Comparison of Cohesive Models in EDEM and LIGGGHTS for Simulating Powder Compaction

Abstract

The purpose of this work was to analyse the compaction of a cohesive material using different Discrete Element Method (DEM) simulators to determine the equivalent contact models and to identify how some simulation parameters affect the compaction results (maximum force and compact appearance) and computational costs. For this purpose, three cohesion contact models were tested: linear cohesion in EDEM, and simplified Johnson-Kendall-Roberts (SJKR) and modified SJKR (SJKR2) in LIGGGHTS. The influence of the particle size distribution (PSD) on the results was also investigated. Further assessments were performed on the effect of (1) selecting different timesteps, (2) using distinct conversion tolerances to export the three-dimensional models to standard triangle language (STL) files, and (3) moving the punch with different speeds. Consequently, we determined that a timestep equal to a 10% Rayleigh timestep, a conversion tolerance of 0.01 mm, and a punch speed of 0.1 m/s is adequate for simulating the compaction process using the materials and the contact models in this work. The results showed that the maximum force was influenced by the PSD due to the rearrangement of the particles. The PSD was also related to the computational cost because of the number of simulated particles and their sizes. Finally, an equivalence was found between the linear cohesion and SJKR2 contact models.

Numerical Modeling for Simulation of Compaction of Refractory Materials for Secondary Steelmaking

“…The "modified simplified Johnson-Kendall-Roberts (SJKR2)" contact model was used in LIGGGHTS. In a previous work [36], the equivalence between these contact models was discussed. Both models work in combination with the Hertz-Mindlin contact model and complement it by the addition of a normal cohesion force.…”

“…Finally, the same STL files were imported into both DEM simulators. In a previous work [36], the influence of using different conversion tolerances was analyzed. A value of 0.01 mm was considered optimum to convert similar geometries.…”

“…A timestep equivalent to approximately 10% of the Rayleigh timestep was fixed in all simulations. In a previous work [36], this value was considered optimum for simulating the compaction process, using the same contact models that were used in this work. The effect of gravity force was taken into account in all simulations.…”

“…Soltanbeigi et al have also made a complete comparison between the results obtained with EDEM and LIGGGHTS, using nonspherical particles that include heap formation, direct shear test, and silo discharge [35]. In a previous work [36], three cohesive contact models implemented in different DEM simulators were used to examine their applicability to simulate the powder compaction. Several simulations were conducted for this purpose, which allowed to analyze the effects of some parameters on the results.…”

“…In this work, the compaction of a refractory mixture to form a green compact was analyzed using DEM. Simulations were conducted using the equivalent contact models implemented in two DEM software packages that were determined previously [36]. A design of experiments (DOE) that comprehended 15 simulations was conducted to examine the influence of three parameters (Young's modulus, cohesion energy density and particle size).…”