Metastructures for mechanical signal processing
Please login to view abstract download link
Structures with self-adapting abilities must be endowed with efficient sensors sending information to systems embedded in the structures themselves, able to interpret and classify the sensed signals which are finally used to activate feed-back and actuation mechanisms. The path from sensing to adaptation is hindered in many cases from the low intensity of the sensed signals and from the lack of autonomous energy sources. The possibility to efficiently govern energy fluxes, guiding them along pre-defined paths, confining and amplifying energy in pre-defined locations represents a major step toward self-adaptive structures. This contribution will leverage on recent results in the field of elastic metastructures which could effectively be used for controlled and efficient information transport, mechanical energy confinement and signal amplification in adaptive structures. Among different elastic wave control mechanisms, a recent line of work employs graded arrays of resonators embedded in a host structure to manipulate wave propagation by taking advantage of the interaction between the structure and the resonators. The term graded refers to the smooth variation of a particular parameter of the resonators along space, allowing to control the propagation of waves in a broadband regime. This modulation strategy promotes a wavenumber transformation that, in turn, activates a spatial decrease of the wave velocity when the wave enters inside the array. Array guided waves slow down as they transverse the array with different frequency components localising at specific spatial positions, resulting in a so-called rainbow effect, which replicates tonotopic phenomena found e.g. in the human ear apparatus. Examples discussed will include graded resonator arrays at micro and meso-scales, additive manufactured devices containing liquids, and bio-inspired cyclically symmetric phononic pseudocrystals exhibiting broadband elastic-wave attenuation.
