Investigating interface modes on elastic structures

Abstract

Phononic crystals and acoustic metamaterials are periodic structures that have drawn much attention to the engineering and physics communities due to their numerous applications in passive vibration and noise control. In this context, some geometric-phase concepts originally developed in electronics have inspired a number of applications in photonics and phononics. These concepts allows the manipulation of topological behavior, such as edge modes or interface modes, as a result of the non-trivial topology of the material's band structure. For acoustic systems, it has been recently shown that interface modes appears at the boundary separating two phononic crystals having different bandgap topological characteristics, which can be explained in terms of the geometric-phase called Zak phase. This leads to an enhancement of the acoustic field at the interface, which can have useful applications where strong sound intensities are required, such as sound detection and biomedical imaging.The purpose of this research project is to explore the Zak phase concept and how it can be applied to the design of periodic systems with interface modes. More specifically, understanding how the concept explains the presence of interface modes on acoustic waveguides will allow its extension to elastic structures, which is the ultimate goal. To this end, simple one-dimensional spectral elements will be used to compute the band structure and simulate the forced response of periodic acoustic waveguides such as cylindrical ducts, elastic rods and beams. The influence of damping and geometric/material variability on the wave enhancement present at the interface will also be considered. The possibility of confining energy in the form of elastic vibrations on an interface separating two periodic structures may have useful applications in energy harvesting scenarios. (AU)