Characterization of artificial spherical particles for DEM validation studies

Cavarretta, I.; O’Sullivan, Catherine; Ibraim, Erdin; Lings, ML; Hamlin, S.; Wood, David Muir

doi:10.1016/j.partic.2011.10.007

Cited by 47 publications

(26 citation statements)

References 12 publications

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“…1 represents a yielding point as transition between stage II and stage III, where the behaviour again diverges from the Hertzian theory. Similar patterns have been found by Cavarretta et al (2012), who showed how the Hertzian fit can be adopted for values of N within the range: N GT , N , nN GT where n is an experimental factor that quantifies the amplitude of the interval within which the Hertzian response applies.…”

Section: Pre-failure Responsesupporting

confidence: 79%

The relevance of roundness to the crushing strength of granular materials

2017

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The prediction of the crushing strength of sands is still an unresolved problem in soil mechanics. For natural sand grains with a regular geometry, Weibull theory has long been adopted to explain the decay of a nominal crushing strength with increasing particle size. The Weibull parameters for a given soil relate strength to size, and, although useful, this is an empirical framework that does not consider the mechanics of crushing. This study aims to provide a more fundamental assessment of the relationship between size, roundness, the stresses induced within the particles, and their crushing strength. A new grain-scale failure criterion is proposed, based on physical experiments on artificial and natural particles, Hertzian analysis and numerical simulations. It considers the physical properties of the particles, including the shape of the grain, as described by the roundness, and both its elastic and plastic features in terms of Young's modulus, Poisson ratio and hardness. The new criterion is suitable for implementation in particle-scale crushing simulations of granular masses, using, for example, the discrete-element method, as well as in improved probabilistic frameworks.

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Section: Pre-failure Responsesupporting

confidence: 79%

The relevance of roundness to the crushing strength of granular materials

2017

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“…0·677 and 5·38 N C 5·63 as p′ increased from 0·1 MPa to 1 MPa. The friction coefficient for the ballotini (μ) was taken as 0·0805 based on Cavarretta et al (2012). Referring to Fig.…”

Section: Discussion and Comparison Between Analysis And Experimentsmentioning

confidence: 99%

“…2. The rough ballotini were made by milling the smooth ballotini as described by Cavarretta et al (2012). Forty surface roughness measurements were conducted on each material using a Fogale Microsurf 3D (Fogale, 2005).…”

Section: Tested Materialsmentioning

confidence: 99%

Quantitative assessment of the influence of surface roughness on soil stiffness

et al. 2015

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The nature of soil stiffness at small strains remains poorly understood. The relationship between soil stiffness (e.g. shear stiffness, G 0 ) and isotropic confining pressure ( p′) can be described using a power function with exponent (b), that is,, where A is a constant and p r is an arbitrary reference pressure. Experimentally determined values of b are usually around 0·5 and these are higher than the value of 0·33 that can be analytically determined using Hertzian theory. Hertzian theory considers contact between two smooth, elastic spheres; however, in reality, inter-particle contacts in soil are complex with particle shape and surface roughness affecting the interaction. Thus Hertzian theory is not directly applicable to predict real soil stiffness. It has, however, provided a useful basis to develop an analytical framework to consider the influence of particle surface roughness on small-strain soil stiffness. Here, earlier contributions using this framework are extended and improved by paying particular attention to roughness and the tangential contact stiffness. Stiffness values calculated using the newly derived analytical expressions were compared with the results of bender element tests on samples of borosilicate glass beads (ballotini) whose surface roughness was quantified using an optical interferometer. The analytical expression captures the experimentally observed sensitivity of the smallstrain shear modulus to surface roughness.

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“…Cavarretta et al (2010Cavarretta et al ( & 2012 used particle compression tests to confirm the applicability of Hertzian theory when N exceeds NT2 and proposed the Cavarretta contact model for rough surfaces.…”

Section: Rough Surface Contact Modelmentioning

confidence: 99%

The influence of particle surface roughness on elastic stiffness and dynamic response

et al. 2017

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Discrete element method (DEM) simulations of planar wave propagation are used to examine the effect of particle surface roughness on the stiffness and dynamic response of granular materials. A new contact model that considers particle surface roughness is implemented in the DEM simulations.Face-centred cubic lattice packings and random configurations are used; uniform spheres are considered in both cases to isolate fabric and contact model effects from inertia effects. For the range of values considered here surface roughness caused a significant reduction in stiffness, particularly at lower confining stresses. The simulations confirm that surface roughness effects can at least partially explain the value of the exponent in the relationship between stiffness and mean confining stress for an assembly of spherical particles. Frequency domain analyses showed that the maximum frequency transmitted through the sample is reduced when surface roughness is considered. The assumption of homogeneity of stress and contacts in analytical micromechanical models is shown to lead to an overestimation of stiffness.

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Characterization of artificial spherical particles for DEM validation studies

Cited by 47 publications

References 12 publications

The relevance of roundness to the crushing strength of granular materials

The relevance of roundness to the crushing strength of granular materials

Quantitative assessment of the influence of surface roughness on soil stiffness

The influence of particle surface roughness on elastic stiffness and dynamic response

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