Abstract
This paper describes a new method for representing concave polyhedral particles in a discrete element method as unions of convex dilated polyhedra. This method offers an efficient way to simulate systems with a large number of (generally concave) polyhedral particles. The method also allows spheres, capsules, and dilated triangles to be combined with polyhedra using the same approach. The computational efficiency of the method is tested in two different simulation setups using different efficiency metrics for seven particle types: spheres, clusters of three spheres, clusters of four spheres, tetrahedra, cubes, unions of two octahedra (concave), and a model of a computer tomography scan of a lunar simulant GRC-3 particle. It is shown that the computational efficiency of the simulations degrades much slower than the increase in complexity of the particles in the system. The efficiency of the method is based on the time coherence of the system, and an efficient and robust distance computation method between polyhedra as particles never intersect for dilated particles.
Highlights
BackgroundMost 3D discrete element method (DEM) models use spherical particles because of their efficiency and simplicity
Spherical particles are not well suited to represent angular particles as their ability to interlock with neighboring particles is limited
We present a novel method of modeling arbitrary discrete element method (DEM) polyhedral particles by a union of convex dilated polyhedra with triangular faces or the ‘Intersecting Dilated Convex Polyhedra’ (IDCP) method
Summary
Most 3D discrete element method (DEM) models use spherical particles because of their efficiency and simplicity. Porosity is unavoidable in modeling solid materials, which can affect the ability to accurately simulate microscale mechanical deformation processes Another difficulty occurs when trying to represent particle interlocking and dilation that occurs during the deformation and failure of granular materials [1]. In [8], polyhedra particles are represented as a union of independent spheres, cylinders, and triangular faces that establish independent contacts with each other This allows concave shapes to be simulated but makes it difficult to accurately calculate the particle’s mechanical properties, such as center of mass and inertia tensor. This approach results in counting the same particle overlap between two particles multiple times, which leads to improper contact mechanics. The computational efficiency of simulations is significantly degraded by the complexity of using many independent parts in the polyhedra representation
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