  Two granular systems (I and II) corresponding oxide nanopowders having
different agglomeration tendency are simulated by the granular dynamics method.
The particle size is 10 nanometer. The interaction of particles involves the
elastic forces of repulsion, the tangential forces of "friction", the
dispersion forces of attraction, and in the case of II system the opportunity
of creation/destruction of hard bonds of chemical nature. The processes of the
uniaxial compaction, the biaxial (radial) one, the isotropic one, the
compaction combined with shear deformation as well as the simple shear
deformation are studied. The effect of the positive dilatancy is found out in
the processes of shear deformation. The loading surfaces of nanopowders are
constructed in the space of stress tensor invariants, i.e., the hydrostatic
pressure and the deviator intensity. It is revealed that the form of the
loading surfaces is similar to an ellipse, which is shifted along the
hydrostatic axis to compressive pressures. The associated flow rule is
analyzed. The nonorthogonality of the deformation vectors to the loading
surface is established in the both systems modeled.
