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.
