Research On The Radial Composite Piezoelectric Ultrasonic Transducers

In the field of high power ultrasonic applications such as ultrasonic cleaning, ultrasonic welding, ultrasonic machining, ultrasonic motors and other fields, we need to design a variety of ultrasonic transducer with different structures and vibrational modes. The composite piezoelectric transducer is widely used in many fields because of its high power density and electromechanical conversion efficiency. The longitude sandwich piezoelectric transducer’(or Langevin transducer) structure is simple and has high electro-acoustic efficiency, and its resonance frequency can be adjusted easily by changing the dimensions of the back and front metal blocks. At present, this kind of transducers’vibrational modes mainly includes longitudinal vibrational mode, torsional vibrational mode and bending vibrational mode. However, with the developing of ultrasound technology and expanding the scope of power ultrasonic, the structure and the radiation of the transducer is put forward new requirements, in order to meet different application requirements. The radial composite ultrasonic transducer which is notable for its large area and high efficiency of radiation has widely application prospects in liquid ultrasonic field.1. The radial and torisonal vibration of an annular ultrasonic concentrator with power function profile is studied. Base on the electromechanical analogy, its equivalent circuit model is derived. The (torsional) displacement amplitude magnification coefficient of the concentrator and resonance frequency equation were obtained. The FEM simulations were illustrated good agreement with the theoretical results.2. A new type of radial composite piezoelectric transducer is studied. It can impose a bi-directional radial pre-stress to the piezoelectric ceramic of the transducer through a metal expandable inner core. Thus the electric power limit of this type of transducer is substantial increased and solve the critical problem of impose radial pre-stress. The radial vibration of the transducer is analyzed and its radial electro-mechanical equivalent circuit is obtained. Base on the electro-mechanical equivalent circuit, the resonance and anti-resonance frequency equations are obtained. Discussed the relationship between the resonance frequency, the effective electro-mechanical coupling coefficient and the geometrical dimensions.3. The modeling software Solid Works and the FEM software COMSOL Multiphysics were used to analysis the radial composite piezoelectric ultrasonic transducer vibration. By testing the resonance frequencies of several samples of radial composite piezoelectric ultrasonic transducer, it is shown that the theoretical results, FEM result were good agreement with the measured results.4. The electro acoustical efficiency is important performance parameters of ultrasonic transducers. Based on theoretical and experimental results above, manufacture series of radial composite piezoelectric transducers and measuring their ultrasonic field distribution under water by sound intensity meter. The radial composite piezoelectric transducers’ electro acoustic efficiency was preliminary obtain.