Resonances of plates and cylinders: Guided waves

Abstract

The study of the normal diffusion of an ultrasonic plane wave by cylinders and plates imbedded in the water shows resonances which are the natural modes of vibration. When a natural mode of an elastic target is excited, the energy which is stored during the forced excitation is emitted after the end of the forced excitation. The observation of backscattered spectra obtained by the Resonance Isolation and Identification Method (RIIM) from an aluminum cylinder shows supplementary resonances. The directivity pattern of the transducer is the cause of these supplementary resonances. The behavior of these resonances is analogous to the resonances of the plate. This leads us to study the natural modes of the cylinder. All the resonances which are experimentally detected may be considered as normal modes of the target. The results obtained on plates and cylinders have a common point: the generation of a guided wave by the excitation of a resonance.