Rubber friction: role of the flash temperature

Abstract

When a rubber block is sliding on a hard rough substrate, the substrate asperities willexert time-dependent deformations of the rubber surface resulting in viscoelastic energydissipation in the rubber, which gives a contribution to the sliding friction. Most surfaces ofsolids have roughness on many different length scales, and when calculating the frictionforce it is necessary to include the viscoelastic deformations on all length scales. The energydissipation will result in local heating of the rubber. Since the viscoelastic properties ofrubber-like materials are extremely strongly temperature dependent, it is necessary to includethe local temperature increase in the analysis. At very low sliding velocity the temperatureincrease is negligible because of heat diffusion, but already for velocities of order10−2 m s−1 the local heating may be very important. Here I study the influence of the localheating on the rubber friction, and I show that in a typical case the temperatureincrease results in a decrease in rubber friction with increasing sliding velocity forv>0.01 m s−1. This may result in stick–slip instabilities, and is of crucial importance in manypractical applications, e.g. for tyre–road friction and in particular for ABS brakingsystems.