In this study, various sensitivity analyses was conducted to investigate elasto-plastic crack propagation in pipes containing circumferential cracks under combined bending and torsion. The experiments consisted of four-point bending tests on pipes equipped with torsion arms oriented perpendicular to the bending direction. Two pipe configurations, TP-1 and TP-2, were tested, differing in the length of the torsion arms. Finite element models were constructed using hexahedral elements with a minimum mesh size of approximately 1.6 mm. The material behavior of SUS304 stainless steel was characterized by tensile tests of round bar specimens and modeled using the Ramberg–Osgood model. Crack propagation was evaluated using the J–R curve obtained from compact tension specimen tests, based on the assumption that crack growth occurs when the calculated J-integral exceeds the resistance curve. Crack propagation was modeled using duplicate nodes along the crack path, with coupling constraints that were incrementally released to simulate crack extension. The numerical results were validated against experimental data in terms of load and load-point displacement. This analysis successfully reproduced the failure behavior trends, with TP-1 and TP-2 showing errors of approximately 1% and less than 10%, respectively, at maximum load before penetration.
Nishikawa et al. (Wed,) studied this question.