Discrete modeling of rockfill materials considering the irregular shaped particles and their crushability

Journal of Applied Mechanics

2018

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.

Section: Introductionmentioning

confidence: 99%

Extended Greenwood–Williamson Models for Rough Spheres

Zhao

Journal of Applied Mechanics

2018

“…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 . Note that such solutions for modelling irregularities of real particles are mostly focused on the macroscopic level.…”

Section: Introductionmentioning

confidence: 99%

“…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.…”

mentioning

confidence: 99%

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

Zhao

Num Anal Meth Geomechanics

Wang

2018

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.

“…There has been an increasing interest, particularly in industrial applications, in using nonspherical particle shapes as primitive discrete elements. Since the 1980s, there has been a continued effort to develop discrete element models for non-spherical primitive objects, such as ellipses [2,3,4], ellipsoids [6,7], super-quadrics [5,12], dilated shapes [8], polygons [9,13] and polyhedra [10,11,13,14]. However, there is still a lack of theoretically derived contact models for non-spherical shaped particles in general [15] and non-smooth particles with edges and sharp corners in particular.…”

Section: Introductionmentioning

confidence: 99%

A generic contact detection framework for cylindrical particles in discrete element modelling

Computer Methods in Applied Mechanics and Engineering

Han

Owen

2017

This paper aims to develop a generic framework for detecting contact between cylindrical particles in discrete element modelling based on a full exploitation of the axisymmetrical property of cylinders. The main contributions include: 1) A four-parameter based local representative system is derived to describe the spatial relationship between two cylinders so that the 3D cylinder-cylinder intersection problem can be reduced to a series of 2D circle-ellipse intersections, which considerably simplifies the contact detection procedure. 2) A two-stage contact detection scheme is proposed in which no-overlap contact pairs are identified in the first overlap check stage, and then the actual overlap region is determined in the second resolution stage and represented by two schemes: the layered representation which is generic, and the edge representation which is numerically more efficient but less accurate. 3) The most significant contribution is the development of two theorems that establish a fundamental relationship between the contact point and contact normal of two contacting cylinders, offering a simple approach to determining the normal direction based on the contact point and vice versa. These theorems are valid not only for cylinders, but also for any axi-symmetrical shapes and their combinations. Some numerical issues are discussed. Numerical examples are presented to illustrate the capability and applicability of the proposed methodologies.