3D-Simulation of ductile failure in two-phase structural steel with heterogeneous microstructure

The effort of this study is to develop a simulation method to predict the effect of micro-structural morphology in two-phase steel, Ferrite–Pearlite steel, on structural performance in terms of ductile failure resistance. This is based on a clarification of a damage mechanism to control the ductile cracking with focusing on the heterogeneity in strength of microstructure. The large number of micro-voids nucleation at lower strength side near two-phase boundary associated with the localization of stress/strain is found to control ductile cracking. According to this experimental result, we develop meso-scale 3D-model to reproduce micro-structural morphology of practical two-phase steel of interest for analyzing stress/strain localization behaviors associated with heterogeneity of microstructure. Moreover, damage evolution model including plastic potential to nucleate micro-void is proposed, so that ductile crack nucleation and subsequent growth and linking could be simulated. The ductile cracking behavior for two-phase structural steel is simulated by means of the developed meso-scale 3D micro-structural FE-model together with the damage evolution model. The effect of applied triaxial stress state on critical macro-strain for ductile cracking as well as damage evolution behavior, in which the critical strain could be decreased with increasing stress triaxiality, is numerically predicted.