Finite element analysis of subsurface crack propagation in a half-space due to a moving asperity contact

Subsurface cracking in a homogeneous half-space due to a moving asperity is analyzed using linear elastic fracture mechanics and finite element simulations. Overlapping of the crack bees and assumptions about the surface traction distribution are avoided with the use of contact elements. Emphasis is given to the direction and the rate of crack propagation due to indentation and sliding contact. The crack propagation directions in shear and tensile mode are predicted based on the maximum range of the shear and tensile stress intensity factor, respectively. The effects of crack length-to-depth ratio, friction at the contact region and the crack interface, and load history on the shear and tensile mode crack propagation directions are elucidated. The likelihood of incipient kink formation due to the tensile mechanism during in-plane shear mode crack growth is interpreted in terms of the location and the length of the crack and the coefficient of friction at the contact region and the crack interface. The rate of in-plane shear mode crack growth is examined using the maximum range of the shear stress intensity factor. Crack mechanism maps showing the occurrence of slip, stick, and opening of the crack faces versus asperity position are presented for different crack length-to-depth ratios and friction conditions. (C) 1997 Elsevier Science S.A.