Laser Interferometric Measurements of Air-Coupled Lamb Waves

In this paper, experimental measurements of the vibration pattern that results when an air-coupled AO Lamb wave mode propagates in a plate are presented. Lamb waves are generated using an air-coupled piezoelectric transducer array. The measurements were performed in 304 stainless steel using laser interferometry. Air coupled piezoelectric ultrasonic array transducers are a novel tool that could lead to interesting advances in the area of non-contact laminar material testing using Lamb wave's propagation techniques, and it is interesting to know the vibration pattern in the plate. Using this system, some snapshots of the interaction of the AO Lamb wave mode with a crack-defect in the plate are also presented.