Mixed experimental-numerical analysis for identifying sheet-metal anisotropic yield surfaces

The plastic behavior of anisotropic sheet steels and aluminum alloys is identified by combining the results of classical uniaxial tensile tests and of heterogeneous biaxial tensile tests on cruciform specimens. The 8- parameter anisotropic yield function proposed by Ferron et al. [1] is used to this end. Uniaxial tensile tests allow the identification of strain-hardening and of yield function parameters related to transverse strain anisotropy (angular variation of the anisotropy coefficient R) and stress anisotropy (angular evolution of the yield stress σ). Strain fields measured in the biaxial tests by means of an image correlation method are used as input data in an optimization procedure that consists of fitting numerical fields with experimental ones, in order to determine the material parameters describing the shape of the yield surface in the expansion range. Finally, simulations of the cup drawing test are performed to check the validity of the identification.