Simulation Research On Sucker-rod Forming And Fatigue Damage

Sucker rod is an important device in pumping wells, which is the main parts transfer load between pump and units. Sucker rod fatigue strength and service life determine the depth and the maximum pump displacement of the entire pumping system.The sucker rods residual stress and damage remained in the sucker rod after processing exist in most oil field used in existing forming, which seriously affected the life of sucker rods, and withstand long-term alternating load during the high-pressure water exploitation, and combined with corrosive liquid wells and other reasons, resulted in rod fracture, seriously affected the normal operation of oil wells, and increased the operating cost. Therefore, it is very important and urgent to determine rod life accurately and in time, this paper analyzed the stress and damage of rod after forming, established fatigue damage numerical model of sucker rod using finite element method, thus organically combine the crack formation with extend, which provided more reliable and accurate prediction methods for rod life, improved the simulation accuracy. Therefore, this simulation method is great significant with broad application prospects.This paper based on the characteristic of sucker rod, analyze and introduce the rod upsetting processing, plan analysis and forge design, based on idea combined rigid viscoplastic finite element with coupled thermo-mechanical, simulated rod sucker rRod 3 steps upsetting, pre-forging and final forging using DEFORM-3D finite element software, obtain the tress distribution and damage distribution during the forming process. The results provided scientific basis for rod upsetting forming process optimization and quality, as well as the accurate initial values of fatigue damage study.According to fatigue damage mechanics theory, focus on analyzing damage mechanics finite element method, using "additional loads - finite element method" to introduce damage, through damage mechanics this paper hand clinking and crack propagation process together. According to pumping rod's median fatigue value, used method of least squares to fitting the fatigue parameter of pumping rod, based on the theory of damage mechanics and damage mechanics finite element method, this paper done a secondary development for ANSYS finite element software, write Subroutine, built fatigue damage model of pumping rod, determined rational boundary conditions, imitated fatigue damage of pumping rod under different initial stress and different initial damage situation and determined fatigue lifetime of pumping rod. This paper give a reliable and precise predicting means for useful time of pumping rod and increased the rate of accuracy of imitation. Therefor, this analogy method has an important implications and illustrate a good prospect of extension.