Multi-Scale Analysis of Deformation and Damage Development in DP1000 Automotive Steel

The use of dual-phase (DP) steels in the automotive industry is rising due to their light weight and ability to enhance safety. The development of next generation DP steels requires better understanding of their microstructure deformation and damage propagation to help predict their mechanical properties. The formability and damage development in DP1000 steels are studied in this research using a multiscale method for better understanding of these phenomena. An in-situ tensile test, in combination with digital image correlation, was performed inside the chamber of a scanning electron microscope to evaluate the microstructure deformation. Martensite fracture and ferrite void localisation were observed and studied in relation to local strain measurements. Further finite element simulation –based damage modelling was developed to analyse damage nucleation in relation to mechanical stress strain fields. The Gurson-Tvergaard-Needleman damage modelling approach was adopted to predict the load-displacement curves of notched tensile samples by calibrating damage parameters. Validation was conducted through the prediction of load-displacement curves of the bespoke tensile geometry of specimens tested inside the Scan electron microscope. The formability of DP1000 was further examined.