SAE J 840-2017 Test Procedures for Shear Strength of Automotive Brake Pads and Brake Lining Assemblies.pdf

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4、70 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/standards.sae.org/J840_201711 SURFACE VEHICLE RECOMMENDED PRACTICE J840 NOV2017 Issued 1962-11 Revised 2017-11 S

5、uperseding J840 AUG2007 Test Procedures for Shear Strength of Automotive Brake Pads and Brake Lining Assemblies RATIONALE The methodology for establishing percent material retention has been updated to directly identify an objective measurement technique. This allows for future test practitioners to

6、 generate comparable percent retention measurements between different locations. Percent material retention is a critical element to quantify as a part of the shear strength test procedure. TABLE OF CONTENTS 1. SCOPE . 2 1.1 Purpose 2 2. REFERENCES . 2 2.1 Related Publications 2 2.1.1 ISO Publicatio

7、n 2 2.1.2 JIS Publication . 2 3. DEFINITIONS 3 4. EQUIPMENT 3 5. TEST FIXTURES AND SAMPLE PREPARATION 3 5.1 Sampling and Sample Preparation 3 5.2 Drum Brake Shoes Fixture . 4 5.3 Disc Brake Pads Fixture. 4 5.4 Test Coupons and Fixtures 5 6. SHEAR TEST PROCEDURE FOR DISC BRAKE PADS AND DRUM BRAKE SHO

8、E ASSEMBLIES . 6 6.1 Ambient Destructive Shear Test Procedure. 6 6.2 Hot Destructive Shear Test Procedure 6 6.3 Temperature Degradation Shear Test Procedure . 7 7. SHEAR FAILURE ASSESSMENT . 7 8. TEST REPORT 8 9. NOTES . 9 9.1 Revision Indicator . 9 SAE INTERNATIONAL J840 NOV2017 Page 2 of 14 Append

9、ix A Cotton tack test 10 Appendix B State-of-cure test 11 Appendix C Image and grid methods to assess friction material retention . 14 Figure 1 Bond plane shear test - drum brake . 4 Figure 2 Disc brake shear test fixture 4 Figure 3 Disc brake shear test equipment . 5 Figure 4 Disc brake shear test

10、fixture offset . 5 Figure 5 Draft angle (exaggerated) for movable ram . 5 Figure 6 Drawing of thermocouple location - drum brake 6 Figure 7 Drawing of thermocouple location - disc brake 7 Figure 8 Standard layers to assess bond fracture see item 8.12 for description . 8 Table 1 Disc brake soak tempe

11、rature and time 7 Table 2 Drum brake soak temperature and time 7 1. SCOPE This SAE Recommended Practice covers equipment capabilities and the test procedure to quantify and qualify the shear strength between the friction material and backing plate or brake shoe for automotive applications. This SAE

12、Recommended Practice is applicable to: bonded drum brake linings; integrally molded disc brake pads; disc brake pads and backing plate assemblies using mechanical retention systems (MRS); coupons from drum brake shoes or disc brake pad assemblies. The test and its results are also useful for short,

13、semi-quantitative verification of the bonding and molding process. This Recommended Practice is applicable during product and process development, product verification and quality control. This Recommended Practice does not replicate or predict actual vehicle performance or part durability. 1.1 Purp

14、ose The purpose of this test is to quantify the load required to cause a shear failure at the interface of the friction material and backing plate or brake shoe. The test also provides a qualification of the failure mode on the assembly at the different layers or components. Test parts can be of dif

15、ferent types and in different conditions: new or used from vehicle or inertia-dynamometer test, prototype or production, complete assemblies or segments, and with or without special treatment like thermal, environmental or corrosion exposure. 2. REFERENCES 2.1 Related Publications The following publ

16、ications are provided for information purposes only and are not a required part of this SAE Technical Report. 2.1.1 ISO Publication Copies of these documents are available online at http:/webstore.ansi.org/. ISO 6312:2001(E) Road vehicles Brake linings Shear test procedure for disc brake pad and dru

17、m brake shoe assemblies 2.1.2 JIS Publication Available from Japanese Standards Association, 4-1-24 Akasaka Minato-ku, Tokyo 107-8440, Japan, Tel: +81-3-3583-8005, www.jsa.or.jp. JIS D4422-1990 Shear Strength Test Procedure for Drum Brake Shoe Assemblies and Pads for Automobiles (Reaffirmed: 1995) S

18、AE INTERNATIONAL J840 NOV2017 Page 3 of 14 3. DEFINITIONS 3.1 COUPON Segment cut from a larger original drum shoe or disc pad. 3.2 OFFSET Distance measured from the exposed surface of the backing plate to the shear ram edge. See Figure 4. 3.3 MECHANICAL RETENTION SYSTEM (MRS) Attachment method where

19、 mechanical protrusions on the backing plate aid the retention of the friction material or the underlayer. 3.4 NORMAL LOAD Fixed load perpendicular to the shear load for disc brake pads or flat coupons. 3.5 SHEAR FAILURE Shear failure is an observable movement of the friction material or complete sh

20、ear from the backing plate or brake shoe. 3.6 SHEAR LOAD Peak load observed during the test at the time of a shear failure. 3.7 SHEAR STRENGTH Force per unit area of the shear load divided by the sample or coupon area at the attachment layer. 4. EQUIPMENT The equipment for performing this test shall

21、 be a compression, tensile, or similar (shear) test machine with the following minimum capabilities: 4.1 Provide a fixture that holds the disc brake pad or shoe assembly firmly 4.2 System or mechanism to provide a normal load of 0.5 N/mm2 0.15 N/mm2 (72.5 psi 22 psi) at right angle to the shear load

22、 on the friction material face for disc brake pads. Note that force application is dependent on pad area at the backing plate. 4.3 Movable ram to apply shear load to the friction material at a constant speed rate of 10 mm/min 1 mm/min (0.40 0.04 in/min) or constant load rate 4500 N/s 1000 N/s (1000

23、lbf/s 225 lbf/s); hand-operated pumps or shock loads are not allowed 4.4 Generate a constant ram speed or loading rate from zero (0) load to a load sufficient to shear the friction material from the backing plate or brake shoe 5. TEST FIXTURES AND SAMPLE PREPARATION 5.1 Sampling and Sample Preparati

24、on Perform a visual inspection of the samples prior to testing. Remove shims, clips, or nibs to ensure proper contact and squareness on the test fixture. When testing using field-returned or tested parts, verify parts for appropriate flatness and parallelism. Perform surface grind if necessary. Unle

25、ss otherwise specified for the project, test five samples. SAE INTERNATIONAL J840 NOV2017 Page 4 of 14 5.2 Drum Brake Shoes Fixture Use a movable ram that contacts the edge of the lining for its full length and thickness within 1 mm 0.2 mm (0.040 inch 0.008 inch) of the shoe table or rim; See Figure

26、 1. The ram shall contact the lining on its entire width in the direction of the shear load. Apply the load in a direction perpendicular to the plane of the shoe web; support the shoe to maintain uniform loading along the length of the lining or segment; avoid distortion of the shoe table or shoe we

27、b during the test. Figure 1 - Bond plane shear test - drum brake 5.3 Disc Brake Pads Fixture Use a movable ram that contacts the edge of the lining for its full length and thickness within 1 mm 0.2 mm (0.040 inch 0.008 inch) of the backing plate. The movable ram shall conform adequately to the linin

28、g edge contour to avoid crushing of the lining edge prior to failure. See Figures 2 through 5. The ram shall contact the lining edge along the axis perpendicular to the ram travel direction. Other offsets different from 1 mm 0.2 mm (0.040 inch 0.008 inch) are acceptable to accommodate different atta

29、chment systems like MRS. Document and report the actual offset if different from the standard value. Figure 2 - Disc brake shear test fixture Loa d c ell M ov able ramH y dra uli c c y linderw ith tr av el m eas uring dev ic eLV DTTes t s ampleSAE INTERNATIONAL J840 NOV2017 Page 5 of 14 Figure 3 - D

30、isc brake shear test equipment Figure 4 - Disc brake shear test fixture offset Figure 5 - Draft angle (exaggerated) for movable ram 5.4 Test Coupons and Fixtures Use coupons when the drum brake shoe or disc pad assembly is too large to accommodate on the machine without modifications or when the she

31、ar load exceeds the machine capability. For brake shoe assemblies make saw cuts in the loading direction to isolate the segment from the rest of the lining; be sure to cut through the friction material and into the shoe rim. For large disc brake pad assemblies or disc brake assemblies using MRS, cut

32、 a coupon as large as feasible to obtain a symmetrical shape along the loading axis. For assemblies using MRS it is acceptable to apply the load in the same direction as the pattern orientation. Document and report the actual loading direction relative to the hook formation. S h e a r ra mc y li n d

33、e rLVDTLoad c e llN o rm a l o r s id e loa dc y li n de rM o v a b le ra mT e s t s a m p le h o ld e rS ID E V IEWN o rm a l o r s ide lo adM o v a b le ramD ra ft a n g le onb ra k e p adM o v a b le ramT e s t s ampleSAE INTERNATIONAL J840 NOV2017 Page 6 of 14 6. SHEAR TEST PROCEDURE FOR DISC BR

34、AKE PADS AND DRUM BRAKE SHOE ASSEMBLIES 6.1 Ambient Destructive Shear Test Procedure 6.1.1 Place and secure the sample on the fixture. 6.1.2 Apply the normal load 0.5 N/mm2 0.15 N/mm2 (72.5 psi 22 psi) at right angle to the shear load when testing disc brake pad assemblies. 6.1.3 Apply shear load at

35、 constant speed or constant load rate after the ram is in contact with the lining edge. 6.1.4 Continue applying load until shear failure occurs. 6.1.5 If partial shear occurs, check the fixture alignment and repeat the test using a new sample. 6.1.6 Record the maximum load attained in N or lbf. 6.1.

36、7 Assess and record the percent distribution of material in the shear plane per item 7. 6.1.8 When requested, determine the approximate adhesive state-of-cure using the Cotton Tack Test (See Appendix A). 6.2 Hot Destructive Shear Test Procedure 6.2.1 Place the disc brake pad or brake shoe assembly o

37、r segment in a heating fixture or oven that will bring the sample bondline to 200 C 5 C (392 F 10 F) within 30 minutes for drum brake shoes and 300 C 5 C (572 F 10 F) within 30 minutes for disc brake pads. 6.2.2 Within 1 minute after reaching the bondline temperature, place the assembly or segment o

38、n the shear test fixture and test per item 6.1. NOTE: The heating fixture may be part of the test equipment or external to it. The shear test fixture may be heated along with the test assembly or coupon. If heating external to the shear test fixture, the bond temperature must be no lower than 10 C b

39、elow the target test temperature at the time of shear failure. Do not hold the sample at temperature for more than 1 minute. Use a thermocouple to measure the temperature at the bond line as shown in Figure 6 for Drum Brake and Figure 7 for Disc Brake. This test is performed primarily to ensure prop

40、er cure of the adhesive. Figure 6 - Drawing of thermocouple location - drum brake D ri ll h o le f o r th e rm o co u p le. L o c a te th e rm o co u p le n e a rth e c e n te r o f th e linin gSAE INTERNATIONAL J840 NOV2017 Page 7 of 14 Figure 7 - Drawing of thermocouple location - disc brake 6.3 T

41、emperature Degradation Shear Test Procedure 6.3.1 Preheat the oven to the test temperature indicated for the project. Use temperatures from Table 1 for disc brake pad assemblies and Table 2 for drum shoe assemblies. Table 1 - Disc brake soak temperature and time Soak Temperature Soak Time 267 C (500

42、 F) 24 hours 315 C (600 F) 6 hours 427 C (800 F) 2 hours 538 C (1000 F) 2 hours Table 2 - Drum brake soak temperature and time Soak Temperature Soak Time 149 C (300 F) 24 hours 204 C (400 F) 24 hours 267 C (500 F) 12 hours 315 C (600 F) 2 hours NOTE: Select the soak temperatures based on the tempera

43、tures expected at the lining/shoe interface during use for the application. Low conductivity (organic or non-asbestos organic) linings typically experience lower bond line temperatures than high conductivity linings (semi-metallic). For disc brake pad assemblies, the 427 C (800 F) and the 538 C (100

44、0 F) are optional for applications with high operating temperatures. For drum shoe assemblies, the 267 C (500 F) and the 315 C (600 F) are optional for applications with high operating temperatures. 6.3.2 After completion of the soak time, remove the disc brake pad or brake shoe assembly or segment

45、and let it cool down to room temperature. 6.3.3 Place the assembly or segment on the shear test fixture and test per item 6.1. 7. SHEAR FAILURE ASSESSMENT Report the percentage of retention at each of the layers applicable to the assembly. On the test report indicate the layer followed by the corres

46、ponding percent retention. See Figure 8. D ri ll h o le f o r th e rm o co u p le. L o c a te th e rm o co u p le n e a rth e c e n te r o f th e linin gSAE INTERNATIONAL J840 NOV2017 Page 8 of 14 Figure 8 - Standard layers to assess bond fracture see item 8.12 for description 8. TEST REPORT Include

47、 the following information unless otherwise specified by the test requestor: 8.1 Test part identification and batch number. 8.2 Number of samples tested. 8.3 Sample type (complete assembly or coupons). 8.4 Constant speed rate or constant load rate and value. 8.5 Normal load applied (yes/no). 8.6 Sam

48、ple area at shear plane. 8.7 Load orientation relative to the MRS pattern orientation (optional). 8.8 Special sample treatment prior to shear test and description (vehicle test, inertia-dynamometer test, thermal soak, environmental, corrosion, or other). 8.9 Temperature and soak time for hot destruc

49、tive test or temperature degradation shear test procedure. 8.10 Minimum, average, and maximum shear load for multiple samples. 8.11 Minimum, average, and maximum shear strength for multiple samples. 8.12 Description of shear failure and assessment of material retention in percent area per item 7: 8.12.1 Layer 1: adhesion failure (bare metal) between brake shoe meta