(130g) A Modified Rolling Theory for Granular Solids

A modified Johanson roll compaction model is proposed. The model improves upon the original Johanson model by introducing a solution that satisfies mass conservation at the nip angle, which is achieved through assuming the existence of a transition zone. This supposition of a transition zone enables the description of a progressive change in powder velocity through the nip region, whereas earlier approaches required an abrupt shift. By further assuming a density and velocity profile in the transition zone, solutions for the powder density at the minimum gap width and roll normal stress distribution are presented. Validation of the modified model against available literature roll compaction run data shows that it is capable of capturing the trends observed from the experimental data accurately. Quantitatively, the RMS error between the model predictions and the experimentally measured counterparts is 0.013 and 8.04 MPa, or 1.84% and 8.36% of the average of the experimentally measured ribbon densities and maximum roll normal stresses, respectively.