Showing papers on "Dynamic Vibration Absorber published in 2014"

The development of an adaptive tuned magnetorheological elastomer absorber working in squeeze mode

Abstract: In the past, adaptive tuned vibration absorbers (ATVAs) based on magnetorheological elastomers (MREs) have mainly been developed in a shear working mode. The enhancing effect of MREs in squeeze mode has already been investigated, but ATVAs in squeeze mode have rarely been studied. This paper reports the development of a compact squeeze MRE absorber and its subsequent performance in various magnetic fields characterized under various frequencies by a vibration testing system. The results revealed that the natural frequency of the MRE absorber working in squeeze mode can be tuned from 37 Hz to 67 Hz. Following this, a theoretical model based on magnetic dipole theory was developed to investigate the dynamic performance of the squeeze MRE absorber, and the vibration attenuation of the squeeze MRE absorber was then verified by mounting it on a beam with supports under both ends. The results revealed that the squeeze MRE absorber extended its vibration attenuation range from 37 Hz to 67 Hz while the passive absorber was only effective around 53 Hz.

Theoretical study and experimental verification of vibration control of offshore wind turbines by a ball vibration absorber

Abstract: In this paper, a ball vibration absorber (BVA) is introduced for vibration control of offshore wind turbines. The dynamic responses of offshore wind turbines equipped with a BVA are presented. Both theoretical and experimental investigations are carried out. An analytical model for the wind turbine tower system with installed BVA is developed based on Lagrange's equation. The BVA-structure integrated equations are derived and solved in both time domain and frequency domain. A series of shaking table tests on a 1/13-scale wind turbine model with and without a BVA were carried out to evaluate the effects of BVA on the vibration mitigation of the wind turbine tower system under earthquakes and equivalent wind-wave loads. Numerical simulations of the system are performed and compared with the experimental results. Good agreement between the numerical and experimental results is observed. The results indicate that BVA could effectively improve the performance of the offshore wind turbine.

Piezoelectric vibration damping using resonant shunt circuits: an exact solution

Abstract: The objective of this paper is to propose an exact closed-form solution to the optimization of piezoelectric materials shunted with inductive-resistive passive electrical circuits. Realizing that Den Hartogʼs method which imposes fixed points of equal height in the receptance transfer function is approximate, the parameters of the piezoelectric tuned vibration absorber are calculated through the direct minimization of the maxima of the receptance. The method is applied to a one-degree-of-freedom primary oscillator considering various values of the electromechanical coupling coefficients.

Vibration and sound damping in polymers

Abstract: Excessive vibrations or loud sounds cause deafness or reduced efficiency of people, wastage of energy and fatigue failure of machines/structures. Hence, unwanted vibrations need to be dampened. This article describes the transmission of vibrations/sound through different materials such as metals and polymers. Viscoelasticity and glass transition are two important factors which influence the vibration damping of polymers. Among polymers, rubbers exhibit greater damping capability compared to plastics. Rubbers reduce vibration and sound whereas metals radiate sound. The damping property of rubbers is utilized in products like vibration damper, shock absorber, bridge bearing, seismic absorber, etc.

Negative impedance shunted electromagnetic absorber for broadband absorbing: experimental investigation

Abstract: The traditional tuned mass absorber is widely employed to control the vibration of a primary structure by transferring the vibrating energy to the absorber. However, the working band of the absorber is very narrow, which limits the application of broadband vibration control. This study presents a novel broadband electromagnetic absorber by first introducing two negative impedance shunts to improve broadband damping of the absorber. The electromagnetic absorber is modeled, and the corresponding electromagnetic coupling coefficient is tested. A cantilever beam is employed to verify the broadband vibration absorption of the negative resistance (NR) shunted electromagnetic absorber (NR absorber) and the negative inductance NR shunted electromagnetic absorber (NINR absorber). The governing equations of the beam with two absorbers are derived, and the experiments are set up. The results point out that the NR and NINR absorbers can attenuate the broadband vibration. The proposed absorbers do not need the feedback system and the real-time controller compared to the active absorber; hence, they have great application potential in aerospace and in submarine applications, as well as in civil and mechanical engineering.

Design and analyses of axial semi-active dynamic vibration absorbers based on magnetorheological elastomers

Abstract: Magnetorheological elastomers are a new kind of magnetorheological materials mainly composed of polymer rubber and micro-sized magnetizable iron particles. Dynamic vibration absorbers based on magnetorheological elastomers are widely used in vibration systems with small amplitude since they have the advantages of no sealing equipments, good stability, and rapid response. In this article, a shear-mode semi-active dynamic vibration absorber based on magnetorheological elastomers is proposed, and the dynamic design principle of an axial semi-active dynamic vibration absorber attached to ship shafting is studied. The material preparation of magnetorheological elastomers and their properties under different magnetic fields are discussed. The structure of a single semi-active dynamic vibration absorber is designed, and theoretical analysis of shift-frequency property of a single semi-active dynamic vibration absorber is also investigated. The magnetic flux density of magnetorheological elastomers in the semi-ac...

Application of DVA theory in vibration reduction of carbody with suspended equipment for high-speed EMU

Abstract: The theory of dynamic vibration absorber (DVA) was applied to restrain the vibration of carbody for high-speed electric multiple unit (EMU). The carbody was modeled as an Euler-Bernoulli beam with the equipment mounted on the chassis regarded as a DVA. Suspension parameters of the equipment were optimized based on the modal analysis of the beam and parameter optimization of the DVA. Vertical motion equations of the carbody and equipment were derived to study the effect of the suspension parameters on the vibration of carbody, which included the suspension frequency, damping ratio, mounting position and mass. Then a 3D rigid-flexible coupled vehicle system dynamics model was built to simulate the response of carbody and equipment to track excitation. The results show that the equipment mounted on the carbody chassis can be regarded as a DVA to reduce the flexible vibration of carbody, and the optimum suspension frequency can be calculated theoretically with the first-order vertical bending mode of carbody considered. Heavy equipment should be mounted to the carbody center as close as possible to obtain a significant vibration reduction, while light equipment has quite limited contribution to that. Also, a laboratory test was conducted on the full-scale test rig which shows a good agreement with the theoretical analysis and dynamic simulations. The faster the vehicle runs, the more significant are the advantages of the elastic suspension.

The Harmonic Balance Method for Advanced Analysis and Design of Nonlinear Mechanical Systems

Abstract: As a tool for analyzing nonlinear large-scale structures, the harmonic balance (HB) method has recently received increasing attention in the structural dynamics community. However, its use was so far limited to the approximation and study of periodic solutions, and other methods as the shooting and orthogonal collocation techniques were usually preferred to further analyze these solutions and to study their bifurcations. This is why the present paper intends to demonstrate how one can take advantage of the HB method as an efficient alternative to the cited techniques. Two different applications are studied, namely the normal modes of a spacecraft and the optimization of the design of a vibration absorber. The interesting filtering feature of the HB method and the implementation of an efficient bifurcation tracking extension are illustrated.

Design, simulation, and large-scale testing of an innovative vibration mitigation device employing essentially nonlinear elastomeric springs

Abstract: SUMMARY This study proposes an innovative passive vibration mitigation device employing essentially nonlinear elastomeric springs as its most critical component. Essential nonlinearity denotes the absence (or near absence) of a linear component in the stiffness characteristics of these elastomeric springs. These devices were implemented and tested on a large-scale nine-story model building structure. The main focus of these devices is to mitigate structural response under impulse-like and seismic loading when the structure remains elastic. During the design process of the device, numerical simulations, optimizations, and parametric studies of the structure-device system were performed to obtain stiffness parameters for the devices so that they can maximize the apparent damping of the fundamental mode of the structure. Pyramidal elastomeric springs were employed to physically realize the optimized essentially nonlinear spring components. Component-level finite element analyses and experiments were conducted to design the nonlinear springs. Finally, shake table tests using impulse-like and seismic excitation with different loading levels were performed to experimentally evaluate the performance of the device. Experimental results demonstrate that the properly designed devices can mitigate structural vibration responses, including floor acceleration, displacement, and column strain in an effective, rapid, and robust fashion. Comparison between numerical and experimental results verified the computational model of the nonlinear system and provided a comprehensive verification for the proposed device. Copyright © 2014 John Wiley & Sons, Ltd.

Magnetorheological damping and semi-active control of an autoparametric vibration absorber

Abstract: A numerical study of an application of magnetorheological (MR) damper for semi-active control is presented in this paper. The damper is mounted in the suspension of a Duffing oscillator with an attached pendulum. The MR damper with properties modelled by a hysteretic loop, is applied in order to control of the system response. Two methods for the dynamics control in the closed-loop algorithm based on the amplitude and velocity of the pendulum and the impulse on–off activation of MR damper are proposed. These concepts allow the system maintaining on a desirable attractor or, if necessary, to change a position from one attractor to another. Additionally, the detailed bifurcation analysis of the influence of MR damping on the number of periodic solutions and their stability is shown by continuation method. The influence of MR damping on the chaotic behavior is studied, as well.

Phase based stiffness tuning algorithm for a magnetorheological elastomer dynamic vibration absorber

Abstract: This paper presents a phase based stiffness tuning algorithm to overcome the uncertainty of the relation between the magnetic current and the natural frequency for magnetorheological elastomer (MRE) dynamic vibration absorbers (DVA) caused by the nonlinearity of the MRE. The phase difference of the relative acceleration of the DVA mass and the absolute acceleration of the primary system was used to check whether the natural frequency of the DVA is adjusted to the excitation frequency. The magnetic current was controlled by the phase difference, which made the proposed algorithm not rely on the model of the MRE DVA. Both the simulation and the experiment demonstrate that the proposed algorithm is efficient for MRE DVA in rapidly tracking the excitation frequency.

Optimal semi-active vibration absorber for harmonic excitation based on controlled semi-active damper

Abstract: The semi-active vibration absorber (SVA) based on controlled semi-active damper is formulated to realize the behaviour of the passive undamped vibration absorber tuned to the actual harmonic disturbing frequency. It is shown that the controlled stiffness force, which is emulated by the semi-active damper to realize the precise real-time frequency tuning of the SVA, is unpreventably combined with the generation of undesirable damping in the semi-active damper whereby the SVA does not behave as targeted. The semi-active stiffness force is therefore optimized for minimum primary structure response. The results point out that the optimal semi-active stiffness force reduces the undesirable energy dissipation in the SVA at the expenses of slight imprecise frequency tuning. Based on these findings, a real-time applicable suboptimal SVA is formulated that also takes the relative motion constraint of real mass dampers into account. The results demonstrate that the performance of the suboptimal SVA is closer to that of the active solution than that of the passive mass damper.

Design of non-traditional dynamic vibration absorber for damped linear structures:

Abstract: The Voigt-type of dynamic vibration absorber is a classical model and has attracted considerable attention in many years because of its simple design, high reliability and useful applications in th...

Damping vibration absorber

Abstract: The invention provides a damping vibration absorber, which comprises a damping material, a mass block and connecting pieces. The mass block is circumferentially arranged outside the damping material, and is tightly connected with the damping material; the connecting pieces are arranged in the damping material in a penetrating manner, are tightly connected with the damping material, and are located in the central area of the whole vibration absorber. According to the damping vibration absorber provided by the invention, the inherent resonance frequency of a mechanical system can be effectively and rapidly broken, so that the mechanical system stably works in an off-resonance frequency band all the time during dynamic operation. The damping vibration absorber provided by the invention not only can be used for eliminating resonance energy output from an engine but also can be used for effectively eliminating excitation and impact energy input by a road surface, and therefore, the protection of an automotive system is effectively completed.

Vibration Modes and Natural Frequency Veering in Three-Dimensional, Cyclically Symmetric Centrifugal Pendulum Vibration Absorber Systems

Abstract: This paper investigates the vibration mode structure of three-dimensional, cyclically symmetric centrifugal pendulum vibration absorber (CPVA) systems. The rotor in the system has two translational, one rotational, and two tilting degrees of freedom. The equations of motion for the three-dimensional model, including the rotor tilting, are derived to study the modes analytically and numerically. Only three mode types exist: rotational, translational-tilting, and absorber modes. The rotational and absorber modes have identical properties to those of in-plane models. Only the translational-tilting modes contain rotor tilting. The veering/crossing behavior between the eigenvalue loci is derived analytically.

Modelling and validation of a regenerative shock absorber system

Abstract: For effective energy regeneration and vibration dampening, energy regenerative suspension systems have received more studies recently. This paper presents the dynamic modeling and a test system of a regenerative shock absorber system which converts vibration motion into rotary motion through the adjustment of hydraulic flow. Hydraulic circuit configuration achieves the one way flow and energy regeneration during both compression and extension strokes. The dynamic modeling is performed for the evaluation of design concept and the feasibility studies of regenerative shock absorber system theoretically. Based on simulated results, the efficiency of hydraulic transmission is optimized and validated in test system. The results show that the performance of hydraulic fluid, the features of rotary motion and the capability of energy regeneration are verified and compared between dynamic modeling and experiments. Meanwhile, the average power of 118.2W and 201.7W with the total energy conversion of 26.86% and 18.49% can be obtained based on experiments under sinusoidal inputs with 0.07854m/s and 0.1256m/s respectively.

Design Methodology of a Micro-Scale 2-DOF Energy Harvesting Device for Low Frequency and Wide Bandwidth

Abstract: A detailed design methodology of a micro-scale 2-DOF energy harvesting device that can harvest human motion energy of low frequency and wide bandwidth is developed Based on the concept of the 2-DOF vibration absorber, device parameters are selected to harvest energy at low frequency of 1-10 Hz and wide bandwidth with ±20% of the mean frequency, which matches the human motion The device dimensions are limited to 40 × 30 × 10 mm3 to fit with the human wrist size Then, a finite element model is developed to investigate the system performance with the selected parameters When subjected to harmonic excitation of 1 g, the proposed 2-DOF device is able to provide a power of at least 10 μW in between the two close resonant peaks of 4 Hz and 6 Hz, which is the target frequency range The device shows very high power per square frequency compared with the reported harvesters

Parametric Analysis of Magnetorheologically Damped Pendulum Vibration Absorber

Abstract: This paper presents numerical and experimental study of an autoparametric pendulum absorber attached to a vertically moving Duffing oscillator. The absorber can be highly efficient for slightly damped systems, when correctly tuned. In the suspension of pendulum absorber, the magnetorheological damper (MR) is installed to allow control. The influence of system parameters: Viscous and magnetorheological damping, stiffness of the spring, parameter which couples both systems on the suppression effectiveness are studied. Additionally, the influence of system parameters on periodic solutions and stability are analyzed using continuation techniques.

Study of Passive Vibration Absorbers Attached on Beam Structure

Abstract: Structural vibration is undesirable, wasting energy and possibly leading to excessive deflections and structure and machine’s failure. In order to reduce structural vibration, one of the common way is considering vibration absorber system attach to the structure. In this study, a vibration absorber is developed in a small scale size. The host structure selected for the study is a fixed-fixed ends beam. The effectiveness of vibration absorbers attached to a beam is investigated through experimental study. In prior to experiment, a finite element analysis of Solidworks® and analytical equations of Matlab® are produced in order to determine the structural dynamic response of the beam, such as the natural frequency and mode shapes. The preliminary results of finite element analysis demonstrate that the first five natural frequency of fixed-fixed end beam are 17Hz, 46Hz, 90Hz, 149Hz and 224Hz, and these results are in agreement with the beam’s analytical equations. However, there are slight discrepancies in experiment result due to noise and error occurred during the setup. In the later stage, the experimental works of beam are performed with attached vibration absorber. Result shows that the attachment of vibration absorber produces better outcome, which is about 45% vibration reduction. It is expected that by adding more vibration absorber to the structure, the vibration attenuation can significant.

Practical design of a nonlinear tuned vibration absorber

Abstract: The aim of the paper is to develop a new nonlinear tuned vibration absorber (NLTVA) capable of mitigating the vibrations of nonlinear systems which are known to exhibit frequency-energy-dependent oscillations. A nonlinear generalization of Den Hartog’s equal-peak method is proposed to ensure equal peaks in the nonlinear frequency response for a large range of forcing amplitudes. An analytical tuning procedure is developed and provides the load-deflection characteristic of the NLTVA. Based on this prescribed relation, the NLTVA design is performed by two different approaches, namely thanks to (i) analytical formulas of uniform cantilever and doubly-clamped beams and (ii) numerical shape optimization of beams with varying width and thickness. A primary system composed of a cantilever beam with a geometrically nonlinear component at its free end serves to illustrate the proposed methodology.