An Inverse Reconstruction Method of Thinning Flaws in Plates Using Discrete Reflection Coefficients of Ultrasonic Guided Waves

The reconstruction of cavity or thinning shapes in elastic plates and pipes by use of reflection data from ultrasonic elastic waves has drawn much attention by many researchers and engineers. A quantitative non-destructive evaluation (QNDE) algorithm requires thorough understanding of wave equations in both forward and inverse manners. Previously, an inverse scattering method based on Born approximation and space-wavenumber inverse Fourier transform has been suggested, which has been able to depict the locations and shapes of flaws, and can be easily understood mathematically. However, the algorithm requires reflection data in full wavenumber range, which is impractical in engineering application. The paper proposes an improved inversion algorithm using only discrete wavenumbers in specialized frequency ranges. Validity of the algorithm is illustrated by numerical examples, and methods for improving accuracy are suggested.