Ryuta Onodera, Zhu Gui He and Tatsuya Morikawa
Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 812-8581
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.
(Received December 5, 2002)
computer simulation, stress-strain curve, blue shortness, low carbon steel, yield point phenomena, serrated flow
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