Radial-mode Vibration Characteristics of Piezoelectric Hollow-disc Transducers

The vibration characteristics of piezoelectric hollow-disc transducers were investigated in this paper. It was assumed that the vibration modes were coupled in the axial and radial directions. Theoretically the differential equations of piezoelectric motions were derived in terms of the axial and radial displacements and the electric potential. Solutions of the boundary value problem yielded the natural frequencies and mode shapes of the transducers. Experiments were carried out by two methods. One is the measurement of piezoelectric natural frequencies by using an impedance analyzer. The other is the measurements of mode shapes by using an in-plane laser vibrometer. The theoretical results were verified by comparing them with experimental results. It appeared that the first mode of the piezoelectric hollow-disc transducers was the radial mode and the fundamental natural frequency was determined by the inner and outer diameter and the radial boundary conditions of the circumferential surfaces.