For continuum mechanics based silo design, the measuring and modelling methods for the shear flow behaviour of cohesive, frictional powders play a central role. Studies of the particle mechanics can provide a better physical "microscopic" understanding of the essential constitutive functions of a powder "continuum". The discrete element method (DEM) is a tool that allows considering the details of the contact and adhesion forces for each particle contact. During bi-axial shear, the DEM results show an elastic regime, yielding, and steady-state flow of a two-dimensional model powder. (c) 2005 Elsevier B.V. All rights reserved.