Study On The Friction And Mechanical Properties Of Guide Joint Bearing Of Downhole Closed-loop Controllable Bend Joint

Directional and downhole closed loop rotary steerable drilling technology is an advanced automatic drilling technology at present.It has unique advantages over other drilling technologies and has great application value.Bearing system in rotary steerable drilling tools is an important part of rotary steerable drilling tools.Guide joint bearing is a key component of downhole closed-loop drilling tool controllable bend joint in the transfer of torque and weight on bit.This paper studies the friction and mechanical properties of guide joint bearing,which lays a foundation for improving the accuracy and stability of biasing of downhole closed-loop controllable bend joint.In this paper,the structure and working principle of the guide joint bearing in the closedloop controllable bend joint are discussed firstly,the section equation of the steel ball and the channel of the guide joint bearing is analyzed,the surface equation of the outer and inner spherical channel of the guide frame is calculated,and the mathematical surface model of the channel surface is analyzed by using MATLAB software.Secondly,according to Hertz contact theory,the variation law of contact stress under four factors,namely ball rotation diameter,ball diameter,curvature coefficient of contact point and contact pressure angle,is calculated.The geometrical model of the outer spherical groove of the steel ball and guide frame was established,and the influence law of the rotation angle and offset angle on the frictional force between the steel ball and groove was obtained by using MATLAB software,and calculate the size of the volume wear rate.According to the section equation of the groove and geometric relations,the size of the circumferential clearance angle is analyzed in the case of zero angle and non-zero angle when the guide shaft is biased.Finally,the finite element software ANSYS Workbench is used to conduct the static analysis of the guide joint bearing.The equivalent stress of the spherical surface and the channel surface,the deformation of the whole surface and the deformation of the steel ball were analyzed with time.The results show that when the rotation angle is fixed,the friction force of the ball in the channel is basically unchanged with the increase of the offset angle.When the guide shaft reaches the maximum offset,increasing the angular velocity will increase the volume wear rate.When the offset angle is not zero,the fluctuation of the total circumferential clearance angle of the steel ball is one of the reasons for the vibration and noise during the rotation of the guide shaft.The maximum equivalent stress in the guide joint bearing does not exceed the allowable stress,and the deformation of the steel ball in the shell is always greater than that of the steel ball in the sleeve.The research results provide a theoretical basis for the accurate offset of the guide shaft and the improvement of the stability of the controllable bend joint.