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Please cite this article as: M. Broseghini, M. D'Incau, L. Gelisio, N.M. Pugno, P. Scardi, Effect of jar shape on high-energy planetary ball milling efficiency: Simulations and experiments, (2016), AbstractEnhanced comminution in a planetary ball mill was achieved by suitably re-designing the jar shape. Compared with a traditional cylindrical vial of circular cross-section, the new jar was modified internally to have a flat wall portion resulting in a half moon cross-section. Results from simulations, using a multibody dynamics software, suggest that this geometry increases the number of high-velocity collisions with energy exchange along the axial direction, deemed as more effective in the comminution process. X-ray diffraction line profiles of calcium fluoride (CaF 2 ) ground in the two jars under equivalent conditions were used to obtain information on the microstructure resulting from the milling process and validate the modelling results. A better homogeneity and a faster reduction of crystallite size was achieved using the new design compared to that using the standard cylindrical vial design. Optimal operating conditions, in terms of jar-to-plate angular velocity ratio, are correlated and discussed according to the model predictions.

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This paper contains data and supporting information of and complementary to the research article entitled “Effect of jar shape on high-energy planetary ball milling efficiency: simulations and experiments” (Broseghini et al.,) [1]. Calcium fluoride (CaF2) was ground using two jars of different shape (cylindrical and half-moon) installed on a planetary ball-mill, exploring different operating conditions (jar-to-plate angular velocity ratio and milling time). Scanning Electron Microscopy (SEM) images and X-Ray Powder Diffraction data (XRPD) were collected to assess the effect of milling conditions on the end-product crystallite size. Due to the inhomogeneity of the end product, the Whole Powder Pattern Model (WPPM, (Scardi, 2008) [2]) analysis of XRPD data required the hypothesis of a bimodal distribution of sizes – respectively ground (fine fraction) and less-to-not ground (coarse fraction) – confirmed by SEM images and suggested by the previous literature (Abdellatief et al., 2013) [3,4]. Predominance of fine fraction clearly indicates optimal milling conditions.

The instability behaviour of eccentrically loaded circular masonry columns is investigated. Two approaches are considered for the analysis. One is based on a semi-analytical formulation of the relevant boundary-value problem for a no-tension material response; the other employs a plasticdamage-contact constitutive model, the CraftS model, to capture the complex microstructural behaviour of the material. The latter has been implemented in the finite element program LUSAS and has been already successfully employed to describe progressive instability in eccentrically loaded brickwork wallettes of rectangular cross section. Equilibrium paths and limit load estimations are computed for both analysis approaches for a range of column aspect ratios and load eccentricities. It is shown that the type of material response becomes less important for specimens with height-to-diameter aspect ratios greater than 7.5 and for loads applied to points in the kernel of the cross section, while for higher eccentricities the presence of a tensile strength increases considerably the limit load. The damage evolution predicted by the models is also investigated for selected cases, showing that the formulation based on the no-tension material is able to capture with good agreement the damaged zone of the column for loads with low eccentricities. For the same type of loading, a useful design formula is provided.