Lamb-Type Waves in a Symmetric Solid-Fluid-Solid Trilayer
Guided waves in a symmetric solid/fluid/solid trilayer are investigated. Derivation of the dispersion equation underlines the existence of global symmetric and antisymmetric modes. These two families are shown to be affected by the coupling very differently. Approximate analytical expressions
are obtained for the case of a thin and compliant fluid layer, with the formation of doublets for moderately thin liquid films. The existence of a low frequency mode whose cut-off frequency is related to the liquid layer thickness, the so-called "vertical mode", is proved. Theoretical results
are confirmed by experiments, based on the identification of modes by analysis of the backscattered or transmitted spectrum. Computed and measured cut-off frequencies are in good agreement, with an error of about 1% or less.
Document Type: Research Article
Publication date: 01 January 1998
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