Evaluation of deformation for titanium alloy sheet in single point incremental forming based on asymmetric yield function

This paper is concerned with evaluation of deformation in single point incremental forming (SPIF) for a Ti6Al4V sheet. Tension and compression properties were experimentally obtained along the RD, DD, and TD to investigate the in-plane anisotropy and the strength differential (SD) effect. To characterize the constitutive equation, an anisotropic and asymmetric yield function (CPB06ex2) was employed for the Ti6Al4V sheet. Uniaxial loading–unloading tests were carried out to confirm the degradation of the elastic modulus due to plastic deformation. The SPIF tests were then conducted through a 3-axis CNC-based incremental forming machine with a tool path for a truncated pyramid. To describe the deformation in the SPIF considering the springback, FE simulations were performed with different constitutive models from isotropic to anisotropic and asymmetric cases considering the elastic modulus degradation. The superiority between the constitutive models was evaluated by comparing the experimental and FE results of the surface profile. It was confirmed that the model that fits the overall shape profile well is the most advanced constitutive model, CPB06ex2, which features the degradation of the elastic modulus.