Flowability Assessment of Weakly Consolidated Powders

Executive Summary

constraint factor increases with an increase in rolling friction coefficient or interface energy.

suggest that the constraint factor remains constant across all stress levels, and that

the addition of coarse material and decrease with the addition of fines. DEM simulations

The constraint factor of bi-disperse, cohesive glass beads has been shown to decrease with

long as they cover a sufficiently wide range.

applied in a shear test are shown to have limited influence on the generated yield locus, so

insufficient to overcome the influence of prior handling. The precise normal stresses

driven by variability in the pre-shear shear stress, thus implying the conditioning is

at lower stresses the variability in measured yield data increases; this appears to be largely

normal stress data being unavailable. Repeated testing in the Schulze shear cell shows that

titania powders. A direct comparison could not be made with the Schulze shear cell due to

been shown to apply normal stresses noticeably greater than the target stresses for these

shear cell and the Schulze RST.XS.s shear cell. At lower pre-shear stresses the FT4 has

The flow behaviour of various titania grades is found to be largely similar between the FT4

universal for all powders.

measurements to be made at lower stresses, though the optimal lid design is unlikely to be

in the shear plane. Reducing the vane height of the shear cell lid allows indentation

to critically consolidated beds since an insufficient fraction of the exposed bed is located

consolidated beds. It is shown that at lower stresses it is challenging to apply indentation

condition, with critically consolidated beds providing a greater hardness than vertically

Indentation hardness measurements have been shown to be dependent on the loading

investigated using the Discrete Element Method (DEM).

experimentally, and the influence of a broader range of particle properties has been

size distribution and interface energy on constraint factor have been assessed

for several grades of titania with two different shear cells. Furthermore, the influence of

has been assessed in ball indentation, and shear cell measurements have been carried out

used to measure flowability of titania under a range of stresses. The bed preparation method

inconsistent. The ball indentation, uniaxial compression and shear cell methods have been

Measurement of powder flowability under low stress conditions is often unreliable or