Finite element analysis of horizontal and branched subsurface cracks in brittle materials

Abstract

Finite element analyses of a horizontal subsurface and branched crack in brittle materials, under repeated sliding contact, were performed. It was found that the horizontal crack experiences pure shear loading. Previous experimental investigation suggests that cracks in brittle materials such as monolithic ceramics propagate at angles close to 45° under pure shear loading. Thus, the horizontal subsurface crack is expected to branch at 45° to the horizontal. Finite element analysis of a branched subsurface crack at 45° to the horizontal, under sliding contact, suggests that such cracks typically experience both mode I and mode II type loading. A method has been proposed to predict the crack growth direction in brittle materials subject to mixed mode loading. The predicted direction of crack propagation agrees well with the values determined experimentally for low K I/ K II ratio. Based on the proposed method, the leading tip of the horizontal subsurface crack is expected to reach the surface before the trailing edge.