Product design of cohesive powders - Mechanical properties, compression and flow behavior

The fundamentals of cohesive powder consolidation and flow behavior are explained using a reasonable combination of particle and continuum mechanics. By the model "stiff particles with soft contacts", universal models are presented which include the elastic-plastic and viscoplastic particle contact behavior with adhesion, load-unload hysteresis and thus energy dissipation, a history-dependent and a nonlinear adhesion force function. With this as the physical basis, incipient powder consolidation, yield and cohesive steady-state flow, consolidation and compression functions, compression and preshear works are explained. As an example, the flow properties of an ultrafine limestone powder are shown. These constitutive models are used to evaluate shear cell test results for apparatus design to ensure reliable powder flow. Finally, conclusions are drawn concerning particle stressing, powder handling behavior and product quality assessment in processing industries.