Negative Refraction and Localized Resonance of Guided Elastic Waves

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The research objective of this award is to study backward wave propagation in elastic waveguides and how it can be harnessed to create novel acoustic wave devices and improved nondestructive evaluation techniques. The research approach is to determine the conditions under which backward waves exist in plates and thin films, and how to efficiently control wave propagation through mode conversion between forward and backward propagating waves at interfaces. Backward wave propagation can lead to non-intuitive physical effects such as negative refraction and negative reflection of elastic waves and localized resonances. Experimental measurements and computational modeling will be used to design and evaluate surface acoustic and plate wave lenses based on negative refraction, and to assess the potential for using negative reflection and localized resonances for the nondestructive evaluation of thin films and plates.If successful, this research will lead to a new approach for manipulating guided elastic waves by controlling the surface profile of waveguides. Structures supporting guided elastic waves are commonplace and the results of the proposed research offer potential improvements to the nondestructive evaluation of aircraft, pipelines, and critical electronic components. Backward wave propagation could prove to be an enabling technology, offering a fundamentally new approach for the design of a wide range of acoustic devices including resonators, filters, and lenses. It could also have an impact on a broad range of fields that incorporate elastic wave propagation, from seismology to energy harvesting. The research will support advanced training for undergraduate and graduate students, and an education program will be developed where high school and undergraduate students are introduced to nondestructive testing through hands-on laboratory work.