SIMULATION OF CHARGE AND STRUCTURE BEHAVIOUR IN A TUMBLING MILL

For a long time discrete element methods (DEM) has been used as simulation tools to gain insight into particulate flow processes. Such a process may be grinding in tumbling mills, where the mechanical behaviour is complex. To include all phenomena that occur in a mill in a single numerical model is today not possible. Therefore, a common approach is to model milling charges using the DEM assuming a rigid mill structure. To close the gap between reality and numerical models in milling, more physically realistic methods must be used. In this work, the finite elem ent method (FEM) and the smoothed particle hydrodynamic (SPH) method are used together to model a ball mill charge in a tumbling mill. The mesh free formulation and the ad aptive nature of the SPH method result in a method that handles extremely large def ormations and thereby suits for modelling of grinding charges. The mill structure c onsists of rubber lifter and liners and a mantel made of solid steel. It is modelled with t he finite element method. For the elastic behaviour of the rubber, a Blatz-Ko hyper-e lastic model is used. The supplier of the lining provided experimental data for the rubbe r. The deflection profile of the lifters obtained from SPH-FEM simulation shows a reasonably good correspondence to pilot mill measurements as measured by an embedded strain gauge sensor. This computational model makes it possible to predict ch arge pressure and shear stresses within the charge. It is also possible to predict c ontact forces for varying mill dimensions and liner combinations.