Scanning Laser Vibrometry and Finite Element Analysis of Lamb Waves for Damage Detection

Lamb waves are widely used to detect damage in both metallic and composites structures. The technique is based on ultrasonic wave packets propagating in solids having one dimension on the order of magnitude of a wavelength. Although Lamb waves have demonstrated great capabilities in detecting even small local defects, they suffer the effect of environmental noise and often require the intervention of an expert technician for the collection and analysis of a large amount of data collected by the sensors. Laser based sensing has the potential to alleviate some of these problems due to its ability to perform automatic acquisition scans over a given array of points selected by the operator. The data analysis can then be carried out through the use of appropriate algorithms. In this paper our preliminary work utilizing a laser vibrometer for Lamb wave sensing is presented. A comparison between experimental data and numerical results obtained from an explicit finite element model is then reported. The goal was to verify the potential of laser vibrometry for Lamb wave sensing.