Wave Control via Phononic Crystals with Adaptively Relaxed Cell Symmetry

该奖项的目的是介绍一系列具有自适应松弛细胞对称性（ARCS）的晶体状超材料，并证明其作为可调声学操纵器的适用性。ARCS晶体的优点在于它们能够在相对较低的频率范围内工作，其中完全依赖于声子带隙的波管理方法的性能受到损害。ARCS概念的调查将进行使用一个原型蜂窝与周期性人口的梁谐振器仪表与补丁的压电材料。通过对所选谐振器簇的局部有效刚度的调制，使单元对称性放松，这导致在介质中建立有效机械特性的非均匀分布。根据所需的对称松弛程度，通过激活簇的压电元件的适当序列的激活来强制执行性质调谐。该研究将通过一组使用3D扫描激光测振仪进行的实验进行验证。如果成功的话，这项研究将提供一种策略，以实现通用的声学控制设备，这些设备不受影响超材料方法的一些主要缺点的影响，例如无源性和剧烈的频率限制。从ARCS概念中受益匪浅的技术应用包括隔离系统、机械滤波器和方向致动器和传感器。将专门为这项工作开发的激光波重建方法将为合成结构材料的实验表征提供新的通用协议。这项工作将为能量收集的研究开辟新的途径，以设计完全自主的波浪控制设备。它还将提供一个平台，并实施一项计划，与当地初中和高中建立伙伴关系，开展旨在促进儿童和青少年科学和工程的主题项目。

The objective of this award is to introduce a family of crystal-like metamaterials with adaptively relaxed cell symmetry (ARCS) and demonstrate their applicability as tunable acoustic manipulators. The virtue of ARCS crystals lies in their ability to operate in relatively low-frequency regimes, where the performance of wave management methodologies relying exclusively on phononic bandgaps is compromised. The investigation of the ARCS concept will be conducted using a prototype honeycomb with a periodic population of beam resonators instrumented with patches of piezoelectric material. The cell symmetry is relaxed through the modulation of the local effective stiffness of a selected cluster of resonators, which results in the establishment of a non uniform distribution of effective mechanical properties in the medium. The property tuning is enforced through the activation of appropriate sequences of piezoelectric elements of the activation cluster, according to the desired degree of symmetry relaxation. The investigation will be verified by a set of experiments performed using a 3D scanning laser vibrometer. If successful, this research will provide a strategy to achieve versatile acoustic control devices that are immune to some major drawbacks that affect metamaterials based approaches, such as passivity and drastic frequency limitations. The technological applications that would greatly benefit from the ARCS concept include isolation systems, mechanical filters and directional actuators and sensors. The methodology for laser-enabled wave reconstruction that will be specifically developed for this work will provide new general protocols for the experimental characterization of synthetic structural materials at large. This work will open new avenues for research in energy harvesting, towards the design of fully autonomous wave control devices. It will also provide a platform and implement a plan to realize partnerships with local middle and high schools for thematic projects aimed at promoting science and engineering among children and teenagers.