Research on damage progression of drill string material based on the extended finite element method.

In this paper, the process of crack propagation is investigated using the extended finite element method at the mesoscale to study the drill pipe fracture mechanism. Firstly, the property of the S135 drill pipe was analyzed through physical and chemical experiments and the scanning electron microscope method. After that, a grain distribution model of the drill pipe material at the mesoscale was established by the Python scripting language on ABAQUS platform. Furthermore, the extended finite element method was applied to study crack dynamic propagation. And the distribution of stress and strain during the crack propagation were obtained at the mesoscale grain model. Finally, by the mesomechanics "homogenization" method, the stress and strain of the crack propagation model at different times were analyzed, and the influence of crack propagation on drill pipe material was obtained. Simulation results show that, although drill pipe material at the macroscopic scale is in the elastic stage, plastic zone and micro-crack propagation may also exist at the mesoscale. The proposed method in this paper studied the stress distribution in the crack tip during the propagation, which is a benefit for exploring the fracture mechanism of drill pipe.