Finite Element Modelling of Shape Metal Deposition

Abstract

Shape Metal Deposition (SMD) is a novel process for rapid prototyping that employs Tungsten inert gas (TIG) welding. The state of the art can be enhanced through modelling and control. It is of industrial interest to develop systematized models to explain observed phenomena and to allow prediction of processing conditions for process planning and optimization. In this work, the thermal and mechanical finite element modelling of SMD are presented. The thermal problem is solved with linear tetrahedral finite elements taking into account the liquid/solid phase change phenomena. The mechanical problem is solved with tri-linear hexahedral elements using a mixed formulation. Special techniques to account for the added material were developed. A set of numerical tests were conducted to determine the heat source model parameters, with validation by compared to experimental in a Ti6Al4V thick plate were developed in order to validate the implemented formulations. Tests consist on TIG washing procedures (welding without wire feeding in order to preheat the plate) followed by welded beads. Finally the experimental results including temperatures and displacements are compared with those obtained with the FEM code.