Finite element modeling for deep-drawing of aluminum alloy sheet 6014-T4 using anisotropic yield and non-AFR models

The predictive capability of a non-associated flow rule (non-AFR) for the strong plastic anisotropy was assessed. Based on Hill's 48 function, a constitutive model under a non-AFR was established for aluminum alloy 6014-T4 sheet, in which the plastic potential function and the yield function were identified by Lankford coefficients (r-values) and yield stresses, respectively. Two constitutive models applying Hill's 48 and Yld2000 functions under the AFR were also established for the comparison with the non-AFR Hill's 48 model. These constitutive models were numerically carried out on Abaqus/Explicit by user subroutine (VUMAT). The representational ability of constitutive models was assessed in terms of the predictions on yield stresses and r-values. To further verify the simulated results, deep-drawing experiments of a cylindrical cup and a seat pan were performed. Simulation results were compared with the experiments from the aspects of the forming force, the earing profile, and the measured strain field using ex situ 3D DIC (Digital Image Correlation). Comparison results showed that non-AFR Hill's 48 model gives the best overall prediction performance and requires less effort than the AFR Yld2000 model, indicating the effectiveness and superiority of non-AFR.