Brake disc corrosion has emerged as an important field of study within the automotive industry due to the wide range of lining materials that are currently used worldwide, and their inherent rust-cleaning properties. The presence of oxide layers irregularly deposited on the cast iron disc surfaces usually leads to a forced, braking-induced vibration that can reach the driver’s position as a pronounced annoyance. Hence, the friction material composition directly impacts on the judder performance during the early corrosion-removal stage.
This study incorporates both dynamometer and vehicle tests into the definition of a predictive methodology that allows corrosion-induced vibrations to be investigated at both system and vehicle levels. The oxide film is artificially generated by means of a salt spray chamber under steady-state climate conditions in order to guarantee a repetitive and robust procedure. The vibration response of the system is objectively evaluated in the form of caliper accelerations and pressure (BPV) / torque (BTV) oscillations throughout a reduced rust-removal test sequence composed of 30 snubs; basic spectral and order analyses are conducted with the gathered data. Furthermore, vehicle-based results are correlated with the subjective ratings that an expert driver gives to the different vibrations perceived at chassis level. The in-service roughness of the oxide layer, on the other hand, is indirectly monitored by using a couple of non-contacting capacitive sensors that measure the variation in disc thickness (DTV).
Ultimately, this paper is intended to characterize the inherent corrosion-cleaning capability of different friction materials -paying special attention to the presence of copper-, as well as revealing their impact on the vehicle judder subsequently induced during the actual removal of the oxide layers.