A Study on Changes of Principal Stress in Welding Residual Stress Fields

In this study, we focused on the principal stress value and direction in weld residual stress fields. We used specimens welded under three heat input conditions, and so the weld metal of each specimen had a different solidification structure. We evaluated the principal stress value and direction of the specimens by X-ray stress measurement. In the specimen welded under the smallest heat input condition, the weld metal showed a clear difference between the maximum principal stress and the minimum principal stress. However, in the specimen welded under the largest heat input condition, the maximum principal stress and the minimum principal stress were almost the same value. The principal stress direction changed significantly and shear stress occurred at the weld metal boundary in the specimens welded under the large heat input condition. In all specimens, the principal stress direction in the base metal changed. As conclusions, when the minimum and the maximum principal stress values were almost the same, the principal stress direction changed more noticeably. Additionally, due to the influence of the edge in the base metal, the principal stress direction changed significantly regardless of the welding condition.