Nonlinear Lamb Waves for the Detection of Localized Defects Using the Cumulative Second and Third Harmonics: Experimental Study

Abstract

Recent studies have proved the usability of the nonlinear S₀ lamb mode without satisfying the phase velocity matching criteria, and the possibility to extend its application to varying thickness plates. Based on that, this work proposes an experimental study of the inspection of macro scale localized defects with a size smaller than the used wavelength, via the second and third harmonics generation. Results were obtained on verifying their cumulative effect with varying the defect’s width and also on finding that the third harmonic is better suited for larger scale inspection using the nonlinear lamb waves, and identifying the propagating modes in the plates using the wavelet transform.