COMPUTER-CONTROLLED SHEAR CELL FOR MEASUREMENT OF FLOW PROPERTIES OF PARTICULATE MATERIALS

A shear tester for powders that allows the determination of a dynamic yield locus from a single test was built and tested. The principle of the computer controlled shear cell (CCSC) is that dynamic yield states can be maintained in a test cell over a range of normal and shear str esses in the same test. This leads directly to a dynamic yield locus. With its flexible design, the CCSC can also be used as a Jenike shear cell or a direct shear cell. The performance of the CCSC used as a dyn amic yield locus tester (YLT) was compared with the CCSC used as a Jen ike shear cell. Wheat flour and sugar were the test materials. The yie ld loci obtained with the CCSC-YLT using fine cohesive material, wheat hour, were not statistically different (at the 95% confidence interva l) from the yield loci obtained with the CCSC-Jenike, while there were marginal differences (at the 95% confidence interval) between the tes ters for the less cohesive material, granulated sugar. Design of the C CSC also eliminated the need for trial and error in determining the nu mber of twists needed for critical consolidation of powder mass. In ad dition, the duration of the test and amount of material needed to gene rate a dynamic yield locus using the CCSC are reduced by 3/4 and 2/3, respectively, compared with those required for the CCSC used as a Jeni ke shear cell.