1、GM DAEWOO Auto Ec = Ec X (ts/tr) Ec : corrected critical strain ts : sample thickness (mm) tr : reference thickness (3.2mm) Ec : critical strain from Table 1. EDS-T-7020TEST METHOD FOR CHEMICAL STRESS RESISTANCE OF PLASTICS PAGE: 3/8 ISSUED DATE: 1996. 04. 06 REVISED DATE: 2006. 06. 19 VERSION: 4 GM
2、 DAEWOO Auto & Technology 6.2. METHOD B 6.2.1. Saturate the stressed test piece in the test fluid for 24 hours. To retain fluid on the surface during the 24 hours period, use gauze or sponge saturated with fluid. 6.2.2. If crazing or cracking occurs at the high strain position on the fixture, repeat
3、 the test using fresh tensile bars at lower strain positions on the fixture until no crazing or cracking occurs. 6.2.3. Determine the critical strain level using the measured craze/crack position and Table 1 as in METHOD A. 6.3. METHOD C 6.3.1. Position the rigid plastic test piece on the bending fo
4、rm at the highest strain level of interest by using the wooden tongue depressor to hold the bar firmly against the form while the clamps are tightened onto the test sample. Care should be taken to avoid contaminating the test piece surface by handling. The wooden tongue depressor is removed when the
5、 test piece has been secured to the fixture. 6.3.2. For test pieces exhibiting edge cracking, apply chemically resistance grease to the edges of the narrow portion of the rigid plastic test piece bar, as well as around the clamps, to prevent contact with the other test piece. 6.3.3. After a 5-minute
6、 time interval from application of stress to the rigid plastic test piece, position the flexible plastic test piece on top of the rigid plastic test piece and ensure complete surface contact between both test pieces over the entire narrow portion area of the rigid plastic test piece bar. 6.3.4. Plac
7、e the entire test assembly and test pieces into an air circulating oven with the specified test temperature. (1) After 24 hours of exposure to the test temperature, examine the surface of the rigid plastic test piece bar for crazes and/or cracks. Record the position of the crazes or cracks using the
8、 gauge marks on the bending form. (2) If no crazes or cracks are observed and the surface of the rigid plastic test piece bar remains unchanged, reposition the flexible test piece over the rigid plastic test piece bar ensuring that complete surface contact is made over the entire narrow portion area
9、 of the rigid plastic test piece bar. Re-examine the test pieces after an additional 24 hours exposure at the test temperature. (3) Repeat 6.3.4.2 if no crazes or cracks are observed after 2 exposure periods of the test pieces. Repeat this testing procedure until a total of 168 hours(7 days) of test
10、 exposure time has been completed. 6.3.5. If crazing or cracking occurs at the high strain position on the fixture, repeat the test using fresh tensile bars of the rigid plastic at lower strain positions on the fixture until no crazing or cracking occurs. 6.3.6. Determine the critical strain level u
11、sing the measured craze/crack position and Table 1 as in METHOD A. and B. 7. ADDITIONAL REQUIREMENTS 7.1. Approved sources for components may be quoted on release notes or component drawings. EDS-T-7020TEST METHOD FOR CHEMICAL STRESS RESISTANCE OF PLASTICS PAGE: 4/8 ISSUED DATE: 1996. 04. 06 REVISED
12、 DATE: 2006. 06. 19 VERSION: 4 GM DAEWOO Auto & Technology 7.2. Other additional requirements may be specified on the relevant component drawings. 8. CODING SYSTEM Chemical stress resistance test to EDS-T-7021 A. 9. REFERENCE GM 9308 P Chemical stress resistance of plastics EDS-T-7511 Test method fo
13、r the tensile property of plastics Standard Number Designation Test method EDS-T-7020TEST METHOD FOR CHEMICAL STRESS RESISTANCE OF PLASTICS PAGE: 5/8 ISSUED DATE: 1996. 04. 06 REVISED DATE: 2006. 06. 19 VERSION: 4 GM DAEWOO Auto & Technology Table 1 X (mm) Ec (%) X (mm) Ec (%) X (mm) Ec (%) X (mm) E
14、c (%) 2.50 0.31 66.00 0.34 129.50 0.43 193.00 0.72 5.10 0.31 68.60 0.34 132.10 0.44 195.60 0.74 7.60 0.31 71.10 0.34 134.60 0.44 198.10 0.76 10.20 0.31 73.70 0.34 137.20 0.45 200.70 0.79 12.70 0.31 76.20 0.35 139.70 0.46 203.20 0.82 15.20 0.31 78.70 0.35 142.20 0.46 205.70 0.84 17.80 0.31 81.30 0.35
15、 144.80 0.47 208.30 0.87 20.30 0.31 83.80 0.35 147.30 0.48 210.80 0.91 22.90 0.32 86.40 0.36 149.90 0.49 213.40 0.94 25.40 0.32 88.90 0.36 152.40 0.50 215.90 0.98 27.90 0.32 91.40 0.36 154.90 0.51 218.40 1.02 30.50 0.32 94.00 0.37 157.50 0.52 221.00 1.07 33.00 0.32 96.50 0.37 160.00 0.53 223.50 1.11
16、 35.60 0.32 99.10 0.37 162.60 0.54 226.10 1.17 38.10 0.32 101.60 0.38 165.10 0.55 228.60 1.23 40.60 0.32 104.10 0.38 167.60 0.56 231.10 1.29 43.20 0.32 106.70 0.39 170.20 0.57 233.70 1.36 45.70 0.32 109.20 0.39 172.70 0.58 236.20 1.44 48.30 0.33 111.80 0.39 175.30 0.60 238.80 1.52 50.80 0.33 114.30
17、0.40 177.80 0.61 241.30 1.62 53.30 0.33 116.80 0.40 180.30 0.63 243.80 1.73 55.90 0.33 119.40 0.41 182.90 0.64 246.40 1.85 58.40 0.33 121.90 0.41 185.40 0.66 248.90 1.99 61.00 0.33 124.50 0.42 188.00 0.68 251.50 2.15 63.50 0.34 127.00 0.42 190.50 0.70 254.00 2.33 NOTE : Values of Critical Strain (Ec
18、) Versus Distance to Craze or Crack From Low Strain End of Elliptical Form (X). Reference Thickness = 3.2mm NOTE : The critical strain on the outer curved surface of a sample on the elliptical bending form is given by : txtatbtatatbEc2/324222)2/()2/()2/(11)2/(2)2/(+= Ec = strain (%) a = semi - major
19、 axis of ellipse (mm) b = semi - minor axis of ellipse (mm) x = distance along major axis (mm) t = sample thickness (mm) EDS-T-7020TEST METHOD FOR CHEMICAL STRESS RESISTANCE OF PLASTICS PAGE: 6/8 ISSUED DATE: 1996. 04. 06 REVISED DATE: 2006. 06. 19 VERSION: 4 GM DAEWOO Auto & Technology Figure 1. El
20、lipse Figure 2. Elliptical bending form assembly EDS-T-7020TEST METHOD FOR CHEMICAL STRESS RESISTANCE OF PLASTICS PAGE: 7/8 ISSUED DATE: 1996. 04. 06 REVISED DATE: 2006. 06. 19 VERSION: 4 GM DAEWOO Auto & Technology Figure 3. Elliptical bending form Figure 4. Thumb screw EDS-T-7020TEST METHOD FOR CHEMICAL STRESS RESISTANCE OF PLASTICS PAGE: 8/8 ISSUED DATE: 1996. 04. 06 REVISED DATE: 2006. 06. 19 VERSION: 4 GM DAEWOO Auto & Technology Figure 5. Clamp holder Figure 6. Clamp
