Numerical simulation of residual stress modification by reverse bending of notched fracture toughness test specimens of multipass welds

Abstract

In the fracture toughness tests of multipass welds of thick steel plates, the fatigue precrack front initiating from a machined notch root frequently be non-uniform affected by the welding residual stress distribution. Reverse bending before fatigue precracking could be an effective measure of residual stress modification. However, the effect of reverse bending is not well understood from the viewpoint of the variation of the residual stress distribution at the notch root. Therefore, the transition of the welding residual stress throughout the multipass welding, notch machining, and reverse bending processes is calculated using a numerical simulation model developed in this study. The compressive plastic deformation at the notch root caused by the reverse bending and successive tensile loading during unloading are the major mechanisms of residual stress modification by reverse bending. A flattened residual stress distribution along the thickness can be achieved if the reverse bending condition is properly controlled.