GB/T 5027-1999 Test method for plastic strain ratio (r value) of metal sheets and strips
Some standard content:
GB/T 5027—1999
This standard is equivalent to ISO10113:1991 "Metallic materials-sheets and strips-Determination of plastic strain ratio". It is the same as ISO10113:1991 in terms of main technical content and structure. This revision of GB/T5027-1985 has made the following major technical contents modified: the chapters have been rearranged;
the principles have been modified, and the test significance has been deleted;
referenced standards have been added;
-the specimen types have been added;
…-the calculation and definition of Chapter 6 have been merged; the content of Chapter 7 has been changed to Appendix A,
and Appendix A, Appendix B and Appendix C have been deleted.
From the date of implementation of this standard, it will replace GB/T50271985 "Metallic sheet plastic strain ratio (r value) test method". Appendix A of this standard is a suggested appendix.
This standard was proposed by the State Bureau of Metallurgical Industry. This standard is under the jurisdiction of the National Technical Committee on Steel Standardization. The drafting units of this standard are Wuhan Iron and Steel (Group) Corporation and the Central Iron and Steel Research Institute. The main drafters of this standard are Dai Ruiling, Wu Guoyun and Li Jiulin. This standard was first issued in March 1985.
GB/T5027:1999
ISO Foreword
ISO (International Organization for Standardization) is a worldwide federation composed of national standardization groups (ISO member groups). The work of formulating international standards is usually completed by the technical committees of ISO (). If each member group is interested in a project established by a technical committee, it has the right to participate in the technical committee. International organizations (official or unofficial) that maintain contact with ISO also participate in the work. In terms of electrical technology standardization, ISO (International Organization for Standardization) maintains a close cooperative relationship with the International Electrotechnical Commission (IEC). The draft international standard adopted by the technical committee is submitted to the member groups for voting. The international standard needs to obtain the consent of at least 75% of the member groups participating in the voting before it can be officially released. The international standard ISO10113 is formulated by ISO/TC164 Technical Committee on Mechanical Properties of Metals. 398
1 Scope
National Standard of the People's Republic of China
Metallic materials---Sheet and strip--Determination of plastic strain ratio (r-values)
Metallic materials---Sheet and strip--Determination of plastic strain ratio (r-values) GB/T 5027—1999
eqv Is0 10113:1991
Replaces GB/T50271985
This standard specifies the definition, symbols, principles, test equipment, specimens, test procedures, test results and test reports of the test method for plastic strain ratio (r-value) of metal sheets and strips. This standard is applicable to the determination of plastic strain ratio (r-value) of metal sheets and strips with a thickness of 0.1~~3mm. 2 Referenced 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/T228—1987 Metal tensile test method GB/T10623—1989 Metal mechanical properties test terminology GB/T16825—1997 Inspection of tensile testing machine JJG762—1992 Extensometer verification procedure
3 Definitions
This standard adopts the following definitions.
3.1 Plastic strain ratio (r): When a metal sheet specimen is stretched axially to produce uniform plastic deformation, the ratio of the true strain in the width direction of the specimen gauge length to the true strain in the thickness direction. r=
Where:
Ea=lnl
Since it is easier and more accurate to measure the change of length than the change of thickness, the following relationship is derived based on the principle of constant volume before and after plastic strain to calculate the plastic strain ratio r. (n/6
Inl.
The calculated r value should indicate the orientation and strain level of the sample relative to the rolling direction, for example: r45/20 (see Table 1). 2
3.2 Weighted average plastic strain ratio (): The weighted average value of the plastic strain ratio measured on the plane of the metal sheet at 0°45° and 90° to the rolling direction.
Approved by the State Administration of Quality and Technical Supervision on November 1, 1999 and implemented on August 1, 2000
GB/T 5027 —1999
+= ro + ro + 2ras
3.3 Plastic strain ratio plane anisotropy (△r): The difference between the arithmetic mean of the plastic strain ratio values at 0° and 90° to the main rolling direction on the metal sheet plane and the plastic strain ratio r value at 45°. ro+ro
For some purple materials, the specimen can choose other orientations. In this case, the formula used will be different from the formula given in 3.2 and 3.3. Therefore, the other formula used should be given in the test report. 3.4 Yield point elongation: At force- The elongation value of the specimen in the entire discontinuous interval on the elongation curve (only refers to materials with obvious yield phenomenon). For other relevant definitions, see GB/T10623.
The symbols and their explanations used in this standard are shown in Table 1. Table 1 Symbols and explanations
5 Principle
Original thickness of the specimen
Original width of the specimen within the gauge length
Thickness of the specimen after tensile deformation
Width of the specimen within the gauge length after tensile deformation
Length of the clamping part of the specimen||tt ||Width of the clamping part of the specimen
Original gauge length of the specimen
Gage length of the specimen after tensile deformation
Travel length of the specimen
Total length of the specimenbzxZ.net
True strain in the thickness direction of the specimen
True strain in the width direction of the specimen
Plastic strain change
The weighted average value of the plastic strain change r/value of the specimen in the X direction (at an angle of X to the rolling direction) at the % strain level
Plastic strain Specific plane anisotropy
Under the action of uniaxial tensile force, the specimen is stretched to the uniform plastic deformation stage. When the specified engineering strain level is reached, the changes in the specimen gauge length and width are measured, and the plastic strain change value is calculated using the formula derived from the principle of constant volume before and after plastic deformation. 6 Test equipment
6.1 Testing machine
6.1.1 The testing machine shall comply with the requirements of GB/T16825, and the level of the testing machine shall not be lower than level 1. 400
GB/T 5027—1999
6.1.2 The clamping method of the specimen shall comply with the provisions of GB/T228. The testing machine shall be able to control the strain rate or the chuck displacement speed according to the requirements of 8.8.1 to conduct uniaxial tensile tests.
6.1.3 The chuck of the testing machine shall ensure that when the specimen is clamped, the center line of the longitudinal axis of the specimen and the center lines of the upper and lower chucks coincide with the tensile axis of the testing machine.
6.1.4 The testing machine shall be calibrated regularly by the metrology department. 6.2 Measuring tools
The measuring tool error for measuring the change of the specimen gauge length shall not be greater than ±0.01mm; the measuring tool error for measuring the change of the specimen width shall not be greater than ±0.005mm. The measuring tools shall be calibrated regularly by the metrology department. 6.3 Extensometer
6.3.1 The extensometer shall meet the requirements of level 1 or higher specified in JG762. 6.3.2 The extensometer shall be calibrated in accordance with JJG762. The working state of the extensometer during calibration shall be as close as possible to that during the test. 6.3.3 The calibrated extensometer shall be carefully checked before the test. When the extensometer is overhauled or abnormal, it shall be recalibrated. 7 Test specimens
7.1 Sampling
7.1.1 The sampling location shall meet the requirements of the relevant product standards or be determined by negotiation between the two parties. 7.1.2 The sampling direction is generally 0°45°.90°, and at least 3 specimens are taken in each direction. Materials that show characteristic values in other directions can also be sampled in those directions after negotiation between the two parties. 7.2 Specimen shape
The specimen should generally have a clamping portion that is wider than the parallel length portion (referred to as a shoulder specimen, see Figure 1). By agreement, the specimen can also be a strip with parallel edges (referred to as a non-shoulder specimen, see Figure 2). For products with a width not exceeding 20mm, the specimen width can be equal to the width of the product. However, for arbitration tests, shoulder specimens should be used. 7.3 Specimen size
Parallel length shall not be less than L. + b/2. For arbitration test, parallel length shall be L. + 2b. For specimens without shoulder with width not more than 20 mm, free length between the grips shall not be less than 1 + 3bg. Table 2 gives the dimensions of two non-proportional specimens. Other types of specimens may also be used if the measurement results with the same accuracy can be obtained. Table 2 Dimensions of two non-proportional specimens
Specimen number Original width b. Original gauge length L. |Parallel length L1
7.4 Specimen preparation
Clamping part (head
Clamping part
Width B
Length h
Free length of maximum width within the gauge length between the chucks of the specimen without shoulder
≥140
7.4.1 The rough specimen must be cut individually. The specimens must be machined to eliminate the influence of work hardening. Difference from the minimum width
Note: For extremely thin specimens, it is recommended to separate the cut rough specimens of equal width piece by piece with oil paper, clamp thicker plates of equal width on both sides and machine them together until the required size is reached.
7.4.2 Test The non-parallelism on both sides of the width within the original gauge length of the sample should be as small as possible, and the difference between the maximum width and the minimum width should not be greater than 0.1% of the average value of the measured width within the gauge length.
7.4.3 Unless otherwise specified, the specimen thickness should be the full thickness of the product, but the difference between the thickness values at any two points within the specimen gauge length should not be greater than 0.01mm; when the thickness is less than 1.0mm, it should not be greater than 1% of the nominal thickness. 7.4.4 There should be no defects such as scratches on the surface of the specimen. 7.4.5 Markings can be engraved with a Vickers diamond indenter or other tools. The markings should be located on the axis of the specimen and symmetrical to the center of the parallel length portion 101
.
GB/T 5027—1999
Note: In order to make the markings clear and not scratch the surface of the specimen, it is recommended to apply a layer of suitable dye film on the surface of the specimen to be tested before marking. AB
R≥20
Specimen with shoulder
Figure 2 Specimen without shoulder
8 Test procedure
8.1 The test is generally carried out at room temperature of 10~35℃. For tests with strict temperature requirements, the room temperature should be 23C±5℃. 8.2 When the tensile properties of the test material are unclear, a conventional tensile test should be carried out in advance, and the force-elongation curve should be recorded to determine its service characteristics, elongation and engineering strain level of the measured value. 8.3 Check the specimen according to the requirements of Chapter 7.
8.4 Pay attention to centering when installing the specimen to ensure axial force. 8.5 For manual measurement, when the specimen When the original gauge length L is not less than 25 mm, at least three widths should be measured at equal intervals within the gauge length and the plastic strain ratio value should be calculated using the average value. When measuring the original gauge length L of the specimen, the allowable measurement deviation is ± 1.0% of the original gauge length 1.8.6 When measuring automatically, the extensometer specified in 6.3.1 should be used to measure the change in gauge length, and at least one width should be measured within the gauge length. 8.7 Test speed:
8.7.1 The moving speed of the chuck of the testing machine should not exceed 50% l/min. 8.7.2 When it is necessary to determine the specified non-proportional elongation stress, yield point, and elongation at the cooking point at the same time as the value test, the test speed should comply with the provisions of GB/T228. When the specimen is deformed to exceed the range required for the determination of the above properties, the test speed can be adjusted to the range required for the determination of the value.
GB/T 5027-- 1999
8.8 Apply force to the specified strain level. The engineering strain level of the value should be greater than the yield strain or the strain corresponding to the end of the elongation at the yield point, and less than the strain corresponding to the maximum force. If there is no other provision, the engineering strain level of 15% or 20% is generally used. 8.9 For manual measurement, measure the gauge length L and width b of the deformed specimen in the same manner and with the same error as the original gauge length and width. The measurement can be carried out under the test force, but the arbitration test should be carried out under unloading. 8.10 For automatic measurement, use the extension specified in 6.3.1 to measure the gauge length L and width 6 at the specified strain level. 8.11 If the specimen is transversely bent (see Figure 3) or longitudinally bent, it will affect the test results. The test should be considered invalid and the test should be repeated.
8.12 If the plastic strain is uneven, the test results should be considered invalid and the test should be repeated. 8.13 Calculate the r, F and Ar values according to formulas (2), (3) and (4) based on the measured bo, Lo, b, L. 8.14 Two specimens should be tested in each sampling direction and the average value of r should be taken. If the results of the two specimens are very different, the third specimen should be measured and the value with the large difference should be discarded.
Transverse bending
Figure 3 Transverse bending of the specimen
9Test results
9.1 For manual measurement, use formulas (2), (3), and (4) to calculate the r, and △r values of specimens with different orientations. 9.2 For automatic measurement, the automatic tensile testing machine and data processing program directly give the r, and △ values of specimens with different orientations. 9.3 The calculated plastic strain ratio r value should be rounded to an accuracy of 0.05. 9.4 Manual measurement and automatic measurement may obtain different test results. In the case of obvious differences, the manual unloading measurement method should prevail. 10 Test report
The test report shall include the following contents:
a) the number of this national standard;
b) description of the test material;
c) the method adopted (manual measurement or automatic measurement);
d) the type of specimen adopted;
e) the orientation of the specimen relative to the rolling direction;
f) the strain level at which the measurement is made;
g) other special conditions in the test;
h) the value of the plastic strain ratio r;
i) the average plastic strain ratio r;
i) the in-plane anisotropy △r;
k) the formula used when the formula for calculating and △r is different from the formulas in 3.2 and 3.3. GB/T50271999
Appendix A
(Suggestive Appendix)
Calculation of test accuracy
The plastic strain ratio r is a derived quantity whose accuracy depends on the accuracy of the strain measurement. A1
A2 The coefficient of variation (r) is used to express the test accuracy of the r value: s(r)
u(r) =:
A2.1 Applying mathematical statistics methods, according to the error transfer formula, a practical calculation formula for (r) can be derived: Al
(r) =((b)(1+)
[1 + exp(- 2eh)3 +u(1.,)[1 + exp(2e.)]; i.2 ....-( A2)E
A2.2 Formula (2) shows that in addition to the r value itself, U() is mainly related to the coefficient of variation of the specimen gauge length and width measurement and the magnitude of the 1-way strain in the length direction. Therefore, the effective measures to improve the test accuracy are: a) improve the dimensional measurement accuracy and increase the number of repeated measurements (i.e. reduce the coefficient of variation of dimensional measurement); b) increase the engineering strain in the length direction within the uniform plastic strain range allowed by the test material, 92 When the tensile properties of the test material are unclear, a conventional tensile test should be carried out in advance, and the force-elongation curve should be recorded to determine its service characteristics, elongation and engineering strain level of the measured value. 8.3 Check the specimen according to the requirements of Chapter 7.
8.4 Pay attention to the centering when installing the specimen to ensure axial force. 8.5 For manual measurement, when the original gauge length L of the specimen is not less than 25mm, at least three widths should be measured at equal intervals within the gauge length and the plastic strain ratio value should be calculated using the average value. When measuring the original gauge length L of the specimen, the allowable measurement deviation is ± 1.0% of the original gauge length 1.8.6 When measuring automatically, the extensometer specified in 6.3.1 should be used to measure the change in gauge length, and at least one width should be measured within the gauge length. 8.7 Test speed:
8.7.1 The moving speed of the chuck of the testing machine should not exceed 50% l/min. 8.7.2 When it is necessary to determine the specified non-proportional elongation stress, yield point, elongation at the cooking point and other properties at the same time as the value test, the test speed shall comply with the provisions of GB/T228. When the specimen is deformed to exceed the above-mentioned properties, the test speed can be adjusted to the range required for the determination of the value.
GB/T 5027-- 1999
8.8 Apply force to the specified strain level. The engineering strain level of the value should be greater than the yield strain or the strain corresponding to the end point of the elongation at the yield point, and less than the strain corresponding to the maximum force. If there are no other provisions, an engineering strain level of 15% or 20% is generally used. 8.9 For manual measurement, the deformed specimen gauge length L and width b are measured in the same way and with the same error as the original gauge length and width. The measurement can be carried out under the test force, but the arbitration test should be carried out under unloading. 8.10 For automatic measurement, use the extension tube specified in 6.3.1 to measure the gauge length L and width 6 at the specified strain level. 8.11 If the specimen is transversely bent (see Figure 3) or longitudinally bent, it will affect the test results. The test should be considered invalid and the test should be repeated.
8.12 If the plastic strain is uneven, the test results should be considered invalid and the test should be repeated. 8.13 Based on the measured bo, Lo, b, L, calculate the r, F and Ar values according to formulas (2), (3) and (4). 8.14 Two specimens should be tested for each sampling direction and the average value of r should be taken. If the results of the two specimens are significantly different, the third specimen should be tested and the value with the largest difference should be discarded.
Transverse bending
Figure 3 Transverse bending of specimens
9 Test results
9.1 For manual measurement, use formulas (2), (3) and (4) to calculate the r, and △r values of specimens with different orientations. 9.2 For automatic measurement, the automatic tensile testing machine and data processing program directly give the values of, and △ for specimens with different orientations. 9.3 The calculated plastic strain ratio r value should be rounded to an accuracy of 0.05. 9.4 Manual measurement and automatic measurement may produce different test results. In the case of obvious differences, the manual unloading measurement method should prevail. 10 Test report
The test report shall include the following contents:
a) the number of this national standard;
b) description of the test material;
c) the method adopted (manual measurement or automatic measurement);
d) the type of specimen adopted;
e) the orientation of the specimen relative to the rolling direction;
f) the strain level at which the measurement is made;
g) other special conditions in the test;
h) the value of the plastic strain ratio r;
i) the average plastic strain ratio r;
i) the in-plane anisotropy △r;
k) the formula used when the formula for calculating and △r is different from the formulas in 3.2 and 3.3. GB/T50271999
Appendix A
(Suggestive Appendix)
Calculation of test accuracy
The plastic strain ratio r is a derived quantity whose accuracy depends on the accuracy of the strain measurement. A1
A2 The coefficient of variation (r) is used to express the test accuracy of the r value: s(r)
u(r) =:
A2.1 Applying mathematical statistics methods, according to the error transfer formula, a practical calculation formula for (r) can be derived: Al
(r) =((b)(1+)
[1 + exp(- 2eh)3 +u(1.,)[1 + exp(2e.)]; i.2 ....-( A2)E
A2.2 Formula (2) shows that in addition to the r value itself, U() is mainly related to the coefficient of variation of the specimen gauge length and width measurement and the magnitude of the 1-way strain in the length direction. Therefore, the effective measures to improve the test accuracy are: a) improve the dimensional measurement accuracy and increase the number of repeated measurements (i.e. reduce the coefficient of variation of dimensional measurement); b) increase the engineering strain in the length direction within the uniform plastic strain range allowed by the test material, 92 When the tensile properties of the test material are unclear, a conventional tensile test should be carried out in advance, and the force-elongation curve should be recorded to determine its service characteristics, elongation and engineering strain level of the measured value. 8.3 Check the specimen according to the requirements of Chapter 7.
8.4 Pay attention to the centering when installing the specimen to ensure axial force. 8.5 For manual measurement, when the original gauge length L of the specimen is not less than 25mm, at least three widths should be measured at equal intervals within the gauge length and the plastic strain ratio value should be calculated using the average value. When measuring the original gauge length L of the specimen, the allowable measurement deviation is ± 1.0% of the original gauge length 1.8.6 When measuring automatically, the extensometer specified in 6.3.1 should be used to measure the change in gauge length, and at least one width should be measured within the gauge length. 8.7 Test speed:
8.7.1 The moving speed of the chuck of the testing machine should not exceed 50% l/min. 8.7.2 When it is necessary to determine the specified non-proportional elongation stress, yield point, elongation at the cooking point and other properties at the same time as the value test, the test speed shall comply with the provisions of GB/T228. When the specimen is deformed to exceed the above-mentioned properties, the test speed can be adjusted to the range required for the determination of the value.
GB/T 5027-- 1999
8.8 Apply force to the specified strain level. The engineering strain level of the value should be greater than the yield strain or the strain corresponding to the end point of the elongation at the yield point, and less than the strain corresponding to the maximum force. If there are no other provisions, an engineering strain level of 15% or 20% is generally used. 8.9 For manual measurement, the deformed specimen gauge length L and width b are measured in the same way and with the same error as the original gauge length and width. The measurement can be carried out under the test force, but the arbitration test should be carried out under unloading. 8.10 For automatic measurement, use the extension tube specified in 6.3.1 to measure the gauge length L and width 6 at the specified strain level. 8.11 If the specimen is transversely bent (see Figure 3) or longitudinally bent, it will affect the test results. The test should be considered invalid and the test should be repeated.
8.12 If the plastic strain is uneven, the test results should be considered invalid and the test should be repeated. 8.13 Based on the measured bo, Lo, b, L, calculate the r, F and Ar values according to formulas (2), (3) and (4). 8.14 Two specimens should be tested for each sampling direction and the average value of r should be taken. If the results of the two specimens are significantly different, the third specimen should be tested and the value with the largest difference should be discarded.
Transverse bending
Figure 3 Transverse bending of specimens
9 Test results
9.1 For manual measurement, use formulas (2), (3) and (4) to calculate the r, and △r values of specimens with different orientations. 9.2 For automatic measurement, the automatic tensile testing machine and data processing program directly give the values of, and △ for specimens with different orientations. 9.3 The calculated plastic strain ratio r value should be rounded to an accuracy of 0.05. 9.4 Manual measurement and automatic measurement may produce different test results. In the case of obvious differences, the manual unloading measurement method should prevail. 10 Test report
The test report shall include the following contents:
a) the number of this national standard;
b) description of the test material;
c) the method adopted (manual measurement or automatic measurement);
d) the type of specimen adopted;
e) the orientation of the specimen relative to the rolling direction;
f) the strain level at which the measurement is made;
g) other special conditions in the test;
h) the value of the plastic strain ratio r;
i) the average plastic strain ratio r;
i) the in-plane anisotropy △r;
k) the formula used when the formula for calculating and △r is different from the formulas in 3.2 and 3.3. GB/T50271999
Appendix A
(Suggestive Appendix)
Calculation of test accuracy
The plastic strain ratio r is a derived quantity whose accuracy depends on the accuracy of the strain measurement. A1
A2 The coefficient of variation (r) is used to express the test accuracy of the r value: s(r)
u(r) =:
A2.1 Applying mathematical statistics methods, according to the error transfer formula, a practical calculation formula for (r) can be derived: Al
(r) =((b)(1+)
[1 + exp(- 2eh)3 +u(1.,)[1 + exp(2e.)]; i.2 ....-( A2)E
A2.2 Formula (2) shows that in addition to the r value itself, U() is mainly related to the coefficient of variation of the specimen gauge length and width measurement and the magnitude of the 1-way strain in the length direction. Therefore, the effective measures to improve the test accuracy are: a) improve the dimensional measurement accuracy and increase the number of repeated measurements (i.e. reduce the coefficient of variation of dimensional measurement); b) increase the engineering strain in the length direction within the uniform plastic strain range allowed by the test material, 91 Using mathematical statistics methods, according to the error transfer formula, a practical calculation formula for (r) can be derived: Al
(r) =((b)(1+)
[1 + exp(- 2eh)3 +u(1.,)[1 + exp(2e.)]; i.2 ....-( A2)E
A2.2 Formula (2) shows that in addition to the r value itself, U() is mainly related to the coefficient of variation of the specimen gauge length and width measurement and the magnitude of the 1-way strain in the length direction. Therefore, the effective measures to improve the accuracy of the value test are: a) improve the accuracy of dimensional measurement and increase the number of repeated measurements (that is, reduce the coefficient of variation of dimensional measurement); b) increase the engineering strain in the length direction within the uniform plastic strain range allowed by the test material, 91 Using mathematical statistics methods, according to the error transfer formula, a practical calculation formula for (r) can be derived: Al
(r) =((b)(1+)
[1 + exp(- 2eh)3 +u(1.,)[1 + exp(2e.)]; i.2 ....-( A2)E
A2.2 Formula (2) shows that in addition to the r value itself, U() is mainly related to the coefficient of variation of the specimen gauge length and width measurement and the magnitude of the 1-way strain in the length direction. Therefore, the effective measures to improve the accuracy of the value test are: a) improve the accuracy of dimensional measurement and increase the number of repeated measurements (that is, reduce the coefficient of variation of dimensional measurement); b) increase the engineering strain in the length direction within the uniform plastic strain range allowed by the test material, 9
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