A review of nonlinear oscillatory shear tests: Analysis and application of large amplitude oscillatory shear (LAOS)

Magnetorheological (MR) materials are a kind of smart materials whose mechanical properties can be altered in a controlled fashion by an external magnetic field. They traditionally include fluids, elastomers and foams. In this review paper we revisit the most outstanding advances on the rheological performance of MR fluids. Special emphasis is paid to the understanding of their yielding, flow and viscoelastic behaviour under shearing flows.

Magnetorheological fluids: a review

During the last few decades, magnetorheological (MR) elastomers have attracted a significant amount of attention for their enormous potential in engineering applications. Because they are a solid counterpart to MR fluids, MR elastomers exhibit a unique field-dependent material property when exposed to a magnetic field, and they overcome major issues faced in magnetorheological fluids, e.g. the deposition of iron particles, sealing problems and environmental contamination. Such advantages offer great potential for designing intelligent devices to be used in various engineering fields, especially in fields that involve vibration reduction and isolation. This paper presents a state of the art review on the recent progress of MR elastomer technology, with special emphasis on the research and development of MR elastomer devices and their applications. To keep the integrity of the knowledge, this review includes a brief introduction of MR elastomer materials and follows with a discussion of critical issues involved in designing magnetorheological elastomer devices, i.e. operation modes, coil placements and principle fundamentals. A comprehensive review has been presented on the research and development of MR elastomer devices, including vibration absorbers, vibration isolators, base isolators, sensing devices, and so on. A summary of the research on the modeling mechanical behavior for both the material and the devices is presented. Finally, the challenges and the potential facing magnetorheological elastomer technology are discussed, and suggestions have been made based on the authors’ knowledge and experience.

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A state-of-the-art review on magnetorheological elastomer devices

https://ro.uow.edu.au/cgi/viewcontent.cgi?article=3667&context=eispapers

MR damper and its application for semi-active control of vehicle suspension system

Due to the inherent nonlinear nature of magnetorheological (MR) dampers, one of the challenging aspects for developing and utilizing these devices to achieve high performance is the development of models that can accurately describe their unique characteristics. In this review, the characteristics of MR dampers are summarized according to the measured responses under different conditions. On these bases, the considerations and methods of the parametric dynamic modelling for MR dampers are given and the state-of-the-art parametric dynamic modelling, identification and validation techniques for MR dampers are reviewed. In the past two decades, the models for MR dampers have been focused on how to improve the modelling accuracy. Although the force–displacement behaviour is well represented by most of the proposed dynamic models for MR dampers, no simple parametric models with high accuracy for MR dampers can be found. In addition, the parametric dynamic models for MR dampers with on-line updating ability and the inverse parametric models for MR dampers are scarcely explored. Moreover, whether one dynamic model for MR dampers can portray the force–displacement and force–velocity behaviour is not only determined by the dynamic model itself but also determined by the identification method.

https://iopscience.iop.org/article/10.1088/0964-1726/20/2/023001/pdf

Magnetorheological fluid dampers: a review of parametric modelling

A linear magnetorheological (MR) damper, supplied by Lord Corporation, was tested and modeled. Under dynamic conditions, the effects of displacement amplitude, frequency, and magnetic fields on the mechanical properties of MR damper, such as damping force, equivalent-damping capability, were experimentally studied with an INSTRON test machine. A viscoelastic-plastic model is proposed to model the MR behavior. It is shown that the damper response can be satisfactorily predicted with this model.

https://iopscience.iop.org/article/10.1088/0964-1726/9/1/310/pdf

Testing and steady state modeling of a linear MR damper under sinusoidal loading

Mechanical properties of magnetorheological (MR) fluids are classified into pre-yield and post-yield regions according to whether the shear stress is below or above the yield stress. MR fluids within the pre-yield region exhibit viscoelastic properties; and these properties are important for understanding MR suspensions, especially for vibration damping applications. MR suspensions composed of reduced iron powders dispersed in silicone oil are utilized to study the viscoelastic properties with the help of a strain-controlled rheometer with plate-plate configuration. Two types of experiments, i.e. strain-amplitude sweep mode and frequency-sweep mode, were carried out to investigate the viscoelastic properties of MR fluids: (a) strain-amplitude sweep mode, the strain amplitude was swept from 0.0001 to 0.001 at a fixed driving frequency of 10 Hz. (b) Frequency-sweep mode, the driving frequency was swept from 1 Hz to 100 Hz at a constant strain amplitude of 0.001. The results show that both storage modulus G´ and loss modulus G´´ decrease with the increment of the strain amplitude, however, the loss factor increases with the increment of the strain amplitude. On the other hand, both the storage modulus and loss modulus increase with the increment of frequency, which is different from the loss factor. Moreover, the effects of magnetic field and volume fraction on the viscoelastic properties are also investigated. The higher the magnetic field, the higher the storage modulus and loss modulus, and the lower the loss factor. The higher the volume fraction, the higher the storage modulus and the loss factor.

https://iopscience.iop.org/article/10.1088/0964-1726/8/4/303/pdf

Viscoelastic properties of MR fluids

Nonlinear viscoelastic properties of the MR fluid, MRF-132LD, under large-amplitude oscillatory shear were investigated. This was accomplished by carrying out the experiments under the amplitude sweep mode and the frequency sweep mode, using a rheometer with parallel-plate geometry. Investigations under the influence of various magnetic field strength and temperatures were also conducted. MR fluids behave as nonlinear viscoelastic or viscoplastic materials when they are subjected to large-amplitude shear, where the storage modulus decreases rapidly with increasing strain amplitude. Hence, MR fluid behaviour ranges from predominantly elastic at small strain amplitudes to viscous at high strain amplitudes. Large-amplitude oscillatory shear measurements with frequency sweep mode reveal that the storage modulus is independent of oscillation frequency and approaches plateau values at low frequencies. With increasing frequency, the storage modulus shows a decreasing trend before increasing again. This trend may be explained by micro-structural variation. In addition, the storage modulus increases gradually with increasing field strength but it shows a slightly decreasing trend with temperature.

Nonlinear viscoelastic properties of MR fluids under large-amplitude-oscillatory-shear

Creep and recovery behaviors of a magnetorheological (MR) fluid under constant stress shear were investigated. This experiment was accomplished by using a rheometer with parallel-plate geometry. The applied constant stress ranges from a small value to a big one which approaches to the yield stress. The effects of magnetic field strength and the temperature on the creep behavior were addressed. The experimental results indicate that MR fluids behave as linear viscoelastic bodies at small stresses; with increasing constant stresses, nonlinear viscoelastic, viscoplastic, or purely plastic properties will dominate. Hence, MR fluid behavior ranges from predominantly elastic at small stresses to plastic at high stresses. Moreover, the creep and recovery behaviors are explained by a typically thick column structure.

Experimental investigation of creep and recovery behaviors of magnetorheological fluids

In this work, the yield stress of ferrofluid-based magnetorheological fluids (F-MRF) was investigated. The fluids are composed of a ferrofluid as the liquid carrier and micro-sized iron particles as magnetic particles. The physical and magnetorheological properties of the F-MRF have been investigated and compared with a commercial mineral oil-based MR fluid. With the addition of a ferrofluid, the anti-sedimentation property of the commercial MR fluids could be significantly improved. The static yield stress of the F-MRF samples with four different weight fractions (ϕ) of micro-sized iron particles were measured using three different testing modes under various magnetic fields. The effects of weight fraction, magnetic strength, and test mode on the yielding stress have been systematically studied. Finally, a scaling relation, $\tau _{\rm ys} = {\rm a}B^{\rm b}$
 , was proposed for the yield stress modeling of the F-MRF system.

G. Chen

Papers

Testing and steady state modeling of a linear MR damper under sinusoidal loading

Viscoelastic properties of MR fluids

Nonlinear viscoelastic properties of MR fluids under large-amplitude-oscillatory-shear

Experimental investigation of creep and recovery behaviors of magnetorheological fluids

Static yield stress of ferrofluid-based magnetorheological fluids