Développement et optimisation de méthodes d’imagerie synthétique pour le contrôle non-destructif par ultrasons de composants industriels complexes

Abstract : The goal of this thesis was, initially, to evaluate phased array methods for ultrasonic Non Destructive Testing (NDT) in order to propose optimizations, or to develop new alternative methods. In particular, this works deals with the detection of defects in complex geometries and/or materials parts.The TFM (Total Focusing Method) algorithm provides high resolution images and several representations of a same defect thanks to different reconstruction modes. These properties have been exploited judiciously in order to propose an adaptive imaging method in immersion configuration. We showed that TFM imaging can be used to characterize more precisely the defects. However, this method presents two major drawbacks: the large amount of data to be processed and a low signal-to-noise ratio (SNR), especially in noisy materials. We developed solutions to these two problems. To overcome the limitation caused by the large number of signals to be processed, we propose an algorithm that defines the sparse array to activate. As for the low SNR, it can be now improved by use of virtual sources and a new filtering method based on the DORT method (Decomposition of the Time Reversal Operator).
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Souad Bannouf. Développement et optimisation de méthodes d’imagerie synthétique pour le contrôle non-destructif par ultrasons de composants industriels complexes. Acoustique [physics.class-ph]. Univeristé Paris Diderot Paris 7, 2013. Français. ⟨tel-01095671⟩

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