Interparticle Friction in Granular Ceramic Materials

Abstract

The frictional behaviour of dry ceramic materials in the form of spherical beads, sand and spray dried powders has been studied. Measurements were made using standardized flow time, shear cell methods and die pressing. Flow time was found to provide a poor measure of internal friction for coarse material. Internal friction increased with decreasing particle size and deviations from sphericity. Powders with high specific surface area had low apparent and tap density and flowed poorly if at all under gravity loading conditions. However, shear cell and die press experiments showed the coefficient of internal friction measured at load was not sensitive to this parameter. The coefficient of internal friction calculated from shear cell measurements in which the maximum stress was 0.4 MPa was in good agreement with that deduced from die stresses during die pressing to 300 MPa, even when particle fracture occurred at the higher pressures, provided the morphology did not change appreciably.