Characterization of Mechanical Heterogeneity and Study of the Mechanical Field at the Tip of the Stationary-Growing Crack in Dissimilar Metal Welded Joints

Abstract

The mechanical heterogeneity in local areas of dissimilar metal welded joints and the micro-area mechanical state at the crack tip are key factors in determining Environment-Assisted Cracking (EAC). Traditional methods for acquiring material mechanical properties often result in destructive damage to specimens, while conventional “sandwich” models exhibit abrupt changes in interfacial mechanical properties and a lack of research into the mechanical field at the tip of the stationary or growing crack. In light of these challenges, this study, based on the analysis of microstructures in localized regions of the welded joint and the acquisition of material mechanical properties through indentation tests, developed a user-defined material subroutine (UMAT) to characterize the mechanical properties of non-uniform local areas within the welded joint. Additionally, it investigated the mechanical field at the tip of the stationary—growing crack using an integral method and a de-bond technique. The results indicate that non-destructive indentation tests can accurately acquire the material mechanical properties of local areas in the welded joint. Notably, significant changes in mechanical properties typically occur in the material interface regions, making them vulnerable points for potential failure. Furthermore, under the same load, mechanical heterogeneity significantly influences the distribution of the mechanical field at the crack tip. Crack propagation induces alterations in crack tip stresses, resulting in noticeable residual stresses and strains along the propagation path.