Numerical Analysis of the Stress Distribution and Concentration Factors of the Tool Joint of the Directional Drill Pipe

Abstract

With the wide application of directional drilling technology in coal mine predraining boreholes, the failure problem of the tool joint of the directional drill pipe has become one of the main factors restricting the drilling efficiency. The main reason for the failure problem of the tool joint of the directional drill pipe is the stress concentration. The stress test rig for the tool joint of the directional drill pipe is designed based on the resistance strain measurement method, and the stress of the tool joint of the directional drill pipe is tested. The tool joint’s 3D finite element model was established based on nonlinear contact theory. The experiment verified the accuracy of this model. The stress distribution of the tool joint of the directional drill pipe was obtained. The research shows that the stress of the tool joint of the directional drill pipe is concentrated at the root between the third and the fourth turn of the engaged thread. The work presented in this study is a reliable guide to the design and field use of the tool joint of the directional drill pipe.