Friction Coefficient of Automotive Friction Materials - Its Sensitivity to Load, Speed, and Temperature

Commercial “organic” friction materials were obtained from three different manufacturers, and were evaluated for their frictional properties. In all cases, the friction force (F) was found to be a power function of the normal load (P) and sliding speed (V) at a fixed temperature, F = K·P^a·V^b at T₁, where K is the coefficient of friction which is constant and independent of the load and speed, and a and b are one set of parameters at the temperature T₁. Usually, the exponent a ranges 0.80-1.25 and b from -0.25 to +0.25, depending upon the temperature. Thus, brake torque becomes a power function rather than a linear function of the line pressure. Brake fade is found to be governed by the three mechanisms-load fade, speed fade, and temperature fade.