Ferritic-Martensitic dual phase steel has good strength and ductility due to the hardness of Martensite and softness of Ferrite phases. This property has led to the widespread application of the current steel in various industries especially for automotive industry. Among the several manufacturing methods for the production of dual phase steel, ‘Rolling’ is one of the most common method to manufacture this type of steel due to its quality improvement and economic efficiency. It is expected from this kind of manufacturing that a portion of produced steel granules to be appeared in the stretched or banding form. Nevertheless, investigation of the damage of dual phase steel in the banding form is one the subject that has been rarely considered by researchers. Therefore, the purpose of this thesis was to investigate the damage of this type of steel experimentally and by computer-simulation. In this regard, the micro-structure of the dual phase steel DP600 was investigated in different planes. According to the laboratory observations indicating that the microstructure of this type of steel is granular and banding in the RD-TD and RD-ND planes respectively, thus the damage mechanisms in the each of these planes has been investigated by uniaxial tension of specimen in various directions. For this purpose, the prepared surface of specimen before and after deformation was analyzed by field-emission scanning electron microscopy (FESEM). Observations showed different damage behavior in RD-TD and RD-ND planes. Ferrite-Martensite interface decohesion in first plane and Ferrite-Martensite interface decohesion and Martensite Cracking in second plane are predominating damage mechanism. In addition to the aforementioned damage mechanisms, the damage mechanism of Ferrite placed between the Martensite granules has also been observed for both of the planes. Moreover, the damage in the Ferrite is observed in the first plane. In the following, the micro-structure of this type of steel has been simulated and investigated by ABAQUS. In this simulation, the damage of Ferrite was modeled according to the GTN damage model. The approximate value of the fracture stress of Martensite was also obtained according to the literature for the modeling of damage in Martensite. Results obtained from simulation had acceptable agreement with experimental data. Therefore, it can be concluded that the damage of dual phase steel would led to wrong results in the analysis only from above plane (i.e. RD-TD). So, for the comprehensive investigation of damage in this type of steel, the micro-structure should be investigated in the both of the planes (i.e. RD-TD and RD-ND). Also, an in-situ tensile set-up was designed in this project for the installation under the optical microscope. Keywords: Dual Phase Steel, Banding Microstructure, Simulation of Microstructure, GTN Damage Model, Frecture of Martensite
