Effect of accurate prediction of real-time crack tip position on dynamic crack behaviors in gas pipeline

One of the difficulties in the simulation of ductile crack propagation in the gas pipeline is the implementation of complex loading. It is difficult for traditional loading methods to accurately predict the real-time crack tip position and then update the boundary conditions accordingly, which makes the simulation results inaccurate. To solve this problem, an iterative loading method considering the prediction of crack tip position (CTPI method) is proposed in this paper. Firstly, the effectiveness of the proposed loading method is checked by comparing the results of the simulation and full-scale burst test. Secondly, the generally used uniform loading method (NGD Method), simplified iterative loading method (S-CTPI Method) and the proposed CTPI method are systematically compared for their ability to describe dynamic crack behaviors in the gas pipeline. Finally, the crack tip opening angle (CTOA) evolution histories of the full-scale pipeline under different internal pressure levels are studied. The results in this paper show that the damage model coupled with the proposed CTPI method which is based on the accurate prediction of real-time crack tip position can simulate the ductile fracture behaviors for gas pipeline well. Further analysis shows that the critical CTOA of the pipeline is independent of the internal pressure and crack velocity, which provides strong proof for the applicability of the CTOA-based arrest criterion.