1、GM DAEWOO Auto & Technology EDS Engineering, GM DAEWOO Auto & Technology Standards METHOD FOR SHOT PEENING EVALUATION EDS-T-7149 ISSUED DATE: 1994. 04. 01 REVISED DATE: 2006. 06. 19 VERSION: 3 EDS-T-7149METHOD FOR SHOT PEENING EVALUATION PAGE: 1/7 ISSUED DATE: 1994. 04. 01 REVISED DATE: 2006. 06. 19
2、 VERSION: 3 GM DAEWOO Auto & Technology 1. PURPOSE This standard aims at helping test personnel perform the test in an appropriate way by describing intensity, coverage and residual stress measurement method to evaluate shot peening processed parts. 2. SCOPE This standard applies to the shot peening
3、 processed parts for the improvement of durability. 3. DEFINITIONS 3.1. Intensity Intensity is measured by the arc height of ALMEN strip in case of shot peening with 100% min. of coverage. This is the one of measurement methods of shot peening and generally indicates degree of shot peening strength.
4、 3.2. Coverage Coverage indicates the degree of the area where a blast of shot made a dent on the product and generally indicates the uniformity of shot peening. 3.3. Residual stress Residual stress means the remaining stress on the product even after the removal of external force and in here indica
5、tes compressed stress remaining on the product surface due to the effects of shot peening. 4. TEST PIECES 4.1. Test pieces shall be the ones specified in the standard. 4.2. The number of test pieces shall be 3 min. of initial approval and at least 1 min. for routine quality control. 5. INTENSITY MEA
6、SUREMENT METHOD 5.1. Apparatus 5.1.1. Test piece (1) Material: ALMEN strip (SAE 1070 steels for cold spring) EDS-T-7149METHOD FOR SHOT PEENING EVALUATION PAGE: 2/7 ISSUED DATE: 1994. 04. 01 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology (2) Shape UNIT : INCH 0.745 0.750 T Fig. 1.
7、Size of Test Piece N test piece : T = 0.031 0.001 A test piece : T = 0.051 0.001 C test piece : T = 0.094 0.0015 (3) Division of test piece a) A test piece : In case intensity is within 0.0006“0.0024“ b) C test piece : In case intensity is 0.024“ min. c) N test piece : In case intensity is 0.006“ ma
8、x. 5.1.2. Holding fixture Fig. 2. Holding fixture 3 0.015 EDS-T-7149METHOD FOR SHOT PEENING EVALUATION PAGE: 3/7 ISSUED DATE: 1994. 04. 01 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology 5.1.3. Gage As shown in Fig. 3, ALMEN No. 2 gage shall be used Fig. 3. Gage(ALMEN No. 2) EDS-T-
9、7149METHOD FOR SHOT PEENING EVALUATION PAGE: 4/7 ISSUED DATE: 1994. 04. 01 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology 5.2. Measure method 5.2.1. Fasten the strip tightly to the holding fixture. 5.2.2. Expose the surface of the strip to shot peening. Record the time of exposure
10、. 5.2.3. Remove the strip from the holding fixture and measure the arc height and record. 5.2.4. Using different exposure times, measure the arc height and then draw the graph as shown below. Fig. 4. Intensity determination curve 5.2.5. The gage reading corresponding to the point where the curve fla
11、ttens out as point “1“ in Fig. 4 is generally taken as the measurement of the intensity of that particular peening. 5.3. Indication method Intensity indicates the arc height and the shape of test strip as follows. Example) In case of arc height of 0.006 and test strip A, intensity: 0.006A 6. THE MET
12、HOD FOR MEASURING COVERAGE 6.1. DYESCAN method This method can be applied directly to the entire product for measurement. 6.1.1. Test piece : Product 6.1.2. Measuring method (1) Remove foreign substances on the surface of the product with an appropriate method. (2) After applying DYESCAN uniformly o
13、n the surface of the product, dry it. (3) Expose the product to shot peening. (4) Measure coverage (Shotted area : dark color, Unshotted area : White color) EDS-T-7149METHOD FOR SHOT PEENING EVALUATION PAGE: 5/7 ISSUED DATE: 1994. 04. 01 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technol
14、ogy 6.2. Surface replica method The surface replica method is not suitable for securing exact measurements of coverage but can be applied to practically any area of a part and the simplest of the methods for measuring coverage. 6.2.1. Test piece : Product 6.2.2. Measuring method (1) Remove foreign s
15、ubstances on the surface of the product with an appropriate method. (2) Apply surface replica solvent (acetone, etc.) to the area where coverage is to be measured. (3) Apply surface replica film to the area where solvent has been placed and press the film to the area with an appropriate pressure for
16、 approximately one minute. (4) Peel the surface replica film carefully and quickly from the surface and then pinch and close it between glass plates. (5) Establish the grade by comparing it with the standard graph (Attached Table 1) under microscope. However, when surface replica is impossible, the
17、grade may be established by observing directly the surface of the product with stereo scope. 6.3. STRAUB method Method of using test pieces. It shows only the relative data. 6.3.1. Test piece : ALMEN strip 6.3.2. Measuring method (1) Polish the test surface of the test strips (2) Expose the polished
18、 surface to shot peening. (3) Take picture of the surface of the test strip with camera(50) and then develop and print the film. (4) Place a transparent glass plate on the printed picture and draw the circle of 50mm on it, and then mark the indented area within this circle. (5) Measure the area of t
19、his indentation with an appropriate measuring device (Image analyzer etc.). 6.4. VALENTINE method This method is mainly for observing the presence of shot peening and comparative method. 6.4.1. Test piece : SAE 1008 sheet material test piece 6.4.2. Measuring method (1) Normalize the test piece at 16
20、50. (2) Expose the test piece to shot peening. (3) Anneal at a temperature of 1300 to produce recrystallization and grain growth. (4) Cut the sample and measure coverage by observing the area where grain growth occurred. EDS-T-7149METHOD FOR SHOT PEENING EVALUATION PAGE: 6/7 ISSUED DATE: 1994. 04. 0
21、1 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology 7. RESIDUAL STRESS MEASURING METHOD 7.1. There are mechanical method, electromagnatic method, ultrasonic method, and X-ray method etc. as residual stress measuring method. Our company, in principle, conducts measurement with residua
22、l stress measuring devise using X-ray. However, the method may be altered through agreement between parties concerned. 7.2. The method for measuring residual stress with a measuring device shall conform to the direction for respective equipment use. 7.3. Indication method Indicate as follows. Exampl
23、e) - 100.5 kg/mm2 In case of compressed residual stress(-) In case of tensile residual stress(+) Size shall be indicated up to the first decimal point Unit 8. REFERENCE GM4283-P Recommended for controlling peening process EDS-T-7149METHOD FOR SHOT PEENING EVALUATION PAGE: 7/7 ISSUED DATE: 1994. 04. 01 REVISED DATE: 2006. 06. 19 VERSION: 3 GM DAEWOO Auto & Technology Appendix 1. COVERAGE STANDARD GRADE TABLE
