Force distributions in frictional granular media

Akella, V. S.; Bandi, Mahesh; Hentschel, H. G. E.; Procaccia, Itamar; Roy, Saikat

doi:10.1103/physreve.98.012905

Cited by 8 publications

(5 citation statements)

References 27 publications

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“…The disks were prepared in-house by curing liquid polymer where the modulus and friction coefficient could be tuned independently; details of disk preparation are presented in Ref. [25].…”

Section: Dilation Under Shear: Experiments a Setup Descriptionmentioning

confidence: 99%

Universal scaling laws for shear induced dilation in frictional granular media

Bandi¹,

Das

Gendelman

et al. 2019

Granular Matter

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Compressed frictional granular matter cannot flow without dilation. Upon forced shearing to generate flow, the amount of dilation may depend on the initial preparation and a host of material variables. On the basis of both experiments and numerical simulations we show that as a result of training by repeated compression-decompression cycles the amount of dilation induced by shearing the system depends only on the shear rate and on the (pre-shearing) packing fraction. Relating the rheological response to structural properties allows us to derive a scaling law for the amount of dilation after n cycles of compression-decompression. The resulting scaling law has a universal exponent that for trained systems is independent of the inter-granules force laws, friction parameters and strain rate. The amplitude of the scaling law is analytically computable, and it depends only on the shear rate and the asymptotic packing fraction.

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“…The disks were prepared in-house by curing liquid polymer where the modulus and friction coefficient could be tuned independently; details of disk preparation are presented in Ref. [25].…”

Section: Dilation Under Shear: Experiments a Setup Descriptionmentioning

confidence: 99%

Universal scaling laws for shear induced dilation in frictional granular media

Bandi¹,

Das

Gendelman

et al. 2019

Granular Matter

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“…The heat transfer process of a pebble bed is mainly carried out through the contact heat conduction between pebbles especially the fixed bed with high solid-fluid thermal conductivity ratio and slow fluid flow rate [15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Under the condition, the contact force chain network between pebbles in contact with each other forms a net-like virtual heat transfer path inside a pebble bed [29][30][31][32][33][34][35], the size of which will affects the effective thermal conductivity and heat transfer behaviors of pebble bed, while the size of the virtual path is closely related to the magnitude of the contact force and the contact area. Thus, the contact force distribution will affect the effective thermal conductivity of the pebble bed.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the contact force distribution will affect the effective thermal conductivity of the pebble bed. What's more, the magnitude and the distribution of contact force play an important role for the prediction of the lifetime and the breakage of pebbles inside a fixed pebble bed [29][30][31][32][33][34][35][36][37][38][39]. Too strong a contact force may cause cracks and fragmentation near the contact point of a pebble, affecting the mechanical behaviors of the fixed pebble bed.…”

Section: Introductionmentioning

confidence: 99%

“…With the increase of the diameter ratio of cylinder to pebble, the global porosity decreases and the coordination increase gradually, and eventually both tend to a constant value [7,8,44]. In addition, numerous numerical simulations and experiments have been conducted on the contact force distribution and force chain inside pebble bed [29][30][31][32][33][34][35][36][37][38][39]. The force chain network, including strong contact force chain and weak contact force chain, formed by the contact force between pebbles gradually evolves with each other under the external excitation, such as gravity, external compression load, thermal expansion, vibration, and so forth.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Pebble Size Distribution and Wall Effect on Inner Packing Structure and Contact Force Distribution in Tritium Breeder Pebble Bed

et al. 2021

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In the tritium breeding blanket of nuclear fusion reactors, the heat transfer behavior and thermal-mechanical response of the tritium breeder pebble bed are affected by the inner packing structure, which is crucial for the design and optimization of a reliable pebble bed in tritium breeding blanket. Thus, the effect of pebble size distribution and fixed wall effect on packing structure and contact force in the poly-disperse pebble bed were investigated by numerical simulation. The results show that pebble size distribution has a significant influence on the inner packing structure of pebble bed. With the increase of the dispersion of pebble size, the average porosity and the average coordination number of the poly-disperse pebble bed gradually decrease. Due to the influence of the fixed wall, the porosity distribution of the pebble bed shows an obvious wall effect. For poly-disperse pebble bed, the influenced region of the wall effect gradually decreases with the increase of the dispersion of pebble size. In addition, the gravity effect and the pebble size distribution have an obvious influence on the contact force distribution inside the poly-disperse pebble bed. The majority of the contact force are weak contact force that is less than the average contact force. Only a few of pebbles have strong contact force that is greater than average contact force. This investigation can help in analyzing the pebble crushing characteristics and the thermal hydraulic analysis in the poly-disperse tritium breeder pebble bed.

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“…The phenomenon described here is intimately connected to the unavoidable correlations between normal and tangential forces in frictional granular matter due to the Coulomb condition. It was shown recently [18] that a maximum entropy formalism for the joint probability distribution functions (pdfs) of the normal and tangential forces predicts that at decreasing pressures there will be a tendency for a divergence near zero of the pdf P(F t −μF n ). This pdf for our present case of Hertzian contacts for two different pressures is shown in fig.…”

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confidence: 99%

Scaling theory of giant frictional slips in decompressed granular media

Hentschel¹,

Procaccia²,

Roy³

2019

EPL

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When compressed frictional granular media are decompressed, generically a fragile configuration is created at low pressures. Typically this is accompanied by a giant frictional slippage as the fragile state collapses. We show that this instability is understood in terms of a scaling theory with theoretically computable amplitudes and exponents. The amplitude diverges in the thermodynamic limit hinting to the possibility of huge frictional slip events in decompressed granular media. The physics of this slippage is discussed in terms of the probability distribution functions of the tangential and normal forces on the grains which are highly correlated due to the Coulomb condition.

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Force distributions in frictional granular media

Cited by 8 publications

References 27 publications

Universal scaling laws for shear induced dilation in frictional granular media

Universal scaling laws for shear induced dilation in frictional granular media

Effect of Pebble Size Distribution and Wall Effect on Inner Packing Structure and Contact Force Distribution in Tritium Breeder Pebble Bed

Scaling theory of giant frictional slips in decompressed granular media

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