Outstanding magnetorheological effect based on discontinuous shear thickening in the presence of a superplastifier molecule

Bossis, Georges; Grasselli, Yan; Meunier, Alain; Volkova, Olga

doi:10.1063/1.4962467

Cited by 19 publications

(17 citation statements)

References 14 publications

(11 reference statements)

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“…Our results concretize recent scientific effort to unravel shear thickening in dense suspensions and to understand its control through the addition of plasticizers [25,52,53], nanofibers [54], or large particles [55] and the application of magnetic fields [56] or transverse shear [57]. Our work may also shed new light on undesirable effects in industrial processes such as stress surges [23,58], granulation, and slurry fracture [59,60], and help to further develop promising applications such as fabrics impregnated with shear-thickening fluids for improved resistance to impact [61][62][63][64].…”

Section: Discussionsupporting

confidence: 79%

Uncovering Instabilities in the Spatiotemporal Dynamics of a Shear-Thickening Cornstarch Suspension

2018

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Recent theories predict that discontinuous shear thickening (DST) involves an instability, the nature of which remains elusive. Here, we explore unsteady dynamics in a dense cornstarch suspension by coupling long rheological measurements under constant shear stresses to ultrasound imaging. We demonstrate that unsteadiness in DST results from localized bands that travel along the vorticity direction with a specific signature on the global shear rate response. These propagating events coexist with quiescent phases for stresses slightly above DST onset, resulting in intermittent, turbulentlike dynamics. Deeper into DST, events proliferate, leading to simpler, Gaussian dynamics. We interpret our results in terms of unstable vorticity bands as inferred from recent model and numerical simulations.

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Section: Discussionsupporting

confidence: 79%

Uncovering Instabilities in the Spatiotemporal Dynamics of a Shear-Thickening Cornstarch Suspension

2018

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“…We also see on this graph that, by increasing the volume fraction, the critical stress increases and the critical shear rate decreases. These critical values are obtained at zero magnetic field, but when the field is increased for a given volume fraction, the critical shear rate will continuously decrease to zero in a field range typically of 0-20 kA/m (Bossis et al, 2016). If instead of applying a ramp of stress we apply a ramp of shear rate, at the critical point we then obtain a jump of stress to very high values which overcomes the range of conventional rheometers.…”

Section: Jamming Transition At High Volume Fractionmentioning

confidence: 90%

“…The corresponding evolution of stress is plotted in Figure 2B vs. the strain. It was obtained in a cylindrical Couette flow with a vane tool and a homemade rheometer to be able to measure high torques (Bossis et al, 2016). The shear rate was increased from 0 to 1.6 s −1 in 2 s then kept constant for 25 s. The stress does not grow until the strain reaches a value around one and then increases up to 150 kPa where it remains constant afterwards.…”

Section: Jamming Transition At High Volume Fractionmentioning

confidence: 99%

The Role of Volume Fraction and Additives on the Rheology of Suspensions of Micron Sized Iron Particles

Bossis¹,

Volkova²,

Grasselli

et al. 2019

Front. Mater.

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The increase of the yield stress vs. the magnetic field is the most important quantity characterizing the efficiency of a magnetorheological suspension. The theory based on the formation of columnar aggregates predicts a linear variation with the volume fraction of magnetic particles. In this paper we review previous models used to calculate forces and yield stress and will introduce a new model based on rupture at zero strain. Predictions of these models are compared with the experimental data obtained for carbonyl iron particles, by different authors. Whereas, previous analytical prediction strongly overestimates experimental yield stress, those calculated using the Finite Element Method (FEM), together with affine trajectories, reproduce the experiments well and show a linear dependence with the volume fraction and a H 3/2 behavior between 50 and 200 kA/m. Nevertheless, at very high-volume fractions (>55%), where the suspension can only flow in the presence of specific additives, the dependence of the yield stress vs. the volume fraction and the magnetic field is dramatically changed. We observed a jamming transition, which is triggered by the application of a low magnetic field and which depends strongly on the volume of the fraction. Here, we will discuss new perspectives arising from the use of these very high-volume fractions.

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“…In the industrial processing of pastes, it is of interest to delay this jamming transition until the highest possible value of stress by the proper choice of the coating polymer; it would be still more interesting to be able to control the critical stress by external means. We have succeeded in doing so by using suspensions of magnetic particles whose interaction forces can be modulated by the application of a magnetic field [16]. Indeed, the critical shear rate is shown to decrease strongly with the amplitude of the magnetic field and, contrarily to expectation, the critical stress is not constant but increases with the magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Discontinuous shear thickening in concentrated suspensions

Bossis¹,

Volkova²,

Grasselli

et al. 2019

Phil. Trans. R. Soc. A.

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The flow of concentrated suspensions of solid particles can be suddenly blocked by the formation of a percolated network of frictional contacts above a critical value of the applied stress. Suspensions of magnetic particles coated with a superplastifier molecule were shown to produce a strong jamming transition. We find that, for these suspensions with an abrupt discontinuous shear thickening, a model using the divergence of the viscosity at a volume fraction that depends on the applied stress does not well describe the observed behaviour both below and above the critical stress. At a constant applied stress above the critical one, we have a stick–slip behaviour of the shear rate whose period can be predicted and scaled as the square root of the relaxation time of the frictional contacts. The application of a small magnetic field allows us to continuously decrease the critical shear rate, and it appears that the yield stress induced by the magnetic field does not contribute to the jamming transition. Finally, it is shown that this jamming transition also appears in the extrusion of a suspension through a die, but with a much slower dynamics than in the case of stress imposed on a rotational geometry. This article is part of the theme issue ‘Heterogeneous materials: metastable and non-ergodic internal structures’.

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Outstanding magnetorheological effect based on discontinuous shear thickening in the presence of a superplastifier molecule

Abstract: , O Volkova. Outstanding magnetorheological effect based on discontinuous shear thickening in the presence of a superplastifier molecule.

Cited by 19 publications

References 14 publications

Uncovering Instabilities in the Spatiotemporal Dynamics of a Shear-Thickening Cornstarch Suspension

Uncovering Instabilities in the Spatiotemporal Dynamics of a Shear-Thickening Cornstarch Suspension

The Role of Volume Fraction and Additives on the Rheology of Suspensions of Micron Sized Iron Particles

Discontinuous shear thickening in concentrated suspensions

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