Effects of strain rate and stress state on mechanical properties of Ti-6Al-4V alloy

Uniaxial compression, uniaxial tension, and new double shear experimental methods are used to study the effect of stress state on the mechanical behaviors of Ti-6Al-4V over a wide range of strain rates (0.001-6500s⁻¹). The experimental results show that strain rate and stress state both have strong influences on the plastic flow and failure properties of the material. With an increasing strain rate, the work-hardening rate increases under uniaxial compression loading, but decreases under uniaxial tension and shear. Moreover, with the increase of strain rates, the initial failure strain increases under uniaxial tension, but decreases under the uniaxial compression conditions. Based on the experimental results, the Johnson-Cook (JC) hardening laws are used in finite element analysis (FEA) to simulate the mechanical responses of the material. It shows that the simulated results and the experimental data are in good agreement. The results indicate that the effects of strain rate and stress state should be considered in the constitutive model. Fractographic examinations are also conducted under different loading conditions. The failure processes of the material are controlled by different micro-mechanisms.