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Etude expérimentale de la propagation, de la diffusion et de la localisation des ondes de Lamb

Abstract : Elastic waves propagating in thin plates are an efficient tool for the fundamental study of waves in complex media. They allow developing experimental setups of macroscopic size, broadband and non-invasive when the generation and detection of ultrasounds are performed by laser. The experimental tool developed in this thesis allows direct access to the whole time dynamics of Lamb wave normal displacements. The amplitude and phase spatial distribution of the modes are obtained by Fourier transform of time measurements. We study two kinds of complex media: homogeneous ones with chaotic shape and heterogeneous ones. For the first, we look at how a closed chaotic medium is modified when it is progressively coupled with the environment. For this, a series of experiments is carried out on a chaotic silicon wafer with increasing local losses. A second study deals with Lamb waves scattering by a non through-hole: the "blind" hole. This scatterer exhibits a high scattering strength thanks to its internal resonances. Thus, it can be used to build complex heterogeneous systems. In such media, waves can be spatially trapped by the disorder, due to complex interference processes. This phenomenon, known as "Anderson localization", is studied in the last part of this work. We describe the conception and experimental analysis of a randomly etched silicon wafer containing about 3400 blind holes.
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https://tel.archives-ouvertes.fr/tel-00652619
Contributor : Olivier Xeridat <>
Submitted on : Thursday, December 15, 2011 - 11:16:50 PM
Last modification on : Monday, October 12, 2020 - 10:27:38 AM
Long-term archiving on: : Friday, March 16, 2012 - 3:00:16 AM

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Olivier Xeridat. Etude expérimentale de la propagation, de la diffusion et de la localisation des ondes de Lamb. Physique Générale [physics.gen-ph]. Université Nice Sophia Antipolis, 2011. Français. ⟨tel-00652619⟩

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