A Basic Definition of Wear

It can be deduced from empirical evidence that the mechanical wear of solid bodies requires the simultaneous presence of these four physical conditions (a) there must be at least two separate and distinct bodies, each with its own bounding surface (fa) these bodies must be in mutual contact over some portion of their surfaces (t) the bodies must be loaded together by a force (d) there must be motion of one contacting surface relative to the other. If these conditions are fulfilled and an irreversible change is observed in the size or the shape of either or both of the bodies, then we conclude that the one or the both of the bodies has suffered wear. 

This is our definition of mechanical wear. It is essentially phenomenological, and in contrast to a purely conceptual model based on a pKlon. assumptions and inexorable logical reasoning, the governing conditions and conclusions of this definition are in terms of observable behavior. Nevertheless the definition is fundamental enough to fit all 

By removing the restriction that all the participating bodies must be solid the scope of the definition can be extended to include cases such as the removal of material by impingement of a liquid, either as a stream or in discrete drops. Some semantic disagreements arise between this extended sense of the definition of wear and traditional points of view, but these do not affect the application of the definition to the behavior of solid bodies. 

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