Static elastic cloaking, low frequency elastic wave transparency and neutral inclusions
arXiv:1910.12866 · doi:10.1098/rspa.2019.0725
Abstract
New connections between static elastic cloaking, low frequency elastic wave scattering and neutral inclusions are established in the context of two dimensional elasticity. A cylindrical core surrounded by a cylindrical shell is embedded in a uniform elastic matrix. Given the core and matrix properties, we answer the questions of how to select the shell material such that (i) it acts as a static elastic cloak, and (ii) it eliminates low frequency scattering of incident elastic waves. It is shown that static cloaking (i) requires an anisotropic shell, whereas scattering reduction (ii) can be satisfied more simply with isotropic materials. Implicit solutions for the shell material are obtained by considering the core-shell composite cylinder as a neutral elastic inclusion. Two types of neutral inclusion are distinguished, \textit{weak} and \textit{strong} with the former equivalent to low frequency transparency {and the classical Christensen and Lo generalised self-consistent result for in-plane shear from 1979. Our introduction of the \textit{strong neutral inclusion} is an important extension of this result in that we show that standard anisotropic shells can act as perfect static cloaks, contrasting previous work that has employed "unphysical" materials.} The relationships between low frequency transparency, static cloaking and neutral inclusions provide the material designer with options for achieving elastic cloaking in the quasi-static limit.
arXiv comment30 pages, 2 figures
References in corpus (12)
- Optical Cloaking with Non-Magnetic Metamaterials
- Acoustic cloaking theory
- Achieving control of in-plane elastic waves
- Transformation elastodynamics and cloaking for flexural waves
- Hyperelastic cloaking theory: Transformation elasticity with pre-stressed solids
- Nonlinear pre-stress for cloaking from antiplane elastic waves
- Wave impedance matrices for cylindrically anisotropic radially inhomogeneous elastic solids
- Broadband cloaking for flexural waves
- Elastic wave cloaking via symmetrized transformation media
- The matrix sign function for solving surface wave problems in homogeneous and laterally periodic elastic half-spaces
- Coated inclusions of finite conductivity neutral to multiple fields in two dimensional conductivity or anti-plane elasticity
- Stable methods to solve the impedance matrix for radially inhomogeneous cylindrically anisotropic structures