Investigation of Residual Stress Modification Method for Fracture Toughness Test of Multipass Welds in Thick Plates

In the fracture toughness test of multipass welds of thick plates, residual stress modification treatment is necessary to ensure the straightness of the front shape of the fatigue precrack. However, the treatment conditions are not clear, and more efficient treatment conditions are required as the thickness and strength of steel plates are becoming higher. In this study, a numerical analysis method to clarify the residual stress change during the modification process was developed. The developed method can describe the welding residual stress distribution by thermo-elastic-plastic analysis and then follow the changing behavior by residual stress modification treatment in detail. Using the developed method, the changing behavior of residual stress by the local compression method and the reverse bending method, which are typical residual stress modification methods, was clarified. The mechanism of residual stress modification is explained by focusing on the plastic deformation introduced by these methods.