Mode I Crack in Elastically Identical Bimaterial Joined by Under-Matched Weld Interlayer: A New Theoretical Model

A novel theoretical model for calculating the intensity of energy release rate at mode I crack tip in the bi-material has been developed. The study discusses the state at crack tip in the bi-material of identical steels connected by a thick but weaker weld inter layer of steel. In such a body, there are two interfaces: one between the stronger parent steel and the weaker weld, and another between the weaker weld and the stronger back up steel. As the fracture develops across the weld interlayer, i.e. strong-weak-strong transition, in the K dominating or SSY regime, the effect of energy transfer owing to the existence of elastically similar but strength mismatched surfaces is measured. The model accounts for non-linearity in plastic characteristics of steel. When the crack tip in parent steel faces the approaching interface of weaker weld during strong-weak transition, the rate of energy release at the crack tip is seen to be greater than the far field value. But when the tip in the weaker weld faces the interface of stronger back up steel during weak-strong transition, the tip energy release rate is reduced. When the crack tip is at the interfaces, the impact of shielding as well as amplification increases.