Elastomeric Damper Research Articles

Momentum transfer on impact damping by liquid crystalline elastomers

The effect of elastomeric damping pads, softening the collision of hard objects, is investigated comparing the reference silicone elastomer and the polydomain nematic liquid crystalline elastomer, which has a far superior internal dissipation mechanism. We specifically focus not just on the energy dissipation, but also on the momentum conservation and transfer during the collision, because the latter determines the force exerted on the target and/or the impactor—and it is the force that does the damage during the short time of an impact, while the energy might be dissipated on a much longer time scale. To better assess the momentum transfer, we compare the collision with a very heavy object and the collision with a comparable mass, when some of the impact momentum is retained in the target receding away from the collision. We also propose a method to estimate the optimal thickness of an elastomer damping pad for minimising the energy in impactor rebound. It has been found that thicker pads introduce a large elastic rebound and the optimal thickness is therefore the thinnest possible pad that does not suffer from mechanical failure. We find good agreement between our estimate of the minimal thickness of the elastomer before the puncture through occurs and the experimental observations.

Bio-based polyurethane/hindered phenol AO-80 composites for room temperature high damping properties

Elastomeric damping materials are essential in modern life. Apart from natural rubber, conventional elastomers are mostly based on petroleum-based sources. Moreover, elastomers exhibit excellent damping properties in the glass transition region, the glass transition temperature (Tg) of elastomers is lower than room temperature, resulting in poor damping properties at room temperature. However, because of limited and unsustainable petrochemical resources and environmental pollution, sustainable development and green environmental protection have become important principles in the design of damping materials, and most damping materials are used at room temperature. Therefore, designing bio-based materials with high damping properties at room temperature to replace conventional cross-linked rubber materials is crucial. Herein, we prepared bio-based millable polyurethane (bio-MPU)/hindered phenol 3,9-bis-{1,1-dimethyl-2[β-(3-tert-butyl-4-hydroxy-5-methylphenyl-)propionyloxy]ethyl}-2,4,8,10-tetraoxaspiro (Wang et al., 2016; Wang et al., 2016) [5,5]-undecane (AO-80) composites to overcome the challenge of sustainable development and high damping properties at room temperature. Bio-MPU samples with high Tg were synthesized from bio-based modified polylactic acid-based polyols, 4, 4′-diphenylmethane diisocyanate, and unsaturated chain extender 3-allyloxy-1, 2-propanediol. AO-80 was mixed with bio-MPU to further increase the Tgand enhance the damping properties of the bio-MPU/AO-80 composites. The properties of the bio-MPUs and bio-MPU/AO-80 composites were systematically evaluated. This study proposes a strategy to design high damping properties from bio-based raw materials and reduce our dependence on fossil resources.

ИССЛЕДОВАНИЕ КОЛЕБАНИЙ ПАССАЖИРСКОГО ВАГОНА, ОБОРУДОВАННОГО ЭЛАСТОМЕРНЫМИ ДЕМПФЕРАМИ

The study objective is to develop and analyze mathematical models of vibrations of a passenger car with elastomeric dampers. The problem to which the paper is devoted is to improve the dynamic characteristics of the undercarriage of passenger cars and increase passenger comfort. The research methods used in this study are typical for solving the problems of rolling stock dynamics. The car is approximated by a system of concentrated masses connected by elastic and dissipative bonds. The external impact is track irregularities of different types. Differential equations of motion are combined using D'Alembert's principle. The set of equations is integrated by numerical method. The novelty of the work is, firstly, in the use of an elastomeric vibration dampener on the bogie of a passenger car, secondly, in the analysis of the dynamic qualities of this car when moving over the irregularities of the main types, and thirdly, in the choice of rational parameters of elastomeric dampers. The results of the study are graphs, nomograms and tables of the dependencies of maximum force values on various parameters, as well as an assessment of the movement smoothness. The conclusions of the work contain an assessment of the dependence of dynamic parameters on speed, recommendations on the characteristics of elastomeric dampers, the validity of using elastomeric dampers.

Determining Dynamic Properties of Elastomer-Dampers by Means of Impact Testing

BackgroundDamping elements made of elastomer materials are used in almost every mechanical system to prevent damage to components caused by impact-like excitations and the resulting high-frequency, large-amplitude oscillations. The dynamics of these operating conditions exceed the performance limits of conventional experimental testing methods, impeding validated predictions of the damper’s transmission behaviour.ObjectiveA method is proposed to directly investigate the influence of impacts on the transmission behaviour of elastomeric dampers by impact testing.MethodsTorsional-loaded elastomer dampers were experimentally investigated using a drop tower. During the experiment, a mass is brought into impact contact with a lever arm connected to the tested coupling. Measurements on resulting torsional oscillations and a comparison of the measurement results with a simple analytical model of the system allow for determining the coupling parameters stiffness and damping ratio.ResultsThe characteristic parameters stiffness and damping ratio of the elastomer damper were mapped as a function of excitation-amplitude and frequency. A comparison of drop-tower test results with servo-hydraulic measurements validated the determined parameters.ConclusionsDetermining the transmission behaviour of elastomeric dampers from highly dynamic and impact-induced oscillation states proved to be a good approach to supplement established testing methods.

On the explicit dynamics implementation and validation of partitioned rate-type constitutive relation for dampers

We propose a simple 3D nonlinear rate-type constitutive relation with just three parameters for elastomeric dampers capable of emulating double-shear data in frequency and strain sweep mode. The nonlinear relation derived using two scalar functions, namely Helmholtz free energy and the rate of dissipation function [1], result in a partitioned constitutive relation: Cauchy stress tensor is described in terms of the left Cauchy-Green stretch tensor and a tensor describing instantaneous elastic response, and the evolution equation for the instantaneous elastic response is derived by maximizing the rate of dissipation function. A compressible version of this model is implemented in Abaqus® The constitutive relation and the implementation are validated by comparing with known semi-inverse solutions obtained by specializing rate-type relation to special deformations. Material parameters are obtained for dampers made of synthetic and natural rubber by fitting the predictions of the model with that of double shear data. By using the same parameters, three dimensional simulations of a cylindrical damper subjected to sinusoidal force akin to that of an unbalanced machinery predict different hysteresis curves in compression/tension and shear. To that end, we show that the non-linear 3 parameter model is one of the simple models that can be formulated within the thermodynamic framework which can predict the inherent non-linearity of the damper operating under combined harmonic loading situations. A robust implementation (VUMAT) of the developed model is included with the article. We believe that this can aid engineers in tailoring dampers for its controlled dissipation across multiple modes of deformation as well as academicians in adding more value by building and implementing sophisticated models within this framework.

Silica Nanoparticle Reinforced Composites as Transparent Elastomeric Damping Materials

Inspired by the structure of the cornea, which is the transparent front part of the eye, we developed a transparent and tough silica composite elastomer consisting of poly[di(ethylene glycol)methyl ether methacrylate] (PMEO2MA) and 110 nm spherical silica particles without using an organic cross-linking agent. While filler composite elastomers, such as reinforced rubbers, have complex compositions containing multiple additives (dispersants, plasticizers, vulcanizing agents, etc.), the composition of our composite elastomer is very simple. With an increased amount of silica particles, the fracture energy of the composite elastomer (20.2 MJ m–3) was improved by 25 times compared to that of unfilled PMEO2MA (0.8 MJ m–3). Nanoscale mapping using atomic force microscopy elucidated the presence of an interface layer (IL) of approximately 15 nm thickness with a high elastic modulus near the silica particles in the composite elastomer. The fracture energy of the composite elastomer was found to be a maximum when the particle surface distance was approximately 30 nm. This particle surface distance meant that the ILs were just in contact with each other. The surface charge density and Hansen solubility parameter of the silica particles indicated the ionization of silanol groups and interactions caused by hydrogen bonding between polymer chains and the silica surface. The array of silica particles embedded with intervals of a few nanometers was expected to be able to effectively dissipate deformation energy as heat due to shear strain and friction between the particle surface and polymer matrices. Measurements of the vibration-damping properties revealed that the loss factor of the composite elastomer was significantly higher than that of the unfilled elastomer, indicating that the composite elastomer in this study could be applied as an interlayer film for laminated glass in automotive and architectural applications.

Erratum for “Modified Generalized Maxwell Model for Hysteresis Behavior of Elastomeric Dampers” by Christos A. Basagiannis and Martin S. Williams

Erratum for “Modified Generalized Maxwell Model for Hysteresis Behavior of Elastomeric Dampers” by Christos A. Basagiannis and Martin S. Williams

Modified Generalized Maxwell Model for Hysteresis Behavior of Elastomeric Dampers

AbstractA constitutive model is presented for the hysteretic behavior of elastomeric material, called the modified generalized Maxwell model (MGMM). A new force-displacement relationship that descr...

Loss Factor of Elastomeric Dampers for Rotating Machinery Application

Elastomeric dampers have potential application in rotating machinery vibration control. They are however not widely used due to lack of reliable data on their loss factor. Most available data on these dampers are obtained from testing undertaken during stationary condition of the shaft. When the shaft rotates, the dampers are subjected to rotating load that may affect their loss factor. The effect of shaft rotation on the loss factor is experimentally examined in this work. Impact test was used to determine the frequency response function (FRF) of the dampers. For the dampers subjected to rotating load, the loss factor values derived from the FRF was found to be in good agreement with those determined from the half-power bandwidth method. The results further showed that the loss factor at resonant frequency determined from testing of the dampers under stationary shaft condition underestimates the values of the loss factor when the shaft is rotating. The effect of shaft rotation on the values of the damper’s loss factor was more noticeable for the response in the X-direction as opposed to the Y-direction, indicating that pre-strain plays a more dominant role in influencing the loss factor of the dampers compared to the dynamic amplitude.

A model of helicopter elastomeric damper for time varying amplitude analysis

A model of helicopter elastomeric damper for time varying amplitude analysis

Enhancing Broadband Vibration Energy Suppression Using Local Buckling Modes in Constrained Metamaterials

Studies on dissipative metamaterials have uncovered means to suppress vibration and wave energy via resonant and bandgap phenomena through such engineered media, while global post-buckling of the infinitely periodic architectures is shown to tailor the attenuation properties and potentially magnify the effective damping effects. Yet, despite the promise suggested, the practical aspects of deploying metamaterials necessitates a focus on finite, periodic architectures, and the potential to therefore only trigger local buckling features when subjected to constraints. In addition, it is likely that metamaterials may be employed as devices within existing engineering systems, so as to motivate investigation on the usefulness of metamaterials when embedded within excited distributed or multidimensional structures. To illuminate these issues, this research undertakes complementary computational and experimental efforts. An elastomeric metamaterial, ideal for embedding into a practical engineering structure for vibration control, is introduced and studied for its relative change in broadband damping ability as constraint characteristics are modified. It is found that triggering a greater number of local buckling phenomena provides a valuable balance between stiffness reduction, corresponding to effective damping magnification, and demand for dynamic mass that may otherwise be diminished in globally post-buckled metamaterials. The concept of weakly constrained metamaterials is also shown to be uniformly more effective at broadband vibration suppression of the structure than solid elastomeric dampers of the same dimensions.

An improved PSO algorithm for parameter identification of nonlinear dynamic hysteretic models

The nonlinear dynamic hysteretic models used in nonlinear dynamic analysis contain generally lots of model parameters which need to be identified accurately and effectively. The accuracy and effectiveness of identification depend generally on the complexity of model, number of model parameters and proximity of initial values of the parameters. The particle swarm optimization (PSO) algorithm has the random searching ability and has been widely applied to the parameter identification in the nonlinear dynamic hysteretic models. However, the PSO algorithm may get trapped in the local optimum and appear the premature convergence not to obtain the real optimum results. In this paper, an improved PSO algorithm for identifying parameters of nonlinear dynamic hysteretic models has been presented by defining a fitness function for hysteretic model. The improved PSO algorithm can enhance the global searching ability and avoid to appear the premature convergence of the conventional PSO algorithm, and has been applied to identify the parameters of two nonlinear dynamic hysteretic models which are the Leishman-Beddoes (LB) dynamic stall model of rotor blade and the anelastic displacement fields (ADF) model of elastomeric damper which can be used as the lead-lag damper in rotor. The accuracy and effectiveness of the improved PSO algorithm for identifying parameters of the LB model and the ADF model are validated by comparing the identified results with test results. The investigations have indicated that in order to reduce the influence of randomness caused by using the PSO algorithm on the accuracy of identified parameters, it is an effective method to increase the number of repeated identifications.

Self-Powered Eddy Current Damper for Rotordynamic Applications

The vibration control of rotors is often performed using elastomeric or fluid dampers together with rolling element or hydrodynamic type bearings. Electromagnetic dampers seem a valid alternative to conventional solutions and also to active magnetic bearings (AMBs) because their simpler architecture, size and, if of transformer type, also for the absence of power electronics, position sensors, and any fast feedback loop. However, transformer eddy current dampers require a constant voltage power supply than can be provided by an embedded generator to reduce cost and improve the reliability. The present paper proposes a self-powered damper to fulfill these requirements. A three-phase permanent magnet electric generator (connected to the rotating shaft) generates the required power for the damping device. The generator is connected to the damping circuit by means of tuned impedance and a three-phase rectifier.

Implementation and application of the unconditionally stable explicit parametrically dissipative KR‐α method for real‐time hybrid simulation

SummaryIn real‐time hybrid simulations (RTHS) that utilize explicit integration algorithms, the inherent damping in the analytical substructure is generally defined using mass and initial stiffness proportional damping. This type of damping model is known to produce inaccurate results when the structure undergoes significant inelastic deformations. To alleviate the problem, a form of a nonproportional damping model often used in numerical simulations involving implicit integration algorithms can be considered. This type of damping model, however, when used with explicit integration algorithms can require a small time step to achieve the desired accuracy in an RTHS involving a structure with a large number of degrees of freedom. Restrictions on the minimum time step exist in an RTHS that are associated with the computational demand. Integrating the equations of motion for an RTHS with too large of a time step can result in spurious high‐frequency oscillations in the member forces for elements of the structural model that undergo inelastic deformations. The problem is circumvented by introducing the parametrically controllable numerical energy dissipation available in the recently developed unconditionally stable explicit KR‐α method. This paper reviews the formulation of the KR‐α method and presents an efficient implementation for RTHS. Using the method, RTHS of a three‐story 0.6‐scale prototype steel building with nonlinear elastomeric dampers are conducted with a ground motion scaled to the design basis and maximum considered earthquake hazard levels. The results show that controllable numerical energy dissipation can significantly eliminate spurious participation of higher modes and produce exceptional RTHS results. Copyright © 2014 John Wiley & Sons, Ltd.

Application of the Hardware-in-the-Loop Technique to an Elastomeric Torsional Vibration Damper

Application of the Hardware-in-the-Loop Technique to an Elastomeric Torsional Vibration Damper

Design of a Super Multispan Continuous Girder Bridge Using Enhanced Seismic Response Modification Technologies

This paper reports the state-of-theart seismic design concept utilizing an extensive combined application of seismic response modification devices, including elastomeric bearings, seismic dampers, and low-friction slide bearings with a particular layout for the super multispan continuous girder bridges, used in the Imagiregawa Bridge project in Japan. The baseline of the design concept is the reduction of the resilient force introduced by the bearing system, while a high level of structural damping is introduced with the use of high-capacity seismic dampers to utilize the seismic force reduction effect of the seismic isolation concept. There are other great advantages in the present design concept for long super multispan continuous girder bridges: statically indeterminate forces that act on multispan continuous girders supported by elastomeric bearings induced by temperature changes, desiccation shrinkage, and creep can be reduced so that any unfavorable effects to the seismic response are reduced. It also eliminates the necessity for adjustment of elastomeric bearing installation with the “post slide” procedure during construction. Since the elastomeric bearings and seismic dampers are installed on a limited number of piers, 22% reduction of the projected construction cost of the substructures is achieved as compared with conventional seismic isolation design.

Impact of the fuselage damping characteristics and the blade rigidity on the stability of helicopter

The aim of this work is to compare in the system of blade articulations, the hydraulic and elastomeric dampers in order to reduce the vibration level in the helicopter rotors. Based on an aerodynamic model, a three-dimensional model of the composite material blade was developed. Numerical calculations on the model developed taking into account the aeroelastic interaction prove that the elastomeric damper of viscoelastic type produces better results compared to other hydraulic damper. The study of the blade stability depending on the orientation of the composite fibers is an important factor to determine the rigidity of the structure.

Frequency and Amplitude Dependent Dynamic Model of Rotor Elastomeric Damper with Refined Nonlinear Stiffness

Elastomeric damper is a very important component for helicopter rotor system; its dynamic property has strong nonlinear behavior characterized by complex hysteresis loops, and dependence on excitation frequency, amplitude and temperature. Based on internal variables theory, combined with the nonlinear spring model, a time domain nonlinear dynamic model of elastomeric damper used for helicopter rotor load prediction is presented. The model was characterized by using the genetic algorithm, the hysteresis loop of elastomeric dampers made of different elastomeric materials under several excitation frequencies and strain amplitudes was calculated with this model and compared with experimental data. It is shown that the presented model can predict the hysteresis loop of the elastomeric dampers with little relative errors, and the model is able to catch the variation of dynamic stiffness. Therefore, the presented method can be used for helicopter rotor load prediction and aeroelastic analysis.

Control Evaluations of Semiactive Fluid-ElastomericHelicopter Lag Damper

A semiactive magnetorheological fluid―elastomeric device has been assembled and evaluated in control experiments to demonstrate its utility to compensate for measured changes as a helicopter lag damper. The baseline used in this study was lag damper (snubber) for a hingeless helicopter rotor that employs both elastomers and fluids: that is, a fluid―elastomeric damper. This damper was disassembled and modified to include two internal magnetorheological control valves, and the existing hydraulic fluid was replaced with magnetorheological fluid. Hence, the resulting prototype damper is a retrofit design that can easily be installed in a test rotor in future evaluations. The magnetorheological fluid―elastomeric damper was subject to extensive performance characterization at displacement amplitudes ranging from 0.8 to 3.4 mm, temperatures ranging from 20 to 55°C, and control currents up to 2.0 A. Using this database and a hydromechanical model of the damper, control systems were designed to track a reference damping profile, which is a function of amplitude only, in the presence of measured amplitude and temperature variations at the rotor lag frequency (3.8 Hz). Both open-loop (interpolating lookup table) and closed-loop (proportional-integral and gain scheduling) techniques were employed in simulations and experiments. The results demonstrated that all of the control schemes were effective, although a minimum tracking error was achieved with the closed-loop systems. Comparing the two closed-loop systems, the gain-scheduling controller provided a faster response overall, but the improvement was marginal.

Analytical expressions for preliminary design of dissipative bracing systems in steel frames

In this paper a direct displacement-based design (DDBD) method for seismic design of steel frames equipped with dissipative braces is proposed. Attention is focused on concentric braced steel frames with pinned beam-to-column joints in which the bracing system (with viscoelastic or elastoplastic dissipative devices) is the main seismic resistant component. The proposed design method uses an equivalent continuous model where flexural deformability and shear deformability are related respectively to columns and diagonals of the bracing system. In this way, analytical expressions of the required flexural and shear stiffness distributions are obtained. These expressions are quite simple and can be conveniently used in preliminary design of dissipative diagonal braces and columns. Examples are shown for steel frames with dissipative braces based on elastomeric dampers (viscoelastic devices) and steel frames with buckling-restrained braces (elastoplastic devices). Results of time history analyses are illustrated and discussed in order to evaluate the effectiveness of the proposed DDBD procedure.