1、 GMDAT ENGINEERING STANDARDS Test Procedure Materials EDS-T-7190 Test Method for Tensile Strain-hardening Exponents (N-values) of Metallic Sheet Materials Copyright 2010 General Motors All Rights Reserved April 2010 Originating Department: GMDAT Engineering Standards Page 1 of 5 Version : 2 1 Scope
2、Note: Nothing in this standard supersedes applicable laws and regulations. Note: In the event of conflict between the Korean and English language, the Korean language shall take precedence. 1.1 Purpose. The purpose of this standard is to specify the method of measuring sheet metal tensile strain-har
3、dening exponents through tension test to enable proper testing. 1.2 Applicability. Strain hardening exponent of sheet metal of thickness 0.156.5mm. 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. KS B 5521 ASTM E
4、4 DIN 51221 2.2 GM Standards/Specifications. EDS-T-7113 2.3 Additional References. Not application 3 Resources 3.1 Facilities. Not application 3.2 Equipment. 3.2.1 Tester used for tension test shall follow KS B 5521, ASTM E4 or DIN 51221 and shall consist of main body, load mover, load measurement d
5、evice, test sample jig and elongation measurement device. 3.2.2 Tester shall be mounted firmly on a base and shall not move easily. 3.2.3 In the event of a disassembly and reassembly or configuration change of the tension testers major components or replacement, check compliance of KS B 5521, ASTM E
6、4 or DIN 51221 before testing. 1 : . : , . 1.1 . , . 1.2 . 0.15 6.5 mm . 2 / : . 2.1 / . KS B 5521 ASTM E4 DIN 51221 2.2 GM / . EDS-T-7113 2.3 / . 3 3.1 . 3.2 . 3.2.1 KS B 5521, ASTM E4 DIN 51221 , , , . 3.2.2 . 3.2.3 , KS B 5521, ASTM E4 DIN 51221 . GMDAT ENGINEERING STANDARDS EDS-T-7190 Copyright
7、2010 General Motors All Rights Reserved April 2010 Page 2 of 5Version : 2 3.2.4 Tester shall be calibrated once a year even when not the case of paragraph 3.2.3 above. 3.3 Test Piece. Test sample shall be manufactured with dimensions according to EDS-T-7113, Appendix “Metal Material Tension Test Sam
8、ple.” Test samples shall have uniform dimensions and should not have residual stress. 4 Test Procedures 4.1 Test Apparatus Preparation. When starting the test, warm it up until tester reaches desired temperature. Test shall be conducted normally in the temp range of 10 35 and record test temperature
9、 as necessary. In particular, for materials that are sensitive to temperature change, (23 5) will be standard range and while following the particular materials standard. 4.2 Test Sample Cross Section Area Measurement. Measure thickness and width of test sample. 4.3 Tester Zero setting. Adjust teste
10、r to make load zero on test sample. 4.4 Install Test Sample K log blog x log y= Then, equation (5) becomes equation (6). b nx y += - (6) Thus, n can be computed from equation (7) and K from equation (8). 2)=N1iiN1i2iN1iN1iiN1iix( - xNx - xNniiyy- (7) exp(b) KNx n - bN1iiN1i=iy- (8) 6 Safety This sta
11、ndard may involve hazardous materials, operations, and equipment. This standard does not propose to address all the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of r
12、egulatory limitations prior to use. 7 Notes 7.1 Glossary. 7.1.1 Strain Hardening. The tendency for materials hardness and strength to increase due to plastic deformation. 7.1.2 Strain Hardening Exponent (n). The index of strain hardening, which is the exponent n in the equation that expresses the re
13、lationship between true stress and true strain. nK = - (1) 5.2 . n . (1) (5) . - (5) K log blog x log y= , ( 5 ) ( 6 ) . b nx y += - (6) n (7) , K (8) . 2)=N1iiN1i2iN1iN1iiN1iix( - xNx - xNniiyy- (7) exp(b) KNx n - bN1iiN1i=iy- (8) 6 , , . . , . 7 7.1 . 7.1.1 . 7.1.2 . (1) n . nK = - (1) log n K log
14、 log += log n K log log +=GMDAT ENGINEERING STANDARDS EDS-T-7190 Copyright 2010 General Motors All Rights Reserved April 2010 Page 5 of 5Version : 2 7.1.3 True Stress ( ). When tension load is applied to test sample, this value refers to load divided by the cross section area of the parallel area. I
15、t has the following relationship with the nominal stress (S). ) e (1 S += - (2) Here, e refers to nominal strain. 7.1.4 True Strain ( ). When tension load is applied to test sample, it is the natural log of the ratio of the measurement point length and measurement point distance in the test sample a
16、s in Equation (3). )ln(0ll= - (3) Here, the true strain and the nominal strain have the following relationship. )1ln( e+= - (4) 7.1.5 Strength Coefficient (K). The true stress value obtained via extrapolation method from the true stress-true strain curve when true strain is 1.00. 7.2 Acronyms, Abbre
17、viations, and Symbols. Not applicable. 8 Coding System This standard shall be referenced in other documents, drawings, etc., as follows: EDS-T-7190 9 Release and Revisions This standard was originated in May 2003. It was first approved by Corrosion / Metallurgical Material Lab Team in May 2003. It w
18、as first published in May 2003. 7.1.3 ( ). , , ( S ) . ) e (1 S += - (2) e . 7.1.4 ( ). , ( (3) . )ln(0ll= - (3) , (e) (4) . )1ln( e+= - (4) 7.1.5 (K). - 1.00 . 7.2 . 8 . EDS-T-7190 9 2003 5 , 2003 5 . 2003 5 / . Issue / Publication Date / Description (Organization) / / () 2 APR 2010 Apply new template and correct EDS Number at the cover sheet (Corrosion / Metallurgical Material Lab Team). / EDS No ( ).
