Local failure behavior of a dissimilar metal interface region with mechanical heterogeneity

• Failure behavior of a dissimilar metal interface region was simulated and analyzed.
• Mechanical heterogeneity has obvious effects on fracture resistance and crack path.
• Local mechanical mismatch and intrinsic toughness determine fracture resistance.
• Fracture properties related to crack locations need to be used in failure analyses.

Failure analyses and assessments for dissimilar metal welded joints are usually conducted by simplified interface regions without considering actual mechanical heterogeneity and limited crack positions. In this work, the finite element simulations based on Gurson-Tvergaard-Needleman damage mechanics model are used to investigate local failure behavior of a dissimilar metal interface region with mechanical heterogeneity and a series of initial crack positions. The results show that the fracture resistance and crack growth paths of the cracks in different locations of the interface region are significantly affected by mechanical heterogeneity. The interactions of different local mechanical (strength and work hardening properties) mismatches and intrinsic toughness around cracks determine the distributions and evolution of plastic strain, stress triaxiality and damage ahead of crack tips, which cause larger variations in fracture resistance and crack growth paths. For accurate and reliable failure analyses and assessments for the cracks in dissimilar metal interface regions with mechanical heterogeneity, it is recommended to obtain and use local fracture resistance properties related to crack locations.