Multipass welding simulation of tig welded AISI 316LN

Residual stresses may have considerable effects on the behaviour of a welded structure. However, these stresses are difficult to measure on site, therefore a numerical tool may provide a suitable means to predict these residual stresses. When dealing with multi-pass welds, numerical procedures found in literature suggest that the user must change the mesh after each weld pass. In doing so, the prediction of the residual stresses becomes quite labour intensive. Therefore, a new approach for the prediction of residual stresses due to multi-pass welding is desirable. In this new approach the plate and the filler material of all the weld passes are present from the start of the analysis. The plate and filler material is modelled using contact bodies. In the thermal analysis the bodies can be (de)activated. The results from the thermal analysis are used for the mechanical analysis, i.e. an uncoupled analysis is performed. At temperatures above the melting point, sliding of the contact bodies is allowed while below the melting point the bodies are effectively glued to their surroundings. For comparison with the thermal analysis, experiments were performed to measure the temperatures in an AISI 316 LN stainless steel plate during the Tungsten Inert Gas (TIG) welding process. The temperatures obtained from the calculations are too high and cooling of the plate is too fast, in comparison with the measurements. The deformation and the residual stresses obtained by the mechanical analysis are found to be too small. However, the approach used here to model a multi-pass weld process can be used with minor adjustments.