Benchmark analysis of ductile fracture simulation for circumferentially cracked pipes subjected to bending

In this study, some benchmark problems on fracture tests for circumferentially through-wall/surface cracked pipes were provided. The participants predicted the ductile crack propagation behavior by their own approaches, including nucleation, growth, and coalescence of voids simulated by Gurson model, ductile crack propagation using stress modified fracture strain (SMFS) model, J-integral based ductile crack propagation using XFEM, CTOA based ductile crack propagation using FEM, stress triaxiality and plastic strain (STPS) based ductile crack propagation using FEM, and ductile crack propagation using peridynamics. Among them, GTN, CTOA and STPS models were not applied to surface crack problems. Discrepancies between the experimental maximum loads and calculated maximum loads were within 10% in most cases and 25% in the maximum case. Element size dependency of analysis parameters were considered in SMFS and GTN models while those were determined from independent material tests. Gurson model can predict slanting crack propagation directions. XFEM which did not need analysis fitting parameters cannot analyze beyond the peaks of load-LPD curves. Crack propagation directions were given and fixed in both CTOA and STPS models. Parameters in Gurson model and peridynamics were optimized to reproduce load-LPD curve in one of the benchmark problems.