GB/T 2424.25-2000 Environmental testing for electric and electronic products Part 3: Test guidelines Seismic test method
Some standard content:
GB/T2424.25—2000
This standard is equivalent to the International Electrotechnical Commission standard IEC68-3-3:1991 "Environmental testing Part 3: Test guidelines Equipment seismic test method" (first edition). This standard describes in detail the seismic test methods for nuclear power plant equipment, building equipment and electrical and electronic products, because these equipment and electrical and electronic products (hereinafter referred to as samples) may be subjected to short-duration non-stationary random dynamic forces during their use. A typical example is the stress generated in the sample by the ground capsule. The characteristics of these stresses and the damping of the sample make the vibration response of the sample unable to reach the steady-state condition. When the relevant specifications stipulate that the equipment identification must be subject to seismic test, this standard provides a series of test methods that can be used to identify its performance. Appendix A of this standard is the appendix of the standard.
This standard is proposed by the Ministry of Information 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. Drafting unit of this standard: Electronic Fifth Research Institute of the Ministry of Information Industry. The main drafters of this standard are Zhang Youlan, Yang Chuan, Ji Chunyang, Wang Shurong and Xu Zhonggen. 253
GB/T2424.25—2000
IEC Foreword
1) The formal resolutions or agreements of the International Electrotechnical Commission (IEC) on technical issues are formulated by technical committees in which all national committees that pay special attention to the issue are represented. They express the international consensus on the issues involved as much as possible. 2) These resolutions or agreements are used internationally in the form of recommended standards and are accepted by all national committees in this sense. 3) In order to promote international unification, the International Electrotechnical Commission hopes that all national committees will adopt the content of the recommended standards of the International Electrotechnical Commission to formulate their own 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 and the 50A Subcommittee (Shock, Vibration and Other Dynamic Testing).
The content of this standard is based on the following documents: Big Monthly Law Document
50A(CO)179
Voting Report
50A(CO)182
Detailed information on the approval of this standard can be found in the voting report specified in the table above. 254
National Standard of the People's Republic of China
Environmental testing for electric and electronic products
Part 3: Test guidance
Seismic test methods
Environmental testing for electric and electronic products-Part 3;Test guidance-
Seismic test methods
GB/T2424.25—2000
idt IEC 6B-3-3:1991
This standard specifies two categories and three test methods. The guidance is included in each test method. The guidance of this standard can be directly used to select the appropriate test method and apply it in seismic tests. This standard is used in conjunction with GB/T2421. Reference standards
The provisions contained in the following standards constitute the provisions of this standard through reference 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—1991 Mechanical vibration and shock terminology (negISO2041:1990) Environmental testing for electric and electronic products Part 1: General (idtIEC68-1:1988) GB/T 2421-1999 1
GB/T2423.10-1995 Environmental testing for electric and electronic products Part 2 Test methods Test Fc and guidance: Vibration (sinusoidal) (idtIEC 68-2-6,1982)
Environmental testing for electric and electronic products Part 2: Test methods Components, equipment and other products in GB/T 2423. 43—1995
Installation requirements and guidelines for dynamic tests such as shock (Ea), collision (Eb), vibration (Fc and Fd) and steady-state acceleration (Ga) (idtTEC68-2-47:1982) Environmental testing for electric and electronic products Part 2
Test method
GB/T 2423.48—1997
Procedure method (idtIEC68-2-57:1989)
GB/T 2423.49.-1997
1 Purpose
Environmental testing for electric and electronic products Part 2
Beat frequency method (idtIEC68-2-59:1990) Part 1 Overview
Test method
Test Ff: Vibration
Test Fe: Vibration
Time history
This standard is mainly applicable to electric and electronic products, and can also be used for other equipment and components. The purpose of equipment test is to prove the ability of the equipment to complete its required functions when subjected to stress and displacement caused by the earth, or after such stress and displacement.
Analysis or test-analysis combination method can be used to verify the performance of the equipment, but it is beyond the scope of this standard; this standard is limited to verification based entirely on dynamic test data.
Approved by the State Administration of Quality and Technical Supervision on October 17, 2000, and implemented on June 1, 2001
GB/T 2424.25—2000
This standard only discusses the seismic tests for full-size equipment that can be tested on a shaking table. When the relevant specifications stipulate that the seismic test is the identification target, this standard provides a classification of test methods. Note: Beyond the scope of this standard, the so-called brittleness test is not considered, because this standard only provides general application guidelines for seismic tests, mainly providing guidelines for the use of GB/T2423 series standard test methods. Test methods can be selected according to the principles of this standard, and these test methods themselves are based on the GB/T2423 series standards. This standard can be used by manufacturers to verify equipment performance, or by users to evaluate and verify equipment performance. 2 General description
Seismic tests are usually divided into two levels! General level and specific level. It cannot be considered that one level is more necessary than the other. The difference between the two magnitudes lies in the effectiveness and/or accuracy of determining the characteristics of the seismic environment. For high-reliability safety equipment used in specific environments, such as safety equipment in nuclear power plants, the specific magnitude should be used instead of the general magnitude. Appendix A gives a flow chart for selecting the test type (general magnitude or specific magnitude) and the four independent test flow charts (A1 to A4) discussed in this standard. To get the most benefit from this standard, it is recommended to thoroughly study these flow charts.
2.1 General magnitude
The general magnitude is applicable to equipment that does not specifically consider the seismic motion affected by regional characteristics, supporting structures or building characteristics. For equipment subjected to this magnitude, the seismic motion is generally characterized by a data such as the peak ground acceleration. This peak acceleration can be obtained from the geological data of the relevant area. When the equipment is not installed on the ground, the transmission rate of the building and/or supporting structure should be considered. 2.2 Specific magnitude
This magnitude is applicable to equipment that specifically considers the seismic motion affected by regional characteristics, supporting structures or building characteristics. For equipment subject to this level of expansion, the ground motion is determined by the response spectrum (which can be calculated from the undamped ratio) or the time history. 3 Definitions
The definitions of terms in this standard are given in GB/T2298, GB/T2421, GB/T2423.10, GB/T2423.48 and GB/T2423.49. Definitions not in these standards or different from those inferred from these standards are given here. 3.1 Assembly
refers to two or more components with the same mounting or common supporting structure. 3.23 dB passband bandpassat3dB
: The frequency interval determined by the points greater than or equal to √2/2 times the maximum value of the characteristic curve (see Figure 1). 3.3 Basic response spectrum basicrespanse spectrum The invariant response spectrum determined by the characteristics of the building and its floor, roughness ratio, etc., and can be obtained from specific ground motions (see Figure 1). Note: The basic response spectrum of the floor is a narrowband type. 3.4 Broadband response spectrum The broad-band response spectrum describes the response spectrum of a motion where there are many interacting frequencies that must be treated as a whole (see Figure 2e). The response spectrum is usually greater than one times the range. 3.5 Critical frequency (technically equivalent to 8.1 of GB/T2423.10-1995) The vibration frequency at which the sample fails and/or performance deteriorates, or the vibration frequency at which mechanical resonance and/or other effects (such as vibration) occur. 3.6: Crossover frequency (technically equivalent to GB/T.2298) The frequency at which the vibration characteristic quantity changes from one relationship to another. Note, for example, the crossover frequency can be the frequency at which the vibration amplitude changes from displacement equal to rate to increase equal to frequency. 3.7 Damping (different from GB/T 2298) "Damping is a general term to characterize the dissipation of many energy in a system. In fact, damping depends on many parameters, such as structure, vibration mode, strain, force, speed, material, connection slip, etc. 256
3.7.1 Critical damping GB/T 2424.25—2000
The minimum viscous damping that allows a displaced system to return to its initial position without oscillation. 3.7.2 Damping ratio ratio
The ratio of actual damping to critical damping in a viscous damping system. 3.8 Direction factor directionfactor
The numerical difference coefficient between the horizontal acceleration and the vertical acceleration of the ground surface caused by the earth. 3.9 Floor acceleration Floar acceleration The acceleration on the floor (or installed floor) of a specific building caused by the ground motion of a known earthquake. Note: In actual construction, the floor acceleration can be decomposed into horizontal and vertical components. 3.10 Geometric factor Geometric factor
The coefficient of interaction between different axes of a multi-axis simultaneous input vibration device that needs to be considered in a uniaxial test. 3.11 Gravitational acceleration "g."
The standard acceleration caused by the earth's gravity, which varies with altitude and latitude. Note: In this standard, the value of g is taken as an integer of 10m/ss. 3.12 Ground acceleration Ground acceleration The ground acceleration caused by a known ground motion. Note: In actual construction, the ground can be decomposed into horizontal and vertical components. 3.13 Lateral frequency Lateral frequency frequency Two frequencies determined by a 3 dB response based on the overall resonant frequency (see Figure 1) 3.14 Malfunction
Loss of the ability of the equipment to start or maintain a required function, or malfunction with adverse consequences for safety Note: Malfunctions will be determined by relevant regulations.
3.15 Narrow-band response spectrum narrow-band response spectrum dominated by single-frequency excitation (see Figure 2)). Note
1 The bandwidth is generally equal to or less than 1/3 times the range frequency band. 2 When there are several well-defined and widely spaced frequencies, each of their responses can be treated separately as a band response spectrum if deemed appropriate (see Figure 2b)) 3.16 Natural frequency natural frequency The free vibration frequency that depends only on the physical properties of the structure itself (mass, stiffness and damping), 3.17 Overall resonant frequency overallresponce refers to the resonant frequency of the entire structure that enhances the excitation motion. Note: In the range of 1 Hz to 35 Hz frequency range, the overall resonance generally corresponds to the first perturbation mode. When the overall common frequency is within the required response spectrum, it is important to consider the overall resonant frequency (see 3.27). 3.18 pause
the time interval between two adjacent test waves (such as sine beats). Note: The time should not lead to effective superposition of the sample response motion. 3.19 preferred testing axis preferredtesting&xes three orthogonal axes corresponding to the axis of the sample most vulnerable to damage. 3.20 required response spectrum requiredresponsespectrun the response spectrum specified by the user (see Figures 1, 2, and 3). 3.21 resonant frequency responcefrequency the common frequency is such a frequency that when it is subjected to oscillation, changes in the excitation frequency will reduce the response of the system. Notes
1 The resonance rate depends on the measured variable. For a given mode, displacement, velocity and acceleration, the reported frequencies will increase in sequence. For normal damping ratios, the differences between these resonance rates are not large. 2 In earthquake tests, it is usually assumed that the resonance frequency is meaningful only when the response transmissibility is greater than 2. 3.22 Response spectrum (different from GB/T2298) A series of maximum response curves of a single-axis system with a certain damping ratio to a specified input motion (see Figures 1, 2 and 3). 3.23 S1 Earthquake The earthquake that may occur during the operating life of the equipment. For this reason, the safety-related equipment should be designed to work continuously without failure. Note: S1 is equivalent to the operating earthquake (OBE) in nuclear power plants. 3.24 S2-earthquake
For S2 earthquakes, certain structures, systems and components should be designed to fundamentally ensure the normal function, structural integrity and safety of the overall system during the earthquake that produces the maximum ground vibration.
Note: S2 earthquake is equivalent to the safe shutdown earthquake (SSE) in nuclear power plants. 3.25 Sine beat sinebeat
A single-frequency continuous sine wave modulated by a lower frequency sine wave. The duration of a sine beat is half the period of its modulation frequency. Note: In this standard, the sine beat is regarded as a single wave. 3.26 Strong part of time-history The part of the time history curve from the time history curve first reaching 25% of the maximum value to the time history curve finally decreasing to 25% of the maximum value (see Figure 5). 3 27 Strong part of the response spectrum The part of the response acceleration of the response spectrum that is higher than the required response spectrum -3dB passband (see Figure 1). Note: The response strength part is generally located in the 1/3 frequency band. 3.28 Superelevation factor The coefficient of the change in floor acceleration caused by the total building and structural transmission rate. 3.29 Synthesized time-history Artificially generated time history, whose response spectrum contains the required response spectrum. 3.30 Test value test level
Maximum peak value of the test waveform.
Note: Acceleration is a common parameter in earthquake tests. 3.31 Test frequency testfrequency
Dangerous frequency and predetermined frequency specified by relevant specifications. 3.32 Test response spectrum testresponse spectrum: Response spectrum obtained by analysis from the actual movement of the shaking table or derived by spectrum analysis equipment (see Figure 1, Figure 2c, Figure 2d)). 3.33 Time history time-history (different from GB/T2298))-Time change function record of acceleration, displacement or velocity generated by a certain movement. 3.34 Zero period acceleration zeroPeriodacceleration High frequency asymptotic value of the response spectrum acceleration (see Figure 1 for an example). NOTE Zero period acceleration has practical significance because it represents the maximum peak acceleration in a time history. This zero period acceleration cannot be filtered out with the peak acceleration of the response spectrum.
4 Matters to be considered for verification
The relevant specifications should contain relevant data on the issues discussed in 4.1, 4.2 and 4.3. 4.1 Conditions of use
The actual conditions of use should be reproduced as much as possible during the testing of samples, especially those conditions of use (electrical, mechanical and thermal pressure, etc.) where the combined effect of the test stresses may affect the operation or integrity of the equipment. When these conditions of use are not considered in the test, the justification for their omission should be stated. 4.2 Failure criteria
When the conditions of use and the functions of use are known or selected, the relevant specifications should specify acceptance and/or failure criteria. 258
GB/T2424.252000
Note: When the final use conditions of the equipment or the use conditions of the test sample are unknown, the fault judgment criteria cannot be accurately determined, so assumptions are made without proper reasoning. For example, in the absence of more appropriate data, it is usually assumed that the circuit fault duration is 5ms. 4.3 Identification Standards
The following identification levels may be used, and specific equipment may be marked with identification level symbols. Level 0: Equipment that does not fail during or after the ground test. Level 1: Equipment that fails during the ground test and returns to normal after the test. Level 2: Equipment that fails during the ground test and needs to be reset or adjusted after the test is completed, but does not require replacement of components or repair. 5 Test Procedures
General non-step tests are carried out in accordance with Chapters 6 to 10, and specific level tests are carried out in accordance with Chapters 11 to 15. 5.1 Installation
The sample should be installed in accordance with the provisions of GB/T2423.43. Note: For samples used with tunnel vibrators, more detailed guidelines are given in Chapter A5 of GB/T2423.10-1995! When installing the sample, the influence of wiring, cables, pipes, etc. should be considered. The ground test should also include the installation structure of the sample in normal use, unless Adam reasons are stated.
The orientation and mounting of the sample during the test shall be specified. This is the only condition for the sample to be qualified, unless there is a valid reason for qualification under the exemption conditions (for example, if it can be shown that gravity does not affect the working performance of the sample). 5.2 Measurements
Measurements shall be made in accordance with the provisions of GB/T2423.10, GB/T2423.48 and GB/T2423.49. 5.2.1 Vibration measurements on a vibration table
Vibration measurements shall be made on a vibration table to ensure that the correct vibration level is applied to the position to be measured. The parameters to be permanently recorded (displacement, velocity, acceleration) shall be specified, as shall the equipment used and the energy of each sensor (base, measurement). 5.2.2 Vibration measurements on the sample
In addition to the vibration table test plate, vibration measurements can be made on the sample to provide further information on the performance of the sample under test. These measurements do not constitute part of the vibration test requirements.
5.2.3 Functional monitoring on samples
The performance of samples to be evaluated for their functionality shall be monitored before, during and after the test. The relevant specifications for the equipment shall give the performance to be permanently recorded. 5.3 Frequency range
The main frequency of the test is generally between 1 Hz and 35 Hz. This frequency range is sufficient to determine the dangerous frequencies of the sample and to carry out the test. In some cases, depending on the existence of dangerous frequencies, the test frequency range of 1 Hz to 35 Hz may be expanded or reduced, but the justification should be stated. General grade
Part II
This part introduces the recommended test methods for general grade samples, for which the environment is unknown or inaccurately known.
6 State
6.7 Selection of test type
To demonstrate the ability of the sample to withstand earthquakes, several types of tests in Table 1 can be considered. In general, single-axis sinusoidal sine beat frequency test or single-axis sinusoidal sine sweep test is preferred for the following reasons: a) Sine beat frequency, whose waveform is similar to the horizontal ground wave of a simple structural floor presenting a single-resonance waveform; b) Sine sweep, which is easy to implement, but its damage authenticity is poorer than that of the actual floor ground wave. Although multi-axis testing is generally not recommended, when there is significant coupling between the three preferred test axes of the sample or when it is undesirable to use geometric correction factors 259
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, multi-axis (biaxial or triaxial) testing can be used. If multi-axis testing is used, single-frequency waves such as sine beat, sine sweep and fixed-frequency sine should be used with caution, because the peak ground accelerations of different axes are usually out of phase. Therefore, complex frequency waves such as time history should be used. Table 1 Test type selection
Test wave
Sine sweep
Sine beat
Time history
Standard sine
Note, a: recommended b: suitable: : generally not recommended. 6.2 Test method selection
There are two test methods:
a) Standard amplitude conventional test:
Used when the equipment use conditions are unknown (see Chapter 7): b) Calculated amplitude test:
Single axis test
Test type
Multi-axis test
Used when the equipment use conditions are known enough to determine its different test parameters (see Chapter 8). 7 Standard amplitude conventional test method
7.1 Application
Conventional test has three performance levels, often called qualification levels (see Table 2). This conventional test is recommended when the equipment use conditions are unknown. The sample user should determine whether the qualification level to which the sample has been tested is suitable for the application. After the equipment reaches a specified setting level, if all other requirements are met, the equipment may be required to be qualified at a level higher than or equal to that level. Table 2 Performance level
Performance level
Horizontal component
Floor acceleration at
Vertical component
*This setting level can be used when the crossover frequency is higher than 1.6 Hz. For 1.6 Hz to 0.BHz, use the velocity amplitude. For less than 0.8 Hz, use the displacement inertia value, see Figure 7a).
7.2 Test conditions
Standard amplitude conventional test method is only used for single-axis tests. Different axes can be excited one by one. The test acceleration can be determined based on the performance level (see 7.2.1), waveform factor (now 9.2.1), and coefficient (see 9.2.2). 7.2.1 Performance level (standard amplitude conventional test) In the standard amplitude conventional test method, the floor acceleration (at) is directly selected from the performance level given in Table 2. 7.2.2 Test waveform
The recommended test waveform is a 5-cycle sine beat or sine sweep. However, other waveforms may be used if there is sufficient justification. The maximum value of the excitation acceleration for the level should be corrected by the waveform factor (see 9.2.1) and the geometric factor (see 9.2.2). 8 Calculated amplitude test method
8.1 Application
If sufficient sample characteristics and installation site information are available, the calculated amplitude test method is recommended because it can more accurately estimate the test level than the standard amplitude conventional test method (see Chapter 7). 8.2 Test conditions
In principle, this is a uniaxial test in which the different axes can be excited one by one. For example, this test method is suitable when the interaction between different axes is small or the interaction can be considered using geometric factors. 8.2.1 Performance level (calculated amplitude test) The test severity level is determined by the following parameter values. The relevant specifications of the equipment should specify the following parameters: a) Test waveform (see 8.2.2)
b) Sample damping (see 8.2. 3) #
c) Superelevation factor (see 8.2.5);
d) Directional factor (see 8.2. 6)
e) Test duration (see 9.1);
f) Test wave amplitude (see 9.2).
8.2.2 Test waveform selection
When the sample damping value is significantly different from 5% (see Figure 6), even if the waveform factor is used, the influence of the selected test waveform on the sample will still be significant.
8.2.3 Damping ratio
When the critical damping of the sample is between 2% and 10%, the recommended damping ratio is 5%. If the damping ratio is outside this range, it is recommended to use the representative value of the actual vibration performance of the sample to determine the waveform factor used. For more detailed description, see 9.2.1 and Figure 6. 8.2.4 Ground acceleration (gg)
The ground acceleration (a) depends on the ground conditions of the sample installation site. Knowing the seismic conditions of the installation site, the relevant specifications should specify the ground acceleration. Otherwise, the recommendation should be selected from the data given in the table. Table 3 Ground acceleration level
Ground wing condition description
Ground acceleration level symbol
Light to moderately strong ground development
Moderately strong to strong earthquake
Weak to strong strong ground
1) Approximate unified building code area (International Building Association). Wang's level
5.5~7. 0
For reference only Xinkao
·Unified building code area!
2) MSK (relative to the front positive McFarland intensity scale) Note: From Figure 7b), it can be seen that the cross-over frequency with equal amplitude of the intensity is 1.6 Hz, and the cross-over frequency with equal amplitude of the displacement is 0.8 Hz. Ground mass MSK*
8.2.5 Superelevation coefficient (K)
The ground acceleration wave coefficient generated by the vibration characteristics of buildings and structures can be calculated using the superelevation coefficient K. Recommended values are given in Table 4, but if the site conditions are known, the relevant specifications may specify other values. Table 4 Recommended superelevation coefficient K
Coefficient K
Samples installed on rigid foundations or flexible structures Devices rigidly connected to buildings
Hard structures connected to buildings with rigidity Devices on low-draft structures connected to buildings 261
8.2.6 Directional coefficient (1))
GB/T 2424.25—2000
The ground motion of the two horizontal axes is generally greater than the ground motion of the vertical axis. If the sample installation condition is specified, the test should be carried out according to the preferred horizontal test axis, and y with 100% test value, while the vertical axis 2 is only tested with 50% test value. For samples with undetermined installation positions, full value tests should be carried out on all three preferred test axes unless otherwise specified in the relevant specifications. The directional coefficients are listed in Table 5.
Table 5 Directional coefficient (D)
Moving axis
Horizontal axis Dx
Horizontal axis D
Vertical axis D,
Vertical axis
Restriction
Only for vertical position of the specification
"When the installation position is not specified
*When the installation position is not specified and the gravity effect does not affect the performance of the sample, a three-drink test must be carried out. Each of the three main axes of the sample is tested in the vertical plane in turn, and the directional coefficient of each test case is D,=1.D,=1,D-0.5.8.2.7 Floor acceleration αt))
In the calculation amplitude test method, the advantage is the use of more data, and the ground acceleration (a) is known or has been specified by the relevant specifications. Therefore, the floor acceleration (ar) can be determined by the following formula: Where: 4g—ground acceleration (see 8.2.4), K——superelevation coefficient (see 8.2.5);
D-~—direction coefficient (see 8.2.6).
9 Test parameters
9.1 Test duration
The duration of the earthquake test shall be equivalent to the duration of the strong part of the earth waist time history (see Figure 5). When testing with a sine beat wave according to 10.2.1, the test duration depends on the specified test frequency, beat frequency and interval. When using a sine sweep according to 10.2.2, the test duration depends on the required frequency range, sweep rate, number of sweep cycles and number of test directions included.
For a fixed-frequency sine test, the test duration shall be at least sufficient to reach the maximum acceleration amplitude of 5 cycles (see Figure 9). 9.2 Test acceleration (at)
The test wave amplitude can be specified as the maximum value of the acceleration, velocity or displacement wave. Only the acceleration is the characteristic of the reference earthquake. Standard amplitude conventional test method (see 7.2. 1) or the calculated amplitude test method (see 8.2.7) is determined using the floor acceleration (at). The floor acceleration (at) is then adjusted according to the test wave used and any interaction between the draw wires at the installation location. The floor acceleration (an) is adjusted using the waveform factor (α) and the geometric factor (G). The al value therefore represents the magnitude of the acceleration to be applied to the sample and is calculated using the following formula:
a, -ar.oG
Where: a1 - floor acceleration (see 7.2.1 and 8.2.7): a - waveform factor (see 9.2.1),
G - geometric factor (see 9.2.2).
9.2.1 Waveform factor (α)
Different types of test waveforms are generated depending on the severity of the equipment damping. This effect is taken into account by the waveform magnification factor, which is 1.5 for a 5-cycle sine beat waveform. The 5-cycle sine beat test waveform is similar to the actual floor waveform after filtering by the inserted structure. 262
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The waveform factor values of other test waves are usually determined by the damping ratio of the 5-cycle. Table 6 gives the waveform factor α values for continuous sine or sine sweeps with different damping ratios. These values can be calculated from Figure 6, which can also be used to obtain the waveform factor for sine beats and damping ratios regardless of the number of cycles per beat. Table 7 in 14.4 gives examples of equipment damping values. Table 6 Form Factor
Equipment Damping (% of Critical Damping) 2%
9.2.2 Geometry Factor (G)
5 cycles/sine beat frequency bZxz.net
If insufficient information is available on the excitation conditions at the sample installation site, the geometry factor G shall be: 1 Uniaxial excitation without interaction with other axes: 1.5 Uniaxial excitation with interaction with other axes. 10 Test Procedure
10.1 Vibration Response Check Test
Continuous Sine and Sine Sweep (toc1/min) 0.3
The vibration response check test provides data on the critical frequency. It can also be used to provide data on the damping ratio and the selection of single-axis or multi-axis tests.
This test uses a single-axis sinusoidal excitation with a cyclic logarithmic sweep over the frequency range of 1 Hz to 35 Hz, with the up and down sweep rate low enough to indicate the critical frequency, but not exceeding 1 oct/min. The vibration amplitude applied during the vibration response check test should not be so large as to produce an effect comparable to that of the test itself. However, the test amplitude should be large enough to take into account the nonlinearity of the dangerous frequencies and damping depending on the amplitude: Note that a vibration amplitude of 2 m/s is commonly used, and this value can be reduced to 1 m/s or lower in the case of severe vibration. It should be noted that these vibration response check tests cannot reveal all dangerous frequencies due to the complexity of the actual situation or the limitation of contact with critical components (such as packaged relays, etc.). Also due to nonlinearity, the frequency and damping of the high-order resonant response may be different from the frequency and damping of the low-order resonant response, and some resonances may not be obvious at low excitation. Therefore, the results of low-order check tests may not always provide complete data on the dynamics of the equipment.
10.2 Test type
10.2.7 Sine beat frequency test
If the relevant specifications do not provide otherwise, according to GB/T2423.49 (see Figure 4 and Appendix A), the test is of the uniaxial type and the test wave consists of a series of five sine beat frequencies.
The acceleration applied to the shaker shall be determined by the performance level in 7.2.1 or 8.2.1. : The test shall be conducted within the frequency range specified in 5.3. a) Equipment without hazardous frequencies
The test frequencies shall be within the frequency range specified in 5.3 in steps not greater than 1/2 oct. Any intended test frequencies not included shall also be applied. Tests conducted at frequencies less than these shall be justified. b) Equipment with hazardous frequencies
The test frequencies shall be the hazardous frequencies and intended test frequencies specified in the relevant specification. Tests conducted at frequencies less than these shall be justified. 10.2.2 Logarithmic sweep test
This test is of the uniaxial type. The velocity applied to the shaker shall be determined by the performance level in 7.2.1 or 8.2.1. The recommended logarithmic sweep rate is 1 oct/min and the frequency range is as specified in 5.3. 10.2.3 Other test waveforms
If other waveforms are used, such as time history, the relevant test procedures should be justified. 263
11 State
GB/T2424.25—2000
Part III Specific Tests
When the following parameters are determined and applicable, it is recommended that the samples be tested according to the procedures described in the specific test level: a) the required response spectrum and the duration of the test (when applicable); or b) the required time history.
For this test level, the S1 and S2 test times to be simulated and the load conditions to be considered (not the ground conditions) should usually be specified.
For specific level tests, the following test waveforms are recommended according to the standard: Sine sweep (mainly used for vibration response inspection, GB/T2423.10) Sine beat frequency (GB/T2423.49)
Time history (GB/T2423.48)
Fixed frequency sine (duration at a fixed frequency in GB/T2423.10) 12 Selection of test waveforms
The content of this chapter should be understood in conjunction with Chapter 14. The selection of test waveforms should take into account the expected characteristics of the sample when it is in the installed position and under the influence of the specified ground. Regardless of the waveform used, the measured test response spectrum should contain the required response spectrum, and the total test duration should be at least equal to the duration of the ground without strength (see Chapter 11). For this standard, the test waveforms are divided into two categories: a) complex frequency waves,
1) time history (natural wave, synthetic wave or random wave); 2) other waves (to be justified),
b) single wave:
3) sine sweep,
4] sine beat frequency
5) fixed frequency sine (Figure 9);
6) other waves (to be justified).
12.1 Complex wave
Vibration is broadband: The test wave should be a complex frequency wave. However, if there are valid reasons (see 12.2), some exceptions are allowed. 12.2 Single wave
Sine sweep tests are generally not used in specific level tests. If the ground vibration is filtered through one of the structural modes, the resulting floor motion can be shown as the main frequency. This is equivalent to a narrowband required response spectrum, in which case a single frequency vibration can be a satisfactory excitation. The single frequency test response spectrum should not be mistaken for the envelope of the test response spectrum obtained at the three-frequency test question. The test response spectrum corresponding to each test frequency shall be greater than or equal to the basic response spectrum (see Figure 1, 3-dB passband). ...
The envelope of the test response spectrum corresponding to each test frequency shall be greater than or equal to the required response spectrum (see 13.2). Usually, only artificially broadening the response spectrum is used to take into account uncertainties such as site variations, structural axes, or design. In this case, and there is no other evidence that the floor motion is a narrow-band response spectrum, it should be assumed that the excitation is complex frequency based on this broadened response spectrum. Single-frequency testing can be used to identify equipment in the following situations: a) There are no interacting resonant frequencies (when the spacing is greater than 1/4oc1, it can be considered to be measured in this case); b) The resonant frequency of the equipment is outside the strong part of the required response spectrum; e) Special cases with justification.
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