WELDING RESEARCH JULY 2016 / WELDING JOURNAL 269-s sonocapillarity have been formulated (Refs. 13, 20–23). Lobova (Ref. 20) found the use of high-intensity ultrasound, which exceeds the cavitation threshold, facilitates the infiltration of the vertically placed quartz capillary with a poorly wetting Ga-In melt (its contact angle on quartz in air at 60°–70°C is 85° ± 5°C) to a height of 0.8–38 mm. This infiltration is due to a sharp increase in liquid pressure at the capillary base. Antonevich (Ref. 13) and Malykh (Ref. 21) attributed the sonocapillary effect to ultrasonic cavitation at the end of the capillary. The researchers observed that the height of the liquid rise is a power more than that resulting from the surface tension when a capillary end is located in a developed cavitation area. This finding is in contrast to the observation that the capillary liquid nonsignificantly increases when the ultrasonic pressure is below the cavitation threshold. Hu (Ref. 22) experimentally confirmed the transportation of water through a bundle of metal wires and its dependence on ultrasonic vibration parameters. However, he inferred that acoustic cavitation is unnecessary for ultrasonic capillary action and argued that ultrasound may weaken the cohesive force among liquid molecules. Thus, the adsorption force between the capillary tube and the liquid may become larger than the cohesive force, thereby enhancing capillary action. Cecchini (Ref. 23) demonstrated that atomization within the fluidic channel followed by surface acoustic wave-assisted coalescence could lead to a net fluid movement. From the hydrodynamic point of view, a pressure difference/gradient is a fundamental factor causing fluid flow. In the present study, the liquid solder flowed from the bath into the clearance and increased above the bath level. A pressure deviation may have existed between the solder bath and the solder in the clearance because the solder rise in the capillary under ultrasonication is nearly independent of its wettability to the aluminum substrate — Figs. 5–9. However, measuring the pressure of the liquid solder outside and inside the clearance is impractical. Thus, we used a sonocapillary system requiring deionized water and a glass Fig. 10 — Variation in solder filling height with ultrasonic amplitude. Fig. 11 — Variation in solder filling height with joint clearance value. Fig. 13 — Acoustic pressure in the water outside and inside the capillary. Fig. 12 — Variation in solder filling height with heating temperature.
Welding Journal | July 2016
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