CAREER: Structure-borne Noise and Vibration Mitigation via Nonlinear Interactions in Phononic Structures

这个教师早期职业发展（CAREER）项目旨在开发一类新的结构材料，也称为“声子”，其中工程非线性相互作用通过操纵应力波的传播直接抑制结构噪声和振动。这将通过模拟在原子水平上观察到的现象的工程非线性相互作用所固有的波混合效应来实现。在运输系统中，结构部件易受恶劣机械环境的影响，包括振动、发动机噪声和空气动力学/声学载荷。噪声和振动的抑制非常关键，因为它直接关系到机械/电气部件的长期耐用性和乘客的舒适度。目前的降噪技术严重依赖于基于阻尼吸收器的经典方法，例如软泡沫、橡胶楔和绝缘毯。虽然这些方法在抑制高频噪声和振动方面是有效的，但是通过结构传播路径衰减低频分量仍然是一个巨大的挑战。这项研究将有助于下一代结构材料的开发，这些材料本身就能够以有效和可控的方式减少结构声噪声和抑制不必要的振动。从教育的角度来看，该项目将通过“捕捉波”活动提高年轻人对机械波传播的理解，从而吸引年轻人进入科学和工程领域。该项目涉及设计、制造和测试一种称为“非线性声子结构”的新型工程周期晶格。“这些声子结构将具有新颖的机制，可以相干地耦合不同应力波模式的传播。一个示例是利用薄壁结构的几何非线性的可变刚度机构。这些非线性声子结构将自然地允许我们通过另一个应力波模式动态地操纵一个应力波模式，这类似于电和光能流装置的工作原理（例如，晶体管）。从基本观点来看，该项目将揭示工程晶格结构的非线性波动动力学，从而发现波的色散，分解和散射方面的新物理现象，这在传统材料系统和结构中是前所未有的。从工程的角度来看，这些发现将通过动态控制波的速度、波形和传输增益来过滤和减轻结构噪声和振动。

This Faculty Early Career Development (CAREER) project aims at developing a new class of structural materials, also known as "phononic", whereby engineered nonlinear interactions suppress structure-borne noise and vibrations directly by manipulating the propagation of stress waves. This will be enabled by wave mixing effects inherent to the engineered nonlinear interactions that mimic phenomena observed at the atomic level. In transportation systems, structural components are susceptible to harsh mechanical environments, including vibrations, engine noise and aerodynamic/acoustic loads. The suppression of noise and vibration is highly critical, since it is associated directly with the long-term durability of mechanical/electrical components and the comfort level of passengers. Current techniques for noise reduction rely heavily on classical methods based on damping absorbers, such as soft foam, rubber wedges, and insulating blankets. While these methods are efficient in suppressing high frequency noise and vibrations, attenuation of low frequency components through a structure-borne path remains a formidable challenge. This research will contribute to the development of next-generation structural materials that are inherently capable of reducing structure-borne acoustic noise and rejecting unwanted vibrations in an efficient and controllable manner. From an educational standpoint, this project will attract young minds to science and engineering by enhancing their understanding of mechanical wave propagation through the "Catch a Wave" campaign.This project involves designing, fabricating, and testing of a new type of engineered periodic lattices called "nonlinear phononic structures." These phononic structures will feature novel mechanisms that couple the propagation of different stress wave modes coherently. One example is a variable stiffness mechanism that leverages geometrical nonlinearities of thin-walled structures. These nonlinear phononic structures will naturally allow us to dynamically manipulate one stress wave mode via another, which is analogous to the working principles of electrical and optical energy flow devices (e.g., transistors). From a fundamental viewpoint, this project will shed light on the nonlinear wave dynamics of engineered lattice structures, leading to the discovery of new physical phenomena in terms of wave dispersion, disintegration, and scattering, unprecedented in conventional material systems and structures. From an engineering standpoint, the findings will open a new paradigm in filtering and mitigating structure-borne noise and vibration by dynamically controlling waves' speed, waveforms, and transmission gains.