Phenomenological Approach to the Automotive Disc-Scoring Phenomena Related to Metal Pick Up Generation on Brake Pad Surface

This study investigates two evidences we observe from the field about metal pick up (MPU) generation on passenger car disc brake pads. The first evidence is that Low-steel (LS) materials usually present MPU issues in wet conditions whereas NAO materials mainly give MPU in dry conditions. A deep energy dispersive X- ray fluorescence (XRF) analysis is performed on LS brake pad surface after wet and dry MPU car testing, while a DoE on NAO material is carried out in order to investigate the effects of some compound on dry MPU generation. On the basis of our results, and according to previous literature works, dry and wet MPUs generation mechanisms are proposed. The second evidence is that some rotors are more prone to MPU generation than others. Vehicle and dyno MPU generation tests have been performed on different rotors using the same brake pad material: a first microstructural analysis of the rotors is reported.