On the Internal Friction of Powdered Materials

Abstract

It is important, in order to understand the mechanical behavior of powdered materials in the operation of mixing, kneading, transporting and forming procedures, that we should be acquainted, among others, with the properties of their internal friction. For the measurement of internal friction of powdered materials, direct shear tests of various sorts have hitherto been performed.
This work was undertaken to determine the relationships between the vertical load σ and the shear stress τ of the consolidated powder beds by a direct shear test.
The powders were consolidated into cylindrical forms each of 2cm in diameter and 3cm in length by pressure up to 191kg/cmcm2 for lactose and magnesia clinker powders and 955kg/cmcm2 for aluminapowders.
These powder beds were measured, the shear stresses τ against the various vertical loads σ, by direct shear test a pparatus which was equipped with a vertical loading system (hydraulic press), a shear cell, a shear force measuring device (loop gauge) and a shearing force device.
It was found that the σ-τ relationships can be represented by the formula
where k, σ0 and n are constants. Discussion is made on the influence of the degree of consolidation, water content and particle size, on these constants, with necessary descriptions.