The Dissipation of Frictional Energy from the Interface of an Annular Disc Brake

Abstract

The performance of resin bonded composite friction materials in a particular brake design is strongly dependent upon the dissipation of frictional heat from the interface. This energy transformation has been studied using finite element techniques for a simulation of the braking friction process in an annular disc brake, which combines both brake performance and brake temperature analysis and avoids many of the assumptions necessary in conventional analyses. Negligible amounts of energy interchange, compared with the total kinetic energy dissipated, arise from chemical reactions within the friction material, but the formation of surface layers and interfacial wear products do have a significant effect upon heat transfer from the interface. Calculated temperature distributions over individual brake applications indicate that interface contact resistance leads to different temperatures at the surfaces of disc and lining so that heat partition between the two mating bodies cannot realistically be assumed constant under braking conditions. The distribution of frictional heat generation over the interface is dependent upon interface pressure distribution and is therefore also affected by material wear and thermal expansion. These effects are incorporated in the analysis, and calculated temperature, interface contact and pressure, and wear distributions are compared with observed and measured experimental results from an annular brake rig.