Enhancing refill friction stir spot welding with ultrasonic waves: An experimental study

This study investigates the integration of ultrasonic vibrations into the Refill Friction Stir Spot Welding (RFSSW) process to assess their impact on weld quality. The results indicate that the application of ultrasonic waves can improve weld strength by increasing penetration depth and allowing for reduced tool rotational speeds. Experiments were conducted on 1 mm thick sheets of 6061 aluminum alloy using a custom-built RFSSW setup that incorporated ultrasonic transducers. The research focused on three primary parameters: tool rotational speed, penetration depth, and ultrasonic power. Ultrasonic vibrations were introduced to the weld joint in vertical and horizontal orientations. The mechanical properties of the welds, including tensile strength, shear strength, and hardness, were evaluated, along with an analysis of fracture characteristics. The findings indicate that ultrasonic vibrations significantly enhance weld strength, with the vertical application outperforming the horizontal configuration.