A comprehensive approach for wavefield-based characterization of ultrasonic shear wave scattering in plates
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The objective of this research is to present a comprehensive approach for characterizing and quantifying the scattering of angle-beam ultrasonic shear waves from a variety of scatterers in plates. The motivation behind analyzing angle-beam shear wave propagation and scattering is to obtain a better understanding of shear wave interactions with defects and improve the reliability and accuracy of inspection techniques for nondestructive evaluation. The scatterers investigated here include through-holes, part-through holes, and notches emanating from through-holes. Scattering from both through-holes and notches, aimed to mimic actual ultrasonic defects in practice, is of particular interest to the aerospace industry because crack-like defects usually grow from fastener holes, which presents a potential hazard to aircraft components if undetected. There are two main contributions of this research. One is the acquisition of a comprehensive set of wavefield data for a variety of scattering scenarios via wavefield imaging. The other is the development of a systematic methodology for ultrasonic shear wave scattering estimation using a complete set of signal processing techniques. All methodologies presented in this thesis are demonstrated to be effective and reliable for showing useful scattering information.