Force Fluctuations in Bead Packs

Liu, C. h.; Nagel, Sidney R.; Schecter, David A.; Coppersmith, S. N.; Majumdar, Satya N.; Narayan, Onuttom; Witten, Thomas A.

doi:10.1126/science.269.5223.513

Cited by 823 publications

(804 citation statements)

References 13 publications

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“…Force transmission is inherently heterogeneous, as it is reliant on certain moieties spanning the bulk and forming chains through which the force can travel. An illustrative image displaying this phenomena has been presented by Liu et al [5]. Force chains carry most of the axial load leaving areas which experience little or no load.…”

Section: Introductionmentioning

confidence: 99%

“…Previous experimental work employing the carbon paper technique has relied on materials with well defined properties [5][6][7][8][9], however, as is commonly the case, it is rare to come across ideal systems in real world situations. The mm sized spherical agglomerates (pellets) used in this study where not externally sourced and where produced in house.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of spherical-agglomerate strength on the distribution of force during uniaxial compression

2011

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PostprintThis is the accepted version of a paper published in Powder Technology. This paper has been peerreviewed but does not include the final publisher proof-corrections or journal pagination.Citation for the original published paper (version of record):Mahmoodi, F., Alderborn, G., Frenning, G. (2011) Effect of spherical-agglomerate strength on the distribution of force during uniaxial compression. We employ the carbon paper technique with the aim of investigating the effect of spherical-agglomerate (pellet) strength on force distributions, through confined compression of approximately 1 mm sized pellets formed from microcrystalline cellulose and polyethylene glycol. The carbon paper technique relies on the transference of imprints from compressed pellets onto white photo quality paper, which are digitised and processed via image processing software. The investigated pellets can both deform plastically and develop localised cracks in response to an applied stress, while remaining largely intact during confined compression. Our results indicate that such crack formation -henceforth referred to as fracture -has a decisive influence on force distributions.Previous work on non-fracturing systems has found that the distribution of normalised forces tends to narrow with increasing particle deformation. No narrowing is observed after the point of fracture in this study and the width of the distributions -as quantified by the standard deviation of non-normalised forces -is found to increase with the difference between non-normalised mean force and fracture force. Additional corroborative results show that spatial force-force correlations typically exhibit a marked change once the fracture force is exceeded.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of spherical-agglomerate strength on the distribution of force during uniaxial compression

2011

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“…Granular disorder and steric exclusions lead to an unexpectedly inhomogeneous distribution of contact forces under quasistatic loading [1][2][3][4][5][6][7][8][9][10]. These force inhomogeneities in granular assemblies were first observed by means of photoelastic experiments [11,12].…”

Section: Introductionmentioning

confidence: 99%

“…A remarkable aspect of weak forces is the fact that their number does not vanish as the force falls to zero [13,17]. Several theoretical models have been proposed allowing to relate the exponential distribution of forces to granular disorder combined with the condition of force balance for each particle [1,18]. Recently, the force pdf's were derived for an isotropic system of frictionless particles in two dimensions from a statistical approach assuming a first shell approximation (one particle with its contact neighbors) [17].…”

Section: Introductionmentioning

confidence: 99%

Force transmission in dry and wet granular media

et al. 2009

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We compare the probability density functions of normal forces in dry and wet granular systems from 3D simulations by molecular dynamics and contact dynamics methods. While the strong forces are characterized by a decreasing exponential distribution, we show that in the range of weak forces the force distribution in a dry granular packing is sensitive to the anisotropy of the packing and the shape of the particles. By means of a model of capillary cohesion, implemented as a force law expressing the capillary force as a function of water volume and the distance between particles, we find that distributions are exponential for both compressive and tensile forces. The particle pressures are shown to form a bi-percolating structure.

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“…The carbon paper technique has been a tool employed in physics, to highlight force distributions within granular assemblies [18][19][20][21]. Force distribution studies have not received much attention in the pharmaceutical sector.…”

Section: Introductionmentioning

confidence: 99%

Effect of lubrication on the distribution of force between spherical agglomerates during compression

2010

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PostprintThis is the accepted version of a paper published in Powder Technology. This paper has been peerreviewed but does not include the final publisher proof-corrections or journal pagination.Citation for the original published paper (version of record):Mahmoodi, F., Alderborn, G., Frenning, G. (2010) Effect of lubrication on the distribution of force between spherical agglomerates during compression.Powder Technology, 198 (1) We employ the carbon paper technique to aid understanding of in die force and spatial distributions, upon compression of approximately 1 mm sized spherical agglomerates (pellets) of microcrystalline cellulose (MCC). The aim in this study was to test for the effect of lubricant film on force and spatial distributions. Pellets of MCC were formed via granulation and extrusion/spheronisation. Investigation of pellet bed compression was performed on a materials tester. Prior to compression studies the pellets were characterised for bulk density, size and deformability. Two pellet types were investigated; MCC and MCC lubricated with magnesium stearate. The carbon paper technique relies upon carbon paper as the medium for transferring imprints from compressed pellets onto photo quality paper. The digitised images of these imprints form the basis of analysis through the use of image processing software. Using the carbon paper technique within the range of 10-30 MPa indicates that lubrication does not have a significant effect on the distribution of forces between spherical agglomerates during uniaxial compression. 2 Spatial analysis of the imprints revealed that the lubricated pellets exhibited a higher packing order than the unlubricated ones at low applied pressures (10 and 20 MPa), a difference that could not be observed at 30 MPa. Hence interparticle friction and/or cohesion appear to influence the initial particle rearrangement, whereas confinement is suggested to dominate at higher pressures.

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Force Fluctuations in Bead Packs

Cited by 823 publications

References 13 publications

Effect of spherical-agglomerate strength on the distribution of force during uniaxial compression

Effect of spherical-agglomerate strength on the distribution of force during uniaxial compression

Force transmission in dry and wet granular media

Effect of lubrication on the distribution of force between spherical agglomerates during compression

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