Influence of phase and interface properties on the stress state dependent fracture initiation behavior in DP steels through computational modeling

In dual phase (DP) steels, fracture can initiate within the ferrite phase, the martensite phase, or at the interfaces between these phases with the dominant fracture initiation mechanism expected to depend on a number of factors, including the phase and interface properties as well as the applied stress state. The present study aims to identify the links among fracture initiation behavior, phase/interface properties, and stress state in DP steels through finite element analysis using representative volume element (RVE) simulations. An idealized RVE model containing a circular martensite particle was loaded under five different stress states. The RVE model incorporated a ductile fracture criterion for ferrite, a brittle fracture criterion for martensite, and a cohesive zone model (CZM) for the ferrite/martensite interface. A parametric study was performed to determine the relative influence of fracture properties of each constituent and stress state on the failure initiation behavior, and to identify the conditions under which the fracture initiation behavior was stress state dependent.