Investigation of the Behaviour of Cohesive Powder in the Biaxial Tester

Abstract

The results from experiments with cohesive limestone powder in a Biaxial Tester are presented. The biaxial tester allows a plane homogeneous deformation and measurement of the complete stress-strain states. It was found that proportional strain paths lead to associated proportional stress paths. Strain paths with a sharp bend lead to asymptotic stress paths. Under pure shear deformation, the limestone exhibits steady-state flow in the critical state. The critical state stress was found to be a function of the volumetric strain, i.e. the porosity, but not of the consolidation procedure. The Cam-Clay model of Roscoe has been extended to include the cohesion exhibited by many fine powders. The cohesive strength is represented by an isotropic tensile stress measure, used to shift the yield curves into the tensile regime. Significant cohesive strength can only be achieved in fairly dense packings. © 1995, Hosokawa Powder Technology Foundation. All rights reserved.