Effect of surface contact conditions on the stick–slip behavior of brake friction material

Brake-induced stick–slip, which determines the propensity of a brake system to generate noise, was investigated by analyzing the friction oscillation at different loads, speeds, and surface topographies. The friction characteristics at the sliding interface were obtained using a pad-on-disk type tribometer and a 1/5-scale brake dynamometer. Results showed that the size and stiffness of the surface contact plateaus significantly affect the propensity of stick–slip and wear. The stick–slip amplitude increased with normal load and decreased with sliding speed. Contact stiffness of the friction material, which was modified by producing shallow slots on the rubbing surface, also strongly affected the stick–slip propensity, whereas Δμ(=μs−μk) was not changed by the surface modification. The strong effects from the contact stiffness suggest that the height distribution of the surface plateaus can change the stick–slip propensity of a brake friction material.