A model for the deformation of an ellipsoid subject to a large number of successive impacts with special reference to spheronisation

A method for modelling the deformation of a deformable ellipsoid subject to a large number of successive impacts is presented. The key element of the proposed approach is the contact law which determines the deformation of a sphere impacting with a rigid surface. This is applied to the ellipsoid using an algorithm which consists of creating an equivalent sphere for the deforming body, applying the contact law followed by an evolution law, which describes how the local contact flattening changes the shape of the body during successive impacts. The model can be used to provide insight into industrial processing operations where particulate materials undergo shape changes. A parametric study was performed to illustrate the effects of key material properties (which determine the deformation following an individual impact) and processing parameters (which specify impact velocity and location). It is shown that random impacts results in elongation of the ellipsoid. However, the impact conditions in specific particulate flow fields during processing are not random and can produce rounding as well as further elongation. The underlying assumptions of the model are discussed and the data requirements for the model are identified for the purpose of material design and process development for particulate materials.

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