<p>Corrosion leads to severe safety and economic problems in most of the industries. To detect corroded structures at an early stage is a critical topic in many research areas. Guided wave tomography provides an efficient and economical technique to obtain the quantitative information of corrosion. This work presents an improved guided wave tomography method called fast inversion tomography (FIT) that can accurately estimate the thickness profile of the aluminum plate. &nbsp;FIT includes two stages: offline training and online testing. The offline stage learns a sequence of descent directions by using supervised descent learning (SDM) method. SDM minimizes the waveform misfit function in an iterative manner without expensive computation of the Hessian matrix. During the online testing stage, the learned descent directions turn into known information and can be used to reconstruct the phase velocity map of the testing sample. The phase velocity map can then be transformed into the thickness map by utilizing the dispersion curve of the aluminum plate at A0 mode. The accuracy and performance of FIT are measured by using synthetic examples with various corrosion shapes and depths. We also compare FIT with full waveform tomography in terms of inversion accuracy and computation efficiency. The results show that FIT is a promising tool to reconstruct the&nbsp;accurate thickness map.</p>

Fast Inversion Tomography for Quantitative Corrosion Detection

Paper Proceedings: https://asmedigitalcollection.asme.org/qnde/QNDE2021/volume/85529

ASME 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE2021)

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