天然气管道拘束焊缝复合加载条件下的抗裂性研究

天然气管道在服役过程中,常受到复杂的外部载荷,在金口焊缝处易发生泄露或开裂。针对天然气管道金口焊缝拘束状态,设计了一套自拘束焊接装置,模拟了金口焊缝的拘束状态;并通过复合加载试验及应力应变检测,探讨了全尺寸管道拘束焊缝在复合加载条件下的抗裂敏感性。试验结果表明:拘束焊缝管道无论在内压+静态弯曲复合加载,还是在内压+冲击弯曲复合加载条件下,其抗开裂性均比无拘束焊缝管道差,缺陷开裂敏感性高。含缺陷管道对外部冲击载荷更为敏感,外部动载更易造成含缺陷管道开裂。在复合加载过程中,拘束焊缝管道缺陷尖端的最大应变值小于无拘束焊缝管道缺陷尖端的应变,无拘束焊缝可承受更大的塑性变形。含缺陷管道对弯曲加载速率较为敏感,弯曲加载速率增大,缺陷更易开裂。

Study on the Crack Resistance of Restraint Weld of Natural Gas Pipeline under Combined Loading

Golden weld joint of natural gas pipeline is much easier to leak or crack, as it often suffers complex external load when pipeline in service. In the paper, the restraint state of weld was simulated by using a constraint fixture for welding. The combined loading test and the stress and strain detection were employed to explore the sensitivity of crack resistance of restraint weld of full-size pipeline. The result showed that cracking resistance of restraint weld were poorer than those without restraint weld, and high crack sensitivity under complex loading conditions, not only in pressure + external static bending load but also in pressure + external impact bending condition. Crack sensitivity of pipeline with defect was more sensitive to external impact load, and external dynamic load was more likely to cause cracking. The maximum strain value of tip of flaw in restraint weld was smaller than that no restraint weld in the combined loading process, the tip of flaw in no restraint weld could withstand greater plastic deformation. Cracking was sensitive to bend loading rate of pipeline contained defects, bend loading rate increased, the defects were more likely to crack.