The Friction and Wear of Rubber Part 2: Micro-Mechanical Description of Intrinsic Wear

Abstract

Abstract The concept of a Damage Orientation Distribution Function was introduced in Part 1 of this series to describe the transient affect on wear generated by a dynamically changing slip orientation. In this Part an analytical model of the micro-mechanical processes that occur in a slipping rubber/abrasive interface is offered and serves as the basis for a new relation for the prediction of rubber wear. The description considers the fatigue fracture processes that occur at the intrinsic nodule level. The assumption is made that each intrinsic nodule undergoes intermittent fractures which are driven by Strain Energy Release Rate levels that range from a minimum at or below the linear region of the material's Fatigue Crack Propagation curve, through the Power Law Region and finally to the catastrophic tear value. The proposed description is tested against the early data of Schallamach. It is shown that the simple relationships offered in the analytical study can be used to predict rubber wear performance over a wide range of pressures and abrasive asperity sizes. In light of this analysis, the Damage Orientation Distribution Function of Part 1 is revisited and found to be a useful tool when considering the fundamental processes that occur during unidirectional wear. Changes in slip direction are found to affect the instantaneous wear rate by affecting the Distribution Function in a different manner than changes in pressure or abrasive size. Changes in slip direction are shown to affect the population of intrinsic nodules immediately available for rupture while changes in pressure or abrasive size are shown to influence wear by changing the rate at which nodules move through the Distribution.