Simultaneous measurement of tool torque, traverse force and axial force in friction stir welding

•The tool torque, traverse force and axial force are measured simultaneously in real time during friction stir welding.•The correlations of the tool torque and the traverse force with the tool rotation speed and the welding speed is established.•The axial force variation during plunging stage is determined.•The best weld appearance is obtained at low welding speed and high rotation speed.

Simultaneous measurement of the tool torque, traverse force and axial force during friction stir welding process is of great significance to the understanding of the underlying process mechanism and the optimizing of the process parameters. Different from the traditional measurement methods using load cell or rotating component dynamometer, an indirect but economical methodology is used in this study for the simultaneous measurement of the traverse force, axial force and tool torque by monitoring the output torques of the servo motors and main spindle three-phase AC induction motor inside the FSW machine. The values of the traverse force, axial force and tool torque are determined under different welding conditions, and the influencing factors are examined. The measured results in friction stir welding of AA2024-T4 aluminum alloys at different combinations of tool rotation speed and welding speed lay foundation for process optimization.