Abstract
The structure and composition of friction films on brake pads and rotors were studied by analytical transmission electron microscopy. The observed films were only 100–500 nm thick and comprised a nanocrystalline microstructure of iron oxide mixed with minor amounts of other pad constituents. A model based on movable cellular automata was applied to simulate the situation at the pad/disc interface. The following features could be shown clearly: formation of a quasi liquid layer, velocity accommodation between the rotating disc and the fixed pad and mechanical mixing of nanoparticles from pad and disc. Furthermore, the model revealed the evolution of the coefficient of friction for different layer compositions. The nanostructure of the friction film was very important with respect to friction force stabilisation and elimination of fluctuations. The simulation results suggest that a volume fraction of 10% of a solid lubricant is essential for good brake performance.
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