Research on the Design and Performance of Drill Pipe Joints Based on Fracture Mechanics Methods

In the actual drilling process, fatigue failure of drill pipe joints predominantly occurs at the threaded connections, leading to a substantial increase in drilling costs. Considering the severe vibrations and abnormal wear experienced by drill pipes under complex working conditions, a three-dimensional finite element model of drill pipe joints was developed. This model is based on fracture mechanics theory, the principle of virtual work, the Von Mises yield criterion, and contact nonlinear theory, while also accounting for the influence of thread cone angles. By evaluating both straight and conical threads with varying tooth profile angles, optimal structural parameters were determined. The results indicate that a 45-degree tooth profile angle represents the optimal structural parameter, meeting the fundamental requirements for water exploration in coal mines.