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Optimisation des modes de Lamb à vitesse de groupe nulle engendrés par laser et évaluation locale de structures collées

Abstract : For some Lamb modes propagating in plane structures, the group velocity vanishes while the phase velocity remains finite. These modes are associated with local and narrow resonances and are sensitive to thickness, elastic properties and boundary conditions. Laser ultrasound techniques are well suited to generate and detect these resonances. In the first part of this thesis, spatial optimization of laser sources (Top-Hat and Gaussian beam, rectangular and Gaussian ring produced by an axicon-lens system) are studied in order to enhance the generation of a Lamb mode at wavelength λ. Optimal radius of a Gaussian beam is demonstrated to be λ/π. Theoretical results are shown to be in a good agreement with semi-analytical simulation and experimental results performed in a Duralumin plate at the S1S2-ZGV mode frequency. The second part of this work is dedicated to the use of ZGV resonances for the inspection of bonded plates. Trilayers are described by rheological model where interfaces are modelized by stiffnesses. The sensitivity of ZGV frequencies to the interfacial stiffnesses as well as adhesive layer parameters has been studied. Stiffnesses and adhesive thickness maps have been extracted from ZGV resonance measurements. In addition, ZGV mode measurements have been shown to allow the differenciation of controled bond strengh samples
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https://tel.archives-ouvertes.fr/tel-02067884
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Submitted on : Thursday, March 14, 2019 - 2:14:08 PM
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  • HAL Id : tel-02067884, version 1

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François Bruno. Optimisation des modes de Lamb à vitesse de groupe nulle engendrés par laser et évaluation locale de structures collées. Physique [physics]. Université Sorbonne Paris Cité, 2017. Français. ⟨NNT : 2017USPCC147⟩. ⟨tel-02067884⟩

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