Fatigue Analysis of HL Rod Based on Damage Mechanics

In order to analyze the influence of a damaged HL-class sucker rod on its safety performance during the process of use, the fatigue damage evolution model of the sucker rod was established according to the principle of damage mechanics combined with the effective stress method with ANSYS finite element software to conduct numerical simulations for the residual fatigue life of HL-class sucker rod under three kinds of damages, namely crack, corrosion pit and eccentric wear. The effects of three damage influencing factors (shape, size, position, etc.) on the residual fatigue life of HL-class sucker rods were analyzed by an orthogonal test, and the relationship between the fatigue life of HL-class sucker rod and the influencing factors was determined by multiple regression method under three kinds of damages. The simulation results showed that for crack damage, the impacts on fatigue life could be listed from top to bottom as the crack position, angle, depth and width. For corrosion pit damage, the impacts listed were the pit position, depth and radius; for the eccentric wear damage, the impacts were the eccentric wear position, depth and length. The adjust decision coefficient of the regression relationship between the fatigue life of HL-class sucker rod and the influencing factors under the three kinds of damages were calculated to be 82.0%, 94.0% and 90.9%, respectively. The research results indicated that the damage position had an extremely significant effect on the fatigue life of HL-class sucker rod. The depth and angle of crack, the depth and radius of the corrosion pit, and the eccentric depth had significant effects on the fatigue life, and the crack width exhibited a certain influence. The regression relationship between the fatigue life of HL-class sucker rod and the influencing factors under three kinds of damages could provide a basis for judging the residual life of HL-class sucker rod.