Stress–strain prediction of dual phase steels using 3D RVEs considering both interphase hardness variation and interface debonding at grain boundaries

The numerical study on the complex failure mechanism in dual phase steels is significant because of their intricate microstructure. Their mechanical behavior depends on the volume fraction of martensite/ferrite and microstructural morphology, such as size, aspect ratio, interconnectivity, and mechanical behavior of individual phases. Like all multiphase materials, the connectivity between different phases and possible changes in mechanical properties near the interface (interphases) play significant roles in microstructural damage initiation and propagation and, therefore, affect the overall mechanical response. This study focused on the stress–strain behavior of DP-800 steel using finite element analysis of three-dimensional representative volume elements. Based on experimental results, local hardening was considered in the ferrite matrix near the martensite islands. Also, various volume fractions and material properties for different hardening zones were implemented to study the stress–strain behavior of DP steels. Interface elements based on cohesive zone modeling were considered to simulate the damage on the ferrite and martensite interface numerically. Furthermore, hydrostatic stress distribution which is known as an indicator to show the void initiation was used to predict damage zones and the stress distribution is compared with the results obtained from the cohesive zone method. The mechanical behaviors of the finite element models by the proposed methodology, considering cohesive elements and hardening zones in three-dimensional representative volume elements, indicated a better adaptation to the experimental results.