Abstract
An ultrasonically vibrating end surface can retain large amount of liquid, the phenomenon of which has been newly discovered by author's group. Amount of adhering liquid linearly increases with vibration amplitude unless the cavitation occurs. At the same amount of adhering liquid, the droplet appearance becomes flatter to the vibrating end surface with an increase in vibration amplitude. The mechanism which allows large amount of liquid adhesion is discussed by focusing on the distribution of radiation pressure in an adhering droplet. The radiation pressure in a droplet exponentially decreases with distance from the horn end surface. A dynamic balance model regarding an adhering droplet was constructed through taking into consideration of the balance of liquid weight. intrinsic surface tension and radiation pressure. The calculated droplet appearance based on the model is good agreement with the experimentally observed one. With dipping and raising-up of an ultrasonically vibrated horn end to molten magnesium alloy, the maximum adhesion attains at 873 K, at which adhering metal is a semi-solid state approved by temperature measurement. Ultrasonic casting of magnesium alloy, in which the adhering molten or semi-solid metal is compressed by the counter molds, was carried out using a high powered ultrasonic transducer for shaping a thin saucer. Cast products are successfully manufactured without appreciable defects, because long molten metal flow is not necessary in the novel casing process.
