Spatially Resolved Temperatures in Inhomogeneous and Continuously Changing Disk Brake Interfaces 2011-01-2347

Widely known is the fact that friction and wear characteristics of disk brakes are subject to pronounced temperature dependencies. For systems with organically bound brake pads, many thermally induced material changes can occur, ranging from degassing of the phenolic resin binder up to degradation of fibers and melting of metallic components. All these effects modulate the surface structure between pad and disk. They are a major contributor to friction layer dynamics [1] and directly influence the system's performance.

Concerning the calculation of contact temperatures in disk brakes, several attempts have been made in the past. Most of them, however, use drastic assumptions (e.g. homogenous materials and ideal contact), which limit the results to qualitative approximations [2]. Recent studies already include the multi-material structure of brake pads. These give indications on how material mixtures must be changed, in order to modify contact temperatures into a certain direction [3].

This paper goes one important step further and introduces a numeric model, which is also capable to account for dynamic changes of the surface topography and chemistry during the actual friction process. It uses a new finite volume scheme for the situation of a rough pad sliding against a rotating disk, which is deduced from the problem of a point source as reference solution [4]. The algorithm can be fitted directly into existing and future cellular automata models for the friction layer dynamics [1], giving spatially resolved information on the temperature field for different surface structures. With this method, new approaches concerning the description and explicit prediction of temperature-dependent friction phenomena are possible. Selected sample problems will be discussed.