Earing in cup-drawing of anisotropic Al-6022-T4 sheets

The prediction of earing during cup-drawing of the anisotropic aluminum alloy Al-6022-T4 is studied through a combination of experiments and analysis. At first, the anisotropy of the material is established experimentally, using uniaxial and plane-strain tension, as well as disk compression experiments. The material is seen to possess mild anisotropy, which however evolves with deformation. Two plastic potentials, Yld89 and Yld2000-2D are then calibrated to that data. The latter potential is flexible enough to represent the experimental plastic work contours almost exactly. Subsequently, the cup-drawing experiments are detailed, including descriptions of the equipment and tooling, measurements during forming as well as measurements of thickness and earing in the drawn-cups. Three analytical models for predicting the maximum drawing force are compared to the experiments. The cups exhibit maximum thinning around the punch-radius, as well as four ears. The ears are oriented along the RD and TD directions, with the TD ears being higher than the RD ones. A simple analytical model is seen to closely capture these results. The experiments are then simulated with shell finite elements in DYNAFORM, which uses the explicit solver of LS-DYNA. The simulations permitted the inverse determination of the friction between the blank and the tooling. The thickness and earing profile predictions from the numerical model are in good agreement with the experiments.