To address the issue of multimodal characteristics limiting the use of Lamb waves for detecting fatigue damage in plate-like welded structures,numerical simulation analysis is conducted on the propagation process of Lamb waves in steel bridge decks with and without damages.Utilizing MATLAB software to calculate the Lamb wave dispersion equation,the dispersion curves of group velocities and phase velocities for both symmetric and antisymmetric modes are obtained.Additionally,a Hanning window function is employed to process the Lamb wave signals.Taking the U-Rib-Deck joint as an example,the propagation processes of Lamb waves in steel bridge decks with and without damages are simulated using Abaqus software.Corresponding amplitude curves are obtained,and the time-frequency signal distribution status of the steel bridge deck is determined through wavelet analysis.The results indicate that when detecting with Lamb waves of the same frequency,the amplitude of the damaged signal increases.Using Lamb waves of different frequencies to detect steel bridge decks with damage,the higher the excitation frequency of the Lamb waves,the greater the signal amplitude.Compared to 150 kHz Lamb waves,200 kHz Lamb waves in time-frequency distribution show a distinct difference,and energy distribution becoming more concentrated,which is more conducive to the precise detection of damages.It is recommended to use 200 kHz Lamb waves for detecting fatigue damages in steel bridge decks.
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