Computer simulation of stress-strain curves of low carbon steel in blue shortness temperature range

Stress-strain curve of low carbon steel tested at room temperature shows the yield point phenomenon at first and then is followed by smooth work-hardening behavior, but in blue-shortness temperature range it shows irregular and/or serrated form. In this paper we tried to simulate these curves based on a constitutive equation. Results of computer calculation suggested that following assumptions are necessary for simulated curves to fit in with experimental ones: 1. Strain rate is determined by effective stress which is defined as the difference between applied stress and internal stress. 2. The internal stress consists of two terms; the one is ordinary internal stress which is work-hardened, and the other is the cause of yield point phenomena, which is work-softened and age-hardened. 3. A deformed region (element) in specimen exerts a kind of interaction stress on neighboring one if there is "strain difference" between both regions. At room temperature the strain difference means the difference in total strain, but in the blue-shortness temperature range we must use a different term "corresponding strain" in place of total strain. And the corresponding strain is defined as a function increased with strain and decreased with time.