Flowability Assessment of Weakly Consolidated Powders

Researcher: Alexandros Stavrou
Principal Investigator: Dr Colin Hare
Co-Investigator(s): Dr Ali Hassanpour
Sponsor: International Fine Particle Research Institute (IFPRI)
Status: Ongoing (2015 - )

Abstract

This project builds on the previous research project "Assessing Flowability of Cohesive Powders from a Small Sample Quantity", with its main aim being the assessment of flowability, for a range of powders, at low consolidation stresses and high strain rates. This will be achieved using the innovative approach of ball indentation into a powder bed, that was developed by Professor Ghadiri's group and has been proven to correlate well with other flowability measurement techniques at high stresses, such as unconfined uniaxial compression and shear cells. Benefits of the indentation technique include the extremely small sample quantity required, and application at very low stresses (< 0.1 kPa) and at high strain rates.  The flowability behaviour at low stresses suggests that extrapolating the yield locus derived from measurements at higher stresses (e.g. using shear cells) may be misleading.  As such the flowability dependency on strain rate at a wide range of stresses and strain rates will be assessed by this method.

Along with the experimental work, numerical simulations will be carried out using the Distinct Element Method (DEM) in order to understand the stress distribution within the powder bed.  In addition the influence of particle properties on strain rate sensitivity of powder flowability will be assessed.

Last but not least, the powders will be characterised using various novel techniques, such as nanoidentation for the determination of the specimens' mechanical properties, and X-ray micro tomography for the description of particle shape.