Three-dimensional mechanical analysis of the double-shouldered tool joint

The present paper established a three-dimensional finite element model of the double-shouldered tool joint,and analyzed mechanical behaviors of the tool joint under make-up torque,axial tension and bending moment by means of the explicit dynamic finite element method.Compared with a two-dimensional axisymmetric model,the three-dimensional finite element model can effectively simulate the make-up behaviors of threaded connection by taking the helix ascending angle of screw thread into consideration.The results show that the make-up torque can produce a certain preload of the threaded connection on the mating surface of threaded teeth,primary shoulder and secondary shoulder,which implements the interference fit between male and female threads.Axial tension increases the contact pressure on threaded teeth but decreases that on the primary and secondary shoulders,which,on one hand,aggravates the load of threaded teeth,and on the other hand,affects the sealing performance of tool joint.The stress distribution of tool joint takes on a distinct asymmetric property under the bending moment.Besides,the load of individual threaded tooth is unevenly distributed under make-up torque and axial tension,the most load is sustained by several threaded teeth at the both ends of the tool joint,while intermediate threaded teeth sustain only a less load.