What Part do Adhesion and Deformation Play in Fine-Scale Static and Sliding Contact?

Abstract

AbstractWe describe experiments involving the static or sliding contact of a 'single asperity' and a flat surface. Plastic deformation and possibly junction growth can occur even at zero applied load, as a consequence of surface forces. The conditions for this to occur, and the different modes of separation of an adhesive contact, are clarified with the help of 'maps': use of the macroscopic concepts involved, such as yield stress and work of adhesion, is sometimes questionable and evidence of the importance of nanometre-scale stepped topography is presented. Strong adhesion between hard non-metals can required thermal activation. Sliding contacts at the sub-micrometre level have shown behaviour ranging from 'unstable ploughing' to adhesive peeling, but the frictional mechanisms involved are often unclear.