DETERMINATION OF RESIDUAL-STRESSES IN THICK-SECTION WELDMENTS

Abstract

The purpose of this study is to develop an analytical method for predicting through thickness distribution of residual stresses in a thick plate with a multipass welding process. The analysis was carried out in two steps. The first step was to develop a thermal model for heat flow analysis in a two-dimensional cross-section of the plate. For a modeling of the heat input to the cross-section, a ramp heat input was used to avoid numerical instability and to include the effect of a moving arc. The best ramp time was selected by an analysis of the root pass on a 1/2-in. (1 2.7-mm) thick plate and comparing it with experiments. The next step was to develop a structural model to predict stress distribution using the thermal loading obtained in the first step. A generalized plane strain assumption was used in the stress analysis. A lumped pass model was developed to reduce the total computational time and cost. Each layer of weld bead was assumed as one lumped pass in this model. The heat input for every pass in that layer was added and applied on the top surface of a weld layer. The results by the lumped model showed good agreement with the experiment and the results of another model, which analyzed every weld pass separately.