An exploration of debris types and their influence on wear rates in fretting

Abstract

This thesis reports on the design and subsequent use of several experiments, to explore the role of debris particles in fretting wear. In these experiments, crossed-cylinder and annulus contacts were employed to study both the production criteria of debris particles, and their effects on subsequent wear mechanisms. These parameters are of importance in the development of the most promising modelling techniques. The experimental work consists primarily of two key studies. The first of these sought to explore how the measurable properties of debris particles (size, shape, elemental composition etc.), influenced the rate of wear. This was achieved through the variation of oxygen availability in the contact. The results indicated that the effect of oxide debris is strongly dependent on the material of the substrate, and that particle size, not hardness was the key debris parameter in determination of wear rates. The second key study investigated the effects of external loading of components on the rate of fretting wear. Crossed-cylinder specimens were held within clamps which applied large external stresses during wear experiments. This revealed that the wear rate was independent of axial tension, compression and torsion, indicating that only tractions should be used in the stress criterion for debris production modelling. Finally, work is described on a second apparatus designed to exploit the valuable intrinsic properties of annulus contacts, in the study of wear. This contact allows for precise control of the key variables (contact pressure and slip displacement), and is ideal for fundamental studies. A study on the effect of contact pressure on wear rate was performed which indicated a clear non-linearity in response.