Thread connection load transfer law

Oil drill male thread root portion due to severe stress concentration in the complex alternating loads , easy to crack initiation , resulting in joint fatigue fracture due to the complex structure , difficult to find a variety of crack fracture strength of the analytic expression patterns generally only be solved numerically . thread contact in three-dimensional calculation is extremely complex, this paper proposes a simplified calculation model gives a reasonable load transfer  Instrument valve manifolds  rules . Using three-dimensional finite element displacement method , more systematic study of the root portion of the male thread with semi-elliptical surface crack in a variety of load stress intensity factor variation . Male thread root for predicting crack after carrying capacity and remaining life , establishing flaw detection cycle , the development of waste sub- standard ,  2 way manifolds  the necessary fracture analysis parameters . Second, the calculation method simplified model of thread contact connection state oil drill pipe joints loaded. Calculating three-dimensional contact with the thread is very complicated and expensive , is not conducive to engineering applications .  Valve manifold , this article assumes the role by the torque T , the thread contact between teeth without the circumferential direction relative slip ; subjected to internal pressure , tensile and bending loads , the contact between teeth without radial relative sliding .