报 告 人：伊利诺伊大学厄巴纳-香槟分校 Alexander F. Vakakis教授
邀 请 人：航空结构工程系 王栋 教授
题 目：Passive Energy Management Across Scales in Dynamics and Acoustics
We explore a new concept for passive energy management of dynamical and acoustical systems based on the synergy of intentional strong local nonlinearity, asymmetry, and internal scale hierarchy. Central to this concept is the inducement of irreversible nonlinear energy transfers from large-to-small scales that break non-reciprocity in controlled and predictable ways. Then, broadband or narrowband input energy is either directed in preferential paths/modes, dissipated locally/globally, or harvested at a priori designated sites in the system through predictable design. These non-reciprocal energy transfers mimic analogous energy cascades that occur often in Nature (e.g., in turbulent flows or granular media), and, as such benefit from the well-known robust and enhanced dissipative features exhibited by these natural phenomena. Our approach dictates advanced theoretical modeling and analysis, but also nonlinear system identification and reduced-order modeling to characterize the experimental realizations that validate the theoretical predictions. In a particular application, we’ll discuss new approaches for designing, analyzing, characterizing and experimentally testing non-reciprocal lattice materials incorporating multiple internal hierarchical scales. The aim is to translate these materials to new technologies and acoustic devices that exploit and showcase acoustic non-reciprocity.
Alexander F. Vakakis received his PhD degree in Applied Mechanics, California Institute of Technology (1987-1990); MSc degree in Advanced Applied Mechanics, Diploma of Imperial College, Imperial College of Science and Technology, University of London (1984-1985), and Diploma Degree of Mechanical Engineering, University of Patras, Greece (1979-1984). Currently he co-directs the Linear and Nonlinear Dynamics and Vibrations Laboratory of the University of Illinois. He is the recipient of the 2014 ASME Thomas K. Caughey Award, the 2012 Thomas Bernard Hall Prize and the 2009 PE Publishing Award, both from the Institution of Mechanical Engineers (UK). He has published over 280 archival publications, holds two patents, and has authored/edited 6 monographs in dynamics, vibrations and acoustics. He has been member of ASME AMD Dynamics and Control of Structures and Systems Technical Committee from 1997 to 1999, member of ASME Technical Committee on Sound and Vibration from1995 to 2001and member of the Technical Committee, European Association of Structural Dynamics (EASD) since 2009. He is also the Affiliate Professor of Department of Aerospace Engineering and Affiliate Faculty of Computational Science and Engineering Program at the University of Illinois at Urbana – Champaign.
Professor Vakakis is now the National High-End Foreign Expert in China and Special Expert of 1000-person Program for Foreign Specialists in Zhejiang Province.