Evaluation of Various Yield Criteria in LS-DYNA3D for Sheet Forming Application for Aluminum

Finite element modeling of sheet forming processes for complex automotive parts using an explicit dynamic code such as LS-DYNA3D is increasingly used for producibility analysis and die development. In modeling sheet metal forming processes, it is very common to represent material behavior by either Von Mises' or Hill's yield criterion using commercial finite element codes. However, these criteria do not provide an accurate representation of aluminum alloys. Recently, a new yield criterion proposed by Barlat has been incorporated into LS-DYNA3D to describe the anisotropic material behavior of aluminum alloys. This paper examines the influence of Von Mises', Hill's (1948) and Barlat's yield criteria on the FEM simulation results for the deep drawing of a square cup and cylindrical cup for aluminum alloys. The sensitivity of predicted results to yield criteria is examined for deformation behavior, strain localization and potential of wrinkling. As expected, Barlat's yield criterion provides better agreement with the experimental results. Strain distribution is significantly different using these three criteria. Barlat's yield criterion shows higher strain localization and higher forming strains than Von Mises' and Hill's yield criteria.