On the dynamics of the friction coefficient

The paper deals with the principal wear mechanism in brake systems and introduces a new dynamical model of the friction coefficient, where necessarily both friction and wear are taken into account. This model explains many open questions on the principal functionality of brake systems. In brake systems, characteristic structures are formed in the contact area by the flow of wear particles. Modulated by the friction power the wear particles are used by the system to build up hard contact patches on the brake pad. Nearly all energetic dissipation of the system is concentrated on these patches. By wear, these contact patches are destroyed after some time. So the friction coefficient is given by the equilibrium of flow of birth and death of contact patches. The resulting dynamical model describes the dynamical behaviour of the friction coefficient and the dependence of the temperature in the friction layer. This theory explains the fading effect of brake systems as well as complex hysteretic effects in the diagram of the friction coefficient versus the velocity, known from instationary measurement procedures. The structure of this theory seems to be quite general to describe other frictional systems too.