Abstract
Powder flow characterization with some of the conventional shear testers can be costly, time consuming and requires a trained operator, therefore the application of a cheaper, simpler, and sometimes faster uniaxial compaction tester (UCT) have often been suggested as an alternative. However, it has been known for many years that the results derived from the two methods are not necessarily the same, due to the lower state of compaction attained in the traditional design of UCT. Additionally, the traditional design of UCT tends to give a wide scatter in the results. To overcome these limitations of the UCT, this work developed an easy-to-use uniaxial tester in order to reduce the difference between flow properties reported by the two techniques. In this regard, flow functions of four powders in the cohesive and very cohesive range were measured with shear testers, conventional uniaxial compaction tester (UCT) and the new uniaxial tester at the University of Greenwich (“Greenwich Uniaxial Tester” or GUT). A method in the style of Janssen approach for correcting wall friction effect on the compaction stress of UCT was applied. Results showed the unconfined yield strength attained from GUT is in line with the results obtained from shear testers while the results from UCT are well below the shear tester results suggesting the advantage of the new GUT.
