Coupled thermo-mechanical analysis for the numerical simulation of welding processes

Abstract

The aim of this paper consists of both the description of the formulation adopted for the numerical simulation of the Metal Deposition process (MD) and the experimental work carried out at ITP Industry (Industria de Turbo Propulsores, SA, Spain). MD process consists of a manufacturing technology similar to the multi-pass welding used for building features such as bosses and flanges on fabricated components. A fully coupled thermo-mechanical solution is considered including phase-change phenomena defined in terms of latent heat release and shrinkage effects. Temperature evolution as well as residual stresses and distortions due to the successive welding layers are accurately studied coupling the heat transfer analysis together with the mechanical field. The material behaviour is characterized by a thermo-elasto-viscoplastic constitutive model (at macro-level) coupled with a metallurgical model (at micro-level). Nickel super-alloy 718 is the target material of this work. Both heat convection and heat radiation models are introduced to dissipate heat through the boundaries. An in-house developed coupled FE software was the starting point to deal with the simulation and an ad-hoc activation methodology has been implemented to simulate the deposition of the different layers of melted material. Thermo-mechanical results are presented in terms of temperature evolution, residual stresses generated and distortions compared with the experimental data obtained at the MD laboratories of ITP. Difficulties and simplifying hypotheses are discussed.