Characterization of sheet metal plastic anisotropy by cross biaxial tensile test
Résumé
Sheet metal forming represents a class of important processes widely used in the manufacture industry. Sheet metals usually exhibit a plastic anisotropy due to previous processes like rolling and annealing. Yield functions are frequently applied to describe the plastic behavior of metallic sheets due to their simplicity and easy implementation into finite element codes. In this research, Bron and Besson yield criterion [1] has been used to investigate the plastic anisotropic behavior of an aluminum alloy AA5086. This criterion, expressed in plane stress conditions, involves 12 parameters, 4 controlling the shape of the yield function and 8 its anisotropy. Biaxial tensile tests with cruciform specimen have been introduced in the identification process of Bron and Besson yield criterion. This test seems particularly interesting since different strain paths can be obtained simultaneously with a unique specimen. Different from the conventional analytical identification method, which requires several types of conventional tests, material parameters can be identified with only biaxial tensile tests. A cruciform specimen has been designed and experiments have been carried out with a servo-hydraulic testing machine. Simultaneously, finite element simulations of the biaxial test have been carried out with the commercial software ABAQUS. In the numerical simulation, experimental force is imposed on the cruciform specimen and principal strain field along the diagonal direction of the specimen's central gauge area has been analysed. Concerning the identification process, inverse analysis has been performed with the software MODEFRONTIER to minimize the experimental and simulated principal strain difference to get a proper parameter set for Bron and Besson yield criterion. Up to now, a preliminary result has been obtained and compared with the isotropic von Mises yield criterion.