Structural Vibration Reduction Research Articles

Optimization of Dynamic Vibration Absorbers for Suppressing Sound Radiation of Plate Structures

Abstract Dynamic vibration absorber (DVA) is a practical tool used for sound and vibration suppression in the specific frequency band. The parameters of DVAs should be optimally tuned to obtain the best sound and vibration suppression application effects. When the DVAs are used for structural vibration reduction, DVAs’ two parameters which are the optimal frequency ratio and damping ratio have simple analytical expressions. However, the concise analytical expressions of the DVAs that are used for suppressing the structural sound radiations have not been reported. First, this paper investigates the characteristics of DVAs in suppressing sound radiation from thin plates. Second, the fixed points’ phenomenon of the sound radiations of the plate carrying DVAs is revealed. In addition, the classical fixed points’ theory is extended into the optimization process of the DVAs that are used for sound radiation control of the plate. The analytical expression of the optimal frequency ratio, as well as the damping ratio optimization method of the DVA, is simultaneously proposed. Third, the installation position of DVAs is also presented to obtain a better acoustic radiation effect. Finally, the numerical simulations are performed to verify the availability of the method. It is showed that the best sound radiation control effect could be obtained by adopting the optimization means proposed in this paper.

Multimodal Reduction of Elastic Vibrations in Plate Structure using Super Absorbent Polymer Beads

This paper deals with multimodal reduction of structural elastic vibrations. Super absorbent polymer beads (SAP beads) have been introduced as a simple damping device inspired by the multimodal vibration reduction effect by passengers on railway vehicles. A series of vibration measurement tests using a 1:10 scale model of railway vehicle floor structure (model underframe) was carried out. The SAP beads which are sold commonly as water retention agent were stacked in a container and applied to the model underframe. From the experiments, multimodal vibration reduction effects have been demonstrated. A drastic difference has been observed when water was added together with SAP beads. To investigate the basic mechanism of the damping effect obtained by the experiments, an analytical model, which consists of multiple masses that are supported at an angle to each other, and its simplified model was proposed and numerical studies were conducted. Some specific combinations of the mass, spring, and damping elements in the model could express the experimental results well, and it has been estimated from the numerical results that each SAP layer act as an un-uniform subsystem.

Displacement Transmissibility of a Four-Parameter Isolator with Geometric Nonlinearity

This study is concerned with structural vibration reduction using a four-parameter isolator designed as a scissor-like structure, which can induce geometric nonlinearity during the deformation process. The displacement transmissibility of the isolator including the geometric nonlinearity under base excitations is thoroughly investigated. First, the dynamic model of the four-parameter isolator is presented. Then, by utilizing the harmonic balanced method (HBM), the steady-state solutions of the inertia mass and auxiliary spring of the proposed isolator are derived. The analytical solutions are validated by comparing with those obtained by the direct numerical integrating method. Besides, the natural frequency of the nonlinear isolation system is presented and investigated. Moreover, the isolation performance of the four-parameter isolator is assessed in terms of the relative and absolute displacement transmissibilities, and compared with that of the linear Zener model, by which the advantages of the present isolator have been clearly revealed. The effects of various design parameters on the displacement transmissibility of the isolator are also analyzed. Finally, a further comparison between the analytical and experimental results under base excitation also shows that the mechanical model used for the four-parameter isolator is accuracy enough. The present results may provide a useful theoretical basis for the design of the four-parameter isolator in engineering practice.

Acoustic Radiation and Dynamic Study of a Steel Beam Damped with Viscoelastic Material

Steel structures subject to dynamic loads are prior to generate excessive vibration and noise. Viscoelastic treatment is an effective measure to mitigate the vibration and noise from thin-walled structures in a broad frequency range. H-shaped steel beams are widely used in civil engineering. So an experiment system is established and a series of impact hammer tests are conducted to assess the modal parameters, dynamic response and acoustic behaviour of an H-shaped steel beam coated with various viscoelastic treatments. Firstly, the spectra of the velocity response and acoustic radiation of the bare beam are analysed based on the tested data. Secondly, the resonance frequencies and modal loss factors of the beam with various viscoelastic treatments derived from the frequency response function are compared. Finally, the effect of the layout and thickness of viscoelastic patches on the mitigation of vibration and noise is discussed experimentally. It is shown that the modal loss factor of the first mode increases from 0.012 to 0.191 when the web is treated with 5 mm thick constrained layer damping (CLD). The viscoelastic patches on the web of the H-shaped beam are more effective to control the vibration and noise of the beam than the patches on the flanges. The viscoelastic treatment has distinct effect on the reduction of structural vibration and noise owing to the different dominant frequencies of vibration and noise as well as the frequency-dependent radiation efficiency. The normal velocity level of the H-shaped beam with an 8 mm thick web can be reduced by more than 10 dB and the sound pressure level around the beam about 8 dB when the web is partially covered with the constrained layer damping composed of 2.0 mm thick damping layer and 3.0 mm thick constraining layer.

Steel tubular friction damper and vibration reduction effects of double-layer reticulated shells

A steel tubular friction damper (STFD) is proposed for vibration reduction in large-span spatial structures. The effects of the amplitude of the applied displacement, the pre-tightening force of the high-strength bolts, and the material of the friction plates on the hysteretic behaviour of the STFD are analysed experimentally. The single-cycle energy consumption increases and the equivalent stiffness decreases with increasing displacement amplitude. In addition, the single-cycle energy consumption and equivalent stiffness of the STFD increase with increasing pre-tightening force. Both the single-cycle energy consumption and the equivalent stiffness of the STFD with aluminium alloy or brass friction plates are larger than that of the STFD with steel friction plates. Then, a mechanical model of the STFD is established for further numerical analysis. Several structural members in a 40-m-span double-layer reticulated shell are replaced with STFDs to provide vibration reduction. Optimal arrangement of STFDs is studied based on additional modal damping ratio. The effects of the replacement rate, earthquake intensity and various ground motions on the vibration reduction effect are investigated via numerical analyses. The reduction ratio first increases and then decreases with increasing replacement rate, and the best performance is observed at a replacement rate of 10%. The vibration reduction effect of the STFDs is more obvious for strong ground motions than for weak ground motions. Under various ground motions, the vibration reduction effect of the STFDs is better for the two ordinary ground motions than for the four long-period ground motions selected herein.

Coupled modeling and dynamic characteristics of TBM cutterhead system under uncertain factors

The cutterhead system is the most critical component of a tunnel boring machine (TBM). Because of its complex structure and the influence of many uncertain factors, which not only aggravate its vibration damage, but also make the prediction of its dynamic characteristics and the damage-resistant design very challenging, coupled modeling and the dynamic characteristic analysis of cutterhead system under uncertain factors are of great significance. In this paper, firstly, we considered the influence of geology and cutter position, the geological uncertainty model and the uncertainty model of the cutter position were established for the first time. The combination and transformation of the uncertainty model and the obtained load interval were realized successfully. Then, the load interval was substituted into the dynamic model, the multi-degree-of-freedom coupled dynamic model of the cutterhead system under uncertain factors was obtained. We combined interval theory with the central difference method to solve the dynamic model and obtained the dynamic response boundary. The necessity of considering uncertainty and the effectiveness of this method were verified by comparing the data under uncertain factors with the field test data and simulation data. Finally, we applied our method to an engineering cutterhead system. The results showed that (1) The five-part cutterhead has better vibration characteristics than the integrated cutterhead and two-part cutterhead; (2) When the mass of the center block accounts for 45–46% of the total, the vibration amplitude is the smallest. This provides a very important theoretical reference for structural design and vibration reduction optimization of the cutterhead system.

Reduction of structural vibrations with the piezoelectric stacks ring

It is known that piezoelectric material shunted with external circuits can convert mechanical energy to electrical energy, which is so called piezoelectric shunt damping technology. In this paper, a piezoelectric stacks ring (PSR) is designed for vibration control of beams and rotor systems. A relative simple electromechanical model of an Euler Bernoulli beam supported by two piezoelectric stacks shunted with resonant RL circuits is established. The equation of motion of such simplified system has been derived using Hamilton’s principle. A more realistic FEA model is developed. The numerical analysis is carried out using COMSOL® and the simulation results show a significant reduction of vibration amplitude at the specific natural frequencies. Using finite element method, the influence of circuit parameters on lateral vibration control is discussed. A preliminary experiment of a prototype PSR verifies the PSR’s vibration reduction effect.

Parameters optimization and performance evaluation for the novel inerter-based dynamic vibration absorbers with negative stiffness

In order to enhance the performance of dynamic vibration absorber (DVA), inerter-based DVA and DVA with negative stiffness have received considerable attention in structural vibration reduction. However, the characteristic of DVA which includes inerter and negative stiffness concurrently remains unclear. In this paper, four kinds of novel inerter-based dynamic vibration absorber with negative stiffness (IN-DVAs) are proposed and analytically researched in detail. The closed-form optimal parameters of four kinds of IN-DVAs are obtained based on the classical fixed-points theory. Analysis of the optimal parameters of the IN-DVAs demonstrates that the coupling relationships between inerter and negative stiffness are distinct for various structural forms of the IN-DVAs. The comparison of the performances of IN-DVAs with those of the existing DVAs shows that IN-DVAs have superior performance. Besides, the effective frequency bandwidth is wider than those of the existing DVAs. Moreover, the results also exhibit that RIN (one of the IN-DVAs in this paper) performs the best under harmonic and random excitations.

Neural network control for earthquake structural vibration reduction using MRD

Structural safety of building particularly that are intended for exposure to strong earthquake loads are designed and equipped with high technologies of control to ensure as possible as its protection against this brutal load. One of these technologies used in the protection of structures is the semi-active control using a Magneto Rheological Damper device. But this device need an adequate controller with a robust algorithm of current or tension adjustment to operate which is further discussed in the following of this paper. In this study, a neural network controller is proposed to control the MR damper to eliminate vibrations of 3-story scaled structure exposed to Tōhoku 2011 and Boumerdes 2003 earthquakes. The proposed controller is derived from a linear quadratic controller designed to control an MR damper installed in the first floor of the structure. Equipped with a feedback law the proposed control is coupled to a clipped optimal algorithm to adapt the current tension required to the MR damper adjustment. To evaluate the performance control of the proposed design controller, two numerical simulations of the controlled structure and uncontrolled structure are illustrated and compared.

Vibration mitigation in offshore wind turbines via tuned mass damper

This paper deals with vibration mitigation via tuned mass damper in bottom-fixed, horizontal-axis offshore wind turbines. Focusing on a baseline 5-MW turbine mounted on a monopile, equipped with an omnidirectional tuned mass damper inside the nacelle, the study explores a wide range of potential tuning frequencies, mass and damping ratios, in both operational and parked rotor conditions. It is found that the tuning frequency to attain optimal reduction of structural vibrations shall be changed depending on the wind velocity in operational conditions while, in contrast, is generally equal to the natural frequency of the first support structure modes only in parked conditions. This result, attributable to inherent non-linearity of rotor dynamics, demonstrates that a conventional design of the tuned mass damper based on the natural frequencies of the support structure modes may not be suitable for offshore wind turbines.

Influence of micro-vibration on the image quality of a GEO remote sensor

GF-4 satellite is the first geosynchronous orbit high-resolution optical remote sensing satellite in China. Given that a geosynchronous orbit is 70 times as high as a sun-synchronous orbit, the geosynchronous optical remote sensing satellite has a stringent requirement of micro-vibration, which is almost two orders of magnitude smaller than that a of low-orbit satellite. On the basis of research on the characteristics of on-board disturbance sources, such as the momentum wheel and cryocooler, an integrated model of opto-mechanical and micro-vibration is first developed for geosynchronous visible and infrared integrated satellite in this paper. A micro-vibration suppression method based on structural optimization, vibration reduction, and vibration isolation is proposed, which has been proved to effectively suppress the in-orbit micro-vibration of the geosynchronous high-resolution optical remote sensor and lays the foundation for GF-4 to obtain excellent images.

Influence of Vibration Isolator Failure on Vehicle Operation Performance and Floating Slab Track Structure Vibration Reduction Effectiveness

At present, steel‐spring floating slabs have been widely used in urban rail transit to reduce the influence of ground vibration caused by vehicle operation on the surrounding environment. As a core part of vibration reduction for floating slab track, the steel‐spring vibration isolator may fail in different forms during operation. In order to study the influence of vibration isolator failure on vehicle operation performance and floating slab track structure vibration reduction effectiveness, a rigid‐flexible coupling dynamic model of vehicle‐rail‐floating slab track is established by multibody dynamics and finite element simulation, and the rationality of the model and its parameters is verified by comparing the theoretical calculation results with the measured data. Based on the model, the failure conditions of steel spring are simulated, considering the failure position and number of steel springs. The results show that the failures of steel‐spring vibration isolators have a significant impact on operating safety and stability of vehicle, and the failure at end is more dangerous than that at midspan. In addition, it also changes the local restraint state of floating slab, resulting in the local vibration mode, which reduces the floating slab track structure vibration reduction effectiveness, mainly within 10 Hz. The different numbers of steel‐spring failures will change the natural modal frequency of floating slab to varying degrees, which may cause the resonance of a certain frequency of the vehicle‐track coupling system, leading to other track structure diseases.

Reduced order finite element formulations for vibration reduction using piezoelectric shunt damping

The present work proposes an original reduced order model for prediction of passive reduction of structural vibration by means of shunted piezoelectric patches. The problem consists of an elastic structure with surface-mounted piezoelectric patches. The piezoelectric elements are connected to a resonant shunt circuits in order to damp specific resonant frequencies of the structure. An efficient electromechanical finite element formulation for the dynamic analysis of the problem is first presented. The classical modal superposition techniques using the system eigenvectors with all patches short-circuited or open-circuited are then recalled. An advanced reduced order models using two new modal projection bases able to solve the problem at lower cost are developed: (i) the combined basis formed by both the short-circuited and open-circuited modes, and (ii) the coupled basis formed by the electromechanical modes that take into account the effect of the inductances of the electrical shunt circuits. Various numerical and experimental results are presented in order to validate and illustrate the efficiency of the proposed new finite element reduced order formulations.

Performance Comparison of Controllers for Suppressing the Structural Building Vibration

<span lang="EN-US">This paper presents the modelling and simulation of controllers for controlling the position of two degree of freedom (2 DOF) mass spring damper system. Proportional integral (PI), fuzzy logic controller (FLC) and sliding mode controller (SMC) are design to minimize the vibration of the system that represent as building structure towards earthquake. A structural building is simulate based on real earthquake occur in El Centro on May 1940. The algorithm for building structure, actuator and controller is derived. Matlab/Simulink is used to analyze the performance of controllers towards the vibration building structure. At the end of the study the time response for two story building for uncontrolled and controlled system is present. Besides, the result for limitation voltage for each controller is also analyse to determine the maximum voltage consume for the system. The simulation results show the comparison of the controllers’ performance in suppressing the building vibration. From performance analysis, SMC provides better performance compared to PI and FLC based on structural vibration reduction.</span>

The effectiveness of polymer adhesive in reduction of vibrations of structural members

In this paper, the idea of using polymer adhesive as a damping layer is proposed. An experimental study of two aluminium cantilevered beams has been conducted. One of them presents a plain cantilevered beam, while the second one considers two aluminium beams bonded with a polymer adhesive of different thickness (0,5; 1,2; 1,75; 3,1 and 5 mm). The polymer adhesive considered in the study is a specially designed flexible two-component grout, which has high damping properties. The aim of the study is to determine dynamic parameters, such as natural frequencies and damping ratios of both beams, based on the tests in which analyzed elements have been induced to vibrations by a modal hammer. The behaviour of the beams under different additional weight, installed at the end of elements, has been studied. The results of the study clearly show that the response of the composite aluminium beam with polymer adhesive inside is substantially different then the response of the plain beam. The application of polymer adhesive leads to significant increase in structural damping. Based on the results, the method of using the polymer adhesive can be considered as an effective one in reduction of structural vibrations.

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

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.

Ride comfort enhancement in railway vehicle by the reduction of the car body structural flexural vibration

The paper approaches the issue of reduction in the vertical bending vibrations of the railway vehicle carbody and the ride comfort enhancement at high velocities, starting from the prospect of isolating the vibrations by the best possible selection of the passive suspension damping in the vehicle. To this purpose, the examination falls on the influence of the vertical suspension damping upon the vibrations regime of the vehicle at the bending resonance frequency and upon the ride comfort. The results of the numerical simulations regarding the frequency response of the carbody acceleration and the comfort index will be therefore used. A value of the secondary suspension damping can be thus identified that will provide the best ride comfort performance. Similarly, the ride comfort can be increased by raising the primary suspension damping ratio.

Multiobjective optimization for vibration reduction in composite plate structures using constrained layer damping

This paper presents a multiobjective optimization approach to minimize weight and maximize modal damping in laminated composite panels with Constrained Layer Damping (CLD) treatments. The design variables are the number and position of the CLD patch treatments on the surface of the laminated plate. The Direct MultiSearch (DMS) solver for multiobjective optimization problems is used in this work. DMS is a solver which does not use any derivatives of the objective functions. A previously developed finite element model for sandwich plates with viscoelastic core and anisotropic laminated face layers is adapted to model the plate with the CLD treatments. Applications for L-shaped and T-shaped plates are presented and both trade-off Pareto optimal fronts and the respective treatment configurations are obtained and the results are analyzed and discussed.

Shunt Damping Vibration Control Technology: A Review

Smart materials and structures have attracted a significant amount of attention for their vibration control potential in engineering applications. Compared to the traditional active technique, shunt damping utilizes an external circuit across the terminals of smart structure based transducers to realize vibration control. Transducers can simultaneously serve as an actuator and a sensor. Such unique advantage offers a great potential for designing sensorless devices to be used in structural vibration control and reduction engineering. The present literature combines piezoelectric shunt damping (PSD) and electromagnetic shunt damping (EMSD), establishes a unified governing equation of PSD and EMSD, and reports the unique vibration control performance of these shunts. The schematic of shunt circuits is given and demonstrated, and some common control principles and equations of these shunts are summarized. Finally, challenges and perspective of the shunt damping technology are discussed, and suggestions made based on the knowledge and experience of the authors.

Vibroacoustics behavior of self-similarly loaded sandwich structures

The reduction of structural vibrations and acoustic radiation is increasingly challenging due to lightweight material use driven by mass reduction, particularly in the aerospace industry. Trim panels are well-known materials with high acoustic transmission and radiation. This study combines semi-analytical modeling, numerical simulations and experiments on the vibroacoustic behavior of sandwich constructions locally overloaded by a pre-fractal mass distribution. The research originality lies in the overload distribution (a self-similar pattern inspired by the Cantor set) which is directly slotted within the honeycomb core, so that the structure load-bearing capability is not altered. As the mass effect spatially localizes the vibrations, the pre-fractal pattern focuses the effect of localization on some specific frequency band gaps, which reduces the total vibrational energy and thus the acoustic radiation. Before the extension to composite plates, simulations of a homogenized beam model have been computed to form a numerical modal database. Experiments have been conducted to compare and tune the mechanical model parameters. Satisfying agreement has been obtained between simulations and experiments. Finally, acoustic radiation simulations of self-similarly loaded structures have been conducted and radiation coefficients are expected to be weaker than for classical bending beams.