The influence of rolling friction on the shear behaviour of non-cohesive pharmaceutical granules – An experimental and numerical investigation

Abstract

Granule shear behaviour was investigated experimentally and numerically to evaluate the reliability of the numerical model. Additionally, parameters affecting the ensuing flow regimeselastic quasi-static and inertial non-collisional -were highlighted. Furthermore, the influence of using the Lees-Edwards periodic boundary conditions or the standard boundary conditions was studied. Experiments were performed with microcrystalline cellulose granules of three size distributions using the FT4 powder rheometer. The numerical parameters, particle size, effective density, and particle stiffness were selected to match the experimental conditions. Experimentally, an unexpected particle size effect was evident where the resistance to shear increased with particle size. Numerically, combining rolling friction and increased shear rate enabled a transition from the inertial non-collisional to the elastic quasi-static regime at a reduced sliding friction coefficient. Presumably, this is an effect of increased particle overlap creating stronger contacts and facilitating force chain formation. Both boundary conditions provided comparable results provided a correction of system size was made, where larger systems were required for the standard boundary conditions. A satisfactory qualitative agreement between the experimentally and numerically determined yield loci emphasised the predictive capacity of the DEM. Rolling friction was in addition concluded to be an essential model parameter for obtaining an improved quantitative agreement.2

Efficient Voronoi volume estimation for DEM simulations of granular materials under confined conditions

“…The initial particle bed had a height of about 5.25 mm and the upper punch was lowered at a rate of 5 mm/s for a period of 0.52 s until a nonporous compact was formed. For illustrative purposes, a standard contact model of the linear spring–dashpot type was used as described in [6] . The particle density was 1.45 g/cm 3 and the normal and tangential stiffness were 100 N/mm.…”

Determination of Material and Interaction Properties of Granular Fertilizer Particles Using DEM Simulation and Bench Testing

“…Lu et al [18] optimized the DEM simulation parameters of the static friction coefficient between bud seeds and stainless plate and the rolling friction coefficient between bud seeds. Irazábal et al [19] investigated bounded rolling friction for spherical discrete element particles, and Persson and Frenning [20] analyzed the effects of rolling friction on the shear behavior of granular particles.…”

Characterisation of Titanium Powder Flow, Shear and Bulk Properties Using the FT4 Powder Rheometer

“…Several powder rheometers are available of which the FT4 powder rheometer is one of them. The FT4 powder rheometer is a fairly new technique in metal powder characterisation even though it has been extensively used in the characterisation of pharmaceutical powders [4][5][6][7].…”