Stress analysis near a small crack within singular stress field in a three-dimensional bonded joint under a tensile load

Abstract

Stress singularity usually occurs at a vertex of interface in a three-dimensional joint. Crack frequently initiates at a vertex and a joint fails under an external force and a thermal load. In the present paper, stress distribution near a small crack occurring at a vertex in a three-dimensional joint is investigated under a tensile load, and stress intensity factor at the crack tip are determined along the crack tip front. The joint is composed of Si and resin. In the analysis, three kinds of crack shape, triangular, quarter circular and concave shapes, are supposed as an initial crack shape. Stresses are normalized using the singular stress around the vertex since the crack exists in the stress singular field. The stress intensity factor in the quarter circular crack increases and that in the others decreases as approaching side surfaces. The quantity of energy release due to a crack initiation is calculated using relative displacements of the crack and the stress distribution of singular stress field. The quantity for the concave shape crack is the largest in the three kinds of crack shape.