Failure predictions of DP600 steel sheets using various uncoupled fracture criteria

Dual-phase (DP) steel sheets have high potential for utilization as automotive structures due to their good combination of strength and ductility. As sheet metal forming processes induce complicated stress-strain states, determination of forming limit is vital, particularly using numerical approaches. This current study aims to examine the fracture behavior of DP600 steel sheets through several ductile fracture criteria in a wide range of stress states. For a better and more accurate understanding of the experimental tests, parallel numerical simulations were performed. First, the models were calibrated using the results of Nakazima tests, and then the fracture loci in principal strains, and equivalent strain-stress triaxiality spaces were predicted by each model. The capability of the criteria was verified through cross-die and bulge tests. Also, errors were quantified for the calculated results using correlation coefficient and relative error methods. The results reveal that Maximum Shear Stress, Modified Mohr Coulomb, and Lou fracture models were able to predict the onset of fracture with acceptable accuracy. However, Maximum Shear Stress required only one experimental test to be calibrated.