Numerical Study on Depth Gauging of Surface Breaking Defects Using Laser-Generated Surface Acoustic Waves

Laser-generated surface acoustic waves scattering from surface cracks of various depths and widths have been calculated by the finite element method, where a surface notch is introduced to represent a fatigue crack for the convenience of modeling. The bipolar Rayleigh waves have been captured clearly using this model, as the laser line source close to the surface crack. In addition, the numerical results demonstrate that there exist clear oscillation signals following the reflected Rayleigh waves, the temporal cycles of which are found to be dependent on only notch depth, the arrival time of which is related mainly to the width of the notch. Therefore, a new crack evaluation method based on the temporal characteristics of surface acoustic wave signals has been proposed and discussed in this paper, which is helpful for measuring the depth of surface cracks accurately.