Evaluation on Accuracies of Phenomenological Yield Criteria for Automotive Al sheets

Abstract

The anisotropic behavior of two typical cold rolled Al alloy sheets, AA5182-O and AA6016-T4, were investigated and used to predictive the yield surface by the well-known yield criteria: Hill90, Barlat89 and Barlat2000. Uniaxial tensile tests with axial and wide extensometers were carried out at different angles to the rolling direction (RD). Then the yield stress σθ and anisotropic coefficient rθ were obtained. Biaxial tensile tests of cross-shaped specimens under certain liner loading paths were conducted on the well-designed biaxial tensile testing machine. The loading paths includes Fx:Fy = 1:4, 2:4, 3:4, 4:4, 4:3, 4:2, 4:1. Yield stresses points (σx, σy) and their strain ratios in the yield locus plane can be obtained from the strain-stress curves of the biaxial tensile tests. Parts of tested values were used to determinate the yield locus according to different yield functions. All experimental data was used to evaluate the precisions of the yield functions by taking into account of the accuracy of σθ and rθ and the yield stress and strain ratios of biaxial tensile tests.