Effect of interface edge angle on stress distribution near the interface edge of bonded dissimilar materials

Abstract

This study investigates the effects of interface edge configuration on the stress distribution near the edge of a ceramics/metal joint system interface using numerical thermal elastoplastic analysis. Finite element bonded dissimilar models were employed, which consisted of an elastic material to represent the ceramics and an elastoplastic material in the case of the metal. In this finite element method (FEM) study, it was assumed that silicon nitride and nickel were bonded at high temperatures and cooled slowly. The thermal elastoplastic behavior on the free surface of the ceramic side near the edge of the interface was determined numerically. The dependence of thermal elastoplastic behavior on geometrical interfacial configuration was also clarified numerically using FEM models with various interface edge configurations. Results of the numerical analysis were compared with the dependence of practical tensile bonding strength on the interface edge angle of a silicon nitride/nickel joints system bonded at 780°C, with the same interface shape as that of the analytical model. The practical tensile bonding strength was improved by setting the optimum interface shape. The optimum interface shape was obtained by determining the effects of the interface wedge angle on practical tensile bonding strength. Results of thermal elastoplastic analysis for the FEM model and fracture patterns suggest that an appropriate interface shape can reduce thermal residual stress near the interface edges on the ceramic side.