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Sélectivité modale d'ondes ultrasonores dans des guides d'ondes de section finie à l'aide d'éléments piézoélectriques intégrés pour le SHM

Abstract : SHM systems (Structural Health Monitoring) based on ultrasonic guided waves propagation are used for large structures, e.g. in Aerospace or Civil Engineering. Lamb or SH waves are usually employed as they propagate over long distances in plate-like structures while probing the entire thickness. However less conventional modes propagate in wave guides with finite crosssection,such as bars, rails or pipes. The number of modes can be very high even at low frequencyin this type of guide, and it is important to carefully select a specific mode. Current methods for modal selectivity, based on the use of several emitters, usually consider identical PZT elements(same sensitivity, same frequency response, etc.) and do not account for real experimental conditions and possible differences (variable coupling between transducers, flawed alignment,variable electronic response, etc.). This work presents a global methodology for modal selectivity in waveguides with finite cross-section, using several piezoelectric elements attached to their surface. This selectivity is based on experimental measurements, with a 3D laser vibrometer,of the amplitudes of the modes generated by each emitter. An optimization process allows to inverse the problem in order to maximize the amplitude of the desired mode, then generated by exciting all the emitters at once. This process requires knowing dispersion curves as well as the displacements of the various modes, calculated with SAFE 2D method. The methodology is tested through numerical simulations and experiments on an aluminium rectangular bar instrumented with 8 PZT elements on top. The method efficiency to generate different pure modes,and to detect and locate calibrated defects, is demonstrated for the aluminium bar. Its potential for SHM application of more complex structures is studied, like a rail or an adhesively bonded composite structure.
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Submitted on : Wednesday, March 13, 2019 - 3:31:14 PM
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  • HAL Id : tel-02066531, version 2

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Valentin Serey. Sélectivité modale d'ondes ultrasonores dans des guides d'ondes de section finie à l'aide d'éléments piézoélectriques intégrés pour le SHM. Mécanique [physics]. Université de Bordeaux; Université de Sherbrooke (Québec, Canada), 2018. Français. ⟨NNT : 2018BORD0403⟩. ⟨tel-02066531v2⟩

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