Modelling the crack propagation behavior in 9Cr/CrMoV welds

•Crack propagation behavior in 9Cr/CrMoV welded joint are simulated by ABAQUS.•The GTN damage model are applied to simulate ductile crack propagation behavior.•The experimental crack propagation resistance curves are well fitted with the calculated results.•Higher equivalent plastic strain and triaxial stress cause lower crack propagation resistance.•Brittle crack propagation behavior are well simulated by brittle cracking model.

Crack propagation behavior in different zones of advanced 9Cr/CrMoV dissimilar steel welded joint was simulated by ABAQUS software. The Gurson–Tvergaard–Needleman (GTN) damage model and brittle cracking model were introduced to analyze the crack propagation behavior for ductile and brittle region on the dissimilar steel welded joint, respectively. It is found that the numerically calculated J–△a resistance curves for the ductile regions i.e., the CrMoV base metal (CrMoV-BM), the heat affected zone of CrMoV (CrMoV-HAZ) and weld metal (WM) matched the experimental results, implying the reliability of the model developed in the present study. Three cases with different initial crack length (a0) were simulated to probe into the effect of a0 on the crack propagation resistance. The simulated results revealed that higher equivalent plastic strain and stress triaxiality occurred on the right ahead of the crack tip for longer initial crack length, which induces the lower crack propagation resistance. The brittle crack propagation behavior in 9Cr base metal (9Cr-BM) and heat affected zone of 9Cr (9Cr-HAZ) was well simulated by the brittle cracking model. The local stress distribution around the crack tip before crack destabilization could be obtained from the established model for BM and HAZ of 9Cr steel.