Influence of thermo-mechanical material properties on the structural response of a welded butt-joint by FEM simulation and experimental tests

This paper deals with the development of a Finite Element (FE) model for the simulation of a two-passes V-groove butt weld joint. Specifically, in order to reduce the computational costs and the efforts aimed to the numerical evaluation of residual stresses distribution in welded joints, a sensitivity analysis has been performed to quantify the level of accuracy provided by the model when the strict dependence of some material properties on the temperature is neglected. Before proceeding with the sensitivity analysis, the reliability of the proposed FE model was assessed against an experimental test; a good agreement between numerical and experiment results has been achieved. In detail, the material properties involved in this sensitivity analysis are: thermal conductivity, specific heat, Young's modulus and thermal expansion coefficient; the investigated outputs are: temperatures, residual stresses, displacements and angular distortion. Several test cases have been simulated by considering all of these material properties as constant, one at a time or all together. The results analysis showed that the levels of accuracy provided by the different simplifications depend on the selected output. Among the most relevant results, it has been found out that the predicted temperatures distributions are not significantly influenced by the considered material simplifications. The effects on the residual stresses in considering the thermal conductivity and the specific heat as constant are negligible. The hypothesis of a constant thermal expansion coefficient provides an acceptable level of accuracy only in proximity of the weld seam. Finally, concerning the displacements field and the angular distortion of the welded plates, by considering the thermal conductivity and Young's modulus as constant, the effectiveness of the model appears to be compromised.