Incorporation of anisotropy for the failure prediction of AA6061 during SPIF process

Fracture prediction using ductile damage models in incremental sheet metal forming has recently become an indispensable approach. Prediction accuracy of damage models depends upon the approach followed to model the anisotropic nature of the sheet metal to a large extent. In this regard, this study is performed to understand the degree of influence of anisotropy in fracture prediction compared to the isotropic model. The Bao and Wierzbicki (2004) damage model was used for predicting fracture in the case of single-point incremental forming (SPIF) of the AA6061-T6 sheet. von Mises and Hill48 yield functions were used to develop the isotropic and anisotropic material behavior in finite element (FE) simulations. A “D” shape geometry with a wall angle of 70° was formed till the fracture. The damage model was calibrated with fracture strains obtained using digital image correlation (DIC) in uniaxial and shear tests. The accuracy of the developed finite element model was validated by comparing the forming height, thickness, and surface strains with experiments. A non-linear damage accumulation rule was utilized to capture the non-linear loading scenarios, and it was calibrated using SPIF of a cylindrical geometry. Finite element simulation using the Hill48 yield function predicted forming height more accurately when compared to the isotropic von Mises yield function.