Contact rolling and deformation in granular media

Kuhn, Matthew R.; Bagi, Katalin

doi:10.1016/j.ijsolstr.2004.05.066

Cited by 96 publications

(64 citation statements)

References 33 publications

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“…However, the effects of the scarce amount of impurities and differently shaped particles are assumed to be negligible. This is also suggested by the small effect of the shape difference between glass spheres and glass pebbles in our measurements and in literature [24].…”

Section: Limitations and Implicationssupporting

confidence: 90%

“…11) agree with the simulations of Kuhn and Bagi, which showed little difference between the amount of particle rotations for spherical and ovoid particles [24]. The shape difference is much larger between the steel granules and spheres than between the glass spheres and pebbles (Fig.…”

Section: Shapesupporting

confidence: 87%

“…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]. Vacu-SL shafts filled with edgy particles are therefore expected to have a higher bending stiffness than those filled with spheres or ellipsoids.…”

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: Limitations and Implicationssupporting

confidence: 90%

Section: Shapesupporting

confidence: 87%

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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“…Instead, grains exhibit strong fluctuations of velocities [5][6][7][8][9]. These fluctuations were reported to form spatially correlated patterns in many different flow configurations.…”

Section: Shear Induced Granular Vorticesmentioning

confidence: 99%

How granular vortices can help understanding rheological and mixing properties of dense granular flows

et al. 2017

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Abstract. Dense granular flows exhibit fascinating kinematic patterns characterised by strong fluctuations in grain velocities. In this paper, we analyse these fluctuations and discuss their possible role on macroscopic properties such as effective viscosity, non-locality and shear-induced diffusion. The analysis is based on 2D experimental granular flows performed with the stadium shear device and DEM simulations. We first show that, when subjected to shear, grains self-organised into clusters rotating like rigid bodies. The average size of these so-called granular vortices is found to increase and diverge for lower inertial numbers, when flows decelerate and stop. We then discuss how such a microstructural entity and its associated internal length scale, possibly much larger than a grain, may be used to explain two important properties of dense granular flows: (i) the existence of shear-induced diffusion of grains characterised by a shear-rate independent diffusivity and (ii) the development of boundary layers near walls, where the viscosity is seemingly lower than the viscosity far from walls.

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“…From a study of particle rolling on oval cross-sectional rods, the same authors conclude that particle rolling appears to be a major microscopic deformation mechanism, especially when interparticle friction is large. Kuhn et al [50] state that particle rotations are known to have a fundamental influence on the behaviour of granular materials. Also, Belheine et al [34] highlight the importance of rolling in the deformation process, arguing that rolling resistance can play a significant role on the contact behaviour of the granular material.…”

Section: Rolling Resistancementioning

confidence: 99%

Micromechanical study of granular assemblies by true triaxial test simulations

Hurtado¹,

Jonathan²

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Geomaterials, such as soils and rocks, are discontinuous and multiphase in nature since they are a mix of particulate elements and different constituents. The discrete nature of geomaterials yields a complex media to deal with regarding predictive capabilities that can only be achieved through expensive computational simulations. The computational modelling of geotechnical problems may consider continuum mechanics or discrete element frameworks to simulate the behaviour of all the features involved. Undoubtedly, continuum-based simulation techniques are predominant in geotechnical engineering practice and have significantly influenced our comprehension of soil response. However, continuum simulations do not consider special features of granular matters at the grain scale that finally determine the characteristic behaviour of particulate materials. On the other hand, the Discrete Element Method (DEM) is in fact based on the inter-particle physical processes at the micro-scale and, in the last decades, has been widely used to simulate a large range of geomaterials, allowing quantitative and qualitative analyses.However, it lacks the scalability and efficiency of models based on continua.This investigation is focused on the modelling of the macroscopic mechanical response of granular assemblies, as a natural consequence of their micromechanical properties, but employing the micro-/mesoscopic method described above. Simulations of true triaxial tests (TTT), an important test in geotechnical engineering, using 3D virtual soil samples are executed with an advanced DEM code that can model assemblies of grains that are made of spherical or non-spherical particles. A DEM-based calibration methodology is thus proposed giving insights on the reliability of the discrete method to replicate soils' mechanical behaviour.ii

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Contact rolling and deformation in granular media

Cited by 96 publications

References 33 publications

Vacuum packed particles as flexible endoscope guides with controllable rigidity

Vacuum packed particles as flexible endoscope guides with controllable rigidity

How granular vortices can help understanding rheological and mixing properties of dense granular flows

Micromechanical study of granular assemblies by true triaxial test simulations

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