On the role of constitutive model in the forming limit of FCC sheet metal with cube orientations

The effect on forming-limit diagrams (FLD) of an initial cube texture and its evolution was studied using the well-known M-K approach in conjunction with a viscoplastic crystal plasticity model (VPSC). We focused on how the strength of the cube texture affects localized necking. In particular, we addressed the results of Wu et al. [Effect of cube texture on sheet-metal formability. Materials Science and Engineering A 2004;364:182-7] who found that a spread about cube exhibits unexpectedly high limit strains. The FLD and yield loci were determined for several spreads about {1 0 0}〈0 0 1〉 with uniform or Gaussian distributions. A smooth transition in predicted limit strains from the ideal cube, through textures with increasing cut-off angles, to a random texture was calculated using the MK-VPSC approach. Results indicate that the constitutive model selected has a critical importance for predicting the behavior of materials that exhibit a qualitative change in the crystallographic texture, and hence, evolve anisotropically during mechanical deformation.