Discrete element model for an attritor mill with impeller responding to interactions with milling balls

This work advances discrete element modeling (DEM) as a tool for predicting milling progress for mechanical alloying, reactive milling, and similar mechanical milling-based techniques for material preparation and modification. DEM is used to predict the rate of energy dissipation by the milling tools, which is correlated with the milling progress. The model is considered for attritor mills, which are most likely to be used in industrial settings. In attritor mills, milling balls may jam causing an increased resistance to the impeller's rotation. The impeller may, therefore, instantaneously slow down, quickly returning to its pre-set rotation rate. Previous DEM models did not account for such rapid changes in the impeller's rotation rate, which caused gross errors in the predicted rates of energy dissipation. Experiments using a laboratory mill established a correlation between the impeller's torque and instantaneous rotation rate. This correlation was programmed in a DEM model, where changes in the rotation rate could occur because of the impeller's interaction with milling balls. Predicted energy dissipation rates were shown to correlate well with the experimental data. A modified DEM approach enables one to accurately predict milling conditions for different scale attritor mills necessary for manufacturing advanced materials.