Spectrum-anchored dimensionless optimization framework of a nonlinear energy sink with inerter (NESI) sky corridor for seismic mitigation of adjacent buildings

Shaking table test study on seismic performance of RC frame structure with NES

In the field of seismic protection of structures, it is crucial to be able to diminish ‘as much as possible’ and dissipate ‘as fast as possible’ the load induced by seismic (vibration-shock) energy imparted to a structure by an earthquake. In this context, the concept of passive nonlinear energy pumping appears to be natural for application to seismic mitigation. Hence, the overall problem discussed in this paper can be formulated as follows: Design a set of nonlinear energy sinks (NESs) that are locally attached to a main structure, with the purpose of passively absorbing a significant part of the applied seismic energy, locally confining it and then dissipating it in the smallest possible time. Alternatively, the overall goal will be to demonstrate that it is feasible to passively divert the applied seismic energy from the main structure (to be protected) to a set of preferential nonlinear substructures (the set of NESs), where this energy is locally dissipated at a time scale fast enough to be of practical use for seismic mitigation. It is the aim of this work to show that the concept of nonlinear energy pumping is feasible for seismic mitigation. We consider a two degree-of-freedom (DOF) primary linear system (the structure to be protected) and study seismic-induced vibration control through the use of Vibro-Impact NESs (VI NESs). Also, we account for the possibility of attaching to the primary structure additional alternative NES configurations possessing essential but smooth nonlinearities (e.g., with no discontinuities). We study the performance of the NESs through a set of evaluation criteria. The damped nonlinear transitions that occur during the operation of the VI NESs are then studied by superimposing wavelet spectra of the nonlinear responses to appropriately defined frequency – energy plots (FEPs) of branches of periodic orbits of underlying Conservative systems.

We study computationally the passive, nonlinear targeted energy transfers induced by resonant interactions between a single-degree-of-freedom nonlinear energy sink and a uniform-plate model of a flexible, swept aircraft wing. We show that the nonlinear energy sink can be designed to quickly and efficiently absorb energy from one or more wing modes in a completely passive manner. Results indicate that it is feasible to use such a device to suppress or prevent aeroelastic instabilities like limit-cycle oscillations. The design of a compact nonlinear energy sink is introduced and the parameters of the device are examined. Simulations performed using a finite-element model of the wing coupled to discrete equations governing the energy sink indicate that targeted energy transfer is achievable, resulting, for example, in a rapid and significant reduction in the second bending mode response of the wing. Finally, the finite element model is used to simulate the effects of increased nonlinear energy sink stiffness, and to show the conditions under which the nonlinear energy sink will resonantly interact with higher-frequency wing modes.

Application of broadband nonlinear targeted energy transfers for seismic mitigation of a shear frame: Computational results

Rotary-oscillatory nonlinear energy sink of robust performance

Application of broadband nonlinear targeted energy transfers for seismic mitigation of a shear frame: Experimental results

This work proposes a clearance-type electromechanical nonlinear energy sink (NES) to increase the electrical energy harvested from non-stationary mechanical waves, such as those encountered during impact and intermittent events. The key idea is to trap energy in the NES such that it can be harvested over a time period longer than that afforded by the passing disturbance itself. This leads to an asymmetrical, piece-wise nonlinear device whose functionality and analysis lie at the intersection of several current research topics, including wave-based energy harvesting, non-reciprocal wave propagation, nonlinear energy sinks (NES’s), and hybrid dynamical systems. The nonlinear energy sink concept explored uses a clearance-type nonlinearity, and resulting impact, to pass the energy of the propagating wave from a primary subdomain to a secondary subdomain where a significant portion of it is subsequently trapped and harvested. Moreover, unlike traditionally-studied single-DOF NESs, both subdomains of the NES (i.e., on either side of the clearance) contain displaceable degrees of freedom, significantly increasing the complexity of analytical solution approaches as compared to systems where one side is constrained by a known (or zero) displacement. Computational and analytical techniques are employed to optimize the energy sink and explore qualitative behavior (to include bifurcations). The analysis includes insight from Poincaré sections and bifurcation diagrams, with and without harvesters. Bifurcation diagrams and trends therein provide insight into the number and state of impact events at the NES as excitation amplitude increases. However, analytic formulations are found which quantify the relationship between the impact amplitude and the energy produced, parameterized by system properties such as the harvester effective resistance, the clearance gap, and the domain mass and stiffness. Importantly, a linear relationship between the input energy amplitude and the number of NES impacts has been observed and captured by an approximate, closed-form Poincaré map. In addition to this linear relationship, a closed-form Poincaré map is derived which maps one NES impact location to the next, greatly simplifying the analysis while providing an important tool for follow-on bifurcation studies. The results may justify further exploration in which complex structures (e.g., plates and/or three-dimensional structures) incorporate one or more of the clearance-type NESs to enhance non-stationary electroacoustic wave energy harvesting.

Nonlinear vibration control and energy harvesting of a beam using a nonlinear energy sink and a piezoelectric device

In order to solve the harm of vortex-induced vibration (VIV), this paper studies the VIV control performance of multi-type nonlinear energy sink (NES) and tube-in-tube (PIP) structures. The multi-degree-of-freedom NES (MDOF-NES) with low linear stiffness coupling control is the best, and the mass block affects the key characteristics of the limit cycle vibration (LCO), and the performance is better than that of the classical type I NES. Rotary NES (R-NES) has better suppression of large mass ratio cylinders, and the mass ratio and rotation radius improve the performance. The damping parameters need to be designed in combination with the mass ratio of the cylinder. The NES with combined nonlinear damping explicitly emphasizes the influence of the control response condition and the amplitude of the external excitation on the frequency detuning coefficient interval. The vertical vibration control performance of NES with cubic stiffness is related to the natural frequency of the main structure. When the frequency is ≥ 3 Hz, the self-weight can be ignored. When the frequency is ≤ 0.8 Hz, the static vertical displacement of the tuned mass damper (TMD) is greater than that of the TMD. The NES stability emphasizes that the system response is caused by the saddle-node bifurcation of the limit cycle of the coupled system, and two conditions need to be satisfied to strengthen the energy transfer. The optimized PIP structure optimizes the flow field and VIV suppression through three-dimensional fluid-solid coupling and computational fluid dynamics simulation, and has the function of heat preservation, which provides a ' heat preservation + vibration reduction ' scheme for marine engineering. Key conclusions: Low linear stiffness MDOF-NES is suitable for nonlinear energy transfer vibration control, and reasonable parameter PIP is preferred for marine engineering.

Nonlinear Energy Sink (NES) absorbers excel in comparison to traditional Tuned Mass Dampers (TMD) due to their superior efficiency over a wider range of frequencies. However, despite the advantages of NES over TMDs, their susceptibility to variations in system energy poses a challenge, particularly in applications where the primary structure is subjected to random excitations. A modified NES, referred to as Asymmetric NES (ANES), has previously demonstrated a substantial enhancement in NES robustness, opening up new possibilities for this particular case. This study investigates the factors contributing to the superior robustness of ANES in comparison to the performance of traditional cubic NES. Through an analysis utilizing Nonlinear Normal Modes (NNM) and Frequency Energy Plots (FEP), this research illustrates that the improved effectiveness of Asymmetric NESs results from a more intricate interaction of the ANES nonlinear normal modes with the kinetic energy FEP of the primary structure. In this work, the NNMs of tuned ANES and NES absorbers with similar mass are generated and plotted alongside the kinetic energy FEP of a three-story shear building subjected to various earthquake ground accelerograms. The findings reveal that the NNM of the ANES absorber intersects more effectively with the system’s energy FEP, explaining the superior robustness of the ANES against variations in the input spectrum power.

Nonlinear energy sink (NES) absorbers excel compared to traditional tuned mass dampers (TMD) due to their superior efficiency over a wider range of frequencies. However, despite the advantages of NES over TMDs, their susceptibility to variations in system energy poses a challenge, particularly in applications where the main structure is subjected to random excitations. A modified NES, referred to as Asymmetric NES, significantly enhances NES robustness, expanding its potential uses. This study investigates the factors contributing to the superior robustness of asymmetric nonlinear energy sink (ANES) in comparison to the performance of traditional cubic NES. Through an analysis utilizing nonlinear normal modes (NNM) and frequency energy plots (FEP), this research shows that the improved effectiveness of asymmetric NESs is due to the intricate interaction between their NNM and the primary structure's kinetic energy FEP, leading to more robust targeted energy transfer (TET). In this work, the NNMs of tuned ANES and NES with similar mass are plotted alongside the kinetic energy FEP of a three-story shear building subjected to various earthquake ground accelerograms. The findings obtained here reveal that the NNM of the ANES absorber intersects more effectively with the system's energy FEP inducing a more effective modal energy redistribution, explaining the superior robustness of the ANES against variations in the input spectrum power.

Multi-ball rotative nonlinear energy sink for galloping mitigation

Design, construction and experimental performance of a nonlinear energy sink in mitigating multi-modal vibrations

Improving product quality of machining components has always met with problems due to the vibration of the milling machine’s spindle, which can be reduced by adding a vibration absorber. The tuned vibration absorber (TVA) has been studied extensively and found to have a narrow bandwidth, but the cutting force possesses wide bandwidth in the process of machining parts. Introducing nonlinearity into the dynamic vibration absorber can effectively increase the bandwidth of vibration suppression and can significantly improve the robustness of the vibration absorber. In addition, a semiactive TVA has proved to be more effective than a passive TVA for many applications, so the main purpose of this study is to find some appropriate semiactive control methods for a nonlinear energy sink (NES), a nonlinear vibration absorber, in structural vibration applications. Two semiactive control methods are considered in this study: continuous groundhook damping control based on velocity and on-off groundhook damping control based on velocity. To fairly compare these vibration absorbers, the optimal parameters of a passive TVA, a passive NES, and two semiactive NESs are designed using numerical optimization techniques to minimize the root-mean-square acceleration. Two cutting forces are introduced in this study, a periodic force and an aperiodic force, and the four vibration absorbers are compared. When the primary structure is excited with aperiodic cutting force, the amplitude of the primary structure decreased by 17.73% with the passive TVA, by 72.29% with the passive NES, by 73.54% with the on-off NES, and by 87.54% with the continuous NES. When the primary structure is excited with periodic cutting force, the amplitude of the primary structure decreased by 49.01% with a passive TVA, by 86.93% with a passive NES, by 96.38% with an on-off NES, and by 99.23% with a continuous NES. The results show that the passive NES is better than the passive TVA; the semiactive NES provides more effective vibration attenuation than the passive NES, and the continuous control is more effective than the on-off control.

Non-linear Energy Sinks (NES) is a new approach in the field of vibration isolation which allows an irreversible transfer of vibration energy from a primary linear system (e.g. a mass -spring where a harmonic excitation is applied) to a secondary non-linear system (e.g. a mass -spring with variable compliance and a damper) where the energy is finally transferred and dissipated. The phenomenon taking place in NES is referred to as Non-linear Energy Transfer (NET). Main applications of NET in the field of engineering range from aero-elastic instabilities control to seismic mitigation in civ il engineering to drill-string systems stabilization. Recent applications in the field of acoustics have seen the use of a thin visco-elastic membrane as NES, where a high amount of the acoustic power provided by waves propagating in a duct is dissipated in NES. However, the use of NES is new in the field of applied acoustics. For this reason, the objectives of this research proposal are investigating the potentiality of NES for both harvesting and dampening the acoustic power