Current Research Projects

Exploiting Impact-induced Intermodal Targeted Energy Transfer (IMTET) for Passive Mitigation of Resonant Vibrations of Rotationally Periodic Structures

Funded by the Deutsche Forschungsgemeinschaft (DFG), Germany

Without countermeasures, lightweight structures like turbine blades break under vibration loads. We investigate a new, fully passive concept for vibration mitigation, namely intermodal Targeted Energy Transfer (IMTET). To induce intense energy transfers, a small impactor is placed freely into a cavity of the host structure, achieving vibration mitigation by Impact Energy Scattering. More specifically, the collisions enable the participation of more system modes in the response and induce intense, almost irreversible nonlinear energy transfers from the critical low-frequency modes to high frequencies, where energy is dissipated more rapidly. Moreover, as vibration energy is transferred from low to high frequencies, the overall level of system vibration is reduced not by adding extra dissipative elements, but rather by redistributing energy to a much larger set of vibration modes (especially high-frequency ones). In other words, by IMTET we radically enhance the system’s inherent dissipative capacity in a predictable and robust way.

This project is in collaboration with Prof. Malte Krack of the University of Stuttgart, Germany.

Robust Stabilization of Subsea Power Cables using Nonlinear Energy Sinks

Funded by the National Offshore Wind Research and Development Consortium

We perform computational studies of passive vortex-induced-vibration (VIV) mitigation of undersea cables equipped with attached nonlinear energy sinks (NESs). Specifically, we model the nonlinear fluid-structure interaction of these cables with their undersea environment and show that the NESs are capable of mitigating cable vibrations over broad frequency ranges, under continuously varying, non-stationary loads from the undersea environment. Then we will proceed with optimization of the NES parameters in order to achieve most effective and robust cable vibration mitigation.

This project is in collaboration with Prof. Lei Zuo of the University of Michigan.

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