Validation of Compressibility Test Systems for Friction Materials
This SAE Recommended Practice (RP) applies to the validation process for test systems used to measure deflection (compressibility, creep, or swell and growth) of friction materials and friction material assemblies. The materials or assemblies can fit passenger cars, light trucks, and commercial vehicles equipped with hydraulic or air brake systems, using disc or drum brakes.
Within any acceptable quality assurance program, the systematic validation of the test system and gage repeatability and reproducibility (Gage R&R) are of primary importance. Manufacturing or product data is only as good as the instruments that evaluate processes or measure products. Therefore, it is of primary importance to ensure that measurement devices are adequate for the required measurements within a manufacturing control plan.
This SAE Recommended Practice (RP) uses three main steps:
Assessment of test system using a predefined checklist to verify main features and control capabilities with deflection profile evaluations.
Measurement of actual deflection using standard proving rings (also known as the standard judge and soft judge).
Gage R&R using actual pads following a pre-selection process.
Using test systems which satisfy the statistical limits and acceptance criteria established in this RP, in addition to any agreed-upon requirements between the testing system supplier and the test system user, provides a robust method to ensure valid and relevant test results.
This RP accompanies and supports the SAE Surface Vehicle Standards SAE J2468 and SAE J3079-2.