Calibration and Validation of GISSMO Damage Model for A 780-MPa Third Generation Advanced High Strength Steel 2020-01-0198

To evaluate vehicle crash performance in the early design stages, a reliable fracture model is needed in crash simulations to predict material fracture initiation and propagation. In this paper, a generalized incremental stress state dependent damage model (GISSMO) in LS-DYNA® was calibrated and validated for a 780-MPa third generation advanced high strength steels (AHSS), namely 780 XG3^TM steel that combines high strength and ductility. The fracture locus of the 780 XG3^TM steel was experimentally characterized under various stress states including uniaxial tension, shear, plane strain and equi-biaxial stretch conditions. A process to calibrate the parameters in the GISSMO model was developed and successfully applied to the 780 XG3^TM steel using the fracture test data for these stress states. The calibrated GISSMO fracture card for 780 XG3^TM steel was then validated in simulations of wedge-bend tests, two notched tensile tests and axial crash tests of octagonal, 12-sided and 16-sided components. The predicted fracture locations, displacement at fracture and force-displacement curves agreed well with the test results. The study also demonstrates that 780 XG3^TM steel, when combined with the 12 and 16-sided advanced section designs, improves axial crash energy absorption efficiency with minimal fracture and offers an opportunity for weight reduction.