YIC2025

Mitigation of elastic Love waves using embedded locally resonant metamaterials

  • Zeighami, Farhad (University of Bologna)

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Love waves are horizontally polarized surface waves that propagate along the interface between a soft layer and a stiffer underlying medium [1]. They are primarily used in geophysics and seismology, where they play a key role in the analysis of earthquake phenomena. Additional applications include non-destructive material testing and the development of sensors for detecting various physical quantities. So far, several strategies have been proposed to control the propagation of Love waves [2-3]. Among these, a recent approach involves the use of locally resonant metamaterials, which are engineered composite materials designed to manipulate elastic wave propagation. In particular, elastic metasurfaces composed of ultra-thin resonant interfaces have been developed to realize gradient index lenses capable of guiding Love waves [3]. However, these metasurfaces are not able to generate a frequency stop band where the propagation of Love waves is suppressed. This study investigates the use of a thick metamaterial layer to achieve this effect. The proposed configuration consists of a bilayer medium where a locally resonant metamaterial layer of arbitrary thickness is placed on top of an isotropic, homogeneous half-space [4]. An array of horizontal resonators, each with dimensions much smaller than the Love wave wavelength, is embedded within the layer. A homogenization technique is applied to determine the effective dynamic properties of the resonant layer in the long wavelength regime. The dispersion relation governing Love wave propagation beneath the homogenized layer is then derived analytically. The interaction between Love waves and the thick metasurface leads to the formation of a low frequency band gap, resulting from the local resonance of the embedded resonators, which effectively inhibits wave propagation in that range. The influence of key resonator design parameters on the band gap width is examined. Finally, design guidelines are proposed for meter-scale resonators to control Love wave propagation within frequency ranges relevant to ground borne vibrations.