Numerical Analysis of Constraint and Strength Mismatch Effects on Local Fracture Resistance of Bimetallic Joints

Abstract

In this paper, the finite element method (FEM) based on GTN model was used to investigate the in-plane/out-of-plane constraint and strength mismatch effects on local fracture resistance of A508/Alloy52Mb bimetallic joint. The J-resistance curves, crack growth paths and local stress-stain distributions in front of crack tips were calculated for cracks with different constraints and strength mismatches. The results show that the local fracture resistance of the interface crack in this joint is sensitive to constraint and strength mismatch effects. With increasing in-plane constraint (crack depth a/W), out-of-plane constraint (specimen thickness B) and strength mismatch degree, the plastic strain and stress triaxiality around crack tip increase, and the corresponding crack growth resistance decreases. The crack with strength mismatch factor M=1 displays a markedly higher crack growth resistance than the other cracks with M>1 and M<1. It also has been found that there is an interaction between in-plane/out-of-plane constraint and strength mismatch for the bimetallic joint. With increasing in-plane/out-of-plane constraint, strength mismatch effect on fracture toughness becomes weaken. For accurate and reliable safety design and failure assessment of the bimetallic joint structures, the effects of constraint and strength mismatch on local fracture resistance need to be considered.