Mechanical performances of double-shoulder threaded drilling pipe̍s joint shoulder based on coupling model

The reserved secondary shoulder clearance of the double shoulder threaded drilling pipe̍s joint has an important influence on the contact stress of the primary and secondary shoulders. In order to ensure the joint performances, it is necessary to explore the mechanical properties of the primary and secondary shoulders. Through the mechanical analysis and finite element simulation on the double shoulder joint, the coupling model was established, and the numerical relationship between the frictional torque of the primary and secondary shoulders, the torque at the thread, and the make-up torque was obtained by statistical fitting according to the coupling model, so as to obtain the complete simulation conditions of the joint. On this basis, taking the NC38 joint as an example, the relationship between the reserved clearance of the secondary shoulder and the contact stress of its shoulder under different make-up torques was studied. The results show that the reserved clearance of the secondary shoulder of the double shoulder joint plays a key role in the joint performance. Under a certain make-up torque, the appropriate reserved clearance of the secondary shoulder should be selected to ensure the primary sealing and reliability of the secondary shoulder. With the increase or decrease of the make-up torque, the reserved clearance should also be changed to give a better play to the performance of the primary and secondary shoulders. This method can help designers better determine the best reserved clearance of the secondary shoulder of the double shoulder joint. © 2022 University of Petroleum, China. All rights reserved.