Time Efficient Simulations of Plunge and Dwell Phase of FSW and its Significance in FSSW

Friction Stir Spot Welding (FSSW) is gathering attention of automotive and aerospace sectors. It is an alternative for rivets, electric resistance welding and offers substantial advantages with regard to energy consumption, environmental protection and mechanical properties of weld. At present, research efforts are being made to gain a better understanding of the process, to explore different tool configurations, to optimize the set of process parameters and to widen the applicability of FSSW. In this regard, having reliable finite element model that is capable of simulating FSSW with minimal possible simulation time can turn out handy to reduce the number of physical experiments required in such studies and applications. The current work investigates the plunge and dwell phase of Friction Stir Welding (FSW) using three-dimensional (3-D) finite element (FE) modelling. A 3-D FE model is developed in the commercial code ABAQUS/Explicit using the Coupled Eulerian-Lagrangian Formulation, the Johnson-Cook material law, and Coulomb's Law of friction. A successful weld depends on proper material flow and temperature existing during the process. This is dictated by selected processing parameters. If the appropriate conditions are not present, cold or hot defects occur, leading to a faulty weld. Since FSSW comprises of plunge and dwell phase, the simulation results are explained in the context of modeling of FSSW. The simulation results include effect of process parameters (tool rotation speed, plunge velocity, plunge depth) and tool geometry (pin profile) on estimating temperature and morphology of weld region. Tools with square and triangular pin profile aided in increasing the process temperature and widening the weld nugget with less power consumption compared to their counterpart. Simulation time reduced to a greater extent in CEL when compared to Lagrangian, Eulerian and ALE.