Boundless metamaterial experimentation: physical realization of a virtual periodic boundary condition

TL;DR

This paper presents an experimental method to create a virtual periodic boundary in elastic metamaterials, enabling better analysis of wave propagation and band gaps by suppressing reflections and mimicking infinite structures.

Contribution

It introduces a novel, data-driven approach for boundary condition treatment in metamaterial experiments, allowing virtual periodicity and improved validation of dispersive wave behaviors.

Findings

Band gap converges to analytical solutions with virtual periodicity

Reflection suppression enhances metamaterial wavefield analysis

New workflow enables boundary control in complex metamaterials

Abstract

We experimentally implement a virtual geometric periodicity in an elastic metamaterial. First, unwanted boundary reflections at the domain ends are cancelled through the iterative injection of the polarity reversed, reflected wavefield. The resulting boundless experimental state allows for a much better analysis of the metamaterials influence on the propagating wavefield. Subsequently, the propagating wavefield exiting on one end of the structure is reintroduced at the opposite end, creating a virtual geometric periodicity. We find that the experimentally observed band gap converges to the analytical solution through the introduction of the virtual periodicity. The established workflow introduces a novel approach to the experimental investigation and validation of metamaterial prototypes in the presence of strongly dispersive wave propagation and internal scattering. The fully data driven, ad-hoc treatment of boundary conditions in metamaterial experimentation with arbitrary mechanical properties enables reflection suppression, virtual periodicity, and the introduction of more general fictitious boundaries.