An Evaluation of Interface Strength at a Vertex in a Three-Dimensional Joint Considering Residual Thermal Stresses Using the Three-Dimensional Boundary Element Method

Abstract

Dissimilar material properties may cause stress singularities, which may lead to the failure of the bonding part in joints. It is important to analyze stress singularity fields in order to evaluate the strength of the interface in three-dimensional joints. Thermal residual stresses occur during cooling after bonding of the joints, and stress singularities can also be caused by these thermal stresses. In the present study, a boundary element method and an eigenvalue analysis based on the finite element method are used to evaluate the intensity of the stress singularity. A three-dimensional boundary element program based on the fundamental solution for two-phase isotropic materials is used. The strength of the interface of two types of Si-resin specimens with different bonding areas is investigated analytically and experimentally. Stress singularity analysis is first carried out for a delamination force acting on the specimen. The stress singularity field for the residual stresses is determined while varying the material property in resin with temperature. Combining the stress singularity field for the delamination force and the residual thermal stress yields a final stress distribution for evaluating the strength of the interface. Finally, the strength of the interface in three-dimensional joints was determined as 0.0914-0.133 MPa·m^0.68.