Comparison of hysteric and adhesive coefficient of friction for rubbers sliding onto self-affine rough surfaces

In this paper we investigate the influence of both the hysteric and adhesive friction for rubber surfaces sliding on self-affine rough surfaces. This type of roughness is described by the roughness amplitude w, the in-plane correlation length ξ, and the roughness exponent H that characterizes the degree of surface irregularity at short length scales (<ξ). It is shown that beyond the typical roughness parameters w and ξ, which are usually used in describing rough surfaces, the influence of the roughness exponent H should be taken carefully into account in order to properly gauge the contributing frictional mechanisms. Indeed, it is shown that for large roughness exponents (H∼1) and/or small roughness ratios w/ξ<10−2, the adhesive friction becomes significant at relatively high sliding velocities beyond the maximum of the hysteric component