MS13.3: Energy Transfer and Harvesting in Nonlinear Systems

This study investigates the concept of clearance-type nonlinear energy sinks (NESs) for the passive mitigation of a model of a five-story shear frame structure subjected to seismic excitation. This is achieved by introducing two local NESs with linear internal restoring springs and dampers, incorporating single-sided clearance stiffness. By increasing the clearance stiffness to a relatively high value, the limit of single-sided vibro-impact (SSVI) is achieved. The introduction of these non-smooth clearance-type NESs yields significant outcomes. Firstly, there is a substantial reduction in the portion of seismic input energy penetrating the structure compared to an unprotected one, while simultaneously maintaining low acceleration levels. Secondly, it facilitates rapid, robust, and irreversible targeted energy transfer (TET) from the linear primary structure to the local NESs, leading to passive energy localization in the attachments. Thirdly, the clearance nonlinearities induce intermodal targeted energy transfer (IMTET) from low to high-frequency structural modes, thereby enhancing energy dissipation performance right from the initial cycle of the structural response. Lastly, properly designed single-sided clearance-type NESs demonstrate robustness across a broad spectrum of seismic input energy levels and frequency content, even under severe ground excitations. The seismic loads are simulated using records from three historical earthquakes: the 1994 Northridge, 1995 Kobe, and 1940 El Centro.

This work explores the implementation of the intermodal targeted energy transfer (IMTET) mechanism for passive mitigation of a three-dimensional non-symmetric linear oscillator subjected to blast excitation. We consider a mechanism for redistribution of the excitation energy among the oscillatory modes. The model under consideration is a three-dimensional rigid mass with six degrees-of-freedom - three independent directions of translation, and three independent rotational directions. To achieve the IMTET behavior, a half ellipsoidal cavity is introduced at the bottom of the mass. In addition, the vibro-impacts are achieved by placing a fixed rigid rod, which its tip is located inside the mass, in the ellipsoidal cavity. At rest, the center of mass coincides with the tip of the rigid rod. Asymmetry is introduced by placing the ellipsoidal cavity at the bottom of the mass. The impacts between the rigid rod and the cavity are the only nonlinear interactions in the system; between the impacts, the dynamics will be assumed linear, for the sake of simplicity. Profound IMTET with substantial decrease of the characteristic damping time is observed.

An analytical design method accompanied by a finite element technique to study the dynamics of a transmission line cable submitted to galloping instability with and without a nonlinear passive control device is developed. The analytical model of the cable span is developed with tools of curvilinear mechanics. The aerodynamic force formulation defined in the analytical model is implemented in the finite element method using the finite element code : code_aster. A piece-wise linear Nonlinear Energy Sink (NES) is coupled to the span. The dynamics of the system is studied in the analytical method via the use of complex variables and multiple time scales. The dynamics obtained with the analytical and the finite element methods are discussed and compared with field data.

Comparison of behaviors and performances between large amplitude nonlinear direct and parametric shunted piezoelectric energy harvesters (PEH) are addressed in this paper. A model of geometrically exact piezoelectric laminated beam with parametric excitation is proposed and simplified with Euler-Bernoulli and inextensible assumptions, Taylor series expansion of transverse displacement and truncation, and first-mode Galerkin expansion. A cantilever beam with two collocated patches is then considered and patches placement and geometry are computed based on coupling-factor optimization. Analytical and numerical resolution methods are compared. PEH behaviors and performances are compared regarding the dissipated power in the resistor at resonance. Three cases are considered: linear-direct, nonlinear-direct and nonlinear-parametric. Results show a gap between direct and parametric PEH performances and the importance of the threshold excitation parametric effect.

The study focuses on targeted energy transfer between two weakly and linearly coupled oscillators. One of the oscillators is subject to time-dependent and nonlinear restoring forcing terms. A previous study (using stochatsic optimization) has demonstrated improved vibration absorption with time-dependent nonlinear rigidity compared to a constant rigidity. An experimental test set-up has been designed and employed for experimentally validation of the optimized targeted energy transfer in the vibro-acoustics domain.