Ultrasonic imaging of different shaped cracks in an isotropic plate by synthesizing time reversal and reverse time migration methods

Abstract

The accuracy of reverse time migration (RTM) image of a crack is greatly affected by the position and excitation waveform of PZT transducer as the transmitter. The position of the transmitter is obtained by processing the direct-arrival flexural waves recorded at the receivers using the time reversal method. The excitation waveform generated by the transmitter is represented by the direct-arrival wave recorded at the closest receiver and their position relation, modifying the deconvolution imaging condition of RTM. Three types of cracks with different shapes located on the back of aluminum plates are investigated by employing two linear arrays composed of PZT transducer and laser vibrometer, and their high-resolution images are reconstructed using the modified RTM method. The results show that the obtained positions and shapes of the cracks are consistent with those of the actual cracks, the MRE and RMSE between them are less than 2.06% and 2.82 mm, respectively.