Effects of Steel Fibers and Surface Roughness on Squealing Behavior of Friction Materials

Noise in vehicle is induced by compounds and surface characteristics particularly in the friction contact. The purpose of the present work is to study the influence of brake pads containing steel fibers as well as to relate surface roughness on the generation of brake squeal. Two brake pads, steel fiber-free and with steel fiber materials, were studied. It was shown that both the materials generated squeal noise at frequency between 7 and 10 kHz but with a slight difference in humidity and friction coefficient. This difference was attributed to the tribological aspects of the friction material. It was also found that the pad surface roughness played a significant role towards the generation of brake squeal. For the sample without steel fibers, it was evident that the surface was neither covered by compacted third bodies nor contact plateaus were evident. However, for the other sample, the internal structure and the topography showed several cracks.