Design of piezoelectric sandwich ultrasonic transducers with large cross-section

The coupled vibration of piezoelectric sandwich ultrasonic transducers with large cross-section was studied. The transducer consists of two piezoelectric ceramic circular plates with central holes, metal head and tail with rectangular cross-section. When the vibration coupling coefficients and the equivalent elastic constants were introduced, the coupled vibration of the transducer was divided into two vibrations: the longitudinal vibration along the central axis, and the lateral vibration perpendicular to the axis. The frequency equation was derived by means of the apparent elasticity method. Compared with one-dimensional theory, no limitations are imposed on the lateral dimensions of the transducer. Compared with numerical methods, the computation is time-saving. It is shown that the resonant frequencies obtained from the frequency equation are in better agreement with the measured results than those from one-dimensional theory.