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.

模拟输气管道延性裂纹扩展的难点之一是复杂加载的实现。传统加载方法难以准确预测实时裂纹尖端位置，进而更新边界条件，导致仿真结果不准确。针对这一问题，本文提出了一种考虑裂纹尖端位置预测的迭代加载方法（CTPI方法）。首先，通过比较模拟和全尺寸爆裂试验的结果来检验所提出的加载方法的有效性。其次，一般采用的均布加载法（NGD Method），系统地比较了简化迭代加载方法（S-CTPI 方法）和所提出的 CTPI 方法描述天然气管道中动态裂纹行为的能力。最后，研究了全尺寸管道在不同内压水平下的裂纹尖端张开角（CTOA）演化历史。研究结果表明，损伤模型与基于实时裂纹尖端位置准确预测的CTPI方法相结合，可以模拟天然气管道井的延性断裂行为。进一步分析表明，管道的临界 CTOA 与内压和裂纹速度无关，这为基于 CTOA 的止动准则的适用性提供了有力的证明。研究了全尺寸管道在不同内压水平下的裂纹尖端张开角（CTOA）演化历史。研究结果表明，损伤模型与基于实时裂纹尖端位置准确预测的CTPI方法相结合，可以模拟天然气管道井的延性断裂行为。进一步分析表明，管道的临界 CTOA 与内压和裂纹速度无关，这为基于 CTOA 的止动准则的适用性提供了有力的证明。研究了全尺寸管道在不同内压水平下的裂纹尖端张开角（CTOA）演化历史。研究结果表明，损伤模型与基于实时裂纹尖端位置准确预测的CTPI方法相结合，可以模拟天然气管道井的延性断裂行为。进一步分析表明，管道的临界 CTOA 与内压和裂纹速度无关，这为基于 CTOA 的止动准则的适用性提供了有力的证明。研究结果表明，损伤模型与基于实时裂纹尖端位置准确预测的CTPI方法相结合，可以模拟天然气管道井的延性断裂行为。进一步分析表明，管道的临界 CTOA 与内压和裂纹速度无关，这为基于 CTOA 的止动准则的适用性提供了有力的证明。研究结果表明，损伤模型与基于实时裂纹尖端位置准确预测的CTPI方法相结合，可以模拟天然气管道井的延性断裂行为。进一步分析表明，管道的临界 CTOA 与内压和裂纹速度无关，这为基于 CTOA 的止动准则的适用性提供了有力的证明。