Fracture prediction for metal sheet deformation under different stress states with uncoupled ductile fracture criteria

Fracture constantly occurs during the plastic forming processes of thin-walled metal sheets due to the local uneven plastic deformation. During the processes, the sheets may experience different stress states, which are crucial factors related to the fracture. To predict fracture in different forming processes, various uncoupled ductile fracture criteria have been proposed due to their advantages of relatively simple expressions and less modeling parameters. Because each fracture criterion focusses on certain aspects of the deformation behavior, the ability of fracture prediction can be dramatically different. Thus, a systematical study on eight widely applied uncoupled ductile fracture criteria is carried out to evaluate their applicability under four different stress states, i. e. pure shear, dog-bone tensile, notched tensile and hydraulic bulging. Each criterion is numerically implemented and embedded into finite element models and is applied for fracture prediction of an anisotropic aluminum alloy sheet. The prediction results are compared to experimental results and the applicability of each criterion is analyzed.