Semiactive control devices have received significant attention in recent years because they offer the adaptability of active control devices without requiring the associated large power sources. Magnetorheological (MR) dampers are semiactive control devices that use MR fluids to produce controllable dampers. They potentially offer highly reliable operation and can be viewed as fail-safe in that they become passive dampers should the control hardware malfunction. To develop control algorithms that take full advantage of the unique features of the MR damper, models must be developed that can adequately characterize the damper's intrinsic nonlinear behavior. Following a review of several idealized mechanical models for controllable fluid dampers, a new model is proposed that can effectively portray the behavior of a typical MR damper. Comparison with experimental results for a prototype damper indicates that the model is accurate over a wide range of operating conditions and is adequate for control design an...

Phenomenological model for magnetorheological dampers

Semi-active control devices have received significant attention in recent years because they offer the adaptability of active control devices without requiring the associated large power sources. Magnetorheological (MR) dampers are semi-active control devices that use MR fluids to produce controllable dampers. They potentially offer highly reliable operation and can be viewed as fail-safe in that they become passive dampers should the control hardware malfunction. To develop control algorithms that take maximum advantage of the unique features of the MR damper, models must be developed that can adequately characterize the damper’s intrinsic nonlinear behavior. Following a review of several idealized mechanical models for controllable fluid dampers, a new model is proposed that can effectively portray the behavior of a typical magnetorheological damper. Comparison with experimental results for a prototype damper indicates that the model is accurate over a wide range of operating conditions and is adequate for control design and analysis.

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Phenomenological Model of a Magnetorheological Damper

Magnetorheological (MR) fluids consist of stable suspensions of magnetic particles in a carrying fluid. Magnetorheological effect is one of the direct influences on the mechanical properties of a f...

Magnetorheological Fluids: Materials, Characterization, and Devices:

Magnetorheological suspensions are complex fluids which show a transition from a liquid behavior to a solid one upon application of a magnetic field. This transition is due to the the attractive dipolar forces between the particles which have been magnetized by the applied field. The formation of a network of particles or aggregates throughout the suspension is the basic phenomena which is responsible for the strength of the solid phase. In this paper we shall give an overview on the fluids and their properties and we shall especially emphasize the interplay between magnetic forces which are responsible for the gelling of the suspension and on the other hand of hydrodynamic and thermal forces which contribute to break this gel and allow the suspension to flow. The combination of these three forces gives rise to a very rich rheology whose many aspects are still not understood.

Magnetorheology: Fluids, Structures and Rheology

In the absence of an applied magnetic field, magnetorheological (MR) fluids typically behave as nearly ideal Newtonian liquids. The application of a magnetic field induces magnetic dipole and multipole moments on each particle. The anisotropic magnetic forces between pairs of particles promote the head-to-tail alignment of the moments and draws the particles into proximity. These attractive interparticle forces lead to the formation of chains, columns, or more complicated networks of particles aligned with the direction of the magnetic field. When these structures are deformed mechanically, magnetic restoring forces tend to oppose the deformation. Substantial field-dependent enhancements of the rheological properties of these materials result, as demonstrated in Figure 1.The myriad potential applications of MR and electrorheological (ER) fluids provide considerable motivation for research on these materials. The availability of fluids with yield stresses or apparent viscosities that are controllable over many orders of magnitude by applied fields enables the construction of electromechanical devices that are engaged and controlled by electrical signals and that require few or no moving parts. Potential automotive applications include electrically engaged clutches for vehicle powertrains and engine accessories as well as semiactive shock absorbers that can adapt in real time to changing road conditions. Semiactive dampers for rotorcraft control surfaces are among the potential aerospace applications. The critical need to mitigate the structural vibrations of large structures has led to the construction of large, high-force MR-fluid-based dampers. A promising application in manufacturing processes is the computer-aided polishing of precision optics in which abrasive particles are suspended in an MR fluid so that the polishing rate is determined in part by the strength of an applied magnetic field.

Behavior of Magnetorheological Fluids

Structure, physical properties and dynamics of magnetorheological suspensions

Physical properties of magnetizable structure-reversible media

The mechanism of heat transfer in magnetorheological systems

Heat transfer in narrow gaps filled with magnetorheological suspensions

This paper discusses micromechanics and structure of magnetorheological suspensions. Experimental investigation gives grounds for using the statistical theory of the flow of dilute suspensions of magnetic ellipsoidal particles in an external magnetic field. The basic principles of theory are described. It is observed in the experiments that the effective viscosity of such suspensions is high in comparison with that of the supporting medium; this is due to the dissipation of energy when the liquid flows past the solid phase. On the whole, the authors feel that the agreement of all the experimental and calculated data should be considered satisfactory.

S.A. Demchuk

Papers

Structure, physical properties and dynamics of magnetorheological suspensions

Physical properties of magnetizable structure-reversible media

The mechanism of heat transfer in magnetorheological systems

Heat transfer in narrow gaps filled with magnetorheological suspensions

Dynamic and physical properties of ferrosuspensions with a structure rearranged by an external magnetic field