CAREER: Guiding and Confining Nonlinear Elastic Waves in Moiré Metastructures

这项教师早期职业发展（Career）基金将资助研究，使新型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设备的设计，从而促进科学进步，促进国家繁荣。不稳定风荷载和极端天气条件引起的涡轮叶片振动导致的结构故障是风力发电扩大产量的主要障碍。如果没有有效的方法来引导或隔离这些结构中的振动能量，对损坏和安全的担忧就会导致次优设计和运行。为了应对这一挑战，该项目研究了迄今为止尚未开发的一类工程材料，称为moir<s:1>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。一套完整的教育和推广活动旨在积极影响工程教育，并为多样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学生研讨会的实践活动，与法国研究小组的国际学生交流，以及来自代表性不足群体的个人参与研究。本研究旨在为设计一类由非线性层间弹簧耦合的双层结构板元结构奠定基础，这种结构允许对色散和非线性进行独立工程，从而可能产生独特的非线性波现象，如孤子、频率梳、波弯曲和单向传播。为了实现这一目标，研究了通过堆叠两层六边形、正方形和Kagome晶格板获得的波纹元结构的非平凡拓扑特性如何导致几乎平坦的色散带，这些色散带可以利用并结合刚度的时空调制来引导或限制波能。该方法依赖于离散弹簧-质量模型的理论分析，基于Bloch模态的不连续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，以及激光多普勒振动仪和高速成像的实验验证。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.