Mode purification for ultrasonic guided waves under pseudopulse excitation

Under broadband excitation, the captured Lamb wave signals contain rich information of the structural properties. However, since multiple modes are highly dispersive and overlapped with each other, Lamb wave signals are especially complicated to be interpreted. To overcome this problem, a mode purification strategy is established under pseudo-pulse excitation. In this strategy, a pseudo-pulse excitation technique is introduced to obtain a high resolution for the inspection firstly. Dispersion compensation method is applied to remove the dispersion of the received signal subsequently, through which all the wave packets associated with the interferential mode propagating through different paths could be compressed into the same shape as the excitation. Benefiting from that, the energy of the wave packets corresponding to the interference mode could be concentrated in time domain as individual temporal pulses, which thereby could be eliminated by zero-amplitude rectangular time windows without affecting the desired mode much. After that, the inverse dispersion compensation is applied to the residual signals to restore the original waveform of the desired mode. Finally, experiments are introduced to validate the availability and robustness of the proposed strategy.