Constitutive modeling of transformation-induced plasticity steels considering strength-differential effect

Transformation-induced plasticity (TRIP) steels undergo martensitic phase transformations due to their austenite phase. In this study, using 1-mm-thick TRIP steel at room temperature, the phase transformation behaviors under tensile and compressive modes were measured using a ferrite scope based on the detection of the magnetic volume. A strength differential (SD) effect was observed, where the tensile strength was lower than the compressive strength. The rate of tensile transformation was faster than that of compressive transformation. To account for the SD effect in finite element analysis, a martensitic kinetics-based constitutive model was developed, which was decomposed into elastic, plastic, Bain, and transformational parts. A larger transformational strain was generated in the tensile mode, and the asymmetric SD effect was captured well by the proposed model.