A rotational tester for the characterization of aerated shear flow of powders

A rotational shear tester for aerated shear flow was built on the work bench of a Peschl shear tester. Measurements with a conventional incipient shear test procedure and a purposely developed dynamic shear test procedure were carried out on two different cohesive powders: a magnesium carbonate powder and a silica powder. Permeability measurements were carried out in the dynamic shear test experiments to assess the effect of shearing. The results obtained at low powder consolidation levels confirm literature findings at higher degrees of consolidation. In particular, aeration does not appear to have the ability to change the rheological properties of the powder. Shear test results at different aeration intensities are the same if the stress changes induced by aeration on the shear plane are correctly accounted for. Permeability measurements were compared following uniaxial powder compaction and shearing powder compaction experiments. The internal powder structure of the magnesium carbonate powder appeared to change between experiments. Further investigations are required to determine if this change also occurs with the silica powder.