Finite Element Simulation of Welding Residual Stresses

Abstract

Prediction of residual stresses in welded joints using nondestructive test (NDT) methods such as X-ray or neutron diffraction techniques can often benefit from numerical analysis of those stresses. Such analyses, which can be carried out either before or after the NDT procedure, are most reliably done with the help of powerful finite element (FE) simulation techniques. Although the finite element method is one of the most attractive approaches for computing residual stresses in welded joints, its application to practical analysis and design problems has been hampered by computational difficulties. These difficulties do not arise in modeling the complex constitutive response of melting and solidifying metal; rather, they occur mostly because of the enormous computational size of any practical problem resulting primarily from the three-dimensional (3D) modeling of a welding process. Although two-dimensional (2D) modeling has been used widely in residual stress problems, current belief holds that 2D analysis cannot render accurate residual stresses that occur due to welding. This study investigates the residual stress fields in a welded T-joint, comparing those computed by 3D models to those computed by 2D models. The study shows that the temperature distribution in the central zone of the joint can be captured successfully by a 2D finite element model and a technique that takes into account the heat transfer balance and welding speed. The residual stresses in the plane of the 2D model computed by this method show fairly good agreement with those computed by the 3D model.