Through Process Modeling of the Fracture Toughness Test of Multipass Welds Incorporating Residual Stress Distribution

Abstract

Weld residual stress inevitably occurs in multipass welds of thick steel plates, and it affects the fracture toughness testing procedure and test results; therefore, it is important to clarify the effect of residual stress on fracture toughness evaluation. However, it is almost impossible to measure the entire residual stress distribution in welded joints and to consider the detailed distribution in fracture toughness testing. Therefore, in this study, a numerical simulation method to model the fracture toughness test considering the weld residual stress is developed. The weld residual stress incorporated into the simulation was validated through experimental measurement. The transition of the residual stress throughout the processes of multipass welding, specimen machining, residual stress modification, precracking, and fracture toughness testing were evaluated using the proposed method. Three-point bend fracture toughness test simulations were performed for the following three cases: (1) base metal, (2) as-welded joint, and (3) residual stress modified (reverse bent) specimen by reverse bending. It was shown that the residual stress distribution in multipass welded joint was effectively modified by reverse bending. Finally, it was demonstrated that residual stress has a considerable influence on the crack-tip opening profile.