1 A Finite Element Modeling for Dilatometric Non-isotropy

It is well known that non-isotropic volume changes in dilatometry have been observed during the phase transformation in steel. In this study, a finite element (FE) model incorporating the transformation plasticity was adopted to describe the non-isotropic dilatometric behavior during the phase transformation in steel. An implicit numerical solution procedure to calculate the deformation during the dilatometric experiment was incorporated into the general purpose implicit FE program. The non-isotropic dilatometric behavior could be successfully reproduced by using the FE simulation considering the transformation plasticity. The transformation plasticity was caused by the small amount of stress which naturally developed in the specimen during the dilatometric experiment. In conventional low carbon steel, the stress in the specimen mainly forms due to the very small external force supplied to support it during the dilatometric experiment. As regards ultra-low carbon steel, whose phase transformation occurs within an extraordinarily narrow temperature range, the inhomogeneous phase transformation due to the temperature deviation in the specimen was mainly responsible for the stress field in the specimen during the dilatometric experiment