THE GENERATION OF WORN SURFACES BY THE REPEATED INTERACTION OF PARALLEL GROOVES

Whenever loaded surfaces are in relative tangential motion, hard asperities on one of them, or perhaps hard particles entrained between them, may be dragged across the softer surface and give rise to surface degradation and wear. Damage caused by individual asperity or particle interactions builds up and the profiles of the worn surfaces are the result of many superimposed wear events. The practical, quantitative prediction of wear rates, and thus of component lives, depends on having both a satisfactory understanding of individual interactions and a suitable procedure for combining these under circumstances when subsequent contacts are made on a surface whose topography and material properties may have been much changed from their initial states. Experiments have been carried out on a novel rig which provides very precise control over the position of a representative asperity and the worn surface it generates, and in this paper we describe a number of tests in which the wear arising from the repeated interaction of parallel wear tracks has been investigated. Three different regimes of wear debris production have been identified, namely micromachining, surface ductile fracture and subsurface fatigue, and the wear rates associated with each measured. An analytical model is being developed to produce a wear map appropriate to the abrasion of a metal surface. On the basis of such a map it is possible to identify the predominant wear mechanisms and predict the wear rates of real wearing surfaces.