Modeling inelastic spin of microstructural vectors in sheet metal forming

This paper develops a new functional form for the inelastic spin that influences the orientation of microstructural vectors during large inelastic deformations in a recently developed Eulerian formulation of sheet metal. For the problems under consideration, a single constant determines the inelastic spin, and the results of the New model are compared to those of a common Lagrangian sheet metal model. It is shown that the same value of this constant causes the New model to predict good results relative to measured data for uniaxial stress at angles relative to the RD, equibiaxial stress and the R-value distribution for AA6022-T4 sheet metal. In contrast, the Lagrangian model predicts zero inelastic spin, which is inconsistent with the measured data. The example of large deformation simple shear is used to further examine the influence of inelastic spin predicted by the New model and the Lagrangian model. The results show that the predictions of the New model, which is insensitive to arbitrariness of a reference configuration, are reasonable, while those of the Lagrangian model exhibit an unphysical dependence on the reference configuration.