Sliding wear mechanism of ductile materials – Effect of sliding direction reversal

Abstract

The work presented in this paper tries to shed more light on the mechanism by which ductile surfaces fail and leave the contact surface during loaded pure sliding contact. An extensive experimental program was designed aimed at exploring the role of plastic shear strain accumulation in surface failure. Reversing the direction of strain during testing was the main variable which was facilitated by reversing the sliding direction. Changes in structure deformation morphology and accumulated plastic strain were analyzed. The effect of different sliding direction reversal regimes during testing, compared to unidirectional sliding to the same sliding distance, was thoroughly investigated. Results came to support that plastic strain accumulation is responsible for contact surface failure and, as a result, material loss from the ductile surface during sliding. It was evident, under the test conditions used, that reversing the sliding direction at different predefined sliding distances has resulted in delaying surface failure, resulting in lower wear loss compared to that found under unidirectional sliding. Multiple strain direction reversals resulted in higher beneficial effect in delaying failure. Furthermore, the earlier the sliding reversal is carried out, the better its effect of delaying failure. Findings have been explained in terms of plastic strain accumulation that leads to failure of the surface layer after reaching a certain strain to failure limit.