New insights into the tribology of brake systems

Abstract

In spite of remarkable efforts the perfect brake pad in terms of friction performance, wear, noise, and costs has not been found to date. This is mostly because the development is still based on the extensive ‘trial-and-error’ method, as a reliable reproduction or even prediction of those issues is still not possible. A theory regarding the interaction of friction and wear in the interface shows that the tribological behaviour of the system is determined by the growth and destruction of characteristic hard structures (‘patches’) on a mesoscopic length scale. A respective equilibrium of flow taking into account that the main part of the friction power is transmitted by the patches leads to a physically derived dynamic friction law. This paper shows the results that can be gained using this sophisticated law and how it explains several measured phenomena on different timescales. Based on this assumption a cellular automaton model is introduced where the choice of its inner variables and its boundary conditions allows a description of the processes in the interface, as a matter of principle. The paper deals with the formulation of the rules considering the interactions between the patches, friction, wear, and temperature and the resulting dynamic effects. The rules are derived from physical laws and measurements. The occurring timescales according to this model are pointed out and a method towards the problem's simplification with the help of specific algorithms is presented.

Overview of disc brakes and related phenomena - a review

“…This behavior can be attributed to many factors. As the temperature and pressure increases during a brake, secondary plateau can grow [17,37]. It also highlights flattening of primary contact plateau surface due to plastic yielding and wear.…”

“…From functional and safety point of view following demands are put on the behavior of friction materials [17,37,38] • High coefficient of friction…”

“…These contact plateaus constitute about 10-20% of the apparent pad surface area [45]. It is supposed that main energy conversion happens at these plateaus [37]. The second approach [38,56,64,65,60] relates the brake performance to the third body layers formed during brake Figure 15: Schematic representation of the first approach showing the primary and secondary contact plateaus, according to [58,17].…”

“…Now some tribological aspects of disc-pad systems which are peculiar to disc brakes will be described. This description is mostly based on the previously published works [45,63,17,38,56,37,67]. In these works friction materials of different compositions were used so some of the phenomenon described here could not be valid for all other materials as also explicitly mentioned in [17,67].…”

Cellular Automata (CA) for Simulations of Complex Geothermal Reservoirs

“…The cellular automata are recently developed and implemented for many complex scientific problems, physical, chemical, biological and in engineering [1,2]. The cellular automata are the discrete modeling method.…”