焊接接头裂端塑性区发展与应力三轴性

采用有限元计算方法分析了平面应变条件下中心裂纹和三点弯曲不同强度匹配和裂纹深度试样中的裂端场．结果发现，焊接接头裂端应力三轴性随加载方式、裂纹长度及焊缝和母材匹配性质不同而变化，并从焊缝和母材塑性区发展及应变硬化方面进行了解释．同时指出，由于焊缝和母材塑性变形及交互作用导致的裂端韧带上拉应力的改变是不同接头中应力三轴性变化的根本原因

Evolution of Plastic Zones and Stress Triaxiality near Crack Tip in Welded Joints

The crack tip stress field for center cracked tensile panel and three point bend specimen with different strength mis matching and crack depth is investigated by using a two dimensional finite element method under the plain strain condition. It is found that the stress triaxiality along the path of the expected crack extension varies not only with the loading mode and crack length relative to the specimen width but also with the degree of weld/base metal mis match in the yield strength. The above results are interpreted in terms of the plastic deformation and strain hardening of the weld metal and base material. It is pointed out that the variation of normal stress near the crack tip on the ligament resulting from the plastic zone extension and interaction between weld metal and base material is the root cause of the changes of stress triaxiality in welded joints with different strength mis matching and crack depth.