Investigation on Transversal Anisotropy of an Aluminum Sheet for Crash Applications

In this paper, we concentrate our efforts on the simulation of an aluminum sheet material used in the automotive industry. A series of experiments using samples with different geometries is performed in order to characterize the material under different stress states. Plasticity is considered using a von Mises based and a Barlat based material model (respectively, *MAT_024 and *MAT_036 in LS DYNA®). For the Barlat-based model, it is assumed that the R-values are the same for all material directions, a suitable assumption for 6000 aluminum sheets. This means that anisotropy is only present through the thickness and not in the plane of the material. In turn, this allows a more straightforward usage of *MAT_036 in complex parts for which no mapping of material directions have to be undertaken because the thickness direction for shell elements is known a priori. Comparison with experimental data (including strain fields measured with DIC) shows that this strategy leads to a somewhat better description of the material deformation observed in physical tests when compared to the predictions of the isotropic model *MAT_024. Finally, the GISSMO failure/damage model is adopted for the failure description in LS-DYNA. It is shown that the numerical results agree very well with the experiments and not only the global force-displacement curve but also the local strain fields.