An experimental evaluation of the accuracy to simulate granule bed compression using the discrete element method

Abstract

PostprintThis is the accepted version of a paper published in Powder Technology. This paper has been peerreviewed but does not include the final publisher proof-corrections or journal pagination.Citation for the original published paper (version of record):Persson, A., Frenning, G. (2012) An experimental evaluation of the accuracy to simulate granule bed compression using the discrete element method. AbstractIn this work, granule compression is studied both experimentally and numerically with the overall objective of investigating the ability of the discrete element method (DEM) to accurately simulate confined granule bed compression. In the experiments, granules of microcrystalline cellulose (MCC) in the size range 200-710 µm were used as model material. Unconfined uniaxial compression of single granules was performed to determine granule properties such as the yield pressure and elastic modulus and compression profiles of the MCC granules were obtained from granule bed compression experiments. By utilizing the truncated Hertzian contact model for elastic-perfectly plastic materials, the rearrangement and plastic deformation stages of the force displacement curve were found to be in reasonable agreement with experiments. In an attempt to account for the final compression stage, elastic deformation of the compact, a simple modification of the contact model was proposed. This modification amounted to the introduction of a maximal plastic overlap, beyond which elastic deformation was the only deformation mode possible. Our results suggest that the proposed model provides an improved, although not perfect, 2 description of granule bed compression at high relative densities and hence may be used as a basis for future improvements.

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

“…As previously determined (Persson and Frenning, 2012) the particle size distributions for the C200 and C350 were consistent with the specifications made by the manufacturer (≥ 85% within the stated range). In addition, the determined median particle size (d 50 ) (Table 1) for the respective granules was found to be larger than the mean particle size calculated from the specified range.…”

“…The critical filling fractions were determined from the intersection of two regression lines. b Obtained from (Persson and Frenning, 2012).…”

“…This indicates that the particle stiffness was overestimated when determined from the plastic part of the force-displacement correlation during single granule compression (Persson and Frenning, 2012).…”

“…Median particle size: The particle size distribution of C200 and C350 was determined in a previous work (Persson and Frenning, 2012) using a flatbed scanner. The same method was however not usable for the C100 granules due to limitations in the image resolution (1600 dpi).…”

The degree of compression of spherical granular solids controls the evolution of microstructure and bond probability during compaction

“…During loading of single pellets, a linear relationship between the applied pressure and the strain was reported (Nordström et al, 2008a) in a region suggested to be characterised by plastic deformation of pellets. The compression of a bed of pellets can be viewed as controlled by the deformation of load bearing columns of pellets (Adams et al, 1994;Persson and Frenning, 2012). The linear relationship between void size and the degree of compression can thus be explained by a direct relationship between degree of compression of the bed of pellets and the plastic deformation of the single pellets.…”