Abstract:
In the process of pressurized feeding, powders are compacted under gas pressurization, resulting in cohesive arching and flow blockage. The main reason for these problems is that the mechanism underlying consolidation of powders under gas pressurization remains largely unexplored. In this work, the consolidation characteristics of powders under gas and mechanical pressurization were investigated. The density distribution of powder bed at different consolidation states was characterized by measuring the force on an intruder immersed in the powder bed, and the mechanisms by which gas pressurization determines the consolidation characteristics of powders was analyzed. The results showed that a smaller increase in the compressive stress under gas pressurization increased the compaction density significantly; However, gas was determined to penetrate into the bed, weakening the mechanical force generated by the pressurized gas on the bed. As a consequence, the consolidation characteristics under gas pressurization and mechanical pressurization were markedly different. The compressive stress on the powder bed under gas pressurization increased linearly with the pressurization rate, and the critical value of compaction density under gas pressurization was only 85% of that of mechanical pressurization, making it relatively easier to compact the powder bed under mechanical pressurization. In addition, the final pressure of gas pressurization hardly affected the compaction density of the powder bed. Our study on the mechanical properties of the powder bed suggested that the density distribution under gas pressurization was more uniform than that under mechanical pressurization. The dimensionless resistance force
Fb/
Fb,0 which determined to characterize the consolidation characteristics of the powder bed was found to increase linearly and exponentially with applied normal stress and compaction density, respectively.