Prediction of mill structure behaviour in a tumbling mill

Computational demands and the lack of detailed experimental verification have limited the value of distinct element method (DEM) modelling approaches in mill simulation studies. This paper presents the results of a study in which the deflection of a lifter bar in a pilot ball mill is measured by an embedded strain gauge sensor and compared to deflections predicted from finite element (FE) simulations. The flexible rubber lifter and the lining in a tumbling mill are modelled with the finite element method (FEM) and the grinding medium is modelled with DEM. The deflection profile obtained from DEM–FE simulation shows a reasonably good correspondence to pilot mill measurements. To study the charge impact on the mill structure two different charges are used in the simulations. The approach is a contribution to the validation of DEM–FE simulations and an introduction to the description of a bendable rubber lifter implemented in a DEM–FEM mill model. It opens up the possibility to predict contact forces for varying mill dimensions and liner combinations. FEM is especially valuable in this case, since there are readily available libraries with material models.

Research highlights
► Combined DEM-FEM mill model.
► Predicts mechanical responses for the whole mill.
► Direct coupling between force, stress and deflection for the whole mill system.
► Predict forces travelling in the lining.