Alexander F. Vakakis
Donald Biggar Willett Professor of Engineering
Department of Mechanical Science and Engineering
UIUC
Presenting in Track 1: Acoustics, Vibration, & Phononics
Presentation Title: Engineering Energy Transfer and Bandwidth in Vibrations
Abstract: We discuss concepts related to engineering and managing energy transfer and bandwidth in general classes of vibrating systems. To this end, we explore constructive implementation of nonlinearity to induce effects such as targeted energy transfer in preferential paths within a system or in favorable frequency bands and away from unfavorable ones. Important applications in vibration engineering include vibration, shock and blast mitigation, energy harvesting, passive break of classical reciprocity and bandwidth quantification and tailoring. Focusing on the last topic, in the sciences and engineering the concept of bandwidth is often subject to interpretation depending upon context and the requirements of the specific technical community. Typically, the classical bandwidth of a resonator is determined by the half-power (-3 dB) method, and the result is often referred to as “half-power bandwidth,” with the underlying assumption being that the resonator performance degrades once its power decreases by 50%. However, there are some important restrictions associated with this classical bandwidth definition, e.g., the assumptions of linearity, single-mode response, low-loss, and time invariance. To alleviate these restrictions, we generalize the concept of bandwidth with the aim to make it applicable to a broad class of practical systems, including multi-degree-of-freedom resonators, systems with modal interactions, and nonlinear or time-varying vibrating systems. Based on this, we discuss ways to engineer bandwidth, and discuss important applications such as, quantifying the dissipative capacity and rate of dissipation of (even) complex vibrating mechanical systems, monitoring of measured test data and structural updating.
Biography: Alexander F. Vakakis received his Ph.D. from Caltech (1990 – T.K. Caughey advisor), M.Sc. from Imperial College, London, UK (1985 – D.J. Ewins advisor), and Diploma in Mechanical Engineering from the University of Patras, Greece (1984 – S.A. Paipetis advisor). Currently he is the Donald Biggar Willett Professor of the College of Engineering at the University of Illinois at Urbana – Champaign (UIUC) where co-directs the Linear and Nonlinear Dynamics and Vibrations Laboratory (http://lndvl.mechse.illinois.edu/); moreover, he is co-affiliate faculty at the University of Stuttgart, Germany. Among other awards, he is the recipient of the Tau Beta Pi Daniel C. Drucker Eminent Faculty Award from the UIUC College of Engineering (2023), the best paper award of the journal Nonlinear Dynamics (2023), an Alexander von Humboldt Research Award (2019), the Edmond J. Safra Visiting Professorship from Technion (2019), and the ASME Thomas K. Caughey Award in nonlinear dynamics (2014). He has published over 370 archival journal publications, holds four patents, and has authored/edited 6 technical texts and monographs. Many of his PhD students and postdoctoral fellows are currently faculty members in US and International Universities and National Laboratories, or researchers in R&D Centres. His research interests include nonlinear dynamics, vibrations and acoustics, passive energy management and targeted energy transfer across scales, phononics and acoustic metamaterials, system identification and reduced order modelling, non-smooth dynamics and vibration energy harvesting.