CAREER: Controlling Nonlinear Wave Propagation in Metastructures with Contact Interfaces

该学院早期职业发展（Career）奖将开展基础研究，揭示元结构中界面的力学响应与非线性机械波传播之间的关系。元结构是一种工程介质，可以控制机械能如何在材料中传播。目前的元结构在工程材料中的应用有限，因为它们要么只能控制小振幅的波，要么需要柔性成分或复杂的约束系统。如何在工程材料中控制和引导更现实的高振幅机械波的知识可能会导致飞机，汽车和能源基础设施中安全，高效运行和持久的部件，这仍然是社会的迫切需求之一。该奖项将通过回答与非线性波动现象的力学有关的基本科学问题来促进科学的进步。该奖项还将引进并实施将音乐和STEM相结合的研究和教育相结合的外展计划，以支持教育。该计划将通过将音乐与声学联系起来的模块来丰富青少年暑期音乐夏令营。此外，将开发一个全校范围的声学社区，整合并扩大外展计划，为本科生和研究生提供独特的指导体验。通过对元结构的研究发现了新的波现象，元结构是一种周期性工程材料，可以控制声波的频率和空间特性。然而，局部非线性的不同形式和变化如何与元结构中的全局非线性波响应相关联，以及如何在物理上实现大范围的非线性，人们还没有很好地理解。虽然现有的工作已经显示了由于赫兹接触在颗粒介质中有益的非线性波响应，但这项工作将建立不同长度尺度的接触界面几何形状、它们的非线性力学响应以及这些接触的周期性配置所产生的全局非线性波现象之间的联系。这将通过测量、分析模型和有限元模拟的紧密结合来完成。频率相关的非线性反射和透射系数将从接触界面测量，具有多种长度尺度的工程几何形状，由金属3D打印制造。然后，将引入解析模型来描述这些界面的非线性响应。将引入混合分析-有限元模型来表征非线性波在所研究的接触界面的一维和二维中通过各种周期排列的传播。这些响应将通过全波场测量得到验证。这一新知识将用于确定物理上可实现的局部力学非线性与元结构中全局波传播之间的关系。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) award will conduct fundamental research to uncover the relationship between the mechanical response of interfaces in metastructures and nonlinear mechanical wave propagation. Metastructures are engineered media that can control how mechanical energy propagates through materials. Current metastructures find limited use in engineering materials as they either only control small-amplitude waves or require compliant constituents or complex constraining systems. Knowledge of how to control and steer more realistic high-amplitude mechanical waves in engineering materials may result in safe, efficiently operating, and long-lasting components in aircraft, automotive, and energy infrastructure, which remains as one of society's pressing needs. This award will promote the progress of science by answering fundamental scientific questions related to the mechanics of nonlinear wave phenomena. This award will also support education by introducing and implementing an outreach program that integrates research and education by combining music and STEM. The program will enrich youth summer music camps with modules that relate music to acoustics. Further, a university-wide acoustics community will be developed that integrates with and broadens the outreach program, to provide a unique mentoring experience for both undergraduate and graduate students.New wave phenomena have been uncovered through the study of metastructures, which are periodically engineered materials that control frequency and spatial properties of acoustic waves. However, it is not well understood how different forms and variations in local nonlinearity relate to global nonlinear wave responses in metastructures, nor how a broad range of nonlinearities can be physically realized. While existing work has shown beneficial nonlinear wave responses due to Hertzian contact in granular media, this work will instead establish links between contact interface geometry at various length scales, their nonlinear mechanical response, and emergent global nonlinear wave phenomena that results from periodic configurations of these contacts. This will be done using a close integration of measurements, analytical models, and finite element simulations. The frequency-dependent nonlinear reflection and transmission coefficients will be measured from contact interfaces with engineered geometries on multiple length scales, fabricated with metal 3D printing. Then, analytical models will be introduced to describe the nonlinear response of these interfaces. Hybrid analytical-finite element models will be introduced to characterize nonlinear wave propagation through various periodic arrangements in 1D and 2D of the studied contact interfaces. These responses will be validated by full wave field measurements. This new knowledge will be used to determine relationships between physically realizable local mechanical nonlinearities and global wave propagation in metastructures.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.