Analytical Modeling of the Friction Stir Welding Using an analytical approach, it is seen that by increasing the number of edges, the amount of heat generation initially increases from the triangular to ABSTRACT Friction stir welding (FSW) is considered a combination of extrusion, forging, and stirring of the material where a high strain rate and temperature are generated. Due to the complex nature of heat generation in FSW, the analytical model defines variables and parameters that dominantly affect heat generation, and many of them cannot be fully mathematically explained. This paper proposes an analytical model for heat generation for FSW using different pin profiles such as triangular, square, pentagon, and hexagon. From the obtained results, it is observed that the lowest temperature is generated during welding using the hexagonal pin profile, while the square pin profile has the highest temperature among all pin profiles under the given set of working conditions. Furthermore, the results obtained from numerical modeling show that increasing the tool rotational speed at constant weld speed increases the heat input, whereas the heat input decreases with an increase in the weld speed at constant tool rotational speed. In addition, the paper describes the application of Comsol to thermal modeling in FSW. Different tool pin profiles used for the analysis for heat generation and temperature distribution are also included. KEYWORDS • Friction Stir Welding (FSW) • Analytical Modeling • Tool Geometry • Heat Generation • Aluminum Alloy Introduction Process Using Different Pin Profiles square pin profile, then decreases to the hexagon pin profile BY V. S. GADAKH, A. KUMAR, AND G. J. VIKHE PATIL Traditionally, the heat generation in friction stir welding (FSW) was considered to be due to friction, but practically it is due to friction as well as deformation. Henceforth, it will better to be termed as ‘deformation stir welding’ rather than FSW (Ref. 1). Heat generation in FSW is a complex transformation process where one part of mechanical energy is delivered to the tool, which is consumed in welding, while another is used for the deformation process and the rest of the energy is transformed into heat (Ref. 2). In the present work, an analytical model for heat generation WELDING RESEARCH using different pin profiles such as triangular (TR), square (SQ), pentagon (PEN), and hexagon (HEX) are developed. As for today, the analytical models developed are for straight cylindrical (SC) (Refs. 3, 4) and taper cylindrical (TC) (Ref. 5) pin profiles. Khandkar et al. (Ref. 3) introduced a torque-based heat input model for SC pin profile, where the torque/power known from experiments is used in the expression for the heat source. Furthermore, Schmidt et al. (Ref. 4) developed an analytical model for heat generation for SC having a concave shoulder in FSW based on different assumptions in terms of contact condition between the rotating tool surface and workpiece. The models developed by Schmidt et al. (Ref. 4) and Ulysse (Ref. 5) assume that heat is dominantly generated on the shoulder tip and neglect the heat generated on the probe. Their models show that 80–90% of the mechanical power delivered to the welding tool transforms into heat. The model developed by Song and Kovačević (Ref. 6) considers all active surfaces in the analysis of heat generation and shows that 60–100% of the mechanical power transforms into heat during FSW. Gadakh and Kumar (Ref. 7) developed an analytical model for heat generation for TC, which is the modification of analytical models developed for SC pin profiles. Elangovan et al. (Ref. 8) have considered five different pin profiles such as SC, TC, TH (threaded cylindrical), SQ, and TR. They reported that the SQ pin profiled tool exhibited superior tensile properties. Pin profiles with flat faces (SQ and TR) are associated with eccentricity, which produces the pulsating stirring action and causes a reduction in grain size and homogenous redistribution of the second phase V. S. GADAKH (gadakh_vijay@rediffmail.com) and A. KUMAR are with the Department of Mechanical Engineering, National Institute of Technology, Warangal, India. GADAKH (PhD research scholar) and G. J. VIKHE PATIL are with the Department of Mechanical Engineering, Amrutvahini College of Engineering, Sangamner, Savitribai Phule University Pune, Pune, India. APRIL 2015 / WELDING JOURNAL 115-s
Welding Journal | April 2015
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