A fracture mechanics analysis of asperity cracking due to sliding contact

Microfracture of surface protrusions residing on contacting surfaces, known as asperities, due to normal and shear surface traction occurs at various scales affecting the durability and performance of many mechanical components. In this study, microfracture of an asperity due to sliding against a rigid asperity was examined using a two-dimensional (plane strain) finite element model and linear elastic fracture mechanics. The effects of the asperity interference depth, sliding friction, crack position, and crack-face friction on the rate, direction, and dominant mode of crack growth were determined by the ranges of the maximum tensile and shear stress intensity factors. The asperity interference depth and sliding friction exhibited the most pronounced effects on the rate and direction of crack growth. A transition from shear to tensile dominant mode of crack growth was encountered with increasing asperity interference depth and/or sliding friction coefficient. Crack mechanism maps revealing the evolution of opening, slip, and stick between the crack faces are presented for a range of crack-face friction coefficient, asperity interference depth, and sliding friction coefficient. The simulation results provide insight into the underlying microfracture mechanics of asperities residing on sliding surfaces that exhibit different friction characteristics. (C) 2019 Elsevier Ltd. All rights reserved.