Buckling collapse of submarine thick-wall pipe under torque and hydraulic pressure based on vector form intrinsic finite element method

Torsion is a prevalent form of stress on pipe. This paper employs experimental and numerical methods to investigate the buckling behavior of thick-walled pipe under combined torsion and external pressure. Firstly, the beam-shell coupling method based on the vector form intrinsic finite element method is utilized to establish a model for torsion and external pressure in thick-walled pipe. The accuracy of the model is verified by the collapsible test of the scaled pipe. On this basis, the influence of different torsion angles on the failure mode and the failure mechanism of bending pipe under dynamic and quasi-static conditions are compared and analyzed. It is found that under different loading conditions, the buckling propagation mode of the downstream pipeline changes greatly. This phenomenon is mainly caused by the action of torque on the elbow. Finally, the effect of different torsion angles on the collapse pressure of the bend is investigated.