Change search
ReferencesLink to record
Permanent link

Direct link
An experimental evaluation of the accuracy to simulate granule bed compression using the discrete element method
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
2012 (English)In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, no 219, 249-256 p.Article in journal (Refereed) Published
Abstract [en]

In 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 mu m 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, description of granule bed compression at high relative densities and hence may be used as a basis for future improvements.

Place, publisher, year, edition, pages
2012. no 219, 249-256 p.
Keyword [en]
Compression, Discrete element method, Contact model, Plastic overlap, Elastic deformation
National Category
Pharmaceutical Sciences
URN: urn:nbn:se:uu:diva-172045DOI: 10.1016/j.powtec.2011.12.054ISI: 000301310400033OAI: diva2:513369
Available from: 2012-04-02 Created: 2012-04-01 Last updated: 2014-05-05Bibliographically approved
In thesis
1. Flow and Compression of Granulated Powders: The Accuracy of Discrete Element Simulations and Assessment of Tablet Microstructure
Open this publication in new window or tab >>Flow and Compression of Granulated Powders: The Accuracy of Discrete Element Simulations and Assessment of Tablet Microstructure
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Simulations are powerful and important tools for gaining insight into powder processes. Ultimately, simulations have the potential to replace experiments. Thus, accurate models and insight into the essential factors for descriptions of powder behaviour are required. In this thesis, discrete element method (DEM) simulations of granule flow and compression were evaluated to deduce parameters and potential models essential for the experimental and numerical correspondence. In addition, the evolution in tablet microstructure during compression was studied using mercury porosimetry.

Granule flow was measured using angle of repose, discharge rate, and shear. The granular flow depended primarily on particle shape and surface texture due to the mutual influence of these two parameters on the inter-particle forces. Rolling friction stabilised both the heap formation and promoted shear in the elastic quasi-static flow regime. Thus, rolling friction was established to be an essential simulation parameter for the correspondence to experiments.

Current compression models often neglect the elastic compact deformation during particle loading. In this thesis, two fundamentally different models were evaluated with focus of including the elastic deformation. The first model comprised a maximal particle overlap, where elastic deformation commences. The second model accounted for the contact dependence and impingement at high relative densities. This model was based on a truncated-sphere followed by a Voronoi extension. The validity of the models was demonstrated by the elastic qualitative correspondence to experimental compressions for ductile materials.

In tablets, the void (inter-granular pore) diameter was dependent on the degree of compression. Thus, the degree of compression provides an indication of the tablet microstructure. The microstructure was subsequently observed to be related to the tablet tensile strength as inferred from a percolation threshold required for formation of coherent tablets.

In summary, this thesis has shed light onto the potential of simulating flow and compression of granulated pharmaceutical powders using DEM. Continuous work in the area are required to further improve the models to increase the experimental and numerical correspondence.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 65 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 180
Discrete Element Method, Granule, Flow, Angle of Repose, Discharge Rate, Shear, Rolling friction, Compression, Elastic deformation, Microstructure, Degree of compression, Tensile strength
National Category
Pharmaceutical Sciences
Research subject
urn:nbn:se:uu:diva-208808 (URN)978-91-554-8769-0 (ISBN)
Public defence
2013-11-22, B42, BMC, Husargatan 3, Uppsala, 09:15 (Swedish)
Available from: 2013-10-30 Created: 2013-10-08 Last updated: 2014-01-23

Open Access in DiVA

fulltext(765 kB)108 downloads
File information
File name FULLTEXT01.pdfFile size 765 kBChecksum SHA-512
Type fulltextMimetype application/pdf

Other links

Publisher's full text

Search in DiVA

By author/editor
Persson, Ann-SofieFrenning, Göran
By organisation
Department of Pharmacy
In the same journal
Powder Technology
Pharmaceutical Sciences

Search outside of DiVA

GoogleGoogle Scholar
Total: 108 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 253 hits
ReferencesLink to record
Permanent link

Direct link