Test Procedures for Shear Strength of Automotive Brake Pads and Brake Lining Assemblies
J840_200708
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 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, 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.
Rationale:
The title for this Recommended Practice has been updated to better reflect the purpose of the test, the characteristic measured (shear strength), and the specific parts where it is applicable (automotive brake pads and brake lining assemblies). The new title also facilitates internet searches, and improves the procedure description when referenced on external documents or technical specifications. Testing a drum brake shoe or a disc brake pad assembly for its shear strength is a valuable parameter during the life-cycle of a brake assembly. All friction brake assemblies have a shear loading equivalent in magnitude to the braking force that depends upon the load input perpendicular to the friction surface, the brake geometry, and the friction coefficient at the transfer layer interface. Regular braking operation also generates heat that migrates through the friction material to the backing plate or shoe rim surface. It is critical for the friction designer, the product engineer, the process manager, application engineer, or purchasing agents, to understand the shear strength and the main influencing factors that will ultimately determine the amount of shear load that the material will withstand without a mechanical failure of the assembly. This revision of the Recommended Practice increases the level of harmonization with other industry standards, allows the testing of mechanical retention systems (MRS), includes the option of testing with the movable ram at constant speed, allows the use of coupons, and improves the repeatability of the test results by introducing the application of a side load for disc brake pads.
