Bi-functional Structural Luneburg Lens for Broadband Structural Wave Cloaking and Waveguide

Abstract: In this paper, we explore the concept of structural Luneburg Lens (SLL) as a design framework for performing dynamic structural tailoring to obtain a structural wave cloak and a structural waveguide. The SLL is a graded refractive index lens, which is realized by using a variable thickness structure defined in a thin plate. Due to the thickness variation of the plate, the refractive index decreases radially from the centre to the outer surface of the lens. By taking advantage of the unique capabilities of SLL for flexural wave focusing and collimation, we develop a structural wave cloak and waveguide based on cascaded SLLs. The cascaded SLL design enables the integration of functional devices into thin-walled structures while preserving the structural characteristics. Analytical, numerical, and experimental studies are carried out to characterize the performance of the SLL cloak and the SLL waveguide. The results demonstrate that that these cascaded SLL devices exhibit excellent performance for structural wave cloaking and waveguiding over a broadband operating frequency range.