Magneto-rheological Suspensions - Physical Mechanisms and Modeling -

Abstract

A magneto-rheological suspension (MRS) is a particulate suspension which shows a dramatic increase in flow resistance upon application of an external magnetic field. The fundamental physical process is believed to be that the field induces polarization of each particle with respect to the carrier material, and the resulting interparticle forces cause aggregates of particles to form in the field direction. While recent years have witnessed the appearance of several applications using these tunable flow properties, optimal use of MRS technology is still hindered by our incomplete understanding of the underlying mechanisms. This paper surveys recent developments which have improved our understanding of several of the key issues governing the rheological behavior of MRS. In particular, experiments using small strain rheometry and oscillatory shear flow have given insights into the viscoelastic nature of the aggregates before they yield. A recent advance in modeling has been the two fluid continuum approach, which may help the establishment of a more general constitutive framework for MRS.

Magnetorheology of fiber suspensions. I. Experimental

“…Magnetorheological (MR) suspensions are complex fluids that undergo a tunable and reversible transition from a solid-like to a liquid-like state upon magnetic field application [Bossis et al (2002); Ginder (1998); Rankin et al (1998); See (2003)]. This property is the base of many applications of MR suspensions in medicine [Liu et al (2001); Sheng et al (1999); Wilhelm et al (2005)] and engineering [Bica (2002); Carlson et al (1996); Jolly et al (1999); Kordonski and Golini (2002)].…”

Preparation and Characterization of Iron-Based Magnetorheological Fluids Stabilized by Addition of Organoclay Particles

“…This “smart” behavior of MR fluids is the base for many potential applications in engineering – and in biomedicine. – As a consequence, MR fluids have been the focus of many recent theoretical and experimental studies. Useful reviews on MR fluids are given by refs – .…”

“…Useful reviews on MR fluids are given by refs . [9][10][11][12][13][14][15] Unfortunately, the stabilization of MR fluids against aggregation and settling of their constitutive magnetic particles is still an irresolute hindrance for most practical applications. 16 Different approaches have been suggested to overcome these problems: (i) addition of surfactants or polymers that prevent aggregation by means of steric repulsion; [17][18][19][20][21][22][23] (ii) addition of magnetic nanoparticles to improve the dispersion of the MR fluids; [24][25][26][27][28] (iii) addition of thickening agents (e.g., carbons fibers, silica nanoparticles) to prevent particle settling; 29 and (iv) use of ionic liquids as carriers.…”