Elastic-plastic contact stress analysis on sphere to cone sealing structure for tubing and casing premium connection

Considering additional make-up torque from sealing interface, the elastic-plastic contact stress analytical model for sphere to cone premium connection is established on the basis of Hertz contact stress and Mises yield criterion. The effects of additional make-up torque from sealing interface on the contact stress distribution are analyzed. The results show that with the additional make-up torque from sealing interface increases, sealing interface contact state gradually shifts from completely elastic contact to elastic-plastic contact, the contact stress distribution by gradually opening downward parabola to parabolic cup, and the contact width, yield width and average contact stress all increase. In order to improve the gas sealing performance of premium connection, the sufficient average contact stress and contact width should be ensured and the yield width also reasonably controlled. In the example, the additional make-up torque from sealing interface should be controlled between 731.7 N·m and 1826.4 N·m. The results are of great significance for guiding the make-up torque operation and improving the gas sealing performance for premium connection.