体积型缺陷几何参数对连续油管疲劳寿命影响

摘要

Coiled tubing is used in a rough dynamic environment that renders it susceptible to volu-metric defects on its outer surface.Such damage can adversely affect the fatigue life of CT by cau-sing localized stresses concentration,or inducing microcracks owing to severely localized plastic deformation.To ensure the safe and economic application of coiled tubing,geometry parameters of the volumetric defects including depth,width,and length dimensions that influence fatigue life must be taken into consideration.The cyclic bending process of coiled tubing is simulated with volumetric defects by using ABAQUS software in this paper.Then the formula of the relationship between the defect geometry parameters and the strain concentration factors are found out,the fa-tigue life prediction equation of CT80 Grade coiled tubing with different volumetric defects and different internal pressures situations is obtained,and the formula to calculate the recommending repair length of polishing repair is finally deduced out.Analysis results show that when internal pressure is below 30 MPa,fatigue life decreases with depth increasing,slightly increases with length increasing,and decreases with width increasing.While the pressure is higher than 30 MPa, the geometric parameters of the defect have little effect on fatigue life.Finally provides a repair standard for volumetric defects grinding.%连续油管服役环境恶劣，外表面体积型缺陷会造成局部应力集中和严重的局部塑形变形，诱发微观裂纹，使其过早地疲劳失效。为了保证连续油管应用的安全性和经济性，必须考虑体积型缺陷的深度、长度、宽度对连续油管疲劳寿命的影响。采用 ABAQUS 软件模拟含体积型缺陷连续油管周期弯曲过程，拟合出体积型缺陷几何参数与应变集中系数的关系式，得到含体积型缺陷连续油管疲劳寿命预测公式。分析结果表明：在内压低于30 MPa 时疲劳寿命随缺陷深度的增加而减小，随长度的增加而小幅度增加，随宽度的增加而减小；内压高于30 MPa 时缺陷几何参数对疲劳寿命影响较小。为体积型缺陷进行打磨修复提供参考。