A Non-Contact Laser-Emat System for Crack and Hole Detection in Metal Plates
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The use of non-contact ultrasonic techniques can have distinct advantages over conventional contact methods, allowing more rapid and practical scanning without suffering from variations introduced by an acoustic couplant. Non-contact ultrasonic testing can also be used for inspecting components on a production line. The system described here uses separate ultrasonic generation and detection techniques. Longitudinal waves are generated in a sample by means of a pulsed laser, and waves scattered from defects within the sample are used to identify the presence and location of simulated surface breaking cracks and side drilled holes. The longitudinal waves are detected using an electromagnetic acoustic transducer (EMAT) on the same side as the ultrasonic generation point, located coaxial to the generation laser beam.