Steady states in granular dynamics

The application of steady-states to the description, and characterisation of rheological properties of powders and granular materials is outlined. The inherent non-equilibrium nature of a powder implies it may only be properly characterised if the process that produces the state at which it exists is uniquely defined. This is achieved by steady-states. These conditions are presently easily accessible in idealised computer models, but should become a design goal of future laboratory experiments. Current computer simulation studies on the behaviour of simple hard-sphere models in three such idealised steady -states, i.e. homogeneous shear, uniaxial compaction, and vibrational fluidisation, are briefly reviewed.