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GB/T 39152-2020 (GBT39152-2020)

GB/T 39152-2020_English: PDF (GBT 39152-2020, GBT39152-2020)
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Standard ID GB/T 39152-2020 (GB/T39152-2020)
Description (Translated English) Test method of the bending stress relaxation for copper and copper alloy
Sector / Industry National Standard (Recommended)
Classification of Chinese Standard H22
Classification of International Standard 77.040.10
Word Count Estimation 10,152
Date of Issue 2020-10-11
Date of Implementation 2021-09-01
Drafting Organization Ningbo Xingye Shengtai Group Co., Ltd., Non-ferrous Metal Technology and Economic Research Institute, Ningbo Xingye Xintai New Electronic Materials Co., Ltd., Anhui Xinke Copper Co., Ltd., Kaimeilong Precision Copper Strip (Henan) Co., Ltd., Shanxi Chunlei Copper Co., Ltd. Company, Jiangxi Jinpin Copper Technology Co., Ltd., China National Nonferrous Metals (Ningxia) Oriental Group Co., Ltd., National Copper and Aluminum Smelting and Processing Product Quality Supervision and Inspection Center (Shandong), Research Institute of Engineering Technology Co., Ltd.
Administrative Organization National Nonferrous Metal Standardization Technical Committee (SAC/TC 243)
Regulation (derived from) National Standard Announcement No. 21 of 2020
Proposing organization China Nonferrous Metals Industry Association
Issuing agency(ies) State Administration for Market Regulation, National Standardization Administration

Standards related to: GB/T 39152-2020

GB/T 39152-2020
ICS 77.040.10
H 22
Test method of the bending stress relaxation for
copper and copper alloy
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Terms and definitions ... 4 
4 Principle of the method ... 5 
5 Instruments and apparatuses ... 6 
6 Sample ... 7 
7 Test conditions ... 8 
8 Determination of various parameters before the test ... 8 
9 Test procedure ... 9 
10 Test data processing ... 9 
11 Test report ... 10 
Test method of the bending stress relaxation for
copper and copper alloy
1 Scope
This Standard specifies the method principles, instruments and apparatuses,
samples, test conditions, determination of various parameters before the test,
test procedures, test data processing, and test reports for the test method of
the bending stress relaxation for copper and copper alloy materials.
This Standard applies to the determination of the bending stress relaxation
properties for copper and copper alloy plates and strips whose thickness is 0.1
mm ~ 1.0 mm under constant strain conditions.
2 Normative references
The following documents are indispensable for the application of this document.
For dated references, only the dated version applies to this document. For
undated references, the latest edition (including all amendments) applies to this
GB/T 8170, Rules of rounding off for numerical values & expression and
judgment of limiting values
GB/T 10623-2008, Metallic material - Mechanical testing - Vocabulary
GB/T 22315, Metallic materials - Determination of modulus of elasticity and
poisson's ratio
GB/T 26303.3, Measuring methods for dimensions and shapes of wrought
copper and copper alloys - Part 3: Sheets and strips
GB/T 34505, Copper and copper alloy materials - Tensile testing at room
3 Terms and definitions
Terms and definitions determined by GB/T 10623-2008 and the following ones
are applicable to this document.
3.1 Bending stress
The normal stress that is generated by the sample in the single-ended bending
3.2 Initial stress
At the beginning of the stress relaxation test, the maximum bending stress that
is generated by the sample at the moment of the specified bending deformation.
Note: Rewrite GB/T 10623-2008, definition 3.27.
3.3 Initial deformation
The artificially set elastic bending deformation that is generated by the sample
at room temperature.
3.4 Initial reference height
Give initial deformation at room temperature; after unloading, the height of the
load point of the sample to the reference surface.
3.5 Relaxed stress
The reduced bending stress on the sample at any time in the stress relaxation
Note: Rewrite GB/T 10623-2008, definition 3.29.
3.6 Permanent deformation
The plastic bending deformation that is caused by stress relaxation.
3.7 Stress relaxation ratio
The percentage of relaxed stress and initial stress, which is expressed as the
ratio of permanent deformation and initial deformation.
4 Principle of the method
Copper and copper alloys maintain a certain bending deformation under the
action of long-term stress and a certain temperature. With the extension of time,
their internal elastic strain will gradually transform into plastic strain, which will
cause stress relaxation, which is an important form of failure of metal
components. Heat the sample to a specified temperature; maintain a constant
bending deformation at this temperature; remove the sample load after the
specified time; measure the permanent deformation of the sample.
The initial deformation (ε0) shall not be greater than 1/2 of the length of the
bending section (ls). The initial deformation is recommended to be 4 mm; other
negotiated values can also be used. Only when the initial deformation is the
same, the stress relaxation ratio can be compared with each other.
8.5 Measurement of the initial reference height
Clamp the sample on the fixture; give the initial deformation at the specified
position of the free end of the sample; unload it after standing at room
temperature for 30 s ~ 35 s; measure the height from the load point of the free
end of the sample to the reference surface, which is the initial reference height
9 Test procedure
9.1 The test temperature is 125° C or 150 °C; the time is 24 h, 48 h, 96 h, 192
h. After negotiation, the temperature and time can also be other values. The
time accuracy shall be within 3%.
9.2 Use a fixture to fix the sample; place it in the heating equipment. When the
temperature reaches 95% of the specified temperature, start timing.
9.3 After reaching the specified test time, remove the fixture from the heating
equipment and place it at room temperature. After the sample is cooled to room
temperature, remove the sample load; measure the distance from the sample
load point to the reference surface, which is the height after stress relaxation
10 Test data processing
10.1 Permanent deformation
For samples which are tested under different test conditions (temperature and
time), after removing the device, calculate the occurred permanent deformation
(εt) according to Formula (2):
εt -- permanent deformation, in millimeters (mm);
Ht -- height after stress relaxation, in millimeters (mm);
Hi -- initial reference height, in millimeters (mm).