Sliding friction and contact mechanics of elastomers on rough surfaces

Abstract

The modeling of rubber frictional properties on rough surfaces is of considerable importance for the prediction of tire traction properties. The presented work consists in a physically based model describing the dynamic contact and the sliding friction of elastomers on rough surfaces. The self-affine character of rough substrates is analytically treated with correlation functions which depend on three surface descriptors. This allows a generalization of the concepts introduced by Greenwood and Williamson and a quantitative estimation of the velocity dependent real area of contact. The hysteresis friction can be modelled in the frame of this theory, originating from the energy losses due to the local deformation of the rubber from the surface asperities during dynamic contact. The experimental results show that the frictional behaviour under wet conditions is fairly described by the hysteresis friction. The transition from wet to dry friction is explained via an adhesion component assumed to be related with the real area of contact. This approach is also confirmed by the experiment and gives a deeper insight in the relationship between the material viscoelastic properties, the surface roughness and the frictional behavior.