Particle Adhesion Fundamentals and Bulk Powder Consolidation

Abstract

The fundamentals of particulate solids consolidation and flow behaviour using a reasonable combination of particle and continuum mechanics are explained. By means of the model "stiff particles with soft contacts" the combined influence of elastic, plastic and viscoplastic repulsion in particle contacts is derived. Consequently, contact normal force displacement FN(hK) and adhesion force models FH(FN) are presented to describe the stationary, instantaneous and time consolidation behaviour in particle contacts as well as in the bulk. On this particle mechanical basis, the stationary, instantaneous and time yield loci as well as uniaxial compressive strength σc(σ1), effective angle of internal friction ϕe(σ1), bulk density ρb(σ1) are derived and shown for a very cohesive sub-micron titania powder. Finally, these models in combination with accurate shear cell test results are used as constitutive functions for computer aided silo design for reliable flow and pressure calculations.