PE80燃气管道热熔焊缝SCG过程的蠕变断裂参量研究

本文采用双边切口拉伸试样（DENT）对PE80熔焊接头和管材进行慢速裂纹扩展（SCG）实验，得到了加栽点位移时间曲线。实验结果表明，熔焊接头的SCG抗力明显小于管材，随着应力水平的增加，蠕变柔量变大。利用全切口蠕变实验（FNCT）结果求得了银纹的断裂时间，和对应于银纹断裂时间的裂纹扩展步长，再现了裂纹扩展的历史。从细观的银纹损伤角度出发采用了一种直观的描述SCG本质的力学参量对熔焊接头的裂纹尖端蠕变损伤进行评价，其值的大小表征了材料蠕变损伤的程度，也表征了裂纹的扩展情况。

Study on Creep Fracture Parameters of PE 80 Gas Pipeline Welded Joints in SCG Process

In this paper, double edge notched tensile （DENT） samples are adopted for both welded joints and base pipes. The load point displacement curves are obtained, Experimental result indicates that the SCG resistance of the welded joints is smaller than the pipes＇. The higher the stress is,the larger the creep eompliance is. The step length corresponding to the fracture time of each craze is obtained with the full notch creep test （FNCT） experimental results,with the crack growth history reproduced. A local damage law variable at the microscopic scale, whose value presents the degree of material creep damage,is used to evaluate the creep damage directly, and the process of SCG on the crack tip of PE80 welded joint is given.