Unified correlation of in-plane and out-of-plane constraints with fracture toughness

In this paper, the specimens with different geometries and loading configurations were used to study the unified correlation of in-plane and out-of-plane constraints with fracture toughness by using numerical simulation method. The results show that the unified constraint parameter A(p) which was defined on the basis of the areas surrounded by the equivalent plastic strain isolines ahead of crack tip can characterise both in-plane and out-of-plane constraints induced by different specimen geometries and loading configurations. A sole linear relation between the normalised fracture toughness J(IC)/J(ref) and root A(p) was obtained. The J(IC)/J(ref) -root A(p) line is a unified correlation line of in-plane and out-of-plane constraints with fracture toughness of a material, and the constraint dependent fracture toughness of a material can be determined from the unified correlation line. The results also demonstrate that the out-of-plane constraint effect is related to the in-plane constraint effect, and there exists interaction between them. The higher in-plane constraint strengthens the out-of-plane constraint effect, whereas the lower in-plane constraint is not sensitive to the out-of-plane constraint effect.