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Ultrasound in aluminum melt sound field distribution and cavitation and its effect on the solidifica

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Tutor: LiXiaoQian
School: Central South University
Course: Mechanical Design and Theory
Keywords: Sound field directivity,Admittance,Mechanical quality factor,Resonant Frequency,
CLC: TG292
Type: Master's thesis
Year:  2008
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Abstract:
Semi-continuous casting is the industrial production of non-ferrous alloy casting one of the most important, it can achieve production process automation, streamline processes, save energy, improve labor productivity, in modern metallurgical production occupies an important position and received wide attention. In China, the conventional semi-continuous casting due to the manufacturing process and other reasons, often produce ingot internal or surface inhomogeneity, casting stress cracks and other defects, especially for traditionally difficult to cast high-alloy ingot especially large. The use of ultrasonic refinement of grain, improve the temperature field, stress field shape is conducive aluminum molding process optimization, to obtain high performance casting products. This thesis focuses on the ultrasonic propagation characteristics of molten aluminum, ultrasonic cavitation, ultrasonic energy propagation mechanism and power ultrasound on aluminum solidification process. The main research contents include the following aspects: 1. According to Huygens' principle, the transducer face is divided into numerous small surface element, using the Rayleigh integral method to calculate the regular hexagon, square, round face horn sound field distribution and the respective sound field directivity function. Using Matlab software, calculated for different face shapes horn at different wavenumbers sound field directivity obtained at different wave numbers, different face transducer sound field directivity variation. And gives the same wave number and the physical conditions of the three transducer sound field directivity comparison. (2) Through the ultrasonic vibration system in the aluminum melt admittance analysis, research transducer mechanical quality factor and sound pressure, sound intensity of mutual relations. According sound twists / reflection principle, derived from ultrasonic vibration system is passed to the tool head contact interface with the melt sound pressure amplitude, while establishing a sound pressure, sound intensity related mathematical models discussed in the aluminum melt power ultrasonic distribution and calculate the ultrasonic sound intensity aluminum melt characteristic values. 3 of ultrasonic cavitation effect molten aluminum at high temperatures the basic principles of physical parameters discussed the influence of ultrasonic cavitation, the establishment of relevant mathematical model, using Matlab software Rayleigh-Plesset equation for numerical calculations to study the melting temperature of aluminum body, ultrasonic frequency, the sound pressure and cavitation bubble radius of the initial balance of the ultrasonic cavitation effect. 4 By Marc software simulation Aluminum Ingot diameter φ300mm semi-continuous casting process simulation of two-dimensional Sump curve combined with ultrasonic horn power and establish sound field distribution in the aluminum melt mathematical model study and explore the ultrasonic The propagation characteristics of molten aluminum sound field distribution, analysis of ultrasonic sound waves propagate to the solidification front catadioptric, and calculate the solidification front sound pressure sound pressure level of each point. And to explore the aluminum melt ultrasonic cavitation occurring behavioral characteristics, by the sound pressure distribution, the use of Matlab software, using the difference quotient iteration method, on cavitation bubble wall exercise our powers to Rayleigh-Plesset equation numerical analysis at different half of the initial radius aluminum casting ultrasonic cavitation occurs scope for exploring cavitation ingots organizations studied. 5 of ultrasound parameters under certain conditions, the power ultrasound on the aluminum melt solidification process. Focuses on cavitation and the resulting high temperature and pressure theory, which discusses local high temperature and pressure in the aluminum melt solidification process triggered by a variety of effects and dynamics, and from the cavitation, acoustic streaming effects and mechanical effects, etc., High power ultrasound probe on aluminum melt during solidification mechanism. Through the organizational structure of aluminum comparative analysis concluded: high power ultrasound on solidification of molten aluminum is the combined result of a variety of effects.
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