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Dynamic yield stress values predicted within the structural-temporal approach based on the incubation time concept and those found from the popular empirical Johnson–Cook and Cowper-Symonds formulas and its known modification are compared with the examples of high strength steels and nickel alloy subjected to high-rate plastic deformation. It is shown that the structural–temporal approach is an efficient and convenient tool for calculations in a much wider range of deformation rates. An advantage of the yield stress calculations based on the incubation time criterion 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. Experimental curves of the static and dynamic deformation (stress-strain curves) for two high strength steels are analyzed on the basis of the relaxation model of plasticity with a constant characteristic relaxation time definable from the structural-temporal approach. It is shown that the relaxation model predicts an existence of the yield drop phenomenon during high-rate deformation for advanced high strength steel and an absence of this effect in a wide range of strain rates for high strength 2.3Ni-1.3Cr steel.
Keywords: steel, plasticity, strain rate effect, dynamic yielding, relaxation plasticity model.© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.