Wave Control via Phononic Crystals with Adaptively Relaxed Cell Symmetry

该奖项的目的是引入一系列具有自适应松弛细胞对称（ARCS）的晶体状超材料，并证明它们作为可调谐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，在这种情况下，完全依赖声子带隙的波管理方法的性能受到损害。ARCS概念的研究将使用一个原型蜂窝进行，该蜂窝带有带有压电材料片的周期性光束谐振器。通过调制选定的谐振器簇的局部有效刚度，从而使介质中有效力学性能的非均匀分布得到放松。根据所需的对称松弛程度，通过激活激活簇中适当的压电元件序列来实现性能调谐。这项研究将通过使用3D扫描激光测振仪进行的一系列实验来验证。如果成功，这项研究将提供一种策略来实现多用途的声学控制设备，这些设备不受一些影响基于超材料的方法的主要缺点的影响，例如无源性和剧烈的频率限制。将从ARCS概念中受益匪浅的技术应用包括隔离系统、机械过滤器、定向致动器和传感器。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研究开辟新的途径，朝着设计完全自主的波浪控制装置的方向发展。此外，还将提供平台，并实施与地方初中、高中合作的计划，以促进儿童和青少年的科学和工程主题项目。

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.