Prediction of forming limit in hydro-mechanical deep drawing of steel sheets using ductile fracture criterion

It has been observed that the fort-ning limit curve at fracture (FLCF) of steel sheets with a relatively higher ductility limit have linear shapes, similar to those of a bulk forming process. In contrast, the FLCF of sheets with a relatively lower ductility limit have rather complex shapes approaching the fort-ning limit curve at neck (FLCN) towards the equi-biaxial strain paths. In this study, die FLCFs of steel sheets were measured and compared with the fracture strains predicted from specific ductile fracture criteria, including a criterion suggested by the authors, which can accurately describe FLCFs with both linear and complex shapes. To predict the forming limit for hydro-mechanical deep drawing of steel sheets, the ductile fracture criteria were integrated into a finite element simulation. The Simulation results based on the criterion suggested by authors accurately predicted the experimental fracture limits of steel sheets for the hydro-mechanical deep drawing process.