Stick–slip instabilities in the shear flow of magnetorheological suspensions

López–López, Modesto T.; Kuzhir, Pavel; Rodríguez‐Arco, Laura; Caballero-Hernández, Jaime; Durán, J.D.G.; Bossis, Georges

doi:10.1122/1.4804358

Cited by 12 publications

(15 citation statements)

References 37 publications

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“…This mechanism was later confirmed by particle level simulations of Klingenberg et al (1991) and Bonnecaze and Brady (1992). More recently, López-López et al (2013) have observed regular saw-tooth-like stress oscillations of a concentrated MR fluid sheared at a low constant shear rate and subjected to an external magnetic field perpendicular to the rheometer plates. These oscillations were accompanied by shear localization in the middle plane of the rheometer gap and occurred at low shear rates belonging to a decreasing part of the steadystate flow curve.…”

Section: Introductionmentioning

confidence: 64%

Instabilities of a pressure-driven flow of magnetorheological fluids

Rodríguez‐Arco

Kuzhir

López–López

et al. 2013

Journal of Rheology

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International audienceIn this work, we studied a pressure-driven flow of a magnetorheological suspension through a cylindrical tube in the presence of a non-uniform magnetic field perpendicular to the tube and varying along its axis. The flow was realized with the help of a commercial capillary rheometer in a controlled-velocity mode. Experimental pressure-flow rate curves exhibited a local minimum, and flow instabilities were observed in the range of flow rates corresponding to the decreasing branch of these curves. The non-monotonic behavior of the flow curves is attributed to the interplay between the hydrodynamic dissipation and the interaction between particle aggregates and walls. Our theoretical model, based on the particle flux conservation, correctly predicts the shape of the pressure-flow rate curves and indicates the speed range within which flow instabilities are expected. These instabilities are manifested by somewhat regular oscillations of the pressure difference and of the outlet flow rate at a constant imposed piston speed. Visualization of particle structures in a transparent tube revealed that the flow oscillations were governed by both the suspension compressibility and the stick-slip of the aggregates on the tube walls. This study is motivated by the problem of particle clogging in magnetorheological smart devices employing non-uniform magnetic fields

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Section: Introductionmentioning

confidence: 64%

Instabilities of a pressure-driven flow of magnetorheological fluids

Rodríguez‐Arco

Kuzhir

López–López

et al. 2013

Journal of Rheology

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“…Above the jamming transition, strong oscillations of the stress are observed if the shear rate is imposed (Lootens et al 2003) or of the shear rate if it is the stress which is imposed. This is also the case in yield stress fluids at low shear rate after yielding (Nagahiro et al 2013) In yield stress fluids different models can predict these oscillations by introducing a "structure variable" whose time evolution is coupled to the shear rate (Nagahiro et al 2013;Lopez-Lopez et al 2013;Head et al 2002). These oscillations are usually interpreted as resulting from an instability related to the negative differential viscosity which appears in the form of an S shape in the stress versus shear rate curve.…”

Section: V-oscillation Regime Above the Critical Stressmentioning

confidence: 99%

Discontinuous shear thickening in the presence of polymers adsorbed on the surface of calcium carbonate particles

Bossis

Boustingorry²,

Grasselli

et al. 2017

Rheol Acta

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International audienceIn the presence of dispersant molecules currently used in cement industry and based on polyethylene oxide (PEO), we found a strong discontinuous shear thickening (DST) at high volume fraction in suspensions of calcium carbonate particles. The transition was reversible and the critical shear rate and shear stress for which this instability appears are reported versus the volume fraction of particles. A model of repulsive forces between polymers, taking into account the thickness of the polymer layer and the density of adsorption on the surface of the particles, can explain the differences of critical stresses observed between these three dispersant molecules. In particular, it explains why a small polymer densely adsorbed can be more efficient to repel the transition at higher stress than a larger molecule less densely adsorbed. Above the transition, we find that the suspension presents a special kind of stick-slip instability with even the presence of a negative shear rate under constant applied stress. A model is proposed which well predicts this regime by taking into account both the inertia of the apparatus and the viscoelasticity of the suspension

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“…As observed, after an initial sharp increase of the shear stress, some saw-tooth-like oscillations appeared at low enough values of the imposed shear rate. In a previous work we studied the origin of these oscillations and showed that from a microscopic viewpoint they were the consequence of the periodic failure and healing of the field-induced particle structures [9]. In more details, we supposed the appearance of a periodic array of gap-spanning cylindrical columns.…”

Section: A Time Evolution Of the Shear Stressmentioning

confidence: 96%

“…For the application of the magnetic field we used solenoids placed co-axially with the measuring geometry, as described in [15]. The experimental protocol used for the rheological measurements is reported in details elsewhere [9]. Briefly, we proceeded as it follows.…”

Section: (I)mentioning

confidence: 99%

“…Very recently, we have found that near the limit of maximum-packing fraction, conventional (based on spherical particles) MR fluids also display a region of negative differential viscosity [9]. It is well documented that a stable flow is impossible within the shear rate range corresponding to the negative differential viscosity [10] and, in fact, we also found that for a given value of the shear rate pertaining to this region, the shear stress oscillated with time, in a way that resembled dry stick-slip motion [9]. In the present work, we focus on the analysis of the complete flow curves of concentrated MR fluids.…”

Section: Introductionmentioning

confidence: 99%

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N-like rheograms of concentrated suspensions of magnetic particles

López–López¹,

Rodríguez‐Arco²,

Zubarev³

et al. 2016

Journal of Rheology

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International audienceWe investigate the rheograms of concentrated suspensions of magnetic particles obtained under imposed shear rate in parallel plate geometry. We show that under magnetic field application the usual trend of the rheogram, i.e., increasing shear stress for the whole range of shear rates, is altered by the appearance of a region in which the shear stress decreases as the shear rate is increased. The existence of this region gives to the rheograms an N-like shape. The two initial regions (pre-yield regime) of these N-like rheograms present unstable flow, characterized by the oscillation of the shear stress with time for each imposed value of shear rate. We also show that rheograms obtained at different sample thicknesses approximately overlap in the developed flow regime, whereas there is a tendency of the shear stress to increase as the thickness is decreased in the pre-yield regime. This tendency is likely due to the strengthening of preexisting particle structures by compression as the gap thickness is decreased. Finally, we analyze the effect of the applied magnetic field strength, H, and demonstrate that the rheograms 2 scale with H 1.5 to a single master curve, for the range of applied magnetic fields under study

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Stick–slip instabilities in the shear flow of magnetorheological suspensions

Cited by 12 publications

References 37 publications

Instabilities of a pressure-driven flow of magnetorheological fluids

Instabilities of a pressure-driven flow of magnetorheological fluids

Discontinuous shear thickening in the presence of polymers adsorbed on the surface of calcium carbonate particles

N-like rheograms of concentrated suspensions of magnetic particles

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