椭球缺陷连续管疲劳寿命分析

Analysis of Fatigue Life of the Coiled Tubing with Ellipsoidal Defect

为防止连续管在作业过程中突然断裂,对含缺陷连续管的疲劳寿命要有一定的预测。用有限元模拟含不同尺寸椭球缺陷的连续管在零内压情况下卷绕矫直过程中的变形和疲劳,并分别用等效应变法和临界面法估算出相应的疲劳寿命,绘制成相应图表。缺陷尺寸包括其他方向上尺寸不变情况下的不同长度、不同深度和不同宽度。缺陷尺寸变化,疲劳寿命也会相应变化,其中长度方向变化对连续管疲劳寿命的影响大于深度方向和宽度方向的影响。研究结果有助于提高连续管设计水平和连续管使用寿命的预估能力,有助于减少疲劳事故所造成的人员和财产损失。

To prevent the coiled tubing from breaking down during operation, the fatigue life ol the coiled tub-ing with delects should be predicted. The deformation and fatigue ol the coiled tubing with different size ol ellipsoid defects without inner pressure during coiling and straightening have been simulated by finite element method. The corresponding fatigue life has been estimated by the equivalent strain method and the critical plane method respec-tively, and then the corresponding diagrams have been attained. The delect size includes different lengths, depths, and widths given the same other dimensions. The fatigue life changes with the defect size. The effect of defect length change is greater than the defect depth or width change on the coiled tubing fatigue life. The results of the study could help to improve the design level of coiled tubing and the prediction of the service life, and also to reduce the significant loss of personnel and property caused by fatigue.