Flowability assessment of weakly consolidated powders

Abstract

The inability of cohesive powders to flow consistently and reliably is a major cause of process downtime and reduced efficiency across a wide range of powder processing industries. Most methods to assess powder flowability fail at low consolidation pressures (<1 kPa). In this paper, the ball indentation technique is used to assess the flow behaviour of two powders at low stresses by determining the bed hardness. In parallel, the powders are subjected to shear testing in a range of high stresses, with the derived unconfined yield strength used, along with the indentation hardness to define the constraint factor (C). By using the latter, which is considered independent of the preconsolidation stress applied, the unconfined yield strength of the powders at low stresses are inferred from the penetration hardness measurements.