If slip is the only mechanism of
plastic deformation of a crystal and Schmid law governs the slip
activity, the overall response of an aggregate of such crystals
features the normality rule of classical plasticity, see
node/15347
for a rigorous recent proof. Any deviation from Schmid law is
referred to as a non-Schmid effect. In general, these effects may be
of two kinds: in addition to the resolved shear stress (on a slip
system), other stress components may influence slip activity or/and
the hardening of a slip system (representative examples for each kind
are described, for example, in Qin and Bassani(1992) and Spitzig