基于椭圆度及壁厚参数的连续油管低周疲劳寿命预测

摘要

The coiled tubing experiences 6 times of bend-straighten plastic deformation in each pipe lifting process, and the low-cycle fatigue failure accident occurs occasionally. Based on the work state of coiled tubing, a set of tailor-made experimental device and specimen on fatigue life was designed. The fatigue life test was carried out on the coiled tubing of Ø60.325 mm. The values of ovality and wall thickness of different cycles were obtained in the experiment. The formulas of ovality and wall thickness were generated based on the mathematical regression method, and the formula of low cycle fatigue life was given. The experimental results show that the fa-tigue life calculation coincidence rate was over 90%. Therefore, the calculation method could be a theoretical basis for the coiled tubing failure prediction and control.%连续油管在每次起下作业中经历多次弯曲-拉直塑性变形，低周疲劳失效事故时有发生。依据连续油管工作状态，设计了专用的连续油管疲劳寿命装置和试件。对Ø60.325 mm连续油管进行了疲劳寿命实验，得到了不同循环次数下连续油管椭圆度、壁厚变化值，基于数学回归方法拟合出椭圆度及壁厚随循环次数计算公式，给出了低周疲劳寿命公式。研究结果表明，连续油管的疲劳寿命符合率达到90%，因此，采用新的计算方法能够为工程连续油管失效预测及控制提供理论依据。