The definition of flow stress under dynamic loading based on relaxation model of plasticity

The unstable behavior of the deformation curve under static and dynamic loading is predicted using the relaxation model of plasticity and Johnson-Cook models (classical and modified) at room temperature. It is shown that the relaxation model of plasticity as continuation of structural-temporal approach describes various types the deformation curve for one material in a wide range of strain rates. The structural-temporal approach is an efficient and convenient tool for calculations in a much wider range of strain rates. An advantage of the yield stress calculations based on the structural-temporal approach is the minimal number of parameters, which do not require further modifications at high strain rates, in contrast to the empirical Johnson-Cook model and Cowper-Symonds formulas. The efficiency of the relaxation model of plasticity and structural-temporal approach is demonstrated using aluminum alloys as an example.