0000000000335930
AUTHOR
Olga S. Volkova
Yield behavior of magnetorheological suspensions
The rheology of suspensions containing magnetic particles of micrometer size is strongly modified by the application of a magnetic field. We first describe a model experiment where the suspension is made of spheres of millimeter size and we show that the experimental dependence of the yield stress is well predicted by a non-affine model where the chains of particles break in the middle. Then we compare these predictions with some experimental results obtained on suspensions of carbonyl iron; it is shown that this model does not apply in this case. We propose a mechanism where after some friction on the walls the aggregates begin to rotate and break at a strain smaller than unity, due to the…
Magnetorheology: Fluids, Structures and Rheology
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 forc…
Flow-induced structures in magnetorheological suspensions
We have measured the yield stress of a magnetic suspension as a function of the external field. To explain the existence of this yield stress, we report a comparison between two models, one based on isolated chains of particles and the other taking into account that the structure is formed by aggregates of particles.