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Simulation-assisted imaging for SHM by elastic guided waves: tomography and shape derivative

Technological challenge: Factory of the future incl. robotics and non destructive testing (learn more)

Department: Département Imagerie Simulation pour le Contrôle (LIST)

Laboratory: Laboratoire Méthodes CND

Start Date: 01-11-2022

Location: Saclay

CEA Code: SL-DRT-22-0660

Contact: tom.druet@cea.fr

Structural health monitoring (SHM) consists of monitoring the health of a structure using integrated sensors. In this context, the LIST is working on innovative elastic guided wave tomography methods to image corroded areas on simple geometries: plates and pipes. The subject of the thesis is to adapt to our dynamic problems the so-called "shape derivative" method, mostly used on static data, to develop iterative imaging based on a digital twin. This method allows a high quality reconstruction for complex geometries but implies the resolution of an expensive numerical problem. The quality of the image is also highly dependent of the initialization, often based on the perfect structure, potentially far from the current state. We propose to address these two points as follows: the initialization of the shape derivative will be obtained from existing tomography methods, thus improving convergence by limiting the number of iterations and the effect of local minima. The numerical problem will be solved using transient high-order spectral finite elements, allowing fast and inexpensive computations. The definition of metrics suitable for the comparison of simulated and experimental signals will also be part of the study. The performances will be validated on experimental data representative of complex cases of interest for the industry (corrosion under support, etc.).

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