Ultrasonic Power Pulse Characteristics And Its Pilot Study

Aluminum alloy casting and roll casting by ultrasonic field is the international research hotspot in nowadays and a new direction of future casting technique. Therefore high performance aluminum alloy strip can be only made by reasonable designed ultrasound casting equipment. On the basis of ultrasound casting equipment research achievement of our researching-group, a kind of ultrasonic power equipment which suitable for these process was studied.The mainly studies in this paper are as follows:1. The main circuit is the ultrasonic generator power transmission system. SCR rectifier circuit, inverter circuit, the protection circuit of transistor and matching network were mainly studied in this paper. The natural frequency of horn will be changed when it is in the high-temperature melt which cause the mismatch between horn and piezoelectric ceramics. A kind of frequency tracking based on DSP was designed to solve this problem.2. The output size of ultrasonic power has important impact on the aluminum alloy melt processing. Pulse drive and pulse current were studied in this paper aim at improving peak output power of the ultrasonic generator. At the same time these two types circuit for producing pulses were studied. From the related date measured in the pulsed ultrasound power experiment we can conclude that the out put peak voltage and peak current of the ultrasonic power in pulse mode is comparatively higher than in continuous mode. The transducer input voltage is affected by pulse frequency and duty cycle.3. According to the experiment of impulse ultrasonic aluminum alloy grain refinement, following conclusions were summarized:1) The influence of low frequency impulse ultrasonic wave on grain refining is similar with continuous ultrasonic wave:the effect of grain refining become worse with the distance to the amplitude rod terminal face increased. At the direction of amplitude rod radius, the grain refining effect is worse than direction of axis for the reason of ultrasonic acting zone is small. While the time is in a certain range, the effect of grain refining is better when the time of application of ultrasonic treatment is longer or the ultrasonic power is bigger.2) There is still difference between the impulse ultrasonic wave and continuous ultrasonic wave on effect of grain refining:Given the same average power, impulse ultrasonic wave on effect of grain refining is better than that of continuous ultrasonic wave.