Packing fractions and maximum angles of stability of granular materials

Olson, J.; Priester, Marquita; Luo, Jun; Chopra, Sameer; Zieve, R. J.

doi:10.1103/physreve.72.031302

Cited by 10 publications

(19 citation statements)

References 15 publications

(16 reference statements)

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“…However, the very same compression of the particles could simultaneously cause the particles to change from circular (in 2D) to shapes that are more resembling hexagons (or other polygons, depending on packing type and particles' shapes). As discussed above, a pile of edgy particles is more stable than a pile of spheres [19]. Therefore, slight particle deformation might increase the bending stiffness of the Vacu-SL haft.…”

Section: Theory and Literaturementioning

confidence: 94%

“…'Packing load' is the load used to compress the packing. Increasing packing load and packing density are known to increase the packing stability and thus to limit displacements of particles [18,19]. In a rigidified Vacu-SL shaft, the packing load is the pressure difference between the vacuum pressure inside the foil tube and the atmospheric pressure outside it and was set equal for all test models.…”

Section: Methodsmentioning

confidence: 99%

“…Particle hopping resembles shearing in granular media, especially when multiple particles or an entire layer of particles moves at once [18]. Olson et al performed experiments on avalanches in piles of particles [19]. They showed that the stability of a pile Other researches showed that particle shape is an important factor in packing stability [20][21][22][23] and that spheres and ellipsoids have similar rolling abilities [24].…”

Section: Theory and Literaturementioning

confidence: 99%

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Vacuum packed particles as flexible endoscope guides with controllable rigidity

et al. 2010

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In order to fully benefit from the functionalities of flexible endoscopes in surgery a simple shaft-guide that can be used to support the flexible endoscope shaft is required. Such a shaft-guide must be flexible during insertion into the human body and rigidified when properly positioned to support the flexible endoscope shaft. A shaft-guide called 'Vacu-SL' was designed, consisting of a foil tube, filled with particles, that is rigidified by creating a vacuum in its tube. It is expected that the bending stiffness of a loaded, rigidified Vacu-SL shaft-guide is significantly influenced by the shape, hardness and size of the filler particles used. The goal of this study was to find the relations between the filler particles' size, shape and hardness and a rigidified Vacu-SL shaft-guide's bending stiffness. Vacu-SL test models were made using polystyrene, acrylic glass, glass, steel, and corundum particles as spheres, pebbles and granulate, with average diameters between 0.16-1.7 mm. These test models were rigidified and then loaded in a tensile tester. The forces needed for 5 and 10 mm deflections of the rigidified test models were measured. The results show that particle size, shape and hardness all influence a rigidified Vacu-SL shaft-guide's bending stiffness. Size and hardness showed an optimum and granules performed better than spheres. Although the maximally measured bending stiffness might be insufficient to enable proper guidance of flexible endoscope shafts, the results suggest several ways to successfully improve the Vacu-SL shaft-guide.

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Section: Theory and Literaturementioning

confidence: 94%

Section: Methodsmentioning

confidence: 99%

Section: Theory and Literaturementioning

confidence: 99%

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Vacuum packed particles as flexible endoscope guides with controllable rigidity

et al. 2010

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“…For further analysis, we use a minimum 4-degree difference between the two angles as a cutoff in avalanche size, discarding any images from smaller rearrangements. As described elsewhere [28], we can also compute the pile's packing fraction from the images. White paper around the outside of the circular drum region and a red For many of the measurements we use brass ball bearings for the single balls, which we can distinguish by color from the steel hexagons.…”

Section: Methodsmentioning

confidence: 99%

“…From previous work [28] we know that hexagons are significantly more stable than single ball bearings. Similar results were reported in [33] for pentagons.…”

Section: Stabilitymentioning

confidence: 99%

Segregation and stability of a binary granular heap

et al. 2009

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We measure stability of two-dimensional granular mixtures in a rotating drum and relate grain configurations to stability. We use two types of grains which differ in both size and shape, with the larger grains reaching a larger average angle before an avalanche. In our mixtures, the smaller grains cluster near the center of the drum, while the larger grains remain near the outer edge, a pattern suggesting that grain size rather than avalanche angle determines the segregation behavior. One consequence of the size segregation is that the smaller grains heavily influence the stability of the heap. We find that the maximum angle of stability is a non-linear function of composition, changing particularly rapidly when small grains are first added to a homogeneous pile of large grains. We conclude that the grain configuration within the central portion of the heap plays a prominent role in stability.

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