予塑性変形を受けたS45Cの曲げ変態塑性挙動の評価

抄録

To examine the effect of pre-plastic deformation of austenite phase on pearlitic transformation plasticity, three point bending tests, wherein the specimens fixed at one end and simply supported at the other were performed. First, specimens were heated to austenitization temperature, then the austenitization temperature of the specimens were kept constant for several minutes and finally cooling and loading processes were performed. During the cooling process, the specimens were subjected to the tensile stress in plastic range on the austenite phase and then, just before transformation start point, the bending stress in elastic range (less than the yield stress) was applied to the specimens during the phase transformation. The maximum bending deflections due to the austenite-pearlite transformation were measured under multiple loading condition and transformation plasticity coefficients were determined. It was shown from the tests that the transformation plastic deflection due to the pearlitic transformation decreases with increasing pre-plastic deformation. The equivalent strain-dependent transformation plastic constitutive equation was constructed on the basis of the test results. Then finite element analysis was performed using this equation. The calculated transformation plastic deflections quantitatively agreed well with the measured ones, suggesting the validity of the proposed equation.