CAREER: Guiding and Confining Nonlinear Elastic Waves in Moiré Metastructures

该学院早期职业发展（CAREER）补助金将资助研究，使新的建筑超材料应用于大容量风力涡轮机叶片的振动保护，以及能够高精度传感和信号处理的表面声波器件的设计，从而促进科学的进步和推进国家的繁荣。扩大风能发电输出的主要障碍是由于不稳定的风载荷和极端天气条件引起的涡轮机叶片振动而导致的结构故障。如果没有有效的手段来引导或隔离这种结构中的振动能量，对损坏和安全的担忧会迫使设计和操作不优化。为了应对这一挑战，该项目研究了一种迄今尚未开发的工程材料，称为莫尔元结构，它可以以传统材料无法实现的方式引导和限制弹性波能量。一套综合的教育和推广活动旨在积极影响工程教育，并为多元化和具有全球竞争力的STEM劳动力做出贡献。其中包括本科课程中的元结构设计挑战，K-12学生工作坊中的实践活动，与法国研究小组的国际学生交流，以及来自代表性不足的群体的个人参与研究。本研究旨在为一类双层建筑板元结构的设计奠定基础，通过非线性层间弹簧耦合，这允许色散和非线性的独立工程，因此，独特的非线性波现象，如孤子，频率梳，波弯曲和单向传播的可能性。它实现了这一目标，通过调查的非平凡的拓扑性质的莫尔亚结构，通过堆叠两层的六边形，正方形，和Kagome晶格为基础的板，导致几乎平坦的色散带，可以利用和结合时空调制的刚度，以引导或限制波能。该方法依赖于离散弹簧-质量模型的理论分析、使用基于Bloch模式的不连续Galerkin基函数的有限元分析、具有所需非线性刚度的耦合弹簧的设计优化和制造，和实验验证使用激光多普勒测振仪和高-该奖项反映了NSF的法定使命，并通过使用基金会的智力价值进行评估，被认为值得支持和更广泛的影响审查标准。

This Faculty Early Career Development (CAREER) grant will fund research that enables the application of new architected metamaterials to vibration protection of large-capacity wind turbine blades, as well as the design of surface acoustic wave devices capable of high-precision sensing and signal processing, thereby promoting the progress of science and advancing the national prosperity. A major impediment to scaling up the output from wind energy generation is structural failure due to vibrations of turbine blades induced by unsteady wind loads and extreme weather conditions. Without effective means to guide or isolate vibrational energy in such structures, concerns about damage and safety enforce suboptimal designs and operation. To address this challenge, this project investigates a hitherto unexplored class of engineered materials, called moiré metastructures, that can guide and confine elastic wave energy in ways that are unattainable in conventional materials. An integrated set of education and outreach activities aims to positively impact engineering education and contribute to a diverse and globally competitive STEM workforce. These include metastructure design challenges in an undergraduate course, hands-on activities at workshops for K-12 students, international student exchange with a research group in France, and participation of individuals from underrepresented groups in research.This research aims to develop the foundations for the design of a class of bilayered architected plate metastructures, coupled by nonlinear between-layer springs, that allow independent engineering of dispersion and nonlinearity and, as a result, the possibility of uniquely nonlinear wave phenomena, such as solitons, frequency combs, wave bending, and unidirectional propagation. It achieves this aim by investigating how nontrivial topological properties of moiré metastructures, obtained by stacking two layers of hexagonal, square, and Kagome lattice-based plates, result in almost flat dispersion bands that can be exploited and combined with space-time modulation of stiffness to guide or confine wave energy. The approach relies on theoretical analysis of discrete spring-mass models, finite-element analysis using discontinuous Galerkin basis functions based on Bloch modes, design optimization and fabrication of coupling springs with the desired nonlinear stiffness, and experimental validation using laser-Doppler vibrometry and high-speed imaging.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.