Mechanisms of scratching frictions and damage maps for rubber compounds

When a hard solid slides or scratches a surface of a soft material, the frictional work is dissipated via deformation or damage of the surface. During such frictional events, the extent of deformation and damage is not only controlled entirely by the amount of the frictional work produced, but also by the process of energy dissipation. This paper attempts to provide a deeper understanding of the generic energy dissipation and damage processes for rubber compounds. Sets of specimens, which had very similar quasi-static mechanical properties but different viscoelastic properties, were carefully selected for scratching studies. The relationship between the frictional force and the observed residual damage of the surface were determined. When the contact condition was altered, various aspects of the damaged surfaces were observed with changes of the friction. Experimental results and corresponding numerical estimations suggest that the contribution of the adhesive term of the friction may be affected by the aspects of the surface damage caused by the change of the cone angle. The reported data have significance in the rationalisation of the choice of abrasion resistant elastomers.