Radially composite cylindrical piezoelectric ultrasonic transducers

Abstract

A new type of radially composite cylindrical piezoelectric ultrasonic transducers is presented and its radial vibration is studied. The composite transducer is composed of a radially polarized piezoelectric ceramic short tube with arbitrary wall thickness and a metal tube. The radial vibrations of the radially polarized piezoelectric tube and the metal tube are analyzed and their electro-mechanical equivalent circuits are obtained. Based on the mechanical boundary conditions between the piezoelectric tube and the metal tube, the six-port electro-mechanical equivalent circuit of the radially composite ultrasonic transducer is obtained and the frequency equation is given. The theoretical relationship between the resonance/anti-resonance frequency and the effective electro-mechanical coupling coefficient with the ratio of the inner radius over the outer radius of the composite transducer is analyzed. At the same time, the radial vibration of the composite transducer is simulated by using Finite Element Method. The vibrational modal shape and the harmonic response are given numerically. At last, some radially composite ultrasonic transducers are designed and manufactured; their resonance/anti-resonance frequencies are measured. It is shown that the analytical resonance/anti-resonance frequencies are in good agreement with the numerically simulated and experimental results. It is expected that this type of radially composite ultrasonic transducers can be used in large scale ultrasonic liquid processing, such as ultrasonic extraction, ultrasonic sonochemistry and other applications where large radiation surface and ultrasonic power are needed.