Advanced Nonlinear Strategies for Vibration Mitigation and System Identification
June 16, 2008 — June 20, 2008
Coordinator:
- Alexander Vakakis (Nat. Technic. Univ. of Athens, Zografos, Athens, Greece)
This short course will address advanced nonlinear topics in the general areas of,
- Vibration mitigation
- System identification
First, a brief overview of current mitigation strategies for systems subjected to loads causing vibration and shock, and of existing methods for the steady-state analysis of weakly nonlinear systems will be provided. Then, advanced methodologies and techniques for analyzing strongly nonlinear systems subjected to transient loads will be discussed, and ways of interpreting complex, multi-frequency transitions in damped nonlinear structural responses will be provided. In the sequence, recently developed techniques for passive vibration mitigation by means of targeted energy transfer (TET) in coupled oscillators will be discussed, leading to a new paradigm for vibration mitigation. This discussion will include the concept of passive nonlinear energy sink (NES) for vibration mitigation, and the discussion of alternative designs of NESs acting as broadband boundary controllers. This will be followed by an outline of strategies for experimentally demonstrating passive TET in discrete and elastic dynamical systems, and a presentation of issues related to the design and construction of practical NESs. It will be shown that nonlinear vibration / shock mitigation is closely tied to the reliable nonlinear system identification of the dynamics. An overview and assessment of current nonlinear system identification techniques will be given, followed by a discussion of their use for modeling nonlinear engineering structures, together with a discussion of the concept of nonlinear normal modes and their application to system identification. This will lead to a presentation of computational methods for nonlinear system identification and signal analysis, combining computational tools such as Wavelet Transforms, Empirical Mode Decomposition, Proper Orthogonal Decomposition, and Complexification – Averaging. Applications of TET to practical problems, including seismic mitigation, vibration and shock isolation, drill-string instability suppression, and passive suppression of aeroelastic instabilities will be presented.
Prerequisites: Participants should have a basic knowledge of ordinary differential equations, linear algebra and basic dynamics and (linear) vibration theory.