1、GM DAEWOO Auto & Technology EDS Engineering, GM DAEWOO Auto & Technology. Standards TEST METHOD FOR PLASTIC STRAIN RATIO( r ) FOR SHEET METAL EDS-T-7189 ISSUED DATE: 2003. 05. 21 REVISED DATE: - VERSION: 1 TEST METHOD FOR PLASTIC STRAIN RATIO( r ) FOR SHEET METAL EDS-T-7189PAGE: 1/4 ISSUED DATE: 200
2、3. 05. 21 REVISED DATE: . . VERSION: 1 GM DAEWOO Auto & Technology 1. PURPOSE This standard specifies the method of obtaining plastic strain ratio of thin metal test samples using tension tester to enable correct testing 2. SCOPE This standard applies to thin metal materials used on motor vehicles.
3、3. TERM 3.1. Plastic Strain Ratio (r) This refers to the ratio of true Strain in the width direction of test sample against true Strain in the thickness direction when plastic deformation occurs by applying contraction tension stress on a tension test sample of panel shape. 3.2. Average Plastic Stra
4、in Ratio (Weighted Average of r values, or ) Weighted average of plastic strain ratios measured at 0, 45 and 90 degrees from the compression direction of test sample panel. 3.3. Internal Anisotropy Coefficient ( ) This value indicates the tendency of non-uniform formation of panel when a circular pa
5、nel is subject to deep drawing. 4. TEST SAMPLE Refer to EDS-T-7113 “METHOD OF TENSILE TEST FOR METALLIC MATERIALS” Appendix 1 “Metal Material Tension Test Sample.” For other details, follow the rules below. 1) Test sample collection method shall follow each material standard specifications. If no sp
6、ecific rules, follow agreement between supplier and GMDAT. 2) Test sample shape shall follow each materials standard specification, If no specific rules, use the shape of EDS-T-7113, item 5, samples 13A or 13B. 3) Width dimension change of parallel areas of a test sample shall be within 0.1% of aver
7、age width between indicated points. 4) When no specific rule on test sample thickness, use the original material thickness. 5) There shall be no scratches or other defects that impact test results negatively on test sample surfaces. 5. TEST EQUIPMENT 5.1. Tension Tester shall follow KS B 5521, ASTM
8、E4 or DIN 51221 and shall consist of main body, load transport device, Load Measurement Device, Test Sample Jig and Elongation Ratio measuring device. r mrrTEST METHOD FOR PLASTIC STRAIN RATIO( r ) FOR SHEET METAL EDS-T-7189PAGE: 2/4 ISSUED DATE: 2003. 05. 21 REVISED DATE: . . VERSION: 1 GM DAEWOO A
9、uto & Technology 5.2. Tester shall be mounted firmly on a base and shall not move easily. 5.3. 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 E4 or DIN 51221 before testing. 5.4. Tester
10、shall be calibrated once a year even when not the case of 5.3 above. 6. TEST PROCEDURE 6.1. TEST 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 as necessary. In particula
11、r, for materials that are sensitive to temperature change, 23 5 will be standard range and while following the particular materials standard. 6.2. Measurement Point Distance Marking & Measurement Before applying strain on test sample, measure the distance between measurement points in width and leng
12、thwise directions with accuracy of 0.01mm. Measurement points shall be total 3 or more in width and lengthwise direction each in equal intervals. Test sample measurement distance of lengthwise direction and strain to apply shall follow each materials standard. If no specific regulation, follow Table
13、 1. Table 1 Measurement Distance & Strain to Apply Test Sample Shape No. Measurement Distance (mm) Strain to Apply (%) No. 5 20, 25, 50 10 20 13A 50, 80 10 20 13B 20, 25, 50 10 20 6.3. Tester Zero Setting Adjust tester to make load zero on test sample. 6.4. Test Sample Install Install test sample to
14、 tester holding jig so that it is aligned with testers axis and measure lengthwise elongation ratio. For automated measurement, install widthwise elongation meter. 6.5. Test Speed The strain increase rate of test sample parallel area shall not exceed 80% each minute. Here, in case of test TEST METHO
15、D FOR PLASTIC STRAIN RATIO( r ) FOR SHEET METAL EDS-T-7189PAGE: 3/4 ISSUED DATE: 2003. 05. 21 REVISED DATE: . . VERSION: 1 GM DAEWOO Auto & Technology =w=t)ln(0wwfw=)ln(0ttft=)ln(00fftwlwl=speed regulation in each material standard, follow such regulation. 6.6. Test Conduct Conduct tension test acco
16、rding to specified test speed until test sample strain reaches specified level. 6.7. Measurement of Measurement Point Distance after Test Remove load and measure lengthwise and widthwise measurement point distances. For automated measurement, store results of the device. 7. RESULT COMPUTATION 7.1. P
17、lastic Strain Ratio Plastic Strain Ratio is expressed in Equation (1). - ( 1 ) Here, Width Direction True Strain Thickness Direction True Strain = Measurement point distance in thickness direction before test = Measurement point distance in thickness direction after test = Measurement point distance
18、 in width direction before test = Measurement point distance in width direction after test Then, the true Strains of Thickness Direction and Width Direction are as follows. - ( 2 ) On the other hand, assuming no volume change during plastic deformation, the true Strain of thickness direction will be
19、 as in Equation (3). - ( 3 ) Here, and represent measurement point distance lengthwise before and after testing, respectively. twr=0tft0wfw0lflTEST METHOD FOR PLASTIC STRAIN RATIO( r ) FOR SHEET METAL EDS-T-7189PAGE: 4/4 ISSUED DATE: 2003. 05. 21 REVISED DATE: . . VERSION: 1 GM DAEWOO Auto & Technol
20、ogy Then, Equation (1) can be written as follows. - ( 4 ) Using Equation (4), we can obtain plastic strain ratio for each direction. 7.2. Average Plastic Strain Ratio Average Plastic Strain Ratio can be computed using Equation (5). - ( 5 ) Here, : Plastic strain ratio of test sample collected parall
21、el to compression direction. : Plastic strain ratio of test sample collected at 45 degree direction to compression direction : Plastic strain ratio of test sample collected at 90 degree direction to compression direction 7.3. Internal Anisotropy Coefficient Internal Anisotropy Coefficient can be com
22、puted using Equation (6). - ( 6 ) 7.4. Precision of Values Plastic strain ratio is computed to second decimal place and is computed to second decimal place when using Equations (5) and (6). Average plastic strain ratio and internal anisotropy coefficients are computed to first decimal place. 8. RELATED STANDARD 8.1. KS D 8511: Method of determining the plastic strain ratiofor metallic sheet and strip 8.2. ASTM E517-96a: Standard Test Methods for Plastic Strain Ratio R of Sheet Metal )ln()ln(000wlwlwwrffftw=4290450rrrr+=2290450rrrr+=0r45r90r
