同心连续管疲劳特性试验研究

Experimental Study on Fatigue Behavior of Concentric Coiled Tubing

迄今为止,还没有关于任何类型同心连续管(CCT)疲劳特性测试和分析的报道。为了给我国CCT疲劳特性研究提供借鉴,推动我国CCT技术的发展,建立了FlexorTU疲劳模型,重点研究了小尺寸内层CT内部压力和环空压力对疲劳寿命的影响和直径增长率。研究结果表明:所有CCT样品的疲劳寿命试验值大于理论模型预测值,说明CT疲劳寿命模型是一个安全有效的方法;基准疲劳试验数据与用模型构建的试验数据有较好的相关性;电阻焊接(ERW)焊缝方向为90°的CCT样品疲劳寿命试验值大于相同有效压力下的基准疲劳试验值;电阻焊接(ERW)焊缝方向为0°或180°的CCT样品疲劳寿命通常较短;内层CT样品的平均直径增长率低于基准试验样品的直径增长率;由于内层CT样品尺寸太小,不足以确定任何经验折减系数,通过与模型预测结果对比,CCT样品的平均疲劳寿命显示了1. 68的折减系数。但由于没有产生足够的数据验证该系数,建议进行更多更深入的试验。所得结论可为CCT疲劳特性的进一步研究提供借鉴。

To provide references for the study of CCT(Concentric Coiled Tubing)fatigue behavior and promote the development of CCT technology in China,a FlexorTU fatigue model is applied to specifically investigate the influence of internal pressure and annular pressure on fatigue life and diameter growth rate of CCT.The results show that the fatigue life of all CCT test samples were larger than the model prediction values,which indicates that the CT fatigue model is a conservative and effective method.The baseline fatigue test data has a good correlation with the test data for model construction.The fatigue life of the CCT sample with a longitudinal electric resistance welding(ERW)seam is longer than the baseline fatigue test value under the same effective pressure.The fatigue life of the CCT sample with a 0°or 180°electric resistance weld(ERW)seam direction usually has a shorter fatigue life.The average diameter growth rate of inner tube sample is lower than the diameter growth rate of the baseline sample.The inner CT sample size is not large enough to identify any empirical derating factor.The average fatigue life of CCT sample shows a 1.68 derating factor compared with the model prediction.Not enough data were generated to propose this factor with any confidence,so more testing is recommended.