Sticky sand

Kudrolli, Arshad

doi:10.1038/nmat2131

Cited by 68 publications

(45 citation statements)

References 9 publications

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“…However, controlling the size and the shape of particles is a difficult task in particular for small cohesive objects. Liquid bridges can also be used to increase the interparticle forces [15] and, under certain conditions, to lubricate contacts [16] in addition to cohesive forces.…”

Section: Introductionmentioning

confidence: 99%

Compaction dynamics of a magnetized powder

2009

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We have investigated experimentally the influence of a magnetic interaction between the grains on the compaction dynamics of a granular pile submitted to a series of taps. The granular material used to perform this study is a mixture of metallic and glass grains. The packing is immersed in an homogeneous external magnetic field. The magnetic field induces an interaction between the metallic grains that constitutes the tunable cohesion. The compaction characteristic time and the asymptotic packing fraction have been measured as a function of the Bond number which is the ratio between the cohesive magnetic force and the grain weight. These measurements have been performed for different fractions of metallic beads in the pile. When the pile is only made of metallic grains, the characteristic compaction time increases as the square root of the Bond number. While the asymptotic packing fraction decreases as the inverse of the Bond number. For mixtures, when the fraction of magnetized grains in the pile is increased, the characteristic time increases while the asymptotic packing fraction decreases. A simple mesoscopic model based on the formation of granular chains along the magnetic field direction is proposed to explain the observed macroscopic properties of the packings.

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Section: Introductionmentioning

confidence: 99%

Compaction dynamics of a magnetized powder

2009

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“…18 The surface tension of the SM was determined with the ring method at 20 C and found to be 34.7 mN/m. Based on this, Eq.…”

Section: Stage 2: Spike In Friction Coefficientmentioning

confidence: 99%

“…Kudrolli 18 comments that the addition of small amounts of liquid to granular matter transforms its mechanical properties. At the beginning of each test the particulate lubricant can be considered as slurry with the interstitial space between particles fully saturated with liquid and cohesion between particles negligible.…”

Section: Stage 2: Spike In Friction Coefficientmentioning

confidence: 99%

Cosmetic powder suspensions in compliant, fingerprintlike contacts

et al. 2011

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Cosmetic powders are regularly employed in skin creams and cosmetic formulations to improve performance and enhance skin feel. A previous study investigated the effect of particle concentration and size on the lubricating properties of powder suspensions in smooth, compliant contacts [Timm et al., Tribol. Int. (2011)]. In this paper the tribological properties of cosmetic powder suspensions are investigated in compliant contacts having model fingerprintlike surface topography. Friction coefficients were measured for a series of powder suspensions with varying particle size and concentration in a polydimethylsiloxane (PDMS)/PDMS contact. A commercial tribometer (MTM, PCS Instruments) was employed to measure friction as a function of rubbing time (20 min), under pure sliding (50 mm/s) and low load (0.5 N) conditions. Compared to results using smooth surfaces, it was clear that surface topography has a pronounced affect on the timedependent tribological behavior of the cosmetic powder suspensions studied. A two-stage friction coefficient versus time curve was observed. By varying the particle size and concentration it was shown that the duration and magnitude of each stage can be controlled.

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“…The friction forces are influenced by the surface properties and by the chemical nature of the grains. The cohesive forces are induced by the presence of liquid bridges [2,3], electric charges [4,5], van der Waals interactions [6] and magnetic dipole-dipole interactions [7,8,9,10,11]. The predominance of one of these cohesive forces depends on both the environmental condition and the physicol-chemical properties of the grains.…”

Section: Introductionmentioning

confidence: 99%

Influence of cohesive forces on the macroscopic properties of granular assemblies

Lumay¹,

Fiscina²,

Ludewig³

et al. 2013

AIP Conference Proceedings

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Abstract. The influence of cohesive forces inside a granular material is analyzed with compaction experiments. To begin, a model cohesive granular material is considered. This granular material is made of millimetric grains with a cohesion induced by an external magnetic field. Therefore, the cohesion between the grains is adjusted through the intensity of the applied magnetic field. Afterward, the cohesion induced by capillary bridges are considered. In the first study concerning capillary forces, the cohesion between neighboring grains is induced by liquid bridges in a wet granular material. The cohesiveness is tuned using different liquids having specific surface tension values. The second study performed with capillary forces concerns initially dry granular materials surrounded by a well controlled air humidity. Then, the cohesion inside the packing is controlled through the relative humidity which influence both triboelectric and capillary effects. The evolution of the parameters extracted from the compaction curves have been analyzed as a function of the cohesiveness. All the results show that the packing fraction of a pile and the compaction dynamics is strongly sensitive to cohesive forces. Therefore, the compaction measurement is a good way to characterize a powder or a granular material for R&D and quality control in industrial applications. Finally, we show that the cohesive forces play an important role when the grain size is typically below 50μm.

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Sticky sand

Cited by 68 publications

References 9 publications

Compaction dynamics of a magnetized powder

Compaction dynamics of a magnetized powder

Cosmetic powder suspensions in compliant, fingerprintlike contacts

Influence of cohesive forces on the macroscopic properties of granular assemblies

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