y zyxwvutsrqp A Computational Model for the Numerical Simulation of CP1252, NUMIFORM 2010, Proceedings of the10 th International Conference edited by F. Barlat, Y. H. Moon, and M.G. Lee © 2010 American Institute of Physics 978-0-7354-0800-5/10/$30.00 FSW Processes C. Agelet de Saracibar a , M. Chiumenti a , D. Santiago b , M. Cervera a , N. Dialami a and G. Lombera b a International Center for Numerical Methods in Engineering (CIMNE) Building C1, Campus Norte, UPC, Gran Capitán s/n, 08034 Barcelona, Spain b Grupo de Ingeniería Asistido por Computadora, Universidad Nacional de Mar del Plata, J.B. Justo 4302, 7600 Mar del Plata, Argentina Abstract. In this paper a computational model for the numerical simulation of Friction Stir Welding (FSW) processes is presented. FSW is a new method of welding in solid state in which a shouldered tool with a profile probe is rotated and slowly plunged into the joint line between two pieces of sheet or plate material which are butted together. Once the probe has been completely inserted, it is moved with a small tilt angle in the welding direction. Here a quasi-static, thermal transient, mixed multiscale stabilized Eulerian formulation is used. Norton-Hoff and Sheppard-Wright rigid thermo- viscoplastic material models have been considered. A staggered solution algorithm is defined such that for any time step, the mechanical problem is solved at constant temperature and then the thermal problem is solved keeping constant the mechanical variables. A pressure multiscale stabilized mixed linear velocity/linear pressure finite element interpolation formulation is used to solve the mechanical problem and a convection multiscale stabilized linear temperature interpolation formulation is used to solve the thermal problem. The model has been implemented into the in-house developed FE code COMET. Results obtained in the simulation of FSW process are compared to other numerical results or experimental results, when available. Keywords: Friction Stir Welding, Thermomechanical Modeling, Stabilization Methods. PACS: 02.60 Cb, 02.70 Dh, 44.05.+e, 46.15.-x, 47.11.Fg INTRODUCTION Friction Stir Welding (FSW) is a new method of welding in solid state, created and patented by “The Welding Institute” (TWI) in 1991 [1]. In FSW a cylindrical, shouldered tool with a profiled probe is rotated and slowly plunged into the joint line between two pieces of sheet or plate material, which are butted together. The parts have to be clamped onto a backing bar in a manner that prevents the abutting joint faces from being forced apart. Once the probe has been completely inserted, it is moved with a small tilt angle in the welding direction. The shoulder applies a pressure on the material to constrain the plasticized material around the probe tool. Due to the advancing and rotating effect of the probe and shoulder of the tool along the seam, an advancing side and a retreating side are formed and the softened and heated material flows around the probe to its backside where the material is consolidated to create a high-quality solid-state weld. The maximum temperature reached is of the order of 80% of the melting temperature. Despite the simplicity of the procedure, the mechanisms behind the process and the material flow around the probe tool are very complex and the computational modeling of FSW processes is one of the most interesting research topics over the last years [2-7]. The material is extruded around the rotating tool and a vortex flow field near the probe due to the downward flow is induced by the probe thread. The process can be regarded as a solid phase keyhole welding technique since a hole to accommodate the probe is generated, then filled during the welding sequence. The material flow depends on welding process parameters, such as welding and rotation speed, pressure, etc., and on the characteristics of the tools, such as materials, design, etc. The first applications of FSW have been in aluminum fabrications. The weld quality is excellent, with none of the porosity that can arise in fusion welding, and the mechanical properties are at least as good as the best achievable 81