Drill Pipe Thread Joint Research And Optimization For Deep-sea Drilling And Sampling

The drill pipe is the main component of natural gas hydrate in deep-sea drilling sampling equipment,its function is to transfer torque and protect the drill internal sampling tools.The drill pipe connected into a whole end to end,bearing the load function of tension,pressure,bending,and torsion.The thread joints are affected by the function of compound load easyly,and may lead to failure or seal failure.In this regard,the domestic and foreign scholars have done a lot on the strength and sealing performance of drill pipe joint.In this paper,according to the special environment of deep-sea drilling sampling requirements,on the basis of previous studies,the thread joint was studied,and the optimized structure size was given.This paper introduced the research method of stress of thread joint,and summarized the analytical method at first.Then using ABAQUS finite element analysis software,a API joint axisymmetric model was founded,the stress distribution under the function of tension,pressure and torsion was analyzed,the stress variation of the stress concentration zone was researched too.At the same time,the sealing mechanism and sealing performance of thread connection was studied.Finally,to improve the stress distribution,the structure of screw expanding cone size,double shoulder structure and stress relief groove was improved gradually,and the optimal size was obtained.The analysis showed that,these improvements have improved the stress distribution of thread joint,reduced the risk of regional stress concentration,and improved the sealing performance of the joint.Using the results above,the resistance of bending was studied through the comparison of the structure.Based on the finite element analysis of the joint fully three-dimensional model,the thread joint stress distribution under the function of pre tightening torque and bending moment of was got.And the bending bearing capacity analytic calculation method was got too.