The effects of feed size distribution on confined-bed comminution of quartz and calcite in piston-die press

Particle degradation and fracture play an important role in natural granular flows and in many applications of granular materials. We analyze the fracture properties of two-dimensional disklike particles modeled as aggregates of rigid cells bonded along their sides by a cohesive Mohr-Coulomb law and simulated by the contact dynamics method. We show that the compressive strength scales with tensile strength between cells but depends also on the friction coefficient and a parameter describing cell shape distribution. The statistical scatter of compressive strength is well described by the Weibull distribution function with a shape parameter varying from 6 to 10 depending on cell shape distribution. We show that this distribution may be understood in terms of percolating critical intercellular contacts. We propose a random-walk model of critical contacts that leads to particle size dependence of the compressive strength in good agreement with our simulation data.

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Section: Introductionmentioning

confidence: 99%

Bonded-cell model for particle fracture

et al. 2015

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“…In contrast, the fragmentation of particles under controlled conditions is used in comminution processes such as the milling of vegetal products or grinding of mineral materials. The evolution of particle size distribution and energy dissipation in such processes depend on many factors such as particle properties (shape, crushability), initial size distribution, loading history and mobility of the grains during the crushing process (Thornton, Yin, & Adams 1996, Fuerstenau, Gutsche, & Kapur 1996, Couroyer, Ning, & Ghadiri 2000, Potapov & Campbell 2001, Nakata, Hyodo, Hyde, Kato, & Murata 2001, Cleary 2001, Bolton, 2, & Cheng 2008, Hosten & Cimilli 2009, Liu, Kafui, & Thornton 2010.…”

Section: Introductionmentioning

confidence: 99%

“…The manufacture of compact shapes by molding powdered materials is the archetypal example of a process in which the bulk crushing of particles plays as much a role as particle rearrangements (Fuerste-nau, Gutsche, & Kapur 1996, Hosten & Cimilli 2009, Das, Nguyen, & Einav 2011, Ben-Nun, Einav, & Tordesillas 2010, Esnault & Roux 2013. However, despite its industrial importance, the compaction process and its underlying microscopic mechanisms are still poorly understood partially due to short length and time scales governing particle breakup.…”

Section: Introductionmentioning

confidence: 99%

Constitutive modelling of granular soils and interfaces considering their internal state

2014

Geomechanics From Micro to Macro

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International audienceBy means of the contact dynamics method together with a particle fracture model, in which the particles are cohesive aggregates of irreducible polygonal fragments, we investigate the evolution of particle size distribution in the process of uniaxial compaction of granular materials. The case of single particle breakup under compressive stress is used to test the method and the influence of discretization (number of irreducible fragments). We show that the breaking threshold of the granular assembly scales with the internal cohesion of the particles but it depends also on the initial size distribution and irregularity of polygonal particle shapes. The evolution of size distribution proceeds by consecutive periods of intense particle crushing, characterized by local shattering instability, and periods of little breaking activity. Starting with either monodisperse or power-law distribution of particle sizes, the latter evolves towards a broad distribution of the fragmented particles with a nearly power-law distribution in the range of intermediate particle sizes. Interestingly, a finite number of large particles survive despite ongoing crushing process due to the more homogeneous distribution of forces in the presence of small fragmented particles filling the pores between larger particles

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“…Particle size reduction during such processes affects the mechanical behavior of a granular material through both energy dissipation and evolution of granular texture [1][2][3][4]. The manufacture of compact shapes by molding powders is a well-known example in which the bulk crushing of particles plays as much a role as particle rearrangements [5][6][7][8][9]. The grinding process of clinker nodules in the cement industry is another example where particle crushing is used to produce the desired size grading.…”

Section: Introductionmentioning

confidence: 99%

Rheology of granular materials composed of crushable particles

Nguyen

Azéma²,

Sornay

et al. 2018

Eur. Phys. J. E

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We investigate sheared granular materials composed of crushable particles by means of contact dynamics simulations and the bonded-cell model for particle breakage. Each particle is paved by irregular cells interacting via cohesive forces. In each simulation, the ratio of the internal cohesion of particles to the confining pressure, the relative cohesion, is kept constant and the packing is subjected to biaxial shearing. The particles can break into two or more fragments when the internal cohesive forces are overcome by the action of compressive force chains between particles. The particle size distribution evolves during shear as the particles continue to break. We find that the breakage process is highly inhomogeneous both in the fragment sizes and their locations inside the packing. In particular, a number of large particles never break whereas a large number of particles are fully shattered. As a result, the packing keeps the memory of its initial particle size distribution, whereas a power-law distribution is observed for particles of intermediate size due to consecutive fragmentation events whereby the memory of the initial state is lost. Due to growing polydispersity, dense shear bands are formed inside the packings and the usual dilatant behavior is reduced or cancelled. Hence, the stress-strain curve no longer passes through a peak stress, and a progressive monotonic evolution towards a pseudo-steady state is observed instead. We find that the crushing rate is controlled by the confining pressure. We also show that the shear strength of the packing is well expressed in terms of contact anisotropies and force anisotropies. The force anisotropy increases while the contact orientation anisotropy declines for increasing internal cohesion of the particles. These two effects compensate each other so that the shear strength is nearly independent of the internal cohesion of particles.

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The effects of feed size distribution on confined-bed comminution of quartz and calcite in piston-die press

Cited by 23 publications

References 14 publications

Bonded-cell model for particle fracture

Bonded-cell model for particle fracture

Constitutive modelling of granular soils and interfaces considering their internal state

Rheology of granular materials composed of crushable particles

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