Evaluation of Powder Flow Prediction by Ring Shear Testing at Low Consolidation Stresses

Abstract

The development of XS-Lr0 low-stress shear cell by Dietmar Schulze (model RST-XS.s) has confirmed the necessity of assessing powder flow at low consolidation stresses for improved powder flow production (Søgaard et al.,2014). This project assessed different powder flow properties at low consolidation stresses via stress walk and discrete shear tests. Previous methodology by Sogaard et al, 2014 was investigated and further developed using different pharmaceutical materials at a wide range of consolidation stresses (0.25 – 4.00 kPa). A polynomial function best described the relationship between consolidation stress and unconfined yield strength, with results being material dependent. The lowest pre-consolidation stress observed for reliable measurements was 0.25 kPa. The findings emphasise the need to refine current methodologies to measure shear stresses at low consolidation stresses to improve powder flow prediction.