CAREER: Controlling Nonlinear Wave Propagation in Metastructures with Contact Interfaces

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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.