2005 Volume 23 Pages 152-162
Modeling of Mechanical Alloying (MA), which is a solid-state powder processing technique, is carried out by examining one widely used laboratory scale milling device, the SPEX 8000 shaker mill. It is a vibratory mill; its vial is agitated at a high frequency in a complex cycle that involves motion in three orthogonal directions. In this work, a popular dynamic simulation technique, Discrete Element Modeling, is applied to examine dynamics of a SPEX 8000 shaker ball mill based on the movement of milling balls. The computational results for energy dissipation rate inside the mill are calculated for different ball sizes and varied total ball to powder mass ratios (charge ratios). The computational results are well correlated with the experimental results tracking milling dose (used to define the degree of milling) as a function of ball sizes and charge ratios. Moreover, the numerical (theoretical) milling dose that correlates well with its experimental analog was found to depend on the energy dissipation rate of the head-on ball collisions. The numerical simulations also indicated that the milling progress is most significantly affected by milling media collisions with the energy within a specific threshold, while the collisions with smaller and greater energies are less effective. Finally, discussion shows how this novel approach of correlating specific scaling terms between experiments and simulations can be applied to other powder processing equipment.
