Study On The High Power Ultrasonic Multi-frequency Transducers

The frequency of transducer is an important factor in ultrasonic applications. According to the theory of half wavelength transducer, when transducer is at resonance, its length is a half of wavelength, so the frequency of transducer just changes within a small range. It makes that applications of transducer are limited. So study of multi-frequency transducer is very important. Wang Chenghao and others put forward a method to adjust frequency by changing electric load. However, the theory about design multi-frequency torsional transducer, the match circuit of multi-frequency transducer and how to realize multi-frequency ultrasonic system is still scarce. It is necessary to farther study. In this article the multi-frequency longitudinal transducer and torsional transducer is studied, the resonance frequency equations of transducers are derived. According to the resonance frequency equations, a multi-frequency longitudinal transducer is designed and made, the resonance frequency of transducer is measured, and the measured results are in good agreement with the theoretical value. Then the electromechanical parameters of a multi-frequency longitudinal transducer is measured by the method of impendence-circle, it can offer data for transducers match. From the result, multi- frequency transducer must adopt dynamic math circuit. Finally, a kind of multi-frequency ultrasonic system is designed, it consists of generator, match circuit and transducer, some parameters are computed, this ultrasonic system can be used in ultrasonic cleaning and Sonochemistry.In detail, the context include several aspects:1 .The longitudinal vibration of piezoelectric rod polarized in thickness direction whose electric terminals are loaded is analyzed; the equivalent circuit of the rod is obtained. Piezoelectric segment stacks whose electric terminals are loaded is studied, the equivalent circuit and resonant frequency are derived. Then a symmetrical multi-frequency longitudinal transducer is designed and made, the resonant frequency is measured, and the measured results are in good agreement with this theoretical value. Finally, an asymmetrical multi-frequency transducer is designed, the resonant frequency of transducer is obtained, that is,This type of transducer can be used in ultrasonic cleaning and other fields.2. The torsional vibration of the tangentially polarized piezoelectric slender pipe and the segment cylinder by stacking a number of identical pieces whose electric terminals are loaded is studied, the electromechanical equivalent circuit and resonant frequency are obtained, and further, two kinds of multi-frequency torsional transducers are designed, the resonant frequency equations are derived, it can be used to design same type of torsional transducer. Finally, the physical principle of adjusting frequency by piezoelectric effect is studied, the results shows that appending inductance load is equal to increase mass of system, it makes frequency fall and appending capacitance is equal to increase mechanical compliance, it makes frequency raise.3. The parameters of electromechanical equivalent circuit of multi-frequency logni- tudinal transducer are measured. The disciplinary of parameters of electromechanical is derived. The result of measure shows that dynamic capacitance Cj, dynamic impedance RI and inductance LI change within a wide range. So multi-frequency longitudinal transducer must adopt dynamic match. In this article digital inductance match circuit is adopted.4. In this part, a project of multi -frequency ultrasonic system consisting of generator, match circuit and transducer is put forward, some parameters of dynamic match circuit and electric load of transducer are computed. A simulative experiment is designed to test the feasibility of the project; experiment results are in good agreement with expected. This ultrasonic system can be used in ultrasonic cleaning and Sonochemistry.