8 March 2014 A passively tunable acoustic metamaterial lens for damage detection applications
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In this paper, we present an approach to the generation of steerable ultrasonic beams in structures for possible application to damage detection. The proposed approach is based on the design of embedded acoustic lenses that exploit fundamental principles of wave propagation in acoustic metamaterials. In particular, the lens design relies on the concept of acoustic drop-channel where multiple waveguides can be coupled and selectively activated by simply tuning the frequency of the excitation. Numerical analyses will show that this design allows generating highly directional excitation by using a single ultrasonic transducer. Plane Wave Expansion and Finite Difference Time Domain methods are used to evaluate the dispersion characteristics of the metamaterial lens as well as to simulate the transient response when the lens is embedded in a plate-like structure. The lens design is then experimentally validated on an aluminum plate where the lens is implemented by through the thickness notches. The overall performances are estimated by reconstructing the dynamic displacement field via Laser Vibrometry.
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H. Zhu, H. Zhu, F. Semperlotti, F. Semperlotti, "A passively tunable acoustic metamaterial lens for damage detection applications", Proc. SPIE 9061, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2014, 906107 (8 March 2014); doi: 10.1117/12.2045531; https://doi.org/10.1117/12.2045531

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