Deformations and stresses in butt-welding of plates numerical simulation and experimental verification

Abstract: Deformation and stresses in butt-welding of plates were studied. The work includes numerical simulation and experimental verification. The simulations were performed by use of the finite element method. Temperature dependence of material properties and phase transformations were considered. A thermo-elastoplastic material model was used. Plane stress conditions were assumed. Automatic butt-welding of plates without backing needs close tolerances of joint geometry. The thermally induced deformations and stresses are of great importance for joint geometry during welding. Therefore the change of gap width in front of the moving arc has been of special interest in these studies. The residual stresses, which may affect inservice behaviour of welded plates, were also calculated and measured. The tack-welds were found to influence the change in gap width in front of the moving arc. A proper tack-welding procedure is important in order to avoid large changes in gap width during butt-welding. The tack-welds should be made as soon after each other as possible. The sequence in which the tack-welds are made also affect the change in gap width. The gap width increased during the last part of the butt-welding in the simulations performed in this work. This increase was larger for wide plates than for narrow plates. Residual stresses close to the weld were large. The effective stress reached the yield limit of the material in the weld line.