Characteristic and Mechanism of Periodic Oscillation of Force in Friction Stir Welding of Aluminum Alloy

doi:10.3901/JME.2022.12.055

Abstract

Abstract: A three-component force sensor is used to measure the plunge force (F_z), traverse force (F_x), and lateral force (F_y) of friction stir welding (FSW) of 8 mm thick 5A06-H112 aluminum alloy. The cause of the periodic oscillation of the force signals and its relationship with welding defects are analysed. Both F_x and F_y showed periodic oscillations, and the frequency is consistent with the rotation frequency of the tool. The waveform of F_y lags behind F_x and the phase difference is π/2. The oscillation amplitude of F_z is small. The average values of F_x and F_y decrease with increasing the rotating speed of the FSW tool, and increases with increasing of the welding speed. When the defective-free joint is obtained, F_x and F_y have no overlap and the waveforms of F_x and F_y are both sinusoidal waves. F_x and F_y overlapped partially and the waveforms of F_x and F_y show distortion when the defective joint is obtained. The numerical simulation results show that F_x presents periodic oscillations with the eccentricity of the tool of 0.01 mm. Furthermore, F_x keeps constant when the tool has no eccentric motion. Therefore, the eccentric rotation of the tool is the main reason for the periodic oscillation of F_x. In addition, the eccentric rotation of the tool causes the periodic variation of the stress and flow of the plasticized material around the tool. With continuous rotating and traversing of the tool, the weld has the periodic internal microstructure and surface morphology.

Key words: aluminum alloy, friction stir welding, three component force, periodic oscillation

CLC Number:

TG156

KANG Su, LI Dongxiao, LI Xiaoguang, GUAN Wei, WU Shaojie, CUI Lei. Characteristic and Mechanism of Periodic Oscillation of Force in Friction Stir Welding of Aluminum Alloy[J]. Journal of Mechanical Engineering, 2022, 58(12): 55-63.

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