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

Abstract

A mismatch of different material properties may cause stress singularities, which lead to the failure of the bonding part in joints. It is very important to analyze a stress singularity field for evaluating the strength of interface in three-dimensional joints. Thermal residual stresses occur in a cooling process after bonding the joints, and the stress singularity for thermal stresses also occurs. In the present study, a boundary element method and an eigen value analysis based on finite element method are used for evaluating the intensity of stress singularity. Three-dimensional boundary element program based on the foundamental solution for two-phase isotoropic body is used. The strength of interface in two kinds of Si-resin specimen with different bonding area is investigated analytically and experimentally. Stress singularity analysis for acting a delamination force to the specimen is firstly carried out. After that, stress singularity field for the residual stresses varying material property in resin with temperature is determined. Combining the stress singularity fields for the delamination force and the residual thermal stress yields a final stress distribution for evaluating the strength of interface. Finally, the strength of interface in three-dimensional joints was determined as 0.0914-0.133 MPa·m0.68.