Bendability assessment of high strength aluminum alloy sheets via V-die air bending method

Abstract

The bendability of high-strength aluminum alloy (AA) sheets for two different thicknesses was experimentally evaluated by the V-die air bending method and the numerical simulation procedure was attempted to comprehend the characteristics of the V-die air bending method. Despite similar bendability along the material direction for a given punch radius in the experiment, the distinguished fracture strains were predicted for each direction based on the punch force and displacement information. For the numerical simulation, V-die air bending was modeled with the full 3D non-quadratic anisotropic yield criterion and compared with the results of the isotropic yield function estimating that bendability along the rolling direction is higher than those along the transverse direction. The thinner material showed higher anisotropy in bendability and the characteristics of V-die air bending were also discussed suggesting a maximum value as an upper bound of the bendability. As a comparison, an anisotropic analytical formulation was also newly developed combined with the kinematic assumption and the limitation was also covered in the study. The analytical fracture strain was discussed as the equivalence to the maximum value suggested in the research.

Keywords

• Bendability
• V-die air bending test
• 7000 series aluminum alloy sheets
• 3D anisotropy yield criterion