB/T2423.48—1997
This standard is formulated based on the first edition of 1989 of IEC68-2-57 "Environmental testing Part 2: Test method Test Ff: Vibration---Time history method" of the International Electrotechnical Commission. This standard is completely equivalent to IEC68-2-57, first edition in 1989. Appendix A of this standard is the appendix of the standard. This standard is proposed by the Ministry of Electronics Industry of the People's Republic of China. This standard is under the jurisdiction of the National Technical Committee for Environmental Conditions and Environmental Testing of Electrical and Electronic Products. The drafting units of this standard are the Fifth Institute of the Ministry of Electronics Industry and the Fourth Institute of the Ministry of Electronics Industry. The main drafters of this standard are Zhang Youlan, Wang Shurong, Zhou Xincai, Lu Zhaoming, Liu Zhonglai, and Zhang Yue. 171
GB/T2423.481997
IEC Foreword
1) The formal resolutions or agreements of the International Electrotechnical Commission (IEC) on technical issues are formulated by technical committees represented by national committees that are particularly concerned about the issue, and they express the international consensus on the issue as much as possible. 2) These resolutions or agreements are used internationally in the form of recommended standards and are accepted by national committees in this sense. 3) In order to promote international unification, the International Electrotechnical Commission hopes that all member countries will adopt the contents of the recommended standards of the International Electrotechnical Commission as their national standards when formulating national standards, as long as the specific conditions of the country permit. Any differences between the recommended standards of the International Electrotechnical Commission and the national standards should be clearly pointed out in the national standards as much as possible. This standard was formulated by the 50th Technical Committee (Environmental Testing) of the International Electrotechnical Commission, Subcommittee 50A (Shock, Vibration and Other Dynamic Testing).
The text of this standard is based on the following documents: Draft Standard
50A(CO)176
More detailed voting information can be found in the voting report specified in the table above. 472
Voting Report
50A(CO)178
National Standard of the People's Republic of China
Environmental testing for electric and electronic products
Part 2: Test methods
Test Ff : Vibration-Time-history methodGB/T 2423.48--1997
idt IEC 68-2-57:1989www.bzxz.net
This standard specifies the time history vibration test method for components, equipment and other electric and electronic products. Because these components, equipment and other electrical and electronic products (hereinafter referred to as samples) may often be subjected to short-duration random dynamic forces during their use, such as earthquakes, explosions, and stresses generated in the equipment by certain transportation situations. The characteristics of these forces and the damping of the sample make the vibration response of the sample unable to reach steady-state conditions. After the initial vibration response check is carried out with sinusoidal vibration, this test will subject the sample to a time history specified by a response spectrum with simulated dynamic stress characteristics.
Time history can be generated and obtained by the following methods: - Natural time history of natural events;
Random samples (artificial time history);
A synthetic signal (artificial time history). In order to adapt to the required severity level, some modifications must usually be made. When using time history, it is allowed to use a single test waveform to envelop a broadband response spectrum. All structural modes in the excitation axis (one or more) may be excited at the same time, so the stress caused by the combined effect of the coupled mode is generally considered. A detailed list of details that must be included in the preparation of relevant specifications is listed in Chapter 12, and guidelines are given in Appendix A (Standard Appendix).
Cited Standards
The provisions contained in the following standards constitute the provisions of this standard through their use in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T2298-91 Mechanical vibration and shock terminology (neISO2041:1975) GB2421-89 General rules for basic environmental testing procedures for electrical and electronic products (eqvIEC68-1:1988) GB/T2423.10-1995 Environmental testing for electrical and electronic products Part 2 Test methods Test Fc and guidance: Vibration (sinusoidal) (idt IEC 68-2-6:1982)
GB/T2423.43-1995 Installation requirements and guidelines for components, equipment and other products in dynamic tests such as impact (Ea), collision (Eb), vibration (Fc and Fd) and steady-state acceleration (Ga) (idtIEC68-2-47:1982) Approved by the State Administration of Technical Supervision on September 1, 1997 and implemented on October 1, 1998
1 Purpose
GB/T 2423.48—1997
Provides a standard procedure for determining the ability of a specimen to withstand transient motions of a specified severity level by the time history method. 2 General Notes
The purpose of this test is to determine the mechanical weaknesses and/or degradation of the specified performance of the specimen in accordance with the specified performance and to use this information in conjunction with the relevant specifications to determine whether the specimen is acceptable. In some cases, this test method may also be used to determine the mechanical strength of the specimen and/or to study its dynamic characteristics.
The relevant specifications should specify that the specimen must be operated or merely subjected to vibration conditions during the test. This standard specifies the test procedure and the method of measuring vibration at a given point, as well as the requirements for the vibration motion and the selection of the severity level (including frequency range, required response spectrum, number of high stress response cycles, and number of time histories). It should be emphasized that vibration testing always involves a degree of engineering judgment. Both the supplier and the purchaser should be fully aware of this fact. It is expected that the relevant specification writer will select the test procedure and the severity level value that is appropriate for the specimen and its use requirements. For the purpose of this test, the specimen is usually fastened to the vibration table during the test. In order to facilitate the use of this standard, the main body and appendix of this standard give the chapter numbers that readers need to refer to each other. This standard should be used in conjunction with GB2421. 3 Definitions
The terms used in this standard are generally defined in GB/T2298.GB2421 or GB/T2423.10. For the convenience of readers, this standard lists the definition of one of the standards, indicates its source, and also points out the differences between the standards. The following additional terms and definitions apply to this standard. 3.1 Critical frequency (technically equivalent to 8.1 in GB/T 2423.10) The frequency at which the test sample fails and (or) performance degrades due to vibration. Or the frequency at which mechanical resonance and other effects (such as flutter) occur.
3.2 Damping (different from the definition in GB/T2298) Damping is a general term to describe the energy loss caused by various mechanisms in the system. In practice, damping depends on many parameters, such as system structure, vibration mode, deformation, applied force, velocity, material, connection slip, etc. 3.2.1 Critical damping The minimum viscous damping that allows a displaced system to return to its initial position without oscillation. 3.2.2 Damping ratio
The ratio of actual damping to critical damping in a viscous damping system. 3.3 Distortion (same as Chapter 3 of GB/T2423.10, different from the definition of GB/T2298) Distortion d
Vaot a?
×100% (calculated as a percentage)
Where: a1 ~ RMS acceleration value at the driving frequency; atot - total RMS acceleration applied (including a value). 3.4 Fixing point (same as 3.1 in GB/T2423.10) The part of the sample that contacts the fixture or the vibration table. This is usually the place where the sample is fastened when in use. Note: If part of the actual mounting structure is used as a fixture, the fixing point is the fixing point of the mounting structure, and the surface is not the fixing point of the sample. 3.5 Acceleration of gravity \g." acceleration of gravity "gn" is the standard acceleration caused by the earth's gravity, which itself varies with altitude and earth's latitude. Note: In this standard, the gn value is an integer of 10m/s. 3.6 High stress cycles highstress cycles174
GB/T 2423.48---1997
The response cycle (number) of stress values that cause fatigue in the sample. 3.7 Measuring points (technically the same as 3.2 in GB2423.10) Special points for collecting data for the test. These points have two main forms and are defined as follows: Note: In order to evaluate the performance of the sample, measurements can be made at many points in the sample. However, these points are not considered as measuring points in this standard. 3.7.1 Check point
A point located on the fixture, vibration table or sample, which is as close as possible to one of the fixed points and, in any case, must be rigidly connected to the fixed point.
"These checkpoints are used to ensure that the test requirements are met. If there are 4 or fewer fixed points, each fixed point is used as a checkpoint. If there are more than 4 fixed points, the relevant specification should 2
specify 4 representative fixed points as checkpoints. 3 In special cases, such as large or complex samples, if the checkpoints are not required to be close to the fixed points, the checkpoints should be specified in the relevant specifications. When a large number of small samples are installed on a fixture, or when a small sample has many fixed points, in order to derive the control signal, a single 4
checkpoint (i.e., reference point) can be selected. Therefore, the control signal is related to the fixture and has nothing to do with the fixed point of the test sample. This method is only feasible when the lowest resonant frequency of the fixture after loading greatly exceeds the upper frequency limit of the test. 3.7.2 Reference point refercncepoint (technically the same as 3.2.2 in GB/T2423.10) A point selected from the checkpoints, its signal is used to control the test to meet the requirements of this standard 3.8 Natural time history natural time-history is a record of acceleration, velocity or displacement (varying with time) caused by a given event. 3.9 oscillator
a single degree of freedom system that can generate or maintain mechanical oscillations. 3.10 pause
the interval between two consecutive time histories,
note: the pause should be such that the response motion of the sample has no significant increase. 3.11 preferred testing axes preferred testing axes are orthogonal axes that correspond to the most vulnerable axis of the sample, 3.12 random motion sample random motion sample is a random motion recording sample with improved frequency range and amplitude to produce the required response spectrum. 3.13 required response spectrum required response spectrum is a response spectrum specified by the user.
3.14 response spectrum response spectrum (different from the definition in GB/T 2298) is the maximum response curve of a series of single degree of freedom objects according to the specified damping ratio to the specified input motion. 3.15 strong part of the time history strong part of the timehistory The time history from the beginning of the curve reaching 25% of the maximum value to the final drop to 25% of the level (see Figure 1). 17
GB/T2423.48
Intense part
Figure 1 Typical time history
3.16 Sweep cycle (technically the same as Chapter 3 of GB/T2423.10) One back and forth in each direction within the specified frequency range, for example 1Hz-35Hz-1 Hz. 3.17 Synthesized time history Synthesized time-history Artificially generated time history whose response spectrum envelopes the required response spectrum. 3.18 Test value test level
The maximum peak value of the test waveform.
3.19 Test response spectrum test response spectrum Response spectrum analyzed from the actual motion of the shaking table or derived using spectrum analysis equipment. 3.20 Time history time-history
A function record of acceleration, velocity, or displacement changing with time. Note: The mathematical term "time history" is defined in GB/T 2298 and is related to the value of a quantity as a function of time. 3.21 Zero period acceleration The high-frequency asymptotic value of the response spectrum acceleration (see Figure 2 for example). Time
Note: Zero period acceleration has practical significance because it represents the maximum peak value of acceleration in the time history, but it should not be confused with the peak value of acceleration in the response spectrum.
4 Requirements for conditional tests
GB/T 2423.48—1997
Test response spectrum points outside the tolerance range
Required response spectrum
Formula test response spectrum
Tolerance range
Zero cycle acceleration
Figure 2 Typical logarithmic curve of required response spectrum
4.1 specifies the requirements for vibration response inspection, 4.2 specifies the requirements for time history test, and 4.3 specifies the installation requirements for conditional test samples.
4.1 Vibration response inspection
When the relevant specifications have requirements, the vibration response inspection shall be carried out in accordance with the method in GB/T2423.10. In particular, the requirements of 4.1.1 to 4.1.9 below should be considered to determine the critical frequency and, if necessary, the damping ratio. 4.1.1 Basic motion
The basic motion shall be a sinusoidal function of time. The specimen shall be substantially in phase and move in parallel straight lines at each fixed point on the shaker as required by the relevant specification. The tolerance requirements specified in 4.1.2, 4.1.3 and 4.1.5 shall be met. 4.1.2 Lateral motion
The maximum vibration on any axis perpendicular to the specified axis at the inspection point shall not exceed 50% of the basic motion. In special cases, such as small specimens, if required by the relevant specification, the peak value of lateral vibration may be limited to 25%. At certain frequencies, large size or large mass specimens, it may be difficult to meet these requirements (Chapter A1). In this case, the relevant specification shall specify the use of the following two.
a) Lateral motion exceeding the above provisions shall be recorded in the test report; b) Lateral motion shall not be monitored.
4.1.3 Rotational motion
When the parasitic rotational motion of the shaker is important, the relevant specification may specify the tolerance level of the parasitic rotational motion, which shall then be written in the test report.
4.1.4 Measuring point
4.1.4.1 Reference point
The relevant specification shall specify whether single-point control or multi-point control is adopted. If multi-point control is specified, it shall be specified whether the average value of the signal at the inspection point or the signal value at the selected point is controlled to the specified value. 4.1.4.2 Inspection point
GB/T 2423.481997
At certain frequencies, it may be difficult to achieve the tolerance required by 4.1.6.2 for samples of large size or large mass (see Chapter A1). In this case, it is hoped that the relevant specification will specify a wider tolerance or write the alternative assessment method used in the test report. 4.1.5 Acceleration distortion
The acceleration waveform distortion measurement shall be carried out at the reference point, and its frequency range shall reach five times the test frequency. The distortion defined in Chapter 3 shall not exceed 25% of the basic motion. NOTE: In some cases it may not be possible to meet these requirements, in which case distortions greater than 25 % may be acceptable if the amplitude of the acceleration of the fundamental frequency control signal is restored to the specified value, e.g. by using a tracking filter. For large or complex specimens, where the specified distortion values may not be met over certain parts of the frequency range and the use of a tracking filter is not practical, the acceleration need not be restored and the distortion should then be reported in the test report (see Clause A1). Whether or not a tracking filter is used, the relevant specification may require that the distortion be reported together with the frequency range affected. 4.1.6 Amplitude tolerances
The basic motion at the check point and reference point along the required axis shall be equal to the specified value and within the following tolerances, which include instrument errors.
4.1.6.1 Reference point
Tolerance of the control signal at the reference point:
±15 % (basic motion).
4.1.6.2 Checkpoints
Tolerance at each checkpoint:
Below 500 Hz: ±25% (acceleration); above 500 Hz: ±50% (acceleration) (see 4.1.4.2). 4.1.7 Frequency tolerance
Tolerance at dangerous frequencies is:
Below 0.25 Hz: ±0.05 Hz;
0.25 Hz~～5 Hz: ±20%;
5 Hz～50 Hz:±1 Hz;
Above 50 Hz: ±2%.
When comparing the critical frequencies before and after the conditioning test, the following tolerances apply (see 8.2): Below 0.5 Hz; ±0. 05 Hz;
0. 5 Hz to 5 Hz: ±10%;
5 Hz to 100 Hz: ±0. 5 Hz;
Above 100 Hz: ±0. 5%.
4.1.8 Frequency sweep
The frequency sweep shall be continuous and vary exponentially with time at a rate not exceeding one octave per minute (see 3.16). NOTE: When a digital control system is used, it is not strictly correct to say that the frequency sweep is "continuous", but the distinction has no practical significance. 4.1.9 Damping ratio
The damping ratio is generally determined from the vibration response examination. This determination depends on the test equipment used and requires engineering judgment. Other methods may be used if the test report considers it appropriate. 4.2 Time history conditional test
For the time history conditional test, the following requirements should be considered: 4.2.1 Basic motion
The time history used can be obtained from either of the following two methods: a) natural time history,
b) time history synthesized by frequency synthesis within the specified frequency range. In this case, the synthetic time history should be generated with an appropriate resolution as follows:
GB/T2423.481997
When the damping of the sample is less than or equal to 2%, it shall not exceed the 1/12 octave band. When the damping of the sample is 2% to 10%, it shall not exceed the 1/6 octave band in general. When the damping of the sample is greater than or equal to 10%, it shall not exceed the 1/3 octave band. The relevant specification may specify the value of the damping ratio (see 3.14), or obtain it by other methods (see 4.1.9). A value of 5% is usually selected. 4.2.2 Lateral motion
Unless otherwise specified in the relevant specification, the maximum peak acceleration or displacement at the check point on any axis perpendicular to the specified axis shall not exceed 25% of the peak value specified in the time history. The recorded measurements need only cover the specified frequency range. At certain frequencies, for large size or large mass samples, it may be difficult to achieve the above values (see Chapter A1). In this case, the relevant specification should indicate which of the following applies. a) Lateral motion exceeding the above provisions shall be recorded in the test report; b) Lateral motion is not monitored.
4.2.3 Rotational motion
When parasitic rotational motion of the vibration table may be important, the relevant specification may specify a tolerance level and record it in the test report.
4.2.4 Tolerance band required for response spectrum
Applicable to the tolerance band required for the response spectrum should be in the range of 0% to 50%, as shown in Figure 3. Amplitude
Damping ratio = 2%
Damping ratio = 5%
Damping ratio - 10%
Zero period acceleration
1/3f22/3f2fg
Figure 3 General RRS (recommended response spectrum) Shape locking rate
Note: If a small number of individual points of the test response spectrum fall outside the tolerance band, the test is still acceptable and the values of these points should be recorded in the test report 170
(see Chapter A1).
The test response spectrum shall be subject to at least the following checks: GB/T 2423.48---1997
If the damping of the specimen is less than or equal to 2%, check it in 1/12 octave bands; if the damping of the specimen is between 2% and 10% (generally), check it in 1/6 octave bands; if the damping of the specimen is greater than or equal to 10%, check it in 1/3 octave bands. NOTE: In some cases, the tolerances in the test specification may need to be modified because the response spectrum is required to be artificially shaped and widened so that the test response spectrum cannot be produced within the tolerance band. 4.2.5 Frequency range
In addition to the frequencies generated by the test device and the specimen, the signal at the reference point shall not include any frequencies outside the test frequency range. The maximum value of the signal generated by the test device outside the test frequency range shall not exceed 20% of the maximum value of the signal specified at the reference point in the absence of the specimen. If the above values cannot be achieved, the values obtained shall be recorded in the test report. Frequencies outside the frequency range shall not be considered in the evaluation of the test response spectrum. 4.3 Installation
The sample shall be installed in accordance with the requirements of GB/T2423.10, as the installation part of this standard adopts GB/T2423.43. If the sample is usually installed on a shock absorber, and the shock absorber must be removed during the test, consideration should be given to modifying the specified excitation value.
The influence of connectors, cables, conduits, etc. should be considered when installing the sample. Note: The test should include the installation structure of the sample in normal use. The relevant specifications should specify the orientation and installation method of the sample during the conditional test, and should be the only condition for the sample to meet the requirements of this standard, unless sufficient reasons can be given to show that the orientation and installation have no effect on the test (for example, if it can be proved that the gravity effect does not affect the performance of the sample).
5 Severity level
The test severity level is determined by the combination of the following parameters: test frequency range;
-required response spectrum;
-number and duration of time history
number of high stress response cycles (if applicable); the relevant specifications shall specify the value of each parameter based on the information given in 5.1~5.4. 5.1 Test frequency range
The relevant specifications shall select a lower limit frequency from Table 1 and an upper limit frequency from Table 2 to give the test frequency range. The recommended frequency range is shown in Table 3.
Table 1 Lower limit frequency
Table 2 Upper limit frequency
Table 3 Recommended frequency range
From fi~f, Hz
0. 1～10
1～35
1～100
10～100*
10~～500
10-2000
55~～2000
Note: There is no frequency range marked with an asterisk in the recommended frequency range of GB/T2423.10. 5.2 Required response spectrum
GB/T 2423.48- 1997
The relevant specifications shall specify the shape and value of the response spectrum required for the conditional test, including the zero-cycle acceleration value. If all axes of the sample are not the same, the sample axis to which the response spectrum is applied shall also be specified. Chapter A2 provides guidance for developing the required response spectrum when the environmental conditions are completely unknown. 5.3 Number and duration of time histories
5.3.1 Number of time histories
The relevant specification shall specify the number of time histories applied to the specimen and the relevant axes. Unless otherwise specified, the number of time histories applied to each axis and each time history level shall be selected from the following series: 1, 2, 5, 1020, 50...
When more than one time history level is applied, the conditioning test shall always start from the lowest value and continue to the higher values. There shall be a rest after each time history.
5.3.2 Duration of time histories
The relevant specification shall specify the duration of each time history. The recommended values in seconds are given in the following series:...1, 2.5.10,
5.3.3 Duration of the intense part of the time history In some cases, the relevant specification may require the percentage of the intense part of the time history to be the total duration. In addition, except when excluded by the requirements of 5.4, the value of the intense part of the time history shall be selected from the following percentages of the total duration: 25%, 50%, 75%. The selected value shall be recorded in the test report.
5.4 Number of high stress cycles
The relevant specification may specify the number of high stress cycles resulting in stress values exceeding the specified value (see Chapter A3). Except when the relevant specification specifies otherwise, the number of high stress cycles shall be selected from the following series: 4, 8, 16.32. The positive and negative alternating cycles shall be approximately equal to the average distribution shown in Figure 4. Acceleration
Exceeds the specified positive peak range
The specified value is 70%!
Specified value 70%H
100%日
Exceeds the specified negative beep value range
Figure 4 Typical response of an oscillator at a specific frequency These high stress cycles should be expressed as a percentage of the required response spectrum for a specific critical frequency that is located in the intense part of the required response spectrum. 481
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Shown. It should be selected from the values of 50%, 70% (preferred value), and 90%. 6 Pretreatment
Pretreatment may be required by the relevant specifications.
7 Initial inspection
The samples should be inspected for appearance, dimensions, and function in accordance with the requirements of the relevant specifications. 8 Conditioning test
8.1 General
Unless otherwise specified in the relevant specification, the specimen shall be excited in each of the three preferred test axes. If not specified in the relevant specification, the order of testing along these axes is not important. When specified in the relevant specification, the control of the specified test quantity should be supplemented by an upper limit on the maximum driving force applied to the shaker. The method of limiting the force should also be specified in the relevant specification. 8.2 Vibration response check
When specified in the relevant specification, the response check should be carried out over the test frequency range in order to study the dynamic characteristics of the specimen under vibration conditions. The vibration response check should be carried out with a sine wave and a certain test amplitude within the test frequency range as specified in the relevant specification. Normally, the vibration response check should be carried out with a logarithmic sweep rate not higher than one octave per minute. However, if a more accurate response characteristic is to be obtained, the sweep rate can be slower, but undue pauses should be avoided. The excitation peak should be selected so that the specimen response remains less than the time history response, but should be kept at a sufficiently high value to detect critical frequencies.
If required by the relevant specification, the specimen shall be operated during the vibration response check. If the mechanical vibration characteristics of the specimen cannot be evaluated because it is in operation, an additional vibration response check shall be carried out with the specimen not in operation. At this stage, the specimen shall be checked to determine the critical frequency and the results of the check shall be recorded in the test report. In some cases, the relevant specification may require an additional vibration response check after the time history condition test has been completed in order to compare the critical frequencies. The relevant specification should specify the measures to be taken if any change in frequency occurs. It is of utmost importance that both vibration response checks are carried out in the same manner and with the same test quantity values. 8.3 Time history condition test
For the time history condition test, the relevant specification shall be based on the severity level values specified in Clause 5. There shall be a pause between consecutive time histories so that the response motions of the specimen are not significantly superimposed. The relevant specification shall also specify whether a single-axis condition test, a dual-axis condition test, or a tri-axis condition test is required.
8.3.1 Single-axis conditioning
Conditioning tests are performed in sequence along each preferred test axis. The order in which the tests are performed along these axes is not important unless otherwise specified in the relevant specification.
8.3.2 Dual-axis conditioning
For each series of tests, two time histories are applied simultaneously along the two preferred axes of the specimen. If the two time histories are not independent, each test is repeated first with a relative phase angle of 0° and then 180°. NOTE: When dual-axis testing is specified, conditioning tests may be performed in a single-slope mounting, but the motion along the two axes is always related. The test response spectrum for each axis shall be adjusted so as to envelop the required response spectrum for that axis. 8.3.3 Triple-axis conditioning
For each series of tests, time histories are applied simultaneously along the two preferred axes of the specimen. For this conditioning test method, the use of a single-axis dual-axis mounting is not appropriate.
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