  We experimentally investigate the effect of vertical vibrations on the
brittle behavior of fine cohesive powders consisting of glass beads of 5
microns in diameter. This is an attempt to understand the sole role of
vibrations in fluidizing Geldart's group C powders, which is known for posing
difficulty while fluidization. We find that the cohesive powder column can be
compacted, fractured, and effectively fluidized by increasing the strengths of
external vibrations. This process of vibration-induced fracturing is summarized
in a full experimental phase diagram showing four distinct phases of the
vibrated powder column: consolidation (CS), static fracture (SF), dynamic
fracture (DF), and convective fracture (CF). We find that the boundary
separating the consolidated and fracture regimes depends on the dimensionless
shaking strength, S. However, in the DF regime, the decompaction wave
propagation speed normalized to gravitational speed is found to be independent
of S. In order to reach our ultimate goal of effective fluidization of group C
powders, we explore geometrical parameters like container shapes, sizes, and
base conditions. We find that the circular cylinder with hemispherical base
condition is the most effective container in order to achieve effective
fluidization of group C powders when vibrated.
