| High power ultrasonic has been widely used in the field of industry and domesticappliances and the power ultrasonic transducers are the most fundamental device of theseappliances. At present, piezoelectric ultrasonic transducers in which the piezoelectricceramics are used as actuating materials dominate the market of ultrasonic transducers.However, the energy density and poor thermal conductivity of piezoelectric ceramic materialare very low. When piezoelectric ceramic material is working in continuous high powersituations, it is easy to cause depolarization and become fragile because its internal heat cannot be promptly delivered to the outside in time. These disadvantages caused the applicationsof this material in field of power ultrasonic transducer are limited. Hence, this material cannotsatisfy the market requirement for higher performance transducers due to the restriction of itsoriginal material properties.The rare earth giant magnetostrictive material is a new functional materials withexcellent properties, such as large strain output, high energy density, high conversionefficiency, fast response speed, high Curie temperature, and superior thermal conductivitythan piezoelectric ceramic. The giant magnetostrictive material has been used to manufacturelow frequency, high power acoustic transducer and has shown some excellent performances.It has obvious advantages using in the high power ultrasonic transducers. In recent years, itsapplication has become the hot spot in high power ultrasonic transducers research.This paper systematically report my research work of Giant Magnetostrictive PowerUltrasonic Transducer (GMPUT). In first, the theory of the work mechanism and relatedapplications of GMPUT were studied. Then, the experimental prototypes of GMPUT weredesigned and made. And the experimental platforms for investigation and measurement ofhysteresis characteristics, dynamic characteristics and impedance characteristics of GMPUTwere constructed. Furthermore, the mathematical model of hysteresis characteristics special toGMPUT was studied experimentally and theoretically, and loss characteristics of theexperimental prototypes were measured and analyzed. The measurement andtheoretical analysis of heat generation and dissipation mechanism of the experimentalprototypes were studied, and the distribution of temperature field of the experimental prototypes were computed and analyzed. Based on the analysis result of temperature filed, thecooling system of transducer was designed. Finally, on the basis of electro-acoustic theories,the impedance characteristics of transducer were analyzed with the combination ofmechanical system and electrical system by the method of electromechanical analogy, andsome key factors that affect the impedance of the transducer have been obtained by aboveanalysis and impedance test of transducer.On the basis of above work, based on the magnetic hysteresis model, the combination ofa quadratic magnetostrictive model and principles of mechanical dynamics, an elasticvibration model of giant magnetostrictive material was proposed in this paper, and frequencyresponse analysis of this model were performed. Besides, a nonlinear dynamic model ofGMPUT was established, and the nonlinear dynamic characteristics of GMPUT were studiedby analytical methods and computer simulations. The main factors influencing transduceroutput stability has been obtained, and the paper put forward an innovative idea that theresults of chaotic analysis are used to guide the design of magnetostrictive ultrasonictransducer system.Based on the analysis of the magnetic field distribution inside the transducer, this papercreatively put forward a design method of the driving coil component of magnetostrictiveultrasonic transducer. A closed magnetic circuit is made up of the transducer drive elementand coil skeleton, which reduces the magnetic flux leakage of coil skeleton and the end effectsof magnetic field. The design can lead distribute of the magnetic field inside the solenoidmore uniformity and improve the conversion efficiency of energy of transducer. And thispaper put on special treatments for the silicon steel sheets and the actuating element, so thatthe eddy current loss was considerably reduced. |
