Calculation of 3D residual notch stress intensity factors by means of the peak stress method

Abstract

In the recent literature new approaches were developed to include the residual stress effects in fatigue strength assessments of welded joints. Among these, the local approach based on the calculation of the Residual Notch Stress Intensity Factors (R-NSIFs) seems very promising. Unfortunately, its main drawback is linked to the difficulty to assess such parameters by means of numerical simulation of the welding process, because of the high mesh density required to capture the residual stress field singularity. In this scenario, new numerical methodologies are needed which use coarse meshes, such as the Peak Stress Method (PSM). In this work, an investigation is described aimed at analyzing the PSM applicability to estimate the R-NSIF values in a 3D butt-welded joint. It was shown that the R-NSIF values obtained ‘via’ the PSM by using 3D models are quite higher (about 45%) as compared to estimations obtained by means of a 2D model, under generalized plain strain condition. This was attributed to the limitation of 2D models to correctly assess the residual stress field induced by welding processes.