Adhesion and friction in hard and soft contacts: theory and experiment

Abstract This paper is devoted to an analytical, numerical, and experimental analysis of adhesive contacts subjected tangential motion. In particular, it addresses the phenomenon instable, jerky movement boundary contact zone its dependence on surface roughness. We argue that “adhesion instabilities” with instable movements cause energy dissipation similarly elastic instabilities mechanism. leads different effective works adhesion when area expands contracts. effect interpreted in terms “friction” boundary. consider two main contributions friction: (a) line contribution (b) contribution. normal rolling contacts, only due friction, while sliding both may be present. The prevails very small, smooth, hard (as e.g., diamond-like-carbon (DLC) coatings), prevailing large soft contacts. Simulations suggest friction governed by “Johnson parameter”. Experiments for bodies like rubber, stresses can characterized a constant critical value. were carried out using setup allowing observing camera placed under transparent rubber layer. Soft show great variety low velocity — depending indentation depth shape contacting bodies. These classified as “microscopic” caused roughness or chemical inhomogeneity surfaces “macroscopic” which appear also smooth latter related interface waves are observed at small depths. Numerical simulations performed Boundary Element Method (BEM).