Abstract: The authors describe the application of laser-ultrasonic sources in combination with interferometric detectors to monitor ultrasonic Lamb waves propagating in metal and composite structure plate samples. Using a high powered pulsed laser source, and temporally and spatially sampling the resultant acoustic field, it was possible to directly measure the Lamb wave phase velocities of several modes simultaneously. A further development has been the demonstration of a low power CW laser source capable of generating Lamb waves in a steel sample at a power density well below the ablation damage threshold. !16
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