On backstresses, overstresses, and internal stresses represented on the mesoscale

The notions 'backstress', 'effective stress', 'overstress' and 'equilibrium stress' are given clear physical meaning by confronting their use with the use of internal stresses represented on the mesoscale as tensorial internal variables. Our way of modeling creep and relaxation is newly presented and agreement with experimental findings demonstrated. It is shown that in the case of a monotonic uniaxial deviatoric loading, the relation of the macroscopic stress to the 'backstress' or 'equilibrium stress' equals the relation of the acting force to that part of this force that is sustained by the infrastructure of barriers that do not undergo plastic deformation or rheological flow.