  It has been claimed that quasistatic granular materials, as well as nanoscale
materials, exhibit departures from elasticity even at small loadings. It is
demonstrated, using 2D and 3D models with interparticle harmonic interactions,
that such departures are expected at small scales [below O(100) particle
diameters], at which continuum elasticity is invalid, and vanish at large
scales. The models exhibit force chains on small scales, and force and stress
distributions which agree with experimental findings. Effects of anisotropy,
disorder and boundary conditions are discussed as well.
