Reverse-time-migration imaging for a crack in a thin plate by dispersed flexural waves

A modified reverse time migration (RTM) method for dispersed flexural waves is proposed to detect and image the crack in a thin plate. The key point of this method is to take the time reversal (TR) of the expanded flexural wave at a receiver as the backward wave in the cross-correlation imaging condition of RTM, thus the expanded backward wave will be re-compressed also due to dispersion of the flexural wave. The backward wave is time reversed again when arriving at a certain point on the plate, and then correlated to the forward wave derived from the original source. The image of the crack is obtained by superimposing the cross-correlation results of many source-receiver pairs in transmitting and receiving arrays. The experimental studies on imaging a crack in a thin plate are conducted, and the transmitted and received waveforms are recorded with high fidelity by a laser vibrometer, thus, ensuring that an accurate and clear image of the crack is obtained by this modified RTM process.A modified reverse time migration (RTM) method for dispersed flexural waves is proposed to detect and image the crack in a thin plate. The key point of this method is to take the time reversal (TR) of the expanded flexural wave at a receiver as the backward wave in the cross-correlation imaging condition of RTM, thus the expanded backward wave will be re-compressed also due to dispersion of the flexural wave. The backward wave is time reversed again when arriving at a certain point on the plate, and then correlated to the forward wave derived from the original source. The image of the crack is obtained by superimposing the cross-correlation results of many source-receiver pairs in transmitting and receiving arrays. The experimental studies on imaging a crack in a thin plate are conducted, and the transmitted and received waveforms are recorded with high fidelity by a laser vibrometer, thus, ensuring that an accurate and clear image of the crack is obtained by this modified RTM process.