Performance analysis and structural optimization of drill pipe connections under complex operating conditions.

In order to reduce the failure of thread joint of drill pipe, its connection performance and sealing performance need to be improved. Based on the mechanical analysis of the joint and yield criterion of von Mises, the three-dimensional finite element model of the single shoulder and double shoulder with NC38 thread profile was established. The failure mechanism under the combined working conditions is discussed by combining test and numerical simulation. A new type joint of TM40 is further proposed, and the mechanical properties of the shoulder and thread section of the joint are compared and analyzed. The results show that the stress of the double shoulder structure is significantly lower than that of the single shoulder structure, and the sealing performance is better. At the same time, the extension threaded joint of TM40 can improve the stress distribution of the threaded section, reduce the stress concentration, ensure the reasonable distribution of the contact pressure on the shoulder.