### ASA 126th Meeting Denver 1993 October 4-8

## 4aPA6. Measurement of elastic properties of transversely isotropic plates
using Rayleigh--Lamb waves.

**Wayne P. Rogers
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*Dept. of Mech. Eng., Univ. of Colorado, Boulder, CO 80309-0427
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This paper presents a novel method to experimentally determine the elastic
constants of a transversely isotropic plate using measurements of phase
velocity of Rayleigh--Lamb waves. The forward problem, i.e., to calculate the
phase velocity versus frequency curves given known elastic constants, has been
solved by numerical solution to the appropriate dispersion equations. The
problem attacked here is the inverse problem, i.e., to determine the elastic
constants given experimental measurements of phase velocity as a function of
frequency. These elastic constants may be found by simultaneous solution of
five distinct dispersion equations corresponding to particular measurements of
phase velocity and frequency. This approach yields accurate solutions provided
that appropriate Lamb waves modes, frequencies, and plate directions are
chosen. The experimental method employs a pair of variable-angle-beam-contact
transducers used in a pitch--catch mode with a harmonic wave phase comparison
technique to measure phase velocity over the frequency range of 30 kHz--1 MHz.
Results are presented for several isotropic plates and for a
unidirectional-continuous-glass-fiber-reinforced epoxy plate. The elastic
constants calculated using this inverse procedure are then used in the forward
problem in order to compare experimental results to theoretical predictions of
the dispersion curves for the first few modes. [Work supported by
NASA---Langley.]