Abstract
Directing and controlling flexural waves in thin plates along a curved trajectory over a broad frequency range is a significant challenge that has various applications in imaging, cloaking, wave focusing, and wireless power transfer circumventing obstacles. To date, all studies appeared controlling elastic waves in structures using periodic arrays of inclusions where these structures are narrowband either because scattering is efficient over a small frequency range, or the arrangements exploit Bragg scattering bandgaps, which themselves are narrowband. Here, we design and experimentally test a wave-bending structure in a thin plate by smoothly varying the plate’s rigidity (and thus its phase velocity). The proposed structures are (i) broadband, since the approach is frequency-independent and does not require bandgaps, and (ii) capable of bending elastic waves along convex trajectories with an arbitrary curvature.
Highlights
Current approaches for manipulating and bending flexural waves depend on either changing the effective refractive index to steer waves[14,23,24], or exploiting frequency bandgaps to guide waves along a pre-defined path[21,25,26,27,28]
Where D = Eh3/12(1 − ν2) represents the flexural rigidity, w the transverse displacement, and subscript tt denotes a second derivative with respect to time
The dispersion relation of plane flexural waves with wavenumber k is obtained as Dk4 − ρhω2 = 0, where the phase velocity is vp[4]
Summary
Current approaches for manipulating and bending flexural waves depend on either changing the effective refractive index to steer waves[14,23,24], or exploiting frequency bandgaps to guide waves along a pre-defined path[21,25,26,27,28]. Both approaches can be achieved using periodic structures such as phononic crystals and metamaterials[29]. The tailored system is tested experimentally to demonstrate the bending of elastic waves over a broad frequency range (20 kHz–120 kHz), which is limited by the frequency bounds of the experimental setup
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