paper

Controlling solid elastic waves with spherical cloaks

arXiv:1403.1847 · doi:10.1063/1.4887454

Abstract

We propose a cloak for coupled shear and pressure waves in solids. Its elastic properties are deduced from a geometric transform that retains the form of Navier equations. The spherical shell is made of an anisotropic and heterogeneous medium described by an elasticity tensor C' (without the minor symmetries) which has 21 non-zero spatially varying coefficients in spherical coordinates. Although some entries of C, e.g. some with a radial subscript, and the density (a scalar radial function) vanish on the inner boundary of the cloak, this metamaterial exhibits less singularities than its cylindrical counterpart studied in [M. Brun, S. Guenneau, A.B. Movchan, Appl. Phys. Lett. 94, 061903 (2009).] In the latter work, C' suffered some infinite entries, unlike in our case. Finite element computations confirm that elastic waves are smoothly detoured around a spherical void without reflection.

Version 3: minor typos corrected. Figures captions improved. 5 figures. Key words: 3D elastic cloaking, seismic metamaterials. This paper is the cover of the 14 July 2014 issue of Applied Physics Letters

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