Detection on Fatigue Crack of Aluminum Alloy Plate Based on Modulation Nonlinear Lamb Waves and Time Reversal Method

AbstractNovel modulation nonlinear Lamb waves (MNLW)and time reversal method for fatigue crack detection are carried out in this paper. MNLW focus on the application of harmonics and sum and difference frequency frequency to discern damages in plates. In combination, we are applying the focusing properties of TRA and the modulation nonlinear properties of cracks to detect damages in the plates. The experiments on 2024 aluminum alloy plates, one with a fatigue crack and the other intact, are comparatively experimented. And this experiment system consists of two piezoelectric transducers, arbitrary waveform generator, power amplifier, laser vibrometer, digital oscilloscope and computer. The experimental results show that there are only two fundamental frequencies and no harmonics and sidebands occur in the intact sample. In the cracked sample, there is an abundance of the harmonics and sidebands. So, these new modulation components can be used to indicate the presence of a crack or damage