Anisotropy in Powder Flow Behavior
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Abstract
Depending on the properties and the process that is applied, a powder may be capable of forming anisotropic structure. Understanding on this behavior may help one to design equipment and to interpret measurement results obtained with different testers. In this project, anisotropy in powder flow behavior has been investigated by the use of a Jenike shear cell and a Flexible Wall Biaxial Tester (FWBT). The FWBT is operated in a strain controlled manner and its performance in conducting this operation is also investigated. The strength anisotropy of three different powders has been measured with the Jenike shear cell. The powders are BCR limestone (4 |xm) , glass beads (60 pm), and a mixture composed of l%w aerosil R-812 and 99%w BCR limestone. In the experiments the consolidation and preshear are performed as normally, but the shear is carried out in different directions than that of the preshear. For each direction a yield locus can be constructed to obtain the corresponding unconfmed yield strength. The plot of unconfined yield strength as a function of shear direction represents the degree of the strength anisotropy of the powder. The results shows that BCR limestone is strongly anisotropic. The effect is less with the mixture and is not seen with the glass beads...