Forward and inverse researches on scattering of ultrasonic surface waves by near-surface

Surface waves have great potential in engineering, such as geological inspection and ultrasonic non-destructive testing for near-surface characteristics. A thorough and effective utilization of their scattering phenomenon is required. This paper deals with the Love wave scattering by cavity-like flaws located on the layer interface in both forward and inverse aspects. We firstly suggest a numerical approach employing method of fundamental solutions (MFS) and modified boundary element method (BEM) incorporating far-field displacement patterns, which is more efficient while more accurate than traditional BEM approach. We also propose here a quantitative reconstruction procedure for the flaw shape using reflection coefficients of the 1st order Love wave. By theoretical deduction, it can be proved that the cavity's geometric shape is approximately expressed as an inverse spatial Fourier transform of far-field reflection coefficients in the wavenumber domain. Numerical examples are given and high consistency is shown between the reconstructed flaw images and the geometric characteristics of the actual flaws.