A transition from the field of micro-heterogeneous strains through the crystal strain orientation
distribution function to the averaging scheme used in slip theory is presented. The conjugate measures
of stress and strain have been derived for slip theory.The theory is utilized here to the modelling of the strongly anisotropic, thermally activated, flow
process observed for untextured aluminium in the plastic strain range from 1*10−6 to 0.5%. The
subsequent yield surfaces are obtained by numerical simulation in time, the whole process
corresponding to the definition of yielding used by Phillips and Tang (1972). It is shown that the
observed athermal stress is closely related to residual stresses and depends strongly on the plastic
strain offset applied. In the present considerations a role of orientation distribution of mobile
dislocation densities in the anisotropic flow of polycrystalline metals is discussed.
