Numerical Study of the Tool Rake Angle Effect on the Material Flow in Friction Stir Welding Process

Abstract

Minimizing consumed energy in friction stir welding (FSW) is one of the prominent considerations in the process development. Modifications of the FSW tool geometry might be categorized as the initial attempt to achieve a minimum FSW effort. Advanced tool pin and shoulder features as well as a low-conductive backing plate, high-conductive FSW tools equipped with cooling fins, and single or multi-step welding processes are all carried out to achieve a flawless weld with reduced welding effort. The outcomes of these attempts are considerable, primarily when the tool pin traditional designs are replaced with threaded, Trifiute or Trivex geometries. Nevertheless, the problem remains as to how an inclined tool affects the material flow characteristics and the loads applied to the tool. It is experimentally proven that a positive rake angle facilitates the traverse motion of the FSW tool; however, few computational evidences were provided. In this study, numerical material flow and heat transfer analysis are carried out for the presumed tool rake angle ranging from −4° to 4°. Afterwards, the effects of the tool rake angle to the dynamic pressure distribution, strain-rates, and velocity profiles are numerically computed. Furthermore, coefficients of drag, lift, and side force and moment applied to the tool from the visco-plastic material region are computed for each of the tool rake angles. Eventually, this paper confirms that the rake angle dramatically affects the magnitude of the loads applied to the FSW tool, and the developed advanced numerical model might be used to find optimum tool rake angle for other aluminum alloys.

Numerical and Experimental Investigations on the Loads Carried by the Tool During Friction Stir Welding

“…The axial force reaches the extreme amount in the highest angular and lowest traverse velocities. This phenomenon may be readily verified if the dynamic pressure distribution along the weld cross-section was studied (Ref 36,37). Plot of Fig.…”

“…However the inertia effect, regardless of its lower extent, augments the lateral force in the higher traverse velocity range but in a negative z-axis direction. This phenomenon will be readily concluded if the dynamic pressure distribution in retreating and advancing sides of the weld is studied ( Ref 36,37). Plotting of the moment in Fig.…”