The merits of Lamb wave testing for the nondestructive evaluation (NDE) of thin plates and pipes have been reiterated in many articles published on the subject. For instance, its advantages over conventional ultrasonic C-scanning have often been emphasized. When a large area of a structure is to be inspected, Lamb waves are more attractive than bulk waves since they can propagate over long distances to inspect a wider area. However, it is a great misfortune, as most authors lament, that Lamb waves are multimode by nature. That is, there exist at least two wave modes at any given frequency, thus making the signals complicated and difficult to interpret.
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