SAE J 445-1957 Metallic Shot and Grit Mechanical Testing.pdf

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1、_ 6$(7HFKQLFDO6WDQGDUGV%RDUG5XOHVSURYLGHWKDW7KLVUHSRUWLVSXEOLVKHGE6$(WRDGYDQFHWKHVWDWHRIWHFKQLFDO and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising tKHUHIURPLVWKHVROHUHVSRQVL

2、ELOLWRIWKHXVHU SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2013 SAE International All rights reserved. No part of this publication may be reproduced, st

3、ored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-4970 (outside USA) Fax: 724-776-079

4、0 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/J445_201308 SURFACE VEHICLE INFORMATION REPORT J445 AUG2013 Issued 1957-01 Reaffirmed 2013-08 Superseding J445 JU

5、L2005 Metallic Shot and Grit Mechanical Testing RATIONALE J445 has been reaffirmed to comply with the SAE five-year review policy. ForewordShot testing machines differ in detail, but are alike in the fundamental principle that a sample of shot issubjected to repeated impacts on a target. The percent

6、age of breakdown is readily determined by means of ascreen analysis. These data can be used to check the uniformity of shipments or to determine the relative fatiguelife. The results obtained from testing machines are not intended to be used in establishing consumption or cost inproduction machines

7、because of other considerations not duplicated in the laboratory. However, the machines canbe used to test incoming shot for consistency and comparative life with previous shipments of the same type ofshot from the same manufacturer under laboratory conditions. Some machines can be fitted with stand

8、ard teststrips1to measure energy transfer.NOTEShot particles may be subject to multiple impacts in a test machine. The target material of test machines aremade of hard steel to resist wear during testing. Hard shot is more elastic than soft shot. Due to theseconsiderations and their influence on sho

9、t failure, care must be exercised when analyzing results from thisaccelerated, laboratory testing.1. ScopeThis SAE Information Report is intended to provide users and producers of metallic shot and grit2with general information on methods of mechanically testing metal shot in the laboratory.1.1 Rati

10、onaleThis document has been reaffirmed to comply with the SAE 5-Year Review policy.2. References2.1 Applicable PublicationsThe following publications form a part of this specification to the extent specifiedherein. Unless otherwise specified, the latest issue of SAE publications shall apply.2.1.1 SA

11、E PUBLICATIONSAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE J442Test Strip, Holder, and Gage for Shot PeeningSAE J443Procedures for Using Standard Shot Peening Test Strip1. See SAE J442 and SAE J443.2. Shot and grit will be hereafter referred to as shot.2.1.2 ASTM PUBLICA

12、TIONAvailable from ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.ASTM B 215Methods of Sampling Finished Lots of Metal Powders3. SamplingSamples for testing shall be representative of each shipment or production lot. The method ofsampling shall be ASTM B 215, Method B.4. CalibrationBe

13、cause results can be influenced by the condition of a test machine, the machine must berecalibrated according to the machine manufacturers recommendation. This may be accomplished byreserving an adequate amount of shot of known life, and comparing the results obtained on tests with that ofthe “stand

14、ard shot.“ The machine must be repaired or adjusted as necessary when off-standard conditions areobserved.5. Examples of Test Procedures5.1 Average Life by Measurement of the Area Under the Breakdown CurveIf a representative sample ofshot is observed as it is broken down in a testing machine, and th

15、e percent of the sample retained on a controlsieve is plotted against the number of cycles, on rectangular coordinate paper, a breakdown curve typical ofthe shot is obtained. The control sieve aperture should be approximately equal to the removal size in the blastoperation. The area under this curve

16、 is a measure of the average number of cycles required to reduce the sizeof the shot particles which pass through the control sieve. This average number of cycles, commonly referredto as the average life of the shot, is a complete evaluation of the life of the shot under the conditions of the test.5

17、.1.1 EXAMPLE PROCEDUREa. Place 50 to 100 g of the sample to be tested into the test machine.b. Run until about 20% passes through the control sieve.c. Screen, weigh, and plot the percent retained on the control sieve against the number of cycles, usingrectangular coordinate paper.d. Return the sampl

18、e retained on the control sieve to the machine and continue running.e. Repeat steps (c) and (d) at intervals dictated by the rapidity of breakdown of the sample, until less than5% of the sample is retained on the control sieve.f. Draw the breakdown curve, extrapolating to 0% at the end of the next t

19、est interval. The breakdowncurve, using the data from the following example, with trapezoids inscribed, is shown in Figure 1.g. Measure the area under the breakdown curve. For example, use a planimeter or sum the areas of theindividual trapezoids inscribed under the breakdown curve. Record the value

20、 as average life, in cycles.5.1.1.1 Examplea. Initial Charge100 g of S660b. Control Sieve Opening600 mc. Test Intervals500 cycles_SAE J445 Reaffirmed AUG2013 Page 2 of 7FIGURE 1BREAKDOWN CURVE S660 SHOT TRAPEZOIDS INSCRIBED AND NUMBERED_SAE J445 Reaffirmed AUG2013 Page 3 of 75.1.1.2 Breakdown Data(S

21、ee Table 1.)The area of a trapezoid is determined by multiplying the average height by the base. The area of trapezoid1 is calculated as follows:(Eq. 1)where:the base = 500 cyclesArea = 95.5% x 500 cycles = 47 750% cyclesThe calculations of areas of all the trapezoids are shown in Table 2.TABLE 1BRE

22、AKDOWN DATA FOR EXAMPLECumulativeCycles% Retained onControl Sieve0 100500 911000 721500 512000 322500 163000 73500 24000 0TABLE 2CALCULATION OF THE AREA UNDER THE BREAKDOWN CURVE AS THE SUMOF THE AREAS OF TRAPEZOIDS INSCRIBED UNDER THE BREAKDOWN CURVETrapezoid No.12345678Height 1, % 100 91 72 51 32

23、16 7 2Height 2, % 91 72 51 32 16 7 2 0Avg. Height, % 95.5 81.5 61.5 41.5 24 11.5 4.5 1Base, cycles 500 500 500 500 500 500 500 500Area, % cycles 47 750 40 750 30 750 20 750 12 000 5750 2250 500NOTESSum of areas 160 500 % cyclesThe average life = 160 500 % impacts divided by 100% =1605 cycles.Average

24、 height = (100% + 91%) divided by 2 = 95%_SAE J445 Reaffirmed AUG2013 Page 4 of 75.2 Stabilized Loss MethodA sample of shot is run in a test machine for a given number of cycles. The sampleis then screened to remove particles which pass through a control sieve. The control sieve aperture shouldappro

25、ximately equal the removal size in the blast operation. New shot is added to replace the amountremoved. Repeat the procedure, always running the same number of cycles until the amount discarded (theloss) achieves stabilization. The stabilized loss data can be used to compute the average life of the

26、sample.NOTEThe loss pattern, when each loss is plotted against test cycles, may go through several peaks andvalleys before true stabilization occurs. Initial samples should be tested through sufficient test cyclesto insure that the sample loss rate has truly stabilized. Stabilization occurs when thr

27、ee consecutivelosses vary by less than 0.50% of the initial charge weight.5.2.1 EXAMPLE PROCEDUREa. Place 50 to 100 g of the shot to be tested into the testing machine.b. Run for a given interval, preferably a number of cycles sufficient to break down about 20% of thesample.c. Screen the shot from t

28、he machine, discarding the portion which passes through the control sieve,weigh the sample, and calculate and record the loss.d. Add new shot to restore the sample retained on the control sieve to the initial charge weight.e. Repeat the procedure, always running the same interval until the amount di

29、scarded (the loss) achievesstabilization.f. The stabilized loss rate equals the average of the last three values obtained, divided by the cyclesintervals used.5.2.1.1 Examplea. Initial Charge100 g of S660 shotb. Control Sieve Opening600 mc. Test Intervals500 cycles5.2.1.2 Breakdown Cycles(See Table

30、3.)(Eq. 2)where:Stabilized loss rate = 27.06 g/500 cycles = 0.0541 g/cycleFinal weight equals initial weight minus stabilized loss = 100 g 27.06 g = 72.94 gTABLE 3BREAKDOWN CYCLESCumulative Cycles Grams Lost500 9.01000 19.81500 24.52000 26.92500 28.93000 27.13500 27.24000 26.9Stabilized loss = (27.1

31、 g + 27.2 + 26.9 g)/3 = 27.06 g_SAE J445 Reaffirmed AUG2013 Page 5 of 7NOTEThe average life, in this example, is calculated as follows: Average life equals the average numberof grams in machine, divided by the stabilized loss rate, in g/cycle, both at stabilized.The average number of grams in the ma

32、chine at stabilization equals the average of the initial weight andfinal weight:(100 + 72.94) g, divided by 2 = 86.47 gAverage life = (86.47 g)/(0.0541 g/cycles) = 1599 cycles5.3 100% Replacement MethodA sample of shot is run in a test machine for a given number of cycles. Thesample is then screened

33、 to remove particles which pass through a control sieve. The control sieve apertureshould approximately equal the removal size in the blast operation. New shot is added to replace the amountremoved. Repeat the procedure until an amount equal to or greater than the initial charge has been added.5.3.1

34、 EXAMPLE PROCEDUREa. Place 50 to 100 g of the shot to be tested into the testing machine.b. Run for a given interval, preferably a number of cycles sufficient to break down about 20% of thesample.c. Screen the shot from the machine, discarding the portion which passes through the control sieve,weigh

35、 the sample, and record the grams (%) retained.d. Add new shot to restore the sample retained on the control sieve to the initial charge weight.e. Repeat (a) to (d), always running the same interval, until the cumulative % discarded (the loss), isequal to or greater than the initial charge weight.f.

36、 Determine the number of cycles at which 100% replacement has occurred, by interpolation, usingEquation 3:(Eq. 3)5.3.1.1 Example(See Table 4.)a. S660Cast steel shotb. Control Sieve Opening425 mc. Test Intervals500 cycles100% replacement value = 3000 (500/19.0) (103.4 100%) = 2911 cyclesTABLE 4BREAKD

37、OWN CYCLESAccumulativeCyclesIndividual% RemainingIndividual% LossCumulative% Loss500 87.7 12.2 12.21000 84.0 16.0 28.21500 82.4 17.6 45.82000 80.9 19.1 64.92500 80.5 19.5 84.43000 81.0 19.0 103.4100% replacement value (in cycles) = total cycles (interval % last loss) (cumulative % loss - 100%)_SAE J

38、445 Reaffirmed AUG2013 Page 6 of 75.4 Transmitted Energy Arc Height TestThe purpose of this test is to evaluate the consistency of thetransmission of the kinetic energy of the moving shot particles into useful energy to the work surface. Someshot testing machines are designed to locate a standard te

39、st strip in the particle blast stream inside themachine. The use of the standard test strips to monitor shot peening intensities (energy transformation) isdiscussed in SAE J442, J443, and other references on shot peening. The standard test strip curvaturedeveloped when the strip is impacted by the s

40、hot being tested can be used as a measure of the energytransmitted to the strip by the shot being tested.5.4.1 EXAMPLE PROCEDUREa. Using a sample splitter, carefully split the operating mix of used shot from the last interval in 5.2, orfrom 5.3, to obtain a sample of 50.0 g 0.1 g.b. Place the sample

41、 from (a) into the test machine.c. Place a standard test strip in the test machine fastened to the test strip holder per SAE J442.d. Peen the standard test strip for 40 cycles.NOTE40 cycles may not represent standard test strip saturation for all shot sizes. It may be necessary todevelop a full satu

42、ration curve, per SAE J442, to fully understand the performance of the shot beingtested.e. Remove the standard test strip and measure the arc height of the strip per SAE J442.f. The results indicate transmitted energy for the given exposure time. Compare results with resultsobtained on previous ship

43、ments of production lots of the same material. If the arc height is equal to orgreater than that achieved using the reference material, the shot is acceptable. If not, the shot issubject to further testing.PREPARED BY THE SAE SURFACE ENHANCEMENT DIVISION OF THE SAE FATIGUE DESIGN AND EVALUATION EXECUTIVE COMMITTEE_SAE J445 Reaffirmed AUG2013 Page 7 of 7