Nondestructive testing technique combining ultrasonic Lamb waves and double-pulse TV holography

Abstract

The combination of ultrasonics with optics has led to the development of emergent technologies for nondestructive testing with outstanding capabilities. In this work we describe a combination that, in our knowledge, was up to now unexplored, directed to the detection of cracks and other types of flaws in metallic plates of medium thickness (several millimeters). We selected a special kind of surface acoustic waves, i.e. Lamb waves, to explore the volume of the plates in the search for flaws, while a whole field interferometric technique, namely double-pulse TV holography, is employed to generate a map of the surface displacements in which the signature of the defects can be seen as a perturbation of the initially smooth wavefronts. Several examples of detection of artificially generated flaws are presented.