Calibration and interpretation of DEM parameters for simulations of cylindrical tablets with multi-sphere approach


A. Kwade, J. H. Finke, R. Cabiscol




Powder Technology



Finishing and transport operations of pharmaceutical tablets such as coating and conveying processes can qualitatively be improved with a better understanding of the interplay of process parameters and product quality attributes.This study provides a first step towards the simulation of these processes with the calibration of the motion modelling of uniaxial-compressed cylindrical tablets using the multi-sphere approach (MS) within the Discrete Element Method (DEM). Only high accuracy in the representation of cylindrical tablet shape, especially regarding edges, yields a good agreement between simulated and experimental packing fraction. Sensitivity regarding model parameter calibration was evaluated based on tumbling drum tests which are of wide occurrence in the industry and the so-called pouring experiment extracting static and dynamic angles of repose, identified sliding and rolling friction as the most sensitive parameters.These were successfully calibrated by an iterative crossed analysis in tumbling drum and pouring tests. Additionally, a complete determination and subsequent calibration strategy is provided for Coefficient of Restitution and Young's modulus. Results of the final numerical modelling are qualitative and quantitative in agreement with experimental test case experiments. A final validation is performed through the simulation of an attrition tester with a single baffle, highlighting one of the main limitations of DEM: the problem-targeted nature of the operation of calibration.


Calibration, cylindrical, Drum, Tablet

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