Friction characteristics of brake pads in automobile

The noise in a car brake is classified by two noises, Brake Squeal noise and Brake Groan noise. Squeal noise, normally generated in high frequency region, has been investigated from earlier, so the identification of its origin and reducing methods has been developed. On the other hand, the generation mechanism of groan noise in low frequency is not clearly identified yet, except that it is easily happened in low braking pressure and low speed and its origin is a brake vibration caused by stick-slip between disk and friction material. Stick-slip means that stick and sliding occur repeatedly between a brake disk and a friction material. Brake noise will be generated because friction force is not constant, but increase and decrease instantly like Fig.1.


Fig. 1. Variation of friction force caused by Stick-slip




Fig. 2(a). Schematic diagram of experimental apparatus


Fig. 2(b). Schematic diagram of experimental apparatus

Because stick-slip regarded as a main cause for groan noise is closely related to the characteristics of friction coefficient change, friction characteristics under various conditions such as surface temperature, humidity, and surface state should be investigated in the research of groan noise. The results of these researches are expected to provide a clue to reduction and elimination of groan noise.

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