Modeling anisotropic ductile fracture behavior of Ti-6Al-4V titanium alloy for sheet forming applications at room temperature

An anisotropic modified Mohr-Coulomb (MMC) ductile fracture criterion was developed to characterize the ductile fracture behavior of the Ti-6Al-4V titanium alloy at room temperature. The stress triaxiality is inherently coupled within the ductile fracture criterion and shows an exponential effect on the material ductility decay. The effect of the Lode angle is considered as well, considering a parabolic trend. The fracture criterion was developed based on the direction-independent plastic strain-rate increment called isotropic equivalent plastic strain-rate increment. To incorporate the influence of directionality on the ductile fracture behavior, the fourth order linear transformation tensor was successfully introduced. The Ti-6Al-4V fracture behavior under uniaxial tension, in-plane shear, plane strain along various loading orientations, and equi-biaxial tension states of stress was successfully predicted using the newly developed fracture criterion. Furthermore, the theoretical Fracture Forming Limit Curve (FFLC) predicted by the anisotropic ductile fracture criterion was compared with experimental forming limit curves from literature. The results show that the developed phenomenological anisotropic MMC ductile fracture criterion has a great advantage to predict the ductile failure of sheet metals characterized by strong anisotropy. (C) 2020 Elsevier Ltd. All rights reserved.