Yield stress in magnetorheological and electrorheological fluids: A comparison between microscopic and macroscopic structural models

Abstract

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Study on the Saturation Properties of Silicone Oil-Based Magnetorheological Fluids in Mechanical Engineering

“…The function relationship between MRFs yield stress and applied magnetic field intensity by experiment was researched by Felt [9]. MRFs with high permeability magnetic particles were researched by Bossis and the positive relationship between yield stress and MRFs volume fraction was investigated [10]. The phenomenon was found by Lemaire that the yield stress increases with the increase of particle diameter when the particle diameter was quite small and yield stress had nothing to do with particle size when the particle diameter was quite big [11].…”

Magnetorheological properties of ferrofluids containing clustered particles

“…In uniform external magnetic field H, the free energy of the magnetic fluid containing large aggre gates can be represented as [15,16] ( 9) where Here, is the projection of the total magnetic moment of the suspension onto the axis of the mag netic field (z axis), N a is the number of large droplets in the system, and is the projection of the magnetic moment of a large aggregate onto the axis of the mag netic field. The value of can obviously be resolved into components and that are parallel and per pendicular to the ellipsoid axis:…”

“…Stress σ as a function of has maximum at some shear value According to the theory [15], corresponds to the static yield stress of the magnetic fluid. When the external shear stress exceeds the system of aggregates cannot statically compen sate for this stress, so the magnetic suspension starts to flow, which is accompanied by detachment of aggre gates from the channel walls.…”

“…A theory of static mechanical stress generated by a system of ellipsoidal aggregates that block the channel of a measuring unit was developed in [15] (see also [9]). According to this theory, stress σ arising in a mag netic suspension at stationary shear can be written as follows:…”

Synthesis and magnetorheology of suspensions of submicron-sized cobalt particles with tunable particle size

“…Now we have to relate the aspect ratio of the aggregates to the yield stress. Firstly we write that the shear stress is the derivative of the magnetic energy U t versus the strain γ with U t (γ) given by (Bossis et al (1997):…”