Magnetorheological Elastomer Core Research Articles

Vibration Response Analysis of MRE Cantilever Sandwich Beam under Non-Homogeneous Magnetic Fields

A three layer sandwich beam with an aluminum face sheet and a magnetorheological elastomer (MRE) core was fabricated. The transverse motion equations of MRE cantilever sandwich beam under non-homogeneous magnetic fields were derived with the fine Mead-Markus model, and the first natural frequency of the beam were calculated. Meanwhile, the first natural frequency of the beam was also simulated using ANSYS software. The numerical simulations accorded with theoretical results in general. The results are expected to provide guidance to develop broadband vibration isolation devices for railways and rolling stock.

Micro-vibration suppression of equipment supported on a floor incorporating magneto-rheological elastomer core

In this study, magneto-rheological elastomers (MREs) are adopted to construct a smart sandwich beam for micro-vibration control of equipment. The micro-vibration response of a smart sandwich beam with MRE core which supports mass-concentrated equipment under stochastic support-motion excitations is investigated to evaluate the vibration suppression capability. The dynamic behavior of MREs as a smart viscoelastic material is characterized by a complex modulus dependent on vibration frequency and controllable by external magnetic fields. A frequency-domain solution method for the stochastic micro-vibration response of the smart sandwich beam supporting mass-concentrated equipment is developed based on the Galerkin method and random vibration theory. First, the displacements of the beam are expanded as series of spatial harmonic functions and the Galerkin method is applied to convert the partial differential equations of motion into ordinary differential equations. With these equations, the frequency-response function matrix of the beam–mass system and the expression of the velocity response spectrum are then obtained, with which the root-mean-square (rms) velocity response in terms of the one-third octave frequency band can be calculated. Finally, the optimization problem of the complex modulus of the MRE core is defined by minimizing the velocity response spectrum and the rms velocity response of the sandwich beam, through altering the applied magnetic fields. Numerical results are given to illustrate the influence of MRE parameters on the rms velocity response and the response reduction capacity of the smart sandwich beam. The proposed method is also applicable to response analysis of a sandwich beam with arbitrary core characterized by a complex shear modulus and subject to arbitrary stochastic excitations described by a power spectral density function, and is valid for a wide frequency range.

Vibration Characteristics of Sandwich Beams with Steel Skins and Magnetorheological Elastomer Cores

Magnetorheological elastomer (MRE) cored sandwich beams with steel skins offer potentially advantageous features when used in the context of structural dynamics. Modelling of the dynamic behaviour is undertaken in this investigation by adopting a higher order sandwich beam theory. Frequency responses from the theoretical modelling are compared with experimental results on MRE cored sandwich beams. The experimental responses are generated from a specially designed test rig to study dynamic behaviour, damping effects, localised magnetic field effects and energy dissipation with varying topology. A numerically based parametric study is conducted to find the optimum geometry for skins and core material to enhance damping performance. Under the same magnetic field strength, sandwich beams with thinner skins and thicker MRE core dissapate more vibration energy. Correlation between the experimental results and numerical studies has been found to be reasonably good.

Magneto-rheological elastomer (MRE) based composite structures for micro-vibration control

Magneto-rheological elastomers (MREs) are used to construct composite structures for micro-vibration control of equipment under stochastic support-motion excitations. The dynamic behavior of MREs as a smart viscoelastic material is characterized by a complex modulus dependent on vibration frequency and controllable by external magnetic fields. Frequency-domain solution methods for stochastic micro-vibration response analysis of the MRE-based structural systems are developed to derive the system frequency-response function matrices and the expressions of the velocity response spectrum. With these equations, the root-mean-square (RMS) velocity responses in terms of the one-third octave frequency band spectrum can be calculated. Further, the optimization problem of the complex moduli of the MRE cores is defined by minimizing the velocity response spectra and the RMS velocity responses through altering the applied magnetic fields. Simulation results illustrate the influences of MRE parameters on the RMS velocity responses and the high response reduction capacities of the MRE-based structures. In addition, the developed frequency-domain analysis methods are applicable to sandwich beam structures with arbitrary cores characterized by complex shear moduli under stochastic excitations described by power spectral density functions, and are valid for a wide frequency range.

Micro-vibration response of a stochastically excited sandwich beam with a magnetorheologicalelastomer core and mass

Magnetorheological (MR) elastomers are used to construct a smart sandwich beam formicro-vibration control. The micro-vibration response of a clamped–free sandwich beamwith an MR elastomer core and a supplemental mass under stochastic supportmicro-motion excitation is studied. The dynamic behavior of MR elastomer as a smartviscoelastic material is described by a complex modulus which is controllable by externalmagnetic field. The sixth-order partial differential equation of motion of the sandwich beamis derived from the dynamic equilibrium, constitutive and geometric relations. Afrequency-domain solution method for the stochastic micro-vibration responseof the sandwich beam is developed by using the frequency-response function,power spectral density function and spatial eigensolution. The root-mean-squarevelocity response in terms of the one-third octave frequency band is calculated, andthen the response reduction capacity through optimizing the complex modulusof the core is analyzed. Numerical results illustrate the influences of the MRelastomer core parameters on the root-mean-square velocity response and the highresponse reduction capacity of the sandwich beam. The developed analysis method isapplicable to sandwich beams with arbitrary cores described by complex shearmoduli under arbitrary stochastic excitations described by power spectral densityfunctions.

Finite element studies on field-dependent rigidities of sandwich beams with magnetorheologicalelastomer cores

Sandwich beams with magnetorheological elastomer (MRE) cores exhibit field-dependentdynamic rigidities due to the field-dependent shear modulus of the MRE cores. Suchstructures have great potential as regards developing stiffness-controllable devices whichrespond to control signals within milliseconds. The purpose of this paper is to investigatethe effect of structural parameters on the field-dependent rigidities of single-layersandwich beams with MRE cores through finite element analysis. Furthermore, amultilayer sandwich configuration is introduced to provide structures with higher bulkfield-dependent rigidities. The structural design rules for multilayer sandwich beams forachieving the desired zero-field rigidities and desired relative change ranges of thefield-dependent rigidities are presented. The results will provide basic guidelinesfor designing stiffness-controllable devices utilizing such MRE based sandwichstructures.

Study on the adjustable rigidity of magnetorheological-elastomer-based sandwichbeams

Due to the field-dependent shear modulus of magnetorheological elastomer (MRE), thebulk dynamic flexural rigidity of sandwich beams with MRE cores can be adjusted byapplied magnetic fields. The maximum relative change of the flexural rigidity adjusted byapplied magnetic fields is referred to as magnetic controllability in this research. This paperwill address the structural design for enhancing the magnetic controllability of MRE-basedsandwich beams. The theoretical approach is based on a high-order theory and anon-dimensional analysis. Numerical simulations are conducted on a simply supportedsandwich beam. This work will benefit the design of MRE-based sandwich beams to yieldthe maximum magnetic controllability index, and will explore the fundamentalunderstanding of the field-adjustable dynamic flexural rigidity of the MRE-based sandwichbeams.

Use of magnetorheological elastomer in an adaptive sandwich beam with conductive skins. Part I: Magnetoelastic loads in conductive skins

In this study, the magnetoelastic loads for a vibrating conductive beam exposed perpendicularly to an applied steady magnetic field are addressed analytically by considering the effect of finite dimensions. The dynamic equation of such vibrating beam is presented and a simply supported conductive beam is simulated. The simulation indicates that the magnetoelastic loads affect the dynamic properties of the vibrating beam significantly only when the thickness of the beam is extremely small. This work is the basis for investigating and analyzing the field-controllable dynamic properties of a sandwich beam composed of conductive thin outer skins and a magnetorheological elastomer core, which will be presented in the second part of this research.