Unified Correlation of Constraint and Strength Mismatch with Fracture Toughness of Bimetallic Joint

A unified constraint characterization parameter Ap has been defined and a unified correlation line of in-plane and out-of-plane constraint with fracture toughness has been obtained based on the homogeneous material A508 in the previous study of authors. In order to study whether the unified correlation of constraint with fracture toughness can be established by using the constraint parameter Ap for the bimetallic joint, in this paper, a bimetallic joint constituted with A508 ferritic steel and Alloy52 M was selected, the finite element numerical simulation method was used to model the equivalent plastic strain (ɛp) distributions ahead of crack tips for specimens with different in-plane and out-of-plane constraints, and the J-resistance curves of specimens were obtained by the finite element method (FEM) simulations based on GTN (Gurson-Tvergaard-Needleman) damage model. Unified correlation of constraint with fracture toughness of bimetallic joint has been investigated. The results show that there exists a sole linear relation between the JIC/Jref and regardless of the in-plane and out-of-plane constraint. The JIC/Jref - line can be regarded as a unified reference line to characterize the dependence of material's fracture toughness on constraint. So the Ap is a suitable unified constraint parameter which can characterize both in-plane and out-of-constraint for bimetallic joint. For there exists heterogeneous of fracture property and strength mismatch in bimetallic joint, the Ap can be also regarded as a suitable unified constraint parameter which can characterize both constraint and strength mismatch.