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Acoustic characteristics of standing waves in ultrasound-assisted laser–metal inert gas hybrid welding

We propose an ultrasound-assisted laser–metal inert gas hybrid welding process, where acoustic effects are introduced by applying ultrasonic vibration in the axial direction of the arc. We studied the acoustic characteristics in the space between the acoustic radiating and reflecting surfaces. Based on a simplified two-dimensional model, we used the finite-element method to study the influence of the height and inclination of the radiating surface on the acoustic characteristics. The simulated sound pressure distribution was highly sensitive to the height and inclination of the radiating surface. The sound pressure decreased as the height of the radiating surface increased from a maximum value at the resonance height, and decreased as the inclination of radiating surface increased. Experimental results of the detachment of a water droplet from a needle were consistent with the simulation results. We simulated the distribution of the standing-wave field under different radiating concave-sphere surfaces to evaluate the acoustic focusing effects. Both experimental and simulation results for ultrasonic standing-wave levitation of plastic beads revealed the concave-sphere shape to be optimal.