Well-posedness of wave scattering in perturbed elastic waveguides and plates: Application to an inverse problem of shape defect detection

• Main Authors: Bonnetier, É (Author), Niclas, A. (Author), Seppecher, L. (Author)
• Format: Article
• Language: English
• Published: Royal Society Publishing 2023
• Subjects: Acoustics; born approximation; Born approximation; Elastic plate; Elastic wave-guides; Elastic waves; elasticity; Fourier series; Frequency data; Frequency scattering; inverse problems; Inverse problems; Lamb modes; Multi frequency; multi-frequency data; Multi-frequency data; Shape defect detection; Wave propagation; Wave scattering; waveguides; Waveguides; Wellposedness
• Online Access: View Fulltext in Publisher

 The aim of this work is to present theoretical tools to study wave propagation in elastic waveguides and perform multi-frequency scattering inversion to reconstruct small shape defects in elastic waveguides and plates. Given surface multi-frequency wavefield measurements, we use a Born approximation to reconstruct localized defect in the geometry of the plate. To justify this approximation, we introduce a rigorous framework to study the propagation of elastic wavefield generated by arbitrary sources. By studying the decreasing rate of the series of inhomogeneous Lamb mode, we prove the well-posedness of the PDE that model elastic wave propagation in two-and three-dimensional planar waveguides. We also characterize the critical frequencies for which the Lamb decomposition is not valid. By using these results, we generalize the shape reconstruction method already developed for acoustic waveguide to two-dimensional elastic waveguides and provide a stable reconstruction method based on a mode-by-mode spacial Fourier inversion given by the scattered field. © 2023 The Author(s).