Energy Dissipation at Spherical Surfaces in Contact Transmitting Oscillating Forces

Abstract

In a previous experimental investigation the author has shown that two spherical surfaces pressed together and subject to an oscillating tangential force, however small, exhibit microscopic interfacial slip which leads to energy dissipation and surface damage in the manner predicted theoretically by Mindlin. The analysis has been extended by Mindlin and Deresiewicz to include the effect of an oscillating force whose line of action lies at an oblique angle to the surface of contact. They show that the angle of obliquity of the oscillating force has a predominant effect on the energy dissipated at the contact and that no slip or dissipation would be expected if the line of action of the force lies within the cone of friction for the two surfaces. These conclusions have been the subject of the experimental investigation reported in this paper. The theoretical predictions are supported by the observations on almost all counts. Such discrepancies as occur are shown to be due to the inadequacy of the theoretical assumption of a constant coefficient of friction to describe accurately the actual behaviour of metallic surfaces in contact which are undergoing oscillating interfacial slip and fretting whose amplitude varies throughout the contact area.