## 3aSAa4. Mode shape and eigenfrequency spectra of elastic plates in the vicinity of the thickness resonance frequency.

### Session: Wednesday Morning, May 15

### Time: 8:45

**Author: Victor T. Grinchenko**

**Location: Inst. of Hydromech., Natl. Acad. of Sciences, Kiev 252057, Ukraine**

**Abstract:**

A number of experimental investigations have been performed to study
vibration characteristics of elastic plates in a high-frequency region. Up to
this time the empirical data have no satisfactory explanation in terms of Lamb
wave coupling. The theoretical analysis of the coupling effects presented in the
article is based on the exact solution of the free-axis-symmetric vibration
problem for a circular plate. Consideration of a special case of zero Poisson's
ratio allows one to distinguish and investigate three independent kinds of
eigenmodes. Two of them are initiated by simply propagated longitudinal waves.
The waves with complex wave numbers (evanescent standing waves) provide a rise
to a third type of eigenform. Eigenfrequencies of these last modes are very
close to the thickness resonance frequency and they increase as radius of a
plate increases. The data for nonzero Poisson's ratios demonstrate an influence
of coupling on a structure of eigenfrequency spectra and mode shape. An
investigation of radius variation effects gives a good indication of the
feasibility of the coupling effect control. The values of the plate radius with
the moderate mode shape disturbances are determined.

from ASA 131st Meeting, Indianapolis, May 1996