Location

Brunswick, ME

Start Date

1-1-1997 12:00 AM

Description

Leaky Lamb waves have been used extensively for ultrasonic non-destructive evaluation of elastic properties: the reader is referred to papers by Dayal and Kinra [1,2], Chimenti and Martin [3], Mal et al.[4], and Chimenti and Nayfeh [5]. The principal disadvantage of this method is the high attenuation of the waves in the immersed solid plate due to continuous radiation to the surrounding fluid. As a result, their amplitudes become immeasurably small after a short distance of travel as observed by Dayal and Kinra. This provided the motivation for the present work: a study of the propagation of harmonic waves in a solid plate loaded by a fluid layer of a finite thickness. In a previous work by the authors [6], the dispersion equation for an isotropic solid/fluid bilayer was obtained. It was seen that a thin layer of fluid coupled the symmetric (5) and antisymmetric (A) modes in the solid layer and that along a branch a quasi-symmetric mode changed character to a quasi-antisymmetric mode near a region where previously the S and the A branches crossed but were uncoupled. In the present work the dispersion equation for an orthotropic solid/fluid bilayer is derived. Mode shapes are studied for a graphite-epoxy/water bilayer for the case of equal thickness of the fluid and solid layers. In this case, coupling between fluid and solid modes is observed.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

16B

Chapter

Chapter 6: Material Properties

Section

Coatings and Layers

Pages

1633-1640

DOI

10.1007/978-1-4615-5947-4_212

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Guided Waves in a Fluid-Orthotropic Solid Bilayer

Brunswick, ME

Leaky Lamb waves have been used extensively for ultrasonic non-destructive evaluation of elastic properties: the reader is referred to papers by Dayal and Kinra [1,2], Chimenti and Martin [3], Mal et al.[4], and Chimenti and Nayfeh [5]. The principal disadvantage of this method is the high attenuation of the waves in the immersed solid plate due to continuous radiation to the surrounding fluid. As a result, their amplitudes become immeasurably small after a short distance of travel as observed by Dayal and Kinra. This provided the motivation for the present work: a study of the propagation of harmonic waves in a solid plate loaded by a fluid layer of a finite thickness. In a previous work by the authors [6], the dispersion equation for an isotropic solid/fluid bilayer was obtained. It was seen that a thin layer of fluid coupled the symmetric (5) and antisymmetric (A) modes in the solid layer and that along a branch a quasi-symmetric mode changed character to a quasi-antisymmetric mode near a region where previously the S and the A branches crossed but were uncoupled. In the present work the dispersion equation for an orthotropic solid/fluid bilayer is derived. Mode shapes are studied for a graphite-epoxy/water bilayer for the case of equal thickness of the fluid and solid layers. In this case, coupling between fluid and solid modes is observed.