Showing papers on "Dynamic Vibration Absorber published in 2018"

Optimal tuned mass‐damper‐inerter (TMDI) design for seismically excited MDOF structures with model uncertainties based on reliability criteria

Abstract: The tuned mass-damper-inerter (TMDI) is a recently proposed linear passive dynamic vibration absorber for the seismic protection of buildings. It couples the classical tuned mass damper (TMD) with an inerter, a two-terminal device resisting the relative acceleration of its terminals, in judicial topologies, achieving mass-amplification and higher-modes-damping effects compared to the TMD. This paper considers an optimum TMDI design framework accommodating the above effects while accounting for parametric uncertainty to the host structure properties, modeled as a linear multi degree of freedom system, and to the seismic excitation, modeled as stationary colored noise. The inerter device constant, acting as a TMD mass amplifier, is treated as a design variable, whereas performance variables sensitive to high-frequency structural response dynamics are used to account for the TMDI influence to the higher structural modes. Reliability criteria are adopted for quantifying the structural performance, expressed through the probability of occurrence of different failure modes related to the trespassing of acceptable thresholds for the adopted performance variables: floor accelerations, interstory drifts, and attached mass displacement. The design objective function is taken as a linear combination of these probabilities following current performance-based seismic design trends. Analytical and simulation-based tools are adopted for the efficient estimation of the underlying stochastic integral defining the structural performance under uncertainty. A 10-story building under stationary Kanai-Tajimi stochastic excitation is considered to illustrate the design framework for various TMDI topologies and attached mass values. It is shown that the TMDI achieves enhanced structural performance and robustness to building and excitation uncertainties compared to same mass/weight TMDs.

Numerical and experimental studies on the car body flexible vibration reduction due to the effect of car body-mounted equipment:

Abstract: To study the effect of car body-mounted equipment on the car body flexible vibration, a vertical rigid-flexible coupling model of a high-speed vehicle is established, which includes a flexible car ...

Dynamics of 1-dof and 2-dof energy sink with geometrically nonlinear damping: application to vibration suppression

Abstract: Nonlinear energy sink (NES) refers to a lightweight nonlinear device that is attached to a primary linear or weakly nonlinear system for passive energy localization into itself. In this paper, the dynamics of 1-dof and 2-dof NES with geometrically nonlinear damping is investigated. For 1-dof NES, an analytical treatment for the bifurcations is developed by presenting a slow/fast decomposition leading to slow flows, where a truncation damping and failure frequency are reported. Existence of strongly modulated response (SMR) is also determined. The procedures are then partly paralleled to the investigation of 2-dof NES for the bifurcation analysis, with particular attention paid to the effect of mass distribution between the NES. To study the frequency response for 2-dof NES, the periodic solutions and their stability are obtained by incremental harmonic balance method and Floquet theory, respectively. Poincare map and energy spectrum are specially introduced for numerical analysis of the systems in the neighborhood of resonance frequency, which in turn are used to compare the efficiency of the NESs to the application of vibration suppression. It is demonstrated that a 2-dof NES can generate extra SMR by adjusting its mass distribution and hence to a great extent reduces the undesired periodic responses and provides with a more effective vibration absorber.

A fully passive nonlinear piezoelectric vibration absorber.

Abstract: The objective this study is to develop the first fully passive nonlinear piezoelectric tuned vibration absorber (NPTVA). The NPTVA is designed to mitigate a specific resonance of a nonlinear host structure. To avoid the use of synthetic inductors which require external power, closed magnetic circuits in ferrite material realize the large inductance values required by vibration mitigation at low frequencies. The saturation of an additional passive inductor is then exploited to build the nonlinearity in the NPTVA. The performance of the proposed device is demonstrated both numerically and experimentally.

Designing an attachable and power-efficient all-in-one module of a tunable vibration absorber based on magnetorheological elastomer

Abstract: This study designs an all-in-one module of a tunable vibration absorber (TVA) using magnetorheological elastomer (MRE) considering easy installation in a plug-and-play concept on an actual industrial plant. The proposed system is designed to overcome several limitations on a typical system composed of an electromagnet and MRE TVA, such as environmental robustness, bulky size, high power consumption and complex installation on an actual plant. The designed TVA module contains sensors for MRE tuning control feedback, an energy-efficient magnetic field density generator, MRE and absorber mass. A novel but simple magnetic field generator is proposed using a small brushless DC gimbal motor and permanent magnets to reduce unnecessary energy consumption for long-term operation. The TVA module is designed so that it can be easily attached to an existing target system, such as a linear compressor. Using the embedded sensors in the module, it can automatically tune the MRE stiffness adaptively to the disturbance vibration on the target system. The prototype performance is validated with experiments showing that it can provide approximately 94% of stiffness change and 58% of vibration suppression for disturbance in the frequency range of 51.6–71.9 Hz.

Seismic Energy Assessment of Buildings with Tuned Vibration Absorbers

Abstract: Seismic analysis and energy assessment of building installed with distributed tuned vibration absorbers (d-TVAs) are presented. The performance of d-TVAs is compared with single tuned vibration absorber (STVA) installed at the top of the building. The placements of the d-TVAs are based on the modal properties of the uncontrolled and controlled buildings. The governing equations of motion of the building with the STVA and d-TVAs are solved by employing Newmark’s integration method. Various energies under earthquake ground excitations are computed to study the effectiveness of using the STVA and d-TVAs. It is concluded that the use of the d-TVAs is the most competent because it effectively dissipates the seismic energy, and they are convenient to install requiring reduced space, as are placed at various floors.

Simultaneous vibration suppression and energy harvesting with a non-traditional vibration absorber:

Abstract: This article investigates the effectiveness of using a non-traditional vibration absorber for the purpose of simultaneous vibration suppression and energy harvesting Unlike the commonly used vibra

Analysis and Optimization of the Novel Inerter-Based Dynamic Vibration Absorbers

Abstract: Passive dynamic vibration absorber (DVA) is widely used in structural vibration reduction, and the higher efficient DVA is always required for some special situations. This paper aims to propose the novel inerter-based dynamic vibration absorbers (IDVAs) to enhance the performance of the passive DVA. First, several novel IDVAs are presented by matching the inerter with DVA in different places. Then, the closed-form optimal parameters of six kinds of IDVAs are obtained based on the classical fixed-point theory. The obtained parameters demonstrates that all the inerters connected between the primary system and absorber system do not provide improvement for the performance of DVAs, while all the inerters connected to the earth can improve the performance of DVAs. Moreover, the comparisons among the IDVAs show that the inerter connected to the earth in the grounded DVA (IR2 in this paper) performs the best performance in vibration absorption. More than 30 % improvement can be obtained from IR2 as compared with other IDVAs. Finally, the further comparison among the IDVAs under white noise excitation also shows that IR2 is superior to other IDVAs. The results may provide theoretical basis for design of the optimal IDVA in engineering practice.

Application of a dynamic antiresonant vibration isolator to minimize the vibration transmission in underwater vehicles

Abstract: Harmonic axial force resulting from a propeller’s first vibration mode is a major cause of tonal sound radiation of an underwater vehicle. To reduce the harmonic force, we employ a dynamic antireso...

Influence of nonlinear subunits on the resonance frequency band gaps of acoustic metamaterial

Abstract: Recently, a significant attention has been directed toward so called ‘acoustic metamaterials’ which have large similarity with already-known ‘electromagnetic metamaterials’ which are applied for elimination of the electromagnetic waves. The stop of electromagnetic waves is realized with the negative refractive index, negative permittivity and negative permeability. Motivated by the mathematical analogy between acoustic and electromagnetic waves, the acoustic metamaterials are introduced. It was asked the material to have negative effective mass. To obtain the negative effective mass, the artificial material, usually composite, has to be designed. The basic unit is a vibration absorber which consists of a lumped mass attached with a spring to the basic mechanical system. The purpose of the unit is to give a band gap where some frequencies of acoustic wave are stopped. We investigated the nonlinear mass-in-mass unit excited with any periodic force. Mathematical model of the motion is a system of two coupled strongly nonlinear and nonhomogeneous second-order differential equations. The solution of equations is assumed in the form of the Ateb (inverse beta) periodic function. The frequency of vibration is obtained as the function of the parameters of the excitation force. The effective mass of the system is also determined. Regions of negative effective mass are calculated. For these values the motion of the forced mass stops. It is concluded that the stop frequency gaps are much wider for the nonlinear than for the linear system. Based on the obtained parameter values, the acoustic metamaterial could be designed.

A tunable dynamic vibration absorber for unbalanced rotor system

Abstract: A tunable dynamic vibration absorber for unbalanced rotor system which is made up of coil springs and magnetic spring is presented. The structure of the absorber is introduced and the stiffness tuning mechanism of the magnetic spring is explained. A finite element model of the rotor-absorber system was built and the influencing factors to the appearance of the absorber were studied numerically. Finally, experiments were carried out to verify the numerical results, and PID control strategy was tested. The numerical and experimental results show that the present absorber is effective for vibration suppression of an unbalanced rotor system, and the control strategy is effective.

Analysis of the vibration characteristics and adjustment method of boring bar with a variable stiffness vibration absorber

Abstract: In deep hole boring process, long and flexible boring bars are often used. Due to the large length-to-diameter ratio, the stiffness of the boring bars is inevitably reduced, where the boring bars’ vibration effects will occur. The influences of vibration will significantly degrade the accuracy and the surface quality, or even lead failure of the production. Therefore, it is of significant importance to develop techniques to reduce vibration in deep hole boring. In this paper, a new boring bar with a variable stiffness dynamic vibration absorber (VSDVA) is presented, where the basic parameters of the proposed boring bar are measured. Based on the proposed dynamic model, the vibration characteristics of the proposed boring bar are analyzed, and the change laws of the vibration reduction performance are obtained under different excitation frequencies. A new vibration reduction method is proposed, where best vibration reduction performance can be achieved by adjusting the stiffness of the VSDVA. Finally, the vibration reduction performance of the proposed boring bar is validated and evaluated by boring experiments. These works could provide guidance for designing new types of boring bars, selecting cutting parameters, and adjusting the vibration reduction performance of the proposed boring bar, and as a result, it provides a new design idea for the design of boring bar.

On vibration mitigation and energy harvesting of a non-ideal system with autoparametric vibration absorber system

Abstract: This paper demonstrates that vibration mitigation and energy harvesting can be achieved simultaneously by using of an electricity-generating from autoparametric vibration absorber system (AVAS) and non-ideal system (NIS) The NIS consists of a simple portal frame excited by a small dc motor with eccentric mass, with limited power supply and located on the top The AVAS consists of a cantilever beam with tip mass parallel coupled to NIS A piezoelectric material is considered for energy harvesting installed in the base of the AVAS and an electric circuit is connected to the piezoelectric material in order to produce voltage output Several numerical simulations were carried out focusing on the passage through the resonance of NIS, when the motor rotational frequency is near the portal frame natural frequency and when the non-ideal subsystem frequency is approximately twice the absorber beam frequency (two-to-one internal resonance) The results showed the existence of Sommerfeld effect in NIS and saturation phenomenon in the NIS–AVAS

Optimizations of distributed dynamic vibration absorbers for suppressing vibrations in plates

Abstract: Dynamic vibration absorber is an ideal device for vibration control at specific frequencies. In order to get a robust vibration control performance, multiple or distributed dynamic vibration absorb...

Reduction of vertical abnormal vibration in carbodies of low-floor railway trains by using a dynamic vibration absorber:

Abstract: A field test on the dynamic performance of a 100% low-floor railway train with five cars was conducted, and a vertical vibration at around 8 Hz was mainly studied for the background of the research...

Design optimization of a viscoelastic dynamic vibration absorber using a modified fixed-points theory

Abstract: A viscoelastic dynamic vibration absorber (VDVA) is proposed for suppressing infrasonic vibrations of heavy structures because the traditional dynamic vibration absorber equipped with a viscous damper is not effective in suppressing low frequency vibrations. The proposed VDVA has an elastic spring and a viscoelastic damper with frequency dependent modulus and damping properties. The standard fixed-points theory cannot be applied to derive the optimum design parameters of the VDVA because both its stiffness and damping are frequency dependent. A modified fixed-points theory is therefore proposed to solve this problem. H∞ design optimization of the proposed VDVA have been derived for the minimization of resonant vibration amplitude of a single degree-of-freedom system excited by harmonic forces or due to ground motions. The stiffness and damping of the proposed VDVA can be decoupled such that both of these two properties of the absorber can be tuned independently to their optimal values by following a specified procedure. The proposed VDVA with optimized design is tested numerically using two real commercial viscoelastic damping materials. It is found that the proposed viscoelastic absorber can provide much stronger vibration reduction effect than the conventional VDVA without the elastic spring.