Discrete-element model for dynamic fracture of a single particle

Abstract

a b s t r a c tWe investigate the dynamic fracture of a single particle impacting a flat surface using 3D DEM simula-tions based on a fragmentation model involving both a stress threshold and a fracture energy. The particle is assumed to be perfectly rigid and discretized into polyhedral Voronoï cells with cohesive interfaces. A cell-cell interface loses its cohesion when it is at a normal or tangential stress threshold and an amount of work equal to the fracture energy is absorbed as a result of the relative cell-cell displacements. Upon impact, the kinetic energy of the particle is partially consumed to fracture cell-cell contacts but also restituted to the fragments or dissipated by inelastic collisions. We analyze the damage and fragmenta-tion efficiency as a function of the impact energy and stress thresholds and their scaling with fracture energy and impact force. In particular, we find that the fragmentation efficiency, defined as the ratio of the consumed fracture energy to the impact energy, is unmonotonic as a function of the impact energy, the highest efficiency occurring for a specific value of the impact energy.

Discrete-element simulations of comminution in rotating drums: Effects of grinding media

“…In the same way, the effect of the ratio C t /C n needs to be investigated. Previous simulations seem to indicate that the dynamic fracture of individual particles by impact is only marginally affected by this parameter [29]. The ternary model of population balance is obviously a rough description of the evolution of particle volumes.…”

“…In both BPM and BCM, the large number of fragments, treated within the DEM as regular particles, requires a compromise between the number of crushable particles and the number of primary particles or cells in each particle. But, as the internal stresses of the particles are correctly (up to discretization effect) calculated, they yield physically correct estimates of the evolution of size distributions if the debonding criterion is consistent with the classical framework of fracture mechanics, as discussed in [29]. For example, the effects of particle fracture on dilatancy and evolution of the distributions of particle sizes and shapes under shearing, the shattering effect, the slow reduction of the sizes of the largest particles as a result of cushioning effect (redistribution of stresses by smaller fragments) and the power-law distribution of intermediate fragments sizes are observed in the DEM-BCM simulations [30].…”

“…The Bonded Cell Method (BCM) is an alternative approach in which the particles have a polygonal shape (or polyhedral in 3D) and they are tessellated into smaller polygonal cells [27,28,29]. Hence, there is no volume loss by body fragmentation of the particles.…”

Scaling behavior of particle breakage in granular flows inside rotating drums

“…In the BCM, each particle is subdivided into smaller independent primary elements or cells by means of a Voronoï tessellation, and thus the particle volume is exactly equal to the sum of cell volumes [26,27,29,30,34]. During the generation process, the average cell size d cell is fixed, but the cell shapes are random.…”

“…In this paper, we use numerical simulations to investigate the effect of system parameters on the grinding process in a 2D rotating drum. We rely on the contact dynamics method as a DEM algorithm and the discretization of the particles into bonded polygonal cells that an break apart, known as Bonded Cell Method (BCM) [10,[26][27][28][29][30]. The particles can thus break into fragments of different sizes down to the smallest cell size.…”