GB/T 2423.62-2018 PDF English
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Environmental testing - Part 2: Test methods - Test Fx and guidance: Multi input multi output vibration test
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GB/T 2423.62-2018: Environmental testing - Part 2: Test methods - Test Fx and guidance: Multi input multi output vibration test
---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT2423.62-2018
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 19.040
K 04
Environmental testing - Part 2.Test methods - Test Fx and
guidance. Multi input multi output vibration test
Issued on. DECEMBER 28, 2018
Implemented on. JULY 01, 2019
Issued by. State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword... 4
1 Scope... 5
2 Terms and definitions... 5
3 Test equipment... 6
4 Test methods and conditions... 12
5 Information requirements... 18
6 Test implementation... 20
7 Analysis of results... 34
8 Contents to be given in relevant specification... 34
9 Information to be given in the test report... 35
Appendix A (Informative) Fixture for multi-excitation vibration test... 37
Appendix B (Informative) Measurement principle for spatial motion of rigid body. 53
Appendix C (Informative) Identification of time-invariant linear multi-DOF system 57
References... 67
1 Scope
This part of GB/T 2423 specifies the terms and definitions test methods, test equipment,
test methods and conditions, information requirements, test implementation, results
analysis requirements of multi input multi output vibration (hereinafter referred to as.
MIMO).
This Part applies to the determination or verification of mechanical weaknesses and/or
degradation of properties of samples, after subjected to excitation by multiple exciters.
This test method can also be used to verify the mechanical structural and functional
integrity of samples AND to study their dynamic properties.
2 Terms and definitions
2.1 Multi input single output; MISO
In the multi-DOF structure, multiple driving signals are input to the excitation
system; AND in the single-DOF structure, the single-parameter measurement output
is obtained from the fixture or sample.
2.2 Multi input multi output; MIMO
In multi-DOF structures, multi-driving signals are input to the excitation system;
AND in multi-DOF structures, multi-measurement outputs are obtained from
fixtures or samples.
2.3 Multi exciters single axis; MESA
The application of multiple exciters to provide dynamic input to the sample, in a
single vector direction.
2.4 Multi-exciter multi axis; MEMA
Multiple exciters are used, to provide dynamic input to the sample, when the
excitation and measurement are fully described by multiple vectors.
2.5 Mechanical decoupling device
A mechanical device which, in the multi-exciter vibration test, is installed between
the exciter and the sample, between the fixture or the whole table, to eliminate or
reduce the influence of the coupled motion of the multiple exciters.
3 Test equipment
3.1 General requirements
The multi-excitation vibration test equipment requires that, according to the type of test
and the state of the sample, select an appropriately configured test platform, a fixture to
install the sample, a controller, an instrument for recording the response of the sample
at the designated control and monitoring position.
3.2 Multi-excitation vibration test system
3.2.1 Exciter
Determine the configuration of the exciter AND select the exciter, according to the
required test type, test frequency range, low frequency displacement, test magnitude,
the size and mass of the sample and fixture.
3.2.2 Test fixture
The design of the fixture shall meet the requirements of the vibration standard. In
practice, the design of the fixture shall also consider the frequency response and the
ability to withstand the reaction force. It is necessary to consider the potential for large
loads during multi-point and multi-axis tests, resulting in simultaneous occurrence of
acceleration at multiple degrees of freedom. The test fixture requirements are as follows.
In addition to the general test fixture design requirements, refer to Appendix A for the
design of multiaxial test fixtures.
3.3 Vibration control system
3.3.1 Overview
The vibration control system shall have the ability to control multiple test target spectra.
The control channel and monitoring channel shall meet the test requirements.
The vibration control system shall be a vibration test system, that controls the excitation
of multiple exciters, which can not only control the uniaxial vibration test system of
multiple exciters, but also control the vibration test system of multiple exciters and
multiple axes to apply different test target spectra. The control system shall be able to
realize closed-loop control; continuously revise the drive signal during the test; improve
the test accuracy. The controller shall have functions such as simultaneous control and
analysis, simultaneous sampling of test channels and control channels, continuous data
logging.
3.3.2 Control spectrum
The control of the multi-exciter vibration test system is generally achieved by
controlling the matrix form (specifying the self-spectral density, phase, partial
coherence, specifying the cross-spectral density). The diagonal elements of the matrix
are the self-spectral density of the control signal; the off-diagonal elements are the
cross-spectral density. The control system can use EITHER the pre-stored cross-
spectral data OR the laboratory-obtained cross-spectral data.
3.3.3 Control location
The location of the control points for multi-excitation vibration tests is usually taken at
the connection part, the location of some important components, the location of the
measuring point that provides field test data, the end location where restrictions need to
be imposed, or the load-bearing point of the structure. If necessary, limit spectra for
other locations shall be specified. In order to meet the test purpose, the control strategy
in the test specification is selected, according to the obtained information. The optimal
control strategy depends on the existing field vibration data, OR the vibration data to
be collected that meets the requirements of the test program. The need for testing and
control strategies, control points, cross-coupling information will affect field data
collection requirements.
4 Test methods and conditions
4.1 Selection of vibration test method
In general, the multi-excitation vibration test method can better distribute the excitation
energy to the sample, as compared with the single excitation test method; meanwhile,
it can minimize the influence of boundary conditions.
4.2 Selection of test method
Multiple excitation vibration tests can use different equipment configurations, to suit
many practical application processes. The test process can generally be divided into the
following four types. This provides only a basic selection of test process. This list
cannot cover all devices or test configurations.
4.3 Determine the test plan
4.3.1 Control definition
The control strategy of vibration test depends on the vibration test data, that can be
provided, to achieve the purpose of vibration test. When independent spectral density,
partial coherence, phase and cross-spectral density can be provided, a multi-exciter
control strategy is possible. When the partial coherence, phase, cross-spectral density
cannot be provided enough, it is necessary to adopt the single axial target spectrum
control strategy firstly, in the vibration test.
4.3.2 Control method
The choice of test method is controlled by many factors, including the external vibration
environment and product type. Control functions for multiple exciter tests include.
4.3.3 Test plan
For the first test of a more complex structure or a new product, a test plan shall be
prepared. The test plan generally includes.
4.4 Determine the test conditions
4.4.1 Overview
Usually, the multi-excitation vibration test needs to determine the test conditions,
according to the measurement data of the vibration response of the sample work site.
Therefore, it is necessary to obtain sufficient field data, to describe the test conditions
and working states of the multi-excitation vibration test. These data are generally time
histories. If the power spectrum is required, the measured data need to be estimated by
auto-power spectrum and cross-power spectrum density, to determine the test
conditions. Of course, when the field data is insufficient, the multi-excitation test
process may determine the test conditions, through theoretical analysis of the samples
AND laboratory measurement data.
For the time-domain reproduction multi-excitation test, field test data is required; the
correlation, between experimental control and field data, cannot be determined without
field test data.
4.6 Test tolerance
4.6.1 Normal test tolerance
Unless otherwise stated in the environmental test specification, the control signal shall
meet the tolerance requirements specified below.
4.6.2 Relaxation of test tolerances
At specific frequencies within the specified test frequency range, the test tolerances
quoted above may be difficult to achieve, when using control strategies. In this case, at
the discretion of the test engineer, certain test tolerance requirements may be reduced,
under the following constraints; whilst other tolerances remain unchanged. The use of
the following test tolerances shall be documented in the test report.
5 Information requirements
5.1 Overview
In order to adequately conduct and document dynamic performance tests, at least the
following information needs to be provided. The schedule is designed according to the
actual situation; adjustments can be made, by adding or removing some items if
necessary.
5.2 Information required before testing
The following information is required, in order to successfully carry out the multi-point
excitation vibration test.
5.3 Information required in the test
The following information shall be collected during the test.
5.4 Information required after the test
The following information shall be recorded after the test.
6 Test implementation
6.1 Test preparation
6.1.1 Preparation before the test
Before the start of the test, determine the test procedure, technical state of the sample,
test magnitude, test duration, excitation method, control method of the exciter,
installation layout of exciter, failure criteria, sample function (performance)
requirements, measuring instrument requirements, test equipment capabilities and
fixtures, etc., according to the information of relevant documents and products. It also
requires.
6.1.2 Pre-test inspection
All samples need to be pre-tested, in a laboratory environment, to obtain benchmark
data. The pre-test detection steps are as follows.
6.2 Test procedure
The following are general guidelines for MIMO vibration test procedures, which is
divided into 4 categories, based on whether or not a common platform is available.
Procedure 1 and procedure 2 are aimed at the public platform test system; procedure 3
and procedure 4 are aimed at the distributed vibration loading test system. The
procedure can be tailored, according to the test plan, control method, relevant test
information.
6.6 Interruptions
6.6.1 Overview
A variety of circumstances can lead to test interruption. Common causes of test
interruptions and recommended solutions are discussed below. It is recommended that
the test recording device be turned on, during any interruption of the test, as long as the
excitation device is energized.
6.6.2 Interruption due to failure of test equipment
If the interruption is due to a failure of the test equipment, it shall analyze the failure
AND determine the root cause. It is also recommended to evaluate control and response
data, to ensure that no undesired transient forces are transmitted to the sample, during
the failure of the test equipment. If the sample is not affected by the over-test due to the
failure of the test equipment, repair the test equipment or replace the test equipment;
restart the test from the interrupted position.
6.6.3 Interruption due to sample run failure
If the sample fails during operation, it shall interrupt the test AND analyze the cause of
the failure. Depending on the circumstances, restart the test as follows.
6.6.5 Interruption due to exceeding test tolerances
Exceeding the test tolerance or a significant change in the dynamic response, may cause
the test engineer to initiate a test interruption, OR an automatic interruption when the
test tolerance exceeds the control strategy. In this case, check the samples, fixtures, test
equipment, to find out the cause.
6.7 Test safety protection measures
For most system-level tests, the samples are expensive or unique, so the safety
protection measures of the test system are very important. Safety protection shall be
carried out, during the test process, to avoid damage or failure of the samples, due to
external abnormal conditions.
7 Analysis of results
During the test, the test operation data is automatically stored as required. The control
software shall be able to provide the following basic signal processing functions.
8 Contents to be given in relevant specification
When this test is used in the relevant specification, as far as applicable, the following
details shall be given as far as possible, paying particular attention to the clauses with
an asterisk (*), because these entries are always required. The items are as follows.
a) Initial vibration response check, method 1 (sinusoidal or random excitation);
b) Vibration response check using sinusoidal or random excitation, method 2 *;
c) Final vibration response check, method 1 and method 2;
d) Fixed point *;
e) Lateral movement;
f) Crest factor or drive signal clipping *;
g) Vibration tolerance;
h) Allowable deviation (method 2) *;
i) Installation;
j) Test frequency range *;
k) Acceleration spectral density value *;
l) Acceleration spectral density spectral type *;
9 Information to be given in the test report
Records shall be made during the test. The content shall include, for example, the time
list of the test operation record with test parameters, the observation and
implementation during the test, the measurement data table. The test report shall give
at least the following information.
a) Customer (name and address);
b) Laboratory (name and address);
c) Test report identification (release date, unique number);
d) Test date;
e) Test category;
f) Test purpose (R&D test, qualification test, etc.);
g) Test standard name and version number (related test procedures);
h) Sample description (unique identification, drawings, photos, quantities, etc.);
i) Installation method of the sample (fixture identification, drawings, photos, etc.);
j) Description of the test equipment (lateral movement, etc.);
k) Control and measurement systems, sensor placement locations (descriptions,
drawings, photos, etc.);
l) The filter used (type of filter and bandwidth);
m) Measurement system's uncertainty (calibration data, date of last calibration, date
of next calibration);
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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