複合組織鋼板のBauschinger効果におよぼす組織間強度差の影響

抄録

For a better understanding of the effect of the strength difference between soft and hard phases on the Bauschinger effect of dual-phase (DP) steels, we experimentally investigated two types of DP steel, i.e., one with a large strength difference and the other with a small difference. Reversed simple-shear tests revealed that the steel with a larger strength difference showed earlier re-yielding under reverse loading; thus, the strength difference between phases enhances the Bauschinger effect. Furthermore, the actual morphology of the steel with a larger strength difference was reproduced in a finite element model of which hard and soft phases were represented by high and low flow stresses, respectively. By changing the flow stress for the hard phase, the effect of the strength difference was analyzed by finite element analyses. In the simulations, the observed difference of the Bauschinger effect was qualitatively reproduced. It was also shown that strains given to the soft phase in the vicinity of the hard phase are relatively low and those areas first re-yield immediately after reverse loading. This was pronounced in the case with a larger strength difference. The earlier re-yielding for the larger strength difference is possibly ascribe to not only the higher back stresses but also the lower strains.