Current Research Projects

Nonlinear intermodal targeted energy transfer (IMTET) in dynamical and acoustical systems

Funded by a Fellowship from the Israeli Council of Higher Education (CHE-VATAT)

This research is devoted to experimental and theoretical exploration of the IMTET phenomenon in practical mechanical systems. The goal is to define, explore and validate the new possibilities for mitigating the undesired vibrations in diverse systems, e.g., mechanical, acoustical, civil infrastructure, etc., by targeted passive redistribution of energy within the modal space of the system itself. The principal outcome of the proposed research will be a comprehensive fundamental understanding of the IMTET phenomenon, and the formulation of design principles for its robust practical implementation. This knowledge will pave the way for design and optimization of the structures with unprecedented enhanced mitigation characteristics.

This project is in collaboration with Professor Oleg V. Gendelman, Technion – Israel Institute of Technology.

Self-adaptive metamaterials and strongly nonlinear locally resonant metamaterials

Funded by the National Science Foundation

This research will focus on nonlinear vibrations and wave propagation to enable the development of new multi-functional metamaterial devices. The novel self-adaptive metamaterials use a sliding mass mechanism to tune the bandgap to different frequency ranges. This self-adaptive mechanism will be integrated in periodic and quasiperiodic arrangements. This project will also investigate strongly nonlinear locally resonant metamaterials and its effect on the birth of breathers.

This project is in collaboration with Prof. Oumar Barry, Virginia Tech.

Prediction of Limit Cycle Oscillations of Fighter Aircraft with Store Nonlinearities

Funded by the Naval Innovative Science and Engineering (NISE) Program

Research will focus on the accurate and computationally economical prediction of limit cycle oscillation (LCO) amplitude, frequency, and onset speed for fighter aircraft carrying external stores with various nonlinearities. A generic fighter aircraft carrying stores with a freeplay nonlinearity at the wing-store connection, part of a KTH-NASA collaborative project focused on building a repository of LCO wind-tunnel data, will be studied using aeroelastic codes such as FUN3D and analytical methods. Experimental data from wind tunnel tests of a full-span model in the Transonic Dynamics Tunnel at NASA Langley Research Center will provide truth data to assist in the development of methodologies for LCO prediction. This research will aim to develop and refine methods for LCO prediction and identify and characterize LCO mechanisms.

This project is in collaboration with Dr. Walter Silva, NASA Langley Research Center.

System ID in Additive Manufacturing and Topological Metamaterials

Funded by a National Science Foundation Graduate Research Fellowship

Research will focus on methods in system identification, nonlinear time series analysis, and machine learning methods for online monitoring of laser power bed fusion processes with an emphasis on constructing mechanical lattices. This fellowship will also support theoretical and numerical work to investigate the influence of strong nonlinearity in mechanical topological insulators for 1D and 2D systems.

This project is in collaboration with Prof. Kathryn Matlack and research staff from Los Alamos National Laboratory

Targeted Energy Transfers due to Nonlinear Interactions in Dynamical and Acoustical Systems

Funded by a Fellowship from the China Scholarship Council

Research will focus on nonlinear targeted energy transfers in dynamical and acoustical systems exhibiting strongly nonlinear interactions between components and under broadband or stochastic excitations. The systems considered include granular interfaces and nonlinear lattices.

This project is in collaboration with Prof. Li-Qun Chen, Shanghai Institute of Applied Mathematics and Mechanics, PR China.

Research Experience and Mentoring (REM) Supplement to EFRI NewLAW: Nonreciprocity in Acoustic Systems with Nonlinear Hierarchical Internal Structure and Asymmetry

Funded by an NSF EFRI REM grant

The EFRI REM supplemental support provides pre-program training; research experiences to two high school students with their STEM Teacher, and five undergraduate students; and post-program mentoring activities at the University of Illinois. These mentoring activities are socio-economically and culturally relevant to our research participants. Team-based research projects are performed, focusing on nonlinear, non-reciprocal dynamics. Moreover, the supplemental support will allow us to validate the viability of this approach and share results within the community through publication. We are uniquely positioned to accomplish this task at the University of Illinois due to several factors: (i) Experienced and committed principal investigators and research collaborators with a wealth of teaching and student mentoring experience and track records; (ii) a strong, in-place group of REM administrative and support professionals that is highly experienced in working with our target audience; (iii) long and established partnership with multiple educational units targeting minority Urbana – Champaign District 4 high school and local community college students, aiming towards a unique opportunity to integrate multiple organizations’ efforts in a comprehensive way; and (iv) students that are increasingly interested in STEM outreach and continue to request additional mentoring and outreach opportunities.

Mr. Joseph Muskin is the educational coordinator of this project; this work is in collaboration with Profs. S. Tawfick, K. Matlack and A. Wissa of the University of Illinois at Urbana-Champaign.

Nonlinear System Identification and Reduced-Order Modeling of Structures and Material Systems

Funded by a Fellowship from the University of the Philippines, Diliman, and a supplemental Fellowship of the Department of Mechanical Science and Engineering of the University of Illinois

We develop and apply powerful new methods for nonlinear system identification and reduced-order modeling of flexible structures and soft material systems. Particular emphasis will be to account for geometric nonlinearities and their effects on the stiffness and damping characteristics, and to study the strongly nonlinear modal interactions that are induced by these nonlinearities. Moreover, the approach is data-driven and relies to as few ad hoc assumptions as possible. The systems considered include (but are not limited to) a model plane with nonlinear stores and material systems in shear. The project involves analytical, computational and experimental methods.

This project is in collaboration with Prof. Melih Eriten, University of Wisconsin at Madison.

EFRI NewLAW: Non-reciprocity in Acoustic Systems with Nonlinear Hierarchical Internal Structure and Asymmetry

Funded by an NSF Emerging Frontiers Research Initiative Award

This research program will investigate new theoretical and practical knowledge on the application of nonlinearity, asymmetry, and mixed scales to design and fabricate ground-breaking materials and devices. The approach will yield materials which overcome traditional bounds on time-reversal symmetry and acoustic reciprocity. These transformative reciprocity-breaking materials and systems are expected to find wide application in diverse fields, including noise-mitigating transportation systems; medical ultrasound devices; atomic force microscope (AFM) sensing; acoustic filters and logic devices; sonar; and energy control and redirection. The research will also broadly impact education through planned curriculum development and outreach activities aimed at increasing exposure of engineering students, and the public, to the exciting physics of acoustic materials. At the same time, these activities will promote interest in science, technology, engineering, and mathematics. Planned activities will include a multidisciplinary collaborative course on non-traditional acoustic materials; broadening opportunities with outreach organizations on campus by inviting high school students and teachers to develop lab modules and earn continuing education credits; a collaboration with Clark Atlanta University to engage faculty and underrepresented undergraduate students in research tasks; and industrial collaboration with the Hughes Research Laboratory to enhance and facilitate technology transfer. This research investigates a new class of reciprocity-breaking acoustic systems characterized by nonlinear internal structures, asymmetry and mixed scales. These systems exhibit directed cross-scale energy transfers which break time reversibility and reciprocity both locally (within each of the system subunits) and globally (for the entire system viewed a whole). Non-reciprocal, large-to-small scale energy transfers mimic analogous nonlinear energy transfer cascades in nature (e.g., turbulence). The research aims to be transformative in the field of nonlinear acoustics, promoting a new paradigm for predictive design with nonlinear non-reciprocity through (i) the theoretical and experimental understanding of acoustic systems with nonlinear hierarchical internal structures; (ii) the uncovering of the combined role of asymmetry, disorder, nonlinearity and cross-scale directed energy transfers on non-reciprocity; (iii) the development of new approaches for fabricating, characterizing and experimentally testing non-reciprocal lattice materials combining multiple macro-to-nano scales; and (iv) the translation of these materials to new technologies and acoustic devices that exploit and showcase transformative capabilities.

This work is performed in collaboration with Professor Michael Leamy of the Georgia Institute of Technology, Professor Chiara Daraio of the California Institute of Technology, and Professor Sameh Tawfick of the University of Illinois at Urbana-Champaign.