Offshore pipelines under both installation and operation are always subjected to tension and torsion. The corrosion causes pipes to be cracked and then collapsed. Therefore, in order to obtain the fracture behavior of pipelines, the modified Mohr-Coulomb (MMC) criterion is applied. By using this criterion, a 3D elastic-plastic finite element model in ABAQUS is established to simulate the mechanical behavior of defected X80 steel pipeline under simultaneous tension and torsion. Besides, parametric studies including the effects of crack depth and crack length are conducted. The resistance curve of the pipe under different ratios of strain and twist is attained.

海上管道在安装和运行过程中始终会受到拉力和扭转。腐蚀使管道破裂然后塌陷。因此，为了获得管道的断裂特性，应用了改进的Mohr-Coulomb（MMC）准则。利用该判据，建立了ABAQUS中的3D弹塑性有限元模型，以模拟缺陷的X80钢管在同时受拉和受扭的情况下的力学行为。此外，还进行了包括裂纹深度和裂纹长度影响在内的参数研究。得出了在不同应变和扭曲比下的管道电阻曲线。