Tensile strength of pressure-agglomerated potato starch determined via diametral compression test: Discrete element method simulations and experiments
AUTHOR(S)
J. Horabik, J. Wiącek, M. Banda, M. Molenda, M. Stasiak, P. Parafiniuk
PUBLISHER
Elsevier
SOURCE
Biosystems Engineering
YEAR
ABSTRACT
Starch is important excipient and binder in agglomerates, tablets, capsules, briquettes, and pellet formulations for food, pharmaceutical, biomass, coal/biomass fuel, and metallurgy applications. The aim of this study was to compare the results of determination of the tensile strength of cylindrical starch agglomerates via a diametral compression test using a macro-approach following Hertz's solution, with those obtained via the micro-approach using the discrete element method (DEM). Potato starch with moisture contents of 12% and 17% was compacted in a cylindrical die 10 mm in diameter with a displacement velocity of 0.02 mm s−1 and compressed to 38, 76, 115, and 153 MPa. The tensile strength was measured in the diametral compression test with a deformation rate of 0.033 mm s−1. EDEM software was used to perform numerical simulations. The components of the stress tensor in the agglomerate were determined in the representative volume element with the shape of a cuboid (0.25 × 0.25 × 1 mm3). DEM simulations using the linear elastic–plastic model with linear adhesion exhibited good agreement with the experimental results. With the agglomerate deformation, the curvature of the compressive-force chains—in the shape of two arches combined with the tension-force chains—increased. At failure, the crack was initiated in the vicinity of the agglomerate centre and propagated towards the loading platens, damaging the connections between the compressive-force chains. Hertz's formula correctly described the tensile strength of the agglomerates for an adhesive stiffness-to-plastic stiffness ratio higher than 0.04.
KEYWORDS
Diametral-Compression Test, Pressure agglomeration, Starch, Tensile strength