The complete characterization of powder flow properties with shear cells is a long and time consuming process that requires specially trained operators. For these reasons, in the industrial practice simpler and less extensive measurement by uniaxial compaction testers is often preferred. However, previous studies in the literature indicate that the results of the two techniques are not directly comparable due to different stress state conditions achieved in the two testers. In this study an experimental campaign to measure the flow function of four different powders with a ring shear tester (RST) and a uniaxial compaction tester (UCT) was performed. Different flowability results arisen for the more cohesive powders are explained with the wall friction effect in the UCT. Re-evaluation of the results accounting for the wall friction gave substantial agreement between the two experimental techniques. The major application limit of the UCT concerning the large minimum consolidation stress value that can be applied on a powder sample was confirmed. The comparison between the two techniques results suggests that straightforward extrapolation of the UCT flow functions to low consolidation condition can lead to underestimation of powder cohesion.
The assessment of a simple method for powder flow characterization
BARLETTA, Diego;POLETTO, Massimo
2006-01-01
Abstract
The complete characterization of powder flow properties with shear cells is a long and time consuming process that requires specially trained operators. For these reasons, in the industrial practice simpler and less extensive measurement by uniaxial compaction testers is often preferred. However, previous studies in the literature indicate that the results of the two techniques are not directly comparable due to different stress state conditions achieved in the two testers. In this study an experimental campaign to measure the flow function of four different powders with a ring shear tester (RST) and a uniaxial compaction tester (UCT) was performed. Different flowability results arisen for the more cohesive powders are explained with the wall friction effect in the UCT. Re-evaluation of the results accounting for the wall friction gave substantial agreement between the two experimental techniques. The major application limit of the UCT concerning the large minimum consolidation stress value that can be applied on a powder sample was confirmed. The comparison between the two techniques results suggests that straightforward extrapolation of the UCT flow functions to low consolidation condition can lead to underestimation of powder cohesion.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
