Elastic Wave Near-Cloaking

TL;DR

This paper presents a practical near-cloaking method for elastic waves that overcomes fundamental invariance challenges, enabling applications in wave control, vibration mitigation, and non-destructive testing.

Contribution

It introduces a decoupling approach into form-invariant potential equations for elastic wave cloaking, addressing a key challenge in the field.

Findings

Effective near-cloaking demonstrated with carpet cloaks

Hides surface defects from various elastic waves

Practical approach suitable for real-world applications

Abstract

Cloaking elastic waves has, in contrast to the cloaking of electromagnetic waves, remained a fundamental challenge: the latter successfully uses the invariance of Maxwell's equations, from which the field of transformational optics has emerged, whereas the elastic Navier equations are not invariant under coordinate transformations. Our aim is to overcome this challenge, at least in practical terms, and thereby unlock applications in mechanics, ultrasound, vibration mitigation, non-destructive evaluation and elastic wave control. We achieve near-cloaking by recognising that, despite the lack of invariance, a decoupling into a system of form invariant potential equations together with a quantifiable approximation, can be used effectively in many cases to control the flow of elastodynamic waves. Here, in particular we \rvc{focus} on the efficiency and practicability of the proposed near-cloaking which is illustrated using carpet cloaks to hide surface defects from incoming compressional and shear in-plane waves and from surface elastic Rayleigh waves.