Shape Derivative Adapted to Elastodynamics for the Reconstruction of Corrosion Defects

Abstract

Today, the residual thickness of a structure is crucial information for many industries, including the nuclear sector. To this end Structural Health Monitoring (SHM) aims to establish continuous monitoring using sensors integrated into the structure to be inspected. We are particularly interested in tomographic methods using guided elastic waves. In the literature, the most widely studied guided elastic wave tomography methods are based on an acoustic propagation model. These methods are based on physical approximations, such as single-mode propagation or propagation in a waveguide-type structure, which allow a rapid estimation of the thickness. However, these assumptions are only valid if the wave packet of interest can be extracted from the rest of the signal and there is no mode conversion at the defects, as this would inevitably affect imaging resolution and potential application cases. We present here an adaptation of a method called ‘shape derivative’ that does not rely on these assumptions.