中文摘要：

由于接头组织和材料力学特性的不均匀,特别是当焊接热影响区的硬化对应力腐蚀破裂有重要的促进作用时,核电一回路316L管道焊接接头的应力腐蚀裂纹更容易扩展。考虑到焊接力学不均匀性,本文分析了恒应力强度因子（KI）和恒载荷条件下316L管道焊缝扩展裂纹尖端的局部应力应变场。研究结果表明,由于焊接力学不均匀性和裂纹长度的影响,恒KI和恒载荷条件下,扩展裂纹端部力学场有很大差异;恒载荷对扩展裂纹尖端应力应变的影响比恒KI要大得多。

英文摘要：

Primary loop recirculation 316 L piping weld joints were more susceptible to stress corrosion cracking because the material and mechanical properties in welded joints were quite heterogeneous. Especially, it is provided that hardening in the welded heat affected zone plays an important role in promoting crack growth. Considering welded mechanical heterogeneity, the local stress and strain fields ahead of propagating crack tips in 316 L piping weld joints were analyzed under constant stress intensity factor（KI） and constant loading conditions. The results show that the mechanical fields of propagating crack tips behave quite different under constant KIand constant loading because of welded mechanical heterogeneity and advanced crack length, which demonstrate that the effect of constant loading on the stress and strain ahead of the propagating crack tip is bigger than that of constant KI.