Vibration characteristics of an ultrasonic transducer composed of inner and outer discs

Abstract

This paper considers an ultrasonic transducer composed of piezoelectric solid and hollow discs. The inner solid disc is a transmitter and the outer hollow disc is a receiver of ultrasound. The purpose of this work is to design a disc-shape transducer with separate transmitter and receiver which are operated at a same frequency and have a same center location. The vibration characteristics of the radial and axial motions in the axisymmetric modes were investigated theoretically and experimentally. Theoretically, the differential equations of piezoelectric motions were derived in terms of mechanical displacements and electric potential, and they were solved to produce characteristic equations providing natural frequencies and mode shapes. The theoretical analysis was complimented by the finite-element analysis, which provided three-dimensional mode shapes. Experimentally, the natural frequencies and the radial in-plane motion were measured using an impedance analyzer and an in-plane laser interferometer, respectively. The results of the theoretical analysis were compared with those of experiments, and the theoretical analysis was verified on the basis of this comparison. It appeared that the fundamental frequency of the transducer was similar to but slightly different from that of a single disc transducer of same size. It was found that the transducer composed of inner solid and outer hollow piezoelectric discs could be designed by selecting suitable diameters of each disc. © 2017 SPIE.