Ductile fracture simulation of cold-formed high strength steel using GTN damage model

The use of high strength steel (HSS) cold-formed hollow section is of significant interest in the construction sector due to competitive costs. The accurate simulation of ductile fracture failure at the micro and macro scale is critical for improving the validity of predicting structural behaviour of HSS cold-formed hollow sections and welded joints. In this study, the ductile failure of the cold-formed S700 material is studied using the Gurson-Tvergaard-Needleman (GTN) damage model. Representative volume element (RVE) models with the void volume fraction (VVF) between 0.1% and 30% are employed to investigate the pressure dependency of the deviatoric limit stress. Different load conditions corresponding to different stress triaxiality levels are applied to unit cells with random spherical pores. The inelastic response of the unit cells are analysed, and the parameters q1, q2, and q3 in the GTN yield surface are calibrated. An equation is proposed to determine parameter q1 for different VVFs. The parameters critical VVF fc and final VVF ff are calibrated by the coupon test from the literature. Finally, the calibrated GTN model is validated against notched coupon tests. The finite element (FE) results show good agreement with the experimental results, indicating that the identified GTN model could efficiently predict the behaviour of the cold-formed HSS.