THE DEFORMATION KINETICS THEORY OF THE STRESS DEPENDENCE OF PLASTIC-DEFORMATION

The fact that plastic deformation is controlled by thermally activated processes leads to the physically rigorous conclusions that the mecha nisms are defined either by a single rate constant or by the kinetics combination of rate constants. For the determination of the kinetics-t hat is, for the establishment of the functional relation of the stress dependence of the work, experiments have to be carried out. When the test results are plotted in the coordinate systems of logarithm of str ain rate vs linear stress, also logarithm of strain rate versus linear reciprocal temperature, the behavior exhibited by the two plots defin es the nature of the stress dependence of the work. The kinetics analy sis of the two representations leads to the functional expression of t he constitutive law in physically exact and rigorous expressions. Appl ications to typical mechanisms are discussed: plasticity limited by di screte obstacles; lattice diffusion controlled creep; dislocation core diffusion controlled creep; plasticity limited by lattice resistance.