Ultrasonic Wavefield Imaging
Ultrasonic wavefield imaging, or the acquisition and subsequent analysis of wave motion generated by a fixed source, is a powerful research tool that is also being considered for nondestructive evaluation (NDE). Many proposed wavefield-based NDE methods have come from the structural health monitoring (SHM) community and are based upon guided waves. If guided wave transducers are already embedded in or mounted on a structure as part of an SHM system, then wavefield-based inspection can potentially take place with very little required disassembly. Wavefield inspection methods may also be practical for stand-alone inspection because of the richness of the data and the noncontact nature of most implementations. In its simplest form, wavefield imaging is a very effective method for visualizing wave motion on the surface of a specimen. However, for it to become a practical NDE method, analysis methods must be applied to the wavefield data to yield quantitative information concerning the detection, localization, and characterization of damage. The focus of this chapter is to provide an introduction to the acquisition and analysis of wavefield data in the context of three case studies: impact damage in composites, bond evaluation for aluminum plates, and characterization of scattering from notched through-holes. References to additional methods and applications are given for the interested reader.
The first case study was supported by Advanced Systems & Technology, Inc., Irvine, CA, as part of a NASA SBIR Phase II Award, Contract No. NNX15CL26C, Dr. Cara Leckey, program manager. The third case study was sponsored by the Air Force Research Laboratory, Contract No. FA8650-10-D-5210, Dr. Eric Lindgren, program manager.
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