Particle Roundness and Sphericity from Images of Assemblies by Chart Estimates and Computer Methods

Hryciw, Roman D.; Zheng, Junxing; Shetler, Kristen

doi:10.1061/(asce)gt.1943-5606.0001485

Cited by 81 publications

(29 citation statements)

References 38 publications

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“…The shape parameters selected and analyzed in this work were taken from previous studies: FD [27,29], S, Rw, Sf and So [24], Sf [16], S and Rw [55], and ¥ [18]. Adequate evaluation of the representativeness of these parameters was achieved due to the design of 18 theoretical particles developed for this purpose.…”

Section: Representativity Of the Shape Parameters Studiedmentioning

confidence: 99%

Representativity of 2D Shape Parameters for Mineral Particles in Quantitative Petrography

et al. 2019

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This paper introduces an assessment of the representation of shape parameter measurements on theoretical particles. The aim of the study was to establish a numerical method for estimating sphericity, roundness, and roughness on artificially designed particles and to evaluate their interdependence. The parameters studied included a fractal dimension (FD), solidity (So), Wadell's roundness (Rw), a perimeter-area normalized ratio (¥), and sphericity (S). The methods of the work included: (a) the design of theoretical particles with different shapes, (b) the definition of optimal analysis conditions for automated measurements, (c) the quantification of particle parameters by computer vision-based image processing, and (d) the evaluation of interdependence between the parameters. The study established the minimum sizes required for analysis of the particle shape. These varied depending on the method used (150 pixels or 50 pixels). Evaluating the relationships between the parameters showed that FD and So are independent of S. Nevertheless, Rw and ¥ are clearly dependent on S and, thus, must be numerically corrected to Rwc and ¥c. FD, So, Rwc, and ¥c were used to establish, mathematically, a new regularity parameter (RBC) that reflects the degree of roundness of a particle. The process was applied to a case study and the evaluation of all parameters corroborated previous petrographic characterizations. Minerals 2019, 9, 768 2 of 21 corners of the particle. Six categories of roundness for sediment grains have been established and, for each category, one grain of low and one of high sphericity was introduced [3,6-9]. The six categories are: Very angular, angular, subangular, sub-rounded, rounded, and well-rounded. Two-dimensional particle shape measurements are particularly applicable when individual particles cannot be extracted from the rock matrix (e.g., thin sections under an optical microscope). Microscopic images are two-dimensional. Therefore, they only show part of the shape of the three-dimensional particle. The assessed image is usually of particles lying on their most stable plane on a flat support, i.e., showing the largest projection area.Traditionally, roundness indices compare the outline of a 2D projection of the particle to a circle. The first comparison defines the roundness as the ratio ri/R, which was shown in [10] (where ri is the radius of the sharpest corner, and R is the radius of the smallest circumscribing sphere). On the other hand, [11] defined the roundness parameter based on the radius of the curvature of particle corners and the radius of the largest inscribed sphere.[6] and [7] used comparison charts with a class limit table for roundness. Some authors considered angularity to be the opposite of roundness, while others considered the degree of angularity [12] to be a combination of the angular relationship between the planes bounding a corner and the distance of the corner from the center of the particle. The overall particle form heavily influences the method. In addition, [12] presente...

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Section: Representativity Of the Shape Parameters Studiedmentioning

confidence: 99%

Representativity of 2D Shape Parameters for Mineral Particles in Quantitative Petrography

et al. 2019

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“…However, basic elements commonly used in DEM are regular geometric entities with smooth surface. An increasing attention [3,4,5,6] has been focused on the influence of geometric uncertainty on the mechanical behaviour of the particulate systems while the related work is mostly concentrated on the macroscopic level [7,8,9,10,11,12,13,14].…”

Section: Introductionmentioning

confidence: 99%

Extended Greenwood–Williamson Models for Rough Spheres

Zhao

Feng

2018

Journal of Applied Mechanics

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The current work aims to develop two extended Greenwood–Williamson (GW) models for spherical particles with surface roughness which can be incorporated into the discrete element modeling (DEM) framework. The defects of the classic GW model when directly adopted in DEM are fully addressed and illustrated by both theoretical and numerical results. The first model, the extended elastic GW (E-GW) model, which evaluates the elastic deformation of the asperities and the bulk substrate separately is developed to consider the positive overlap involved in the contact problem. The capability of incorporating the extended elastic model into the DEM is illustrated by the comparison between the classic and extended models. The second model, the extended elasto–plastic GW (EP-GW) model, is further developed to consider the plastic deformation of the asperities which reduces the pressure increased by the surface roughness. Numerical comparisons between the E-GW and EP-GW models are also conducted to demonstrate the effect of the plastic deformation on the pressure and deformation distributions in the contact region.

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“…The surfaces of all the elements are assumed to be smooth. Issues related to geometric uncertainty and its influence on the mechanical behaviour of the particulate system are gaining an increasing attention . In addition to representing complicated shapes by bonding or clumping together several basic entities, there has been a continuous effort in DEM to introduce nonspherical entities such as polygons, polyhedra, super‐quadrics, cylinders, etc .…”

Section: Introductionmentioning

confidence: 99%

“…Issues related to geometric uncertainty and its influence on the mechanical behaviour of the particulate system are gaining an increasing attention. 3,4 In addition to representing complicated shapes by bonding or clumping together several basic entities, [5][6][7][8][9] there has been a continuous effort in DEM to introduce nonspherical entities such as polygons, polyhedra, super-quadrics, cylinders, etc. [10][11][12][13][14][15] Note that such solutions for modelling irregularities of real particles are mostly focused on the macroscopic level.…”

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confidence: 99%

An extended Greenwood‐Williamson modelbased normal interaction law for discrete element modelling of spherical particles with surface roughness

Zhao

Feng

Wang

2018

Num Anal Meth Geomechanics

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Summary The current work aims to develop an improved random normal interaction law based on an extended Greenwood‐Williamson (GW) model for spherical particles with surface roughness in the discrete element modelling of particle systems. The extended GW model overcomes some theoretical defects of the classic GW model when incorporated into the discrete element framework. Based on 2 nondimensional forms in which only 2 surface roughness parameters are involved, an empirical formula of the improved interaction law is derived by the curve‐fitting technique. The resulting interaction law is incorporated into discrete element modelling to investigate the mechanical response of particle systems with different surface roughness. Numerical simulations are performed to model 1‐dimensional and 3‐dimensional compression tests to explore the macro and micro characteristics of granular particles with surface roughness. The results show that surface roughness makes the initial packing of a particle assembly looser and has a greater influence on looser packed samples as expected, but an assembly with moderate roughness may exhibit a higher strength. The limitations of the current development are also highlighted.

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Particle Roundness and Sphericity from Images of Assemblies by Chart Estimates and Computer Methods

Cited by 81 publications

References 38 publications

Representativity of 2D Shape Parameters for Mineral Particles in Quantitative Petrography

Representativity of 2D Shape Parameters for Mineral Particles in Quantitative Petrography

Extended Greenwood–Williamson Models for Rough Spheres

An extended Greenwood‐Williamson modelbased normal interaction law for discrete element modelling of spherical particles with surface roughness

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