Discrete element investigation of stress fluctuation in granular flow at high strain rates

Schwarz, Otto; Horie, Y.; Shearer, Michael

doi:10.1103/physreve.57.2053

Cited by 23 publications

(16 citation statements)

References 12 publications

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“…Similar plastic flow phenomena should be observable in colloidal mixtures on expanded scales, as a future experimental system. It is of great interest how our findings can be related to the other well-known examples of enhanced stress fluctuations, where the effect of the size dispercity should be further examined [5,11,12,13].…”

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confidence: 85%

“…There remain a number of puzzles in polycrystal rheology not yet simulated microscopically, such as the Portevin-Le Chatelier effect in dilute alloys caused by intermittent yielding [5]. On the other hand, in physics, dynamics of sheared glassy materials has been studied extensively [6, 7], including microscopic particle systems [8,9,10], granular materials [11,12], and foams [13], while not enough attention has been paid to polycrystal rheology.Recently, using molecular dynamics simulation, we have examined the dynamics of polycrystal states realized on very small scales in a model binary mixture [14]. The parameters we have changed are the size ratio of the diameters of the two components σ 2 /σ 1 , the temperature T , and the composition c. Polycrystal states appear as intermediate states between crystal and glass, where the grain boundary motions are severely slowed down with size dispersity.…”

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confidence: 99%

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Plastic flow in polycrystal states in a binary mixture

2008

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Using molecular dynamics simulation, we examine the dynamics of sheared polycrystal states in a binary mixture composed of small and large particles in two dimensions. We vary the composition c of the large particles and the shear rate ._gamma to realize changeovers among crystal, polycrystal, and glass. We find large stress fluctuations arising from sliding motions of the particles at the grain boundaries, which occur cooperatively to release the elastic energy stored. These stress fluctuations decrease as the system crosses over from polycrystal to glass. The dynamic processes are visualized with the aid of a sixfold angle alpha(j)(t) representing the local crystal orientation and a disorder variable D(j)(t) representing a deviation from the hexagonal order for particle j.

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confidence: 85%

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confidence: 99%

Plastic flow in polycrystal states in a binary mixture

2008

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“…However, because of gravity, this homogeneous state is not achieved in existing experiments [15,16] but is obtained in discrete particles simulations. Most of the results found in the literature are obtained imposing the wall velocity and measuring the shear stress [17,18,19,20,21]. Some are carried out controlling the shear force applied to the moving wall in order to study the flow thresholds [22].…”

Section: Set-upmentioning

confidence: 99%

On dense granular flows

Midi¹

2004

Eur. Phys. J. E

1,619

462

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Abstract. The behaviour of dense assemblies of dry grains submitted to continuous shear deformation has been the subject of many experiments and discrete particle simulations. This paper is a collective work carried out among the French research group GDR Milieux Divisés. It proceeds from the collection of results on steady uniform granular flows obtained by different groups in six different geometries both in experiments and numerical works. The goal is to achieve a coherent presentation of the relevant quantities to be measured i.e. flowing thresholds, kinematic profiles, effective friction, etc. First, a quantitative comparison between data coming from different experiments in the same geometry enforces the robust features in each case. Second, a transversal analysis of the data across the different configurations, allows us to identify the relevant dimensionless parameters, the different flow regimes and to propose simple interpretations. The present work, more than a simple juxtaposition of results, underlines the richness of granular flows and enhances the open problem of defining a single rheology.

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“…These methods have evolved and have recently been used to study shear flows in granular materials [24]. They are suited to the low pressure regime in which compressibility can be neglected.…”

Section: 2mentioning

confidence: 99%

Compaction waves in granular HMX

Menikoff¹,

Kober²

2000

AIP Conference Proceedings

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DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document. Piston driven compaction waves in granular HMX are simulated with a two-dimensional continuum mechanics code in which individual grains are resolved. The constitutive properties of the grains are modeled with a hydrostatic pressure and a simple elastic-plastic model for the shear stress. Parameters are chosen to correspond to inert HMX. For a tightly packed random grain distribution (with initial porosity of 19%) we varied the piston velocity to obtain weak partly compacted waves and stronger fully compacted waves. The average stress and wave speed are compatible with the porous Hugoniot locus for uniaxial strain. However, the heterogeneities give rise to stress concentrations, which lead to localized plastic flow. For weak waves, plastic deformation is the dominant dissipative mechanism and leads to d i s persed waves that spread out in time. In addition to dispersion, the granular heterogeneities give rise to subgrain spatial variation in the thermodynamic variables. The peaks in the temperature fluctuations, known as hot spots, are in the range such that they are the critical factor €or initiation sensitivity. LA-13546-MS

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Discrete element investigation of stress fluctuation in granular flow at high strain rates

Cited by 23 publications

References 12 publications

Plastic flow in polycrystal states in a binary mixture

Plastic flow in polycrystal states in a binary mixture

On dense granular flows

Compaction waves in granular HMX

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