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Ultrasonic Excitation by Phase Velocity Scanning of Laser Beam and Application to Nondestructive Evaluation

It is essential for advanced nondestructive evaluation that single mode of acoustic waves be selectively generated. We have proposed the phase velocity scanning (PVS) method for this purpose. In this work, we improved the PVS method by using an acoustooptic deflector to scan a laser beam at high velocity with high repeatability. In aluminum plates, we succeeded to generate narrow-band single-mode Lamb waves, which propagated a distance more than 1.7 m. We propose to apply this method to detection of defects on large plate structures.