Computer simulation of the yield point phenomena based on the work-softening model

The yield point phenomena in low carbon steel have been explained by the Co ttrell or the Johnston-Gilman theory in terms of microscopic variables such as dislocation density, dislocation velocity and the interaction energy be tween dislocation and solute atom. However, the lower yield stress and the amount of the Luders strain (stretcher strain) seems not to have been predi cted by the above theories. In the present work we tried to explain the phe nomena quantitatively by a phenomenological (rheological) model using macro scopic Variables such as work-hardening rate and the strain rate sensitivit y of flow stress which we can be measured by tensile test. In the model a n ew internal stress was introduced which is supposed to be work (strain)-sof tened and age-hardened. Numerical calculation showed that the model can pre dict the Values of the upper and lower yield stress and the amount of the L uders strain, and the effect of strain rate on these characteristics.