Fracture limit prediction for roller hemming of aluminum alloy sheet

Roller hemming limit is predicted based on ductile fracture criterion in this approach. Plastic deformation in sheets made of aluminum alloy 6061-T6 is studied experimentally. Combined isotropic and kinematic hardening rule is considered in roller hemming numerical analysis. Forming limit stress curve at fracture (FLSCF) is derived from Cockcroft–Latham ductile damage criterion to determine fracture during roller hemming simulation. Serrated strain paths are detected along hemline. The zones where fracture takes place obtained by experiments and FE simulations are compared. It is demonstrated that FLSCF, which is on the basis of ductile damage criteria and basically irrelevant to linearity of strain path could be used to predict fracture of roller hemming correctly.