Crack initiation and propagation close to the interface in a ferrite-austenite joint

The safety assessment of welded structures and joints still remains an important industrial problem. In this study, a simple diffusion bonded bi-material joint has been made in order to analyze the plastic mismatch effect. It consists of an assembly of ferritic and austenitic steels which are representative of nuclear pressure vessel components. Tests were performed on various specimens including smooth and notched tensile bars, Charpy V-notch specimens and single-edge notch bend specimens. Homogeneous and bimaterial specimens were tested. On deeply notched specimens, the effect of the distance between the notch root and the interface on fracture initiation and crack propagation direction was studied. Tests were modeled using elasto-plastic finite element simulations. These simulations were post-processed in order to determine crack initiation based on the Rice and Tracey criterion according to the “local approach of fracture” procedure.