5 th International & 26 th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12 th –14 th , 2014, IIT Guwahati, Assam, India 28-1 Effect of tool geometry and process parameters on the material flow of friction stir welding. Arun Kumar Kadian 1 , Gautam Puri 2 , Suman Das 2 , Pankaj Biswas 3* 1 Mechanical Engineering, IIT Guwahati, 781039, arun.kadian@iitg.ernet.in 2 Mechanical Engineering, IIT Guwahati, 781039,g.puri@iitg.ernet.in 2 Mechanical Engineering, IIT Guwahati, 781039,suman.das@iitg.ernet.in 3* Mechanical Engineering, IIT Guwahati,781039,pankaj.biswas@iitg.ernet.in Abstract The material flow behavior of friction stir welding is an emerging research area in past few years. In this present work two different tool geometries has been considered to study the material flow patterns of the welding process. A 3-D CFD analysis is performed with suitable boundary conditions to study the nature of material flow behavior of FSW process. A comparative study has been done based on the results obtained from numerical analysis for the two different tool geometries. The parameters used for the analysis of welding process also varied one by one for both the cases to achieve a good comparison on the effect of tool geometry on the material flow. The estimated material flow behavior compared well with those of the published results thus validating the various assumptions made in the work. It was observed that in FSW tool geometries has significant effect on material flow behavior. Keywords: Finite Element Analysis, Transient Thermal Analysis, Combined Stick & Slip Condition, Friction Stir Welding. 1 Introduction Friction Stir Welding (FSW) is a solid state welding method having a non-consumable tool without using filler material. The process was invented by The Welding Institute (TWI), Cambridge, UK and patented in 1991(W.H. Thomas). During this process the rotating tool moves material from advancing side to retreating side. So, it is important to know the manner in which the material behaves when it gets plasticized. The way in which the material flows in a friction stir welding process is need to understand to know the quality of the weld. The different parameter of the welds leads to different material flow behavior such as rotational speed, traverse speed etc. and a lot more depends upon the base material to be welded and its material properties at room temperature and when it reaches plastic state. The tool geometry is also considered the most important factor on which the material flow depends. The material flow directly influences the quality of weld or the kind of defect may arise after the welding. Since the material flow is not visible to naked eyes or any instrument in an experiment. It is very difficult to understand what is actually happening inside the welding process by experimental methods. So far, a very few attempts have been made to study the material flow behavior of Friction stir welding. E. Feulvarch et al. (2012)proposed a simple and robust moving mesh technique for finite element simulation of friction stir welding in which the heat transfer analysis and a material flow analysis can be achieved with a trigonal pin geometry. H. W. Zhang et al. (2007), (2004)H. Jamshidi Aval et al. (2011)investigated the material flow using temperature dependent material properties with the help of a finite element code using ABAQUS package. Some researchers like Lorrainet al. (2010),WU Chuan-songet al.(2012),Carter Hamiltonet al.(2008),K. Kumaret al. (2008) made an attempt to understand the flow of material experimentally for an unthreaded cylindrical tapered tool and studied the microstructure of the weld zone. Rodrigueset al.(2014) worked on polymethyl methacrylate (PMMA) to investigate the material flow and thermo- mechanical analysis of friction stir welding.S.D. Jietal.(2012) used different threaded tool geometry to investigate the flow of material inside the base material in ANSYS Fluent package. They investigated the effect if tool shoulder on material flow. R. Kovacevic et al. (2003) introduced a moving coordinate in a transient 3D heat transfer analysis with the help of a mathematical model and analyzed a 3D model for different process parameter in commercial Finite Element package ANSYS considering sliding condition. Similar type of work was performed by G. buffa et al.(2011,12),D. Trimble et al. (2007) to predicted the residual stresses distribution with a 3D elasto plastic model Finite element model in DEFORM-3D™ and achieved a reduction in computational time.D. Jacquin et al. [17](2011) worked on a 3D thermo-mechanical model based on the model proposed by Heurtier et al. (2006) based on Eularian approach. Dongun Kim et al.(2010) utilized FVM code in STAR-CCM+ (based on eularian formulation) to study the temperature histories at different welding parameters. So far not much work is done on material flow. It is an important area to work