Three-Dimensional Elastic Scattering Coefficients and Enhancement of the Elastic Near Cloaking

This paper is concerned with the elastic near cloaking for the Lamé system in three-dimensions using the notion of elastic scattering coefficients (ESC). Accordingly, the ESC of arbitrary three-dimensional objects are designed and some of their properties are discussed using elements of the elastic layer potential theory. Then, near-cloaking structures, coined as ESC-vanishing-structures, are constructed for the elastic cloaking at a fixed frequency or a band of frequencies. These multi-layered structures are designed so that their first few significant ESC vanish ahead of transformation-elastodynamics. The invisibility effect is achieved as the arbitrary elastic object inside the cloak has near-zero scattering cross-section for a band of frequencies. The cloaking effect for the Lamé system is significantly enhanced by the proposed near-cloaking structures.