Mechanical brakes are safety-relevant components of motor vehicles. Drivers are therefore dependent on this component, which should fulfill its task reliably in all conceivable driving situations. For this reason, brakes are subjected to performance tests, in which friction dynamics play an important part. Over the last 20 years, intensive researches have been conducted to find out more about the phenomena involved in those friction dynamics. It has been shown, that time-variant contact surfaces in the tribological boundary layer of brakes contribute significantly to the friction performance. The evolution of these contact surfaces is essentially influenced by heat and wear dust development. It can be described by balance equations and be modelled by spatially resolved simulation tools. After friction dynamics, the need for time-resolved wear predictions is now getting into the focus of research activities. Wear measurements with high-precision optical measuring tools at the Institute of Dynamics and Vibrations have shown that the wear intensity has its own time dynamics. It seems to be particularly dependent on the so-called reservoir dynamics – the filling and emptying of surface cavities in the friction contact.
Jacek Kijanski, Institute of Dynamics and Vibrations, TU Braunschweig, Germany; Georg-Peter Ostermeyer