A mismatch of different material properties in joints may cause stress singularities, which lead to the failure of the bonding part. It is very important to reveal a stress singularity field for evaluating the strength of interface in three-dimensional joints. Furthermore, thermal residual stresses occur in a cooling process after bonding the joints, and the stress singularity for thermal stress 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 fundamental solution for two-phase isotropic 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 applying an external force for debonding the joints 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 mechanical force and the residual thermal stress yields a final stress distribution for evaluating the strength of interface. Finally, a relationship of force for delamination in joints with different bonding areas is derived.

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