A novel 3D evaluation method for surface defects using broadband laser-generated Rayleigh waves with wavenumber analysis.

To address the issues of large imaging errors for small defects and the difficulty in depth evaluation using local wavenumber estimation for surface defect imaging, a novel three-dimensional (3D) evaluation method for surface defects using broadband laser-generated Rayleigh waves with wavenumber analysis is proposed. A finite element model is established to investigate the interaction between the Rayleigh wave and the surface defect and reveal the wavenumber change mechanism of the non-dispersive Rayleigh wave in the case of defects. It is discovered that when the Rayleigh wave encounters the surface defect, various mode-converted scattered waves are generated, resulting in the appearance of new components with wavenumbers lower than that of the incident Rayleigh wave in the wavenumber domain.