Lamb wave focusing by gradient-index phononic crystal lens in layered composites

Chenxi Xu; Gorkem Okudan; Hrishikesh Danawe; Didem Ozevin; Serife Tol

doi:10.1117/12.2612906

18 April 2022 Lamb wave focusing by gradient-index phononic crystal lens in layered composites

Chenxi Xu, Gorkem Okudan, Hrishikesh Danawe, Didem Ozevin, Serife Tol

Proceedings Volume 12047, Nondestructive Characterization and Monitoring of Advanced Materials, Aerospace, Civil Infrastructure, and Transportation XVI; 120470J (2022) https://doi.org/10.1117/12.2612906
Event: SPIE Smart Structures + Nondestructive Evaluation, 2022, Long Beach, California, United States

Abstract

One of the current challenges in the guided wave ultrasonic testing of large-scale structures is attenuation. In this study, elastic wave propagation characteristics of a composite plate that is sampled from aerospace industry made of an orthotropic material are augmented with a gradient-index phononic crystal lens. The mechanical lens is made of cylindrical stubs periodically arranged on the plate and is investigated with unit cell simulations involving Bloch-Floquet periodic boundary conditions. The finite element models of the stubbed unit cells are built to generate dispersion curves for the cases with stubs made of structural steel, aluminum-1100, brass, and acrylic plastic. The final choice of material for the stubs is determined to be acrylic plastic due to the highest variation in phase velocities and highest frequency range of the resonance band gap. The changes in the phase velocity of the symmetric Lamb wave mode S0 are simulated to have the highest sensitivity to the changes in the stub heights, making it the target of the lens design. Refractive indices are computed based on the phase velocities. The dimensions of the stubs are tailored by adjusting their heights according to the hyperbolic secant profile to form the effective lens resulting in wave focusing. Multiphysics simulations in the time domain are performed to verify that the ultrasonic guided wave energy is focused on the focal point of the lens, where an amplification of the wave amplitude is expected to happen.

Conference Presentation

Citation Download Citation

Chenxi Xu, Gorkem Okudan, Hrishikesh Danawe, Didem Ozevin, and Serife Tol "Lamb wave focusing by gradient-index phononic crystal lens in layered composites", Proc. SPIE 12047, Nondestructive Characterization and Monitoring of Advanced Materials, Aerospace, Civil Infrastructure, and Transportation XVI, 120470J (18 April 2022); https://doi.org/10.1117/12.2612906

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