Asperity failure due to repetitive sliding is a common process of wear particle formation. Linear elastic fracture mechanics and the finite element method (FEM) were used to analyze asperity cracking due to sliding against another rigid asperity. The maximum ranges of the tensile and shear stress intensity factors (SIFs) were used to determine the crack growth direction and the dominant mode of fracture. Simulations of repetitive sliding showed a strong dependence of the wear particle size and wear rate on the direction and rate of crack growth. The maximum ranges of tensile and shear SIFs were used to determine the dominant mode of crack growth. The effects of asperity interaction depth, sliding friction, initial crack position, crack-face friction, and material properties on crack growth direction, dominant fracture mode, and crack growth rate are discussed in the context of FEM results. It is shown that the asperity interaction depth and sliding friction exhibit the most pronounced effects on the crack growth direction and growth rate. A transition from shear- to tensile-dominant mode of crack growth was observed with the increase of the asperity interaction depth and/or sliding friction coefficient. Crack-face opening, slip, and stick mechanisms are discussed in the light of crack mechanism maps constructed for different asperity interaction depths and sliding friction coefficients.

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