Determining biaxial tensile stresses by fracture cruciform specimen at different temperatures and strain rates for Ti–6Al–4V alloy

Fracture loci of a ductile sheet metal, in some stress subspaces, can be predicted by determining the fracture stress points in the same subspace. This paper deals with determining the fracture stress points for Ti–6Al–4V alloy, under biaxial tension loading, at different temperatures and strain rates. For this purpose, biaxial tension of a fracture cruciform specimen was numerically simulated, using the ABAQUS software. In order to validate the finite element simulations, biaxial tensile fracture of an AA5083 cruciform specimen was numerically and experimentally studied. The material properties of AA5083 needed as the input data for simulations, were determined by performing experimental tests. Moreover, a dependent biaxial tensile mechanism was designed, manufactured and installed on an INSTRON-1343 uniaxial testing machine, to conduct the biaxial experimental tests. The numerical predictions for the location of fracture initiation, the path of fracture evolution and the force diagram in each of the specimen arms were compared with the experimental results. A good correlation was observed which confirms the validity of the finite element simulations. Then, the simulations were repeated for Ti–6Al–4V specimen. Hill1948 criterion was used to model the anisotropic plasticity, while Johnson–Cook damage model was incorporated to predict the fracture initiation and evolution path for different temperatures and strain rates. The results showed that the biaxial fracture stress points, corresponding to different displacement ratios, are mainly accumulated in the vicinity of equi-biaxial stress state. It can be concluded that, regardless of the anisotropy model, the fracture cruciform specimen cannot reveal a wide range of biaxial tension stress points.