Three-dimensional stress analysis of titanium alloy tool joints under complex loads

The increasing drilling depths of oil and gas wells make the load conditions of drill strings more and more severe. Using titanium alloy drill pipe can effectively reduce hook load and improve the safety margin of wellhead drill pipe. The tool joint is the weak link of drill string. However, there are few researches on mechanical properties of titanium alloy tool joint under complex loads. In view of the above, a three-dimensional finite element model of double shoulder titanium alloy tool joint was established by ABAQUS software, and its ultimate tensile and torsional capacities and the mechanical properties were analyzed under complex loads (make-up torque, axial tension, bending moment and internal pressure). The results show that the maximum von Mises stress of titanium alloy tool joint under complex loads is less than the ultimate strength of material, thus the tool joint meets the requirements of applied load conditions. By determining the ultimate tensile load and ultimate working torque of tool joint, it can provide a significant reference for selecting the axial tension and working torque reasonably and avoiding the failure of titanium alloy tool joint.