STRESS INTENSITY FACTORS AND CRACK INITIATION DIRECTIONS FOR CERAMIC METAL JOINT/

Four points bending tests for Si3N4/Cu/S45C joint specimen showed that the bending strengths depend on the residual stresses that originated from joining process. The residual thermal stresses caused an edge su b-interface crack to initiate in the ceramic. The stress intensity fac tors (SIFs) of the edge sub-interface crack located at distance h from the interface with or without interlayer metal were calculated by the Green's function obtained from a finite element analysis. The crack p ath at the joint specimen under four points bending loading with the i nfluence of residual stresses was also evaluated by the maximum tensil e stress criterion. Finally the effect of residual stress on the crack path was found numerically; the interlayer metal decreases the deflec tion angle of crack from interface by reducing the residual stress. (C ) 1998 Elsevier Science Ltd. All rights reserved.