THE VISCOPLASTICITY THEORY APPLIED TO THE INELASTIC ANALYSIS AT ELEVATED-TEMPERATURES

Monotonic and cyclic loading tests on strain rate changes are conducted on 2 1/4Cr-1Mo steel at 600-degrees-C. The examination of the tensile stress-strain response suggests that the viscosity function which characterizes the rate-dependency in the viscosity theory used previously at room temperature should not only depend on the overstress but also on the strain. A new extended viscosity control function is introduced to represent such strain dependency. The material constants of this modified viscoplasticity model are determined at temperatures of 25-degrees-C to 600-degrees-C and the model is applied to deformation tests on 2 1/4Cr-1Mo steel carried out under time-varying temperature conditions and other conditions. The extended viscoplasticity theory is shown to reproduce such various experimentally observed stress-strain behavior at elevated temperatures.