22nd International Congress of Mechanical Engineering (COBEM 2013) November 3-7, 2013, Ribeirão Preto, SP, Brazil Copyright © 2013 by ABCM APPLICABILITY OF THE GAUSSIAN DISTRIBUTION HEAT SOURCE MODEL TO THE THERMAL SIMULATION OF WELDING PROCESSES Douglas Bezerra de Araújo Paulo Roberto de Freitas Teixeira Luiz Antônio Bragança da Cunda Universidade Federal do Rio Grande – FURG, Av. Itália, km 8, Campus Carreiros, 96203-900, Rio Grande, RS, Brazil daraujo@furg.br, pauloteixeira@furg.br, luizcunda@furg.br Abstract. Welding processes are considered a thermal-mechanical-metallurgical coupled issue. The most important boundary condition in the thermal analysis is the heat source model. Although many studies have been carried out to propose different types of heat source models, the limitations of each model application have not been clearly specified. The Gaussian heat source is a model in which heat is generated over a surface; therefore, it may not be suitable to be applied to thick plates. In this study, the accuracy of the Gaussian heat source model is investigated in bead-on-plate welding by the TIG process. Analyses are performed by the ANSYS ® software, considering the convection and the radiation phenomena. Several cases with different parameters of heat distribution, heat input and plate thickness have had their weld pool geometries analyzed and compared with those obtained experimentally. Analyses of the influence of the radial distance from the center of the Gaussian heat source and the thickness of the plate on the bead width and the penetrated depth of the fusion zone boundary are presented. Results have shown the adequacy and the limitations of the Gaussian heat source model in the welding simulation. Keywords: welding process, numerical simulation, heat source model, ANSYS ® software 1. INTRODUCTION The application of the numerical simulation to the welding process has recently grown mainly due to the increase in the capacity of computers and the availability of commercial numerical codes. The Finite Element Method (FEM) has been the most common technique for the analysis of welding problems which involve thermal, metallurgical and mechanical phenomena simultaneously. Lindgren (2001) and Dong (2005) have shown that thermal-mechanical decoupled analysis provides accurate results and simplifies the numerical solution. Similarly, other authors, such as Coret and Combescure (2002), Wu et al. (2009) and El-Ahmar (2007) have considered that the influence of the mechanical model on thermal and metallurgical simulations is not significant in the welding process application. However, coupling between thermal and metallurgical analyzes is employed to determine temperature and phase fraction fields. The first studies of numerical simulation of phenomena that occur in welding process were carried out by Friedman (1975) who developed a thermal-mechanical model based on MEF to calculate temperature, stress and distortion distributions. Computational programs based on MEF which take into account the elasto-plastic behavior of the material were developed by Muraki et al. (1975) to monitor the thermal stress and the metal movement. Afterwards, Papazoglou and Masubuchi (1982) have described a technique to analyze temperature, thermal stress and residual stress distributions by MEF, including phase transformations. The authors have emphasized the importance of the phase transformation, mainly for tempered and annealing steel welding. Mochizuki et al. (2005) have recently investigated the relation between the residual stress and the phase transformation by employing the SYSWELD ® computational program. This program includes the following characteristics: moving heat source, material deposition, metallurgical transformations, material properties that depend on the temperature and plasticity. The authors observed that thermal and residual stresses are highly sensitive to the cooling rate effects and the phase transformations. Free and Goff (1989) have got good results when using mechanical and thermal formulations to forecast residual stresses in multipass welding processes by MEF, assuming the transversal section as the computational domain and the perfect plasticity of the material. Josefson (1993) estimated the residual stresses in multipass welding cases by SOLVIA ® and ABAQUS ® computational programs, which are commercial codes available to carry out non-linear analyzes by MEF. Brickstad and Josefson (1998) simulated residual stresses due to welding by ABAQUS ® , considering thermal and mechanical fields. They employed the element birth technique to represent the welding bead setting and to avoid some incompatibility of displacement or deformation at nodes that connect welding elements to base material ones. Fanous et al. (2002) have employed another technique to consider the metal deposition using moving elements and have taken into account the influence of temperature on material properties. The main difficulty of the thermal field simulation in a welding process is the heat source modeling. Since Rosenthal (1941) proposed the analytical solution considering a punctual or a line heat source, several more realistic heat source distributions have been developed. Eagar and Tsai (1983), Cho and Kim (2002), Deng et al. (2007) and Rayamyaki et al. (2007) developed and applied a surface heat source model based on the Gaussian distribution. Other researchers, such as Balasubramanian et al. (2008), Zaeh and Schober (2008) and Ziolkowski and Brauer (2009), ISSN 2176-5480 10023