Constitutive modeling and the effects of strain-rate and temperature on the formability of Ti-6Al-4V alloy sheet

The constitutive model considering the strain-rate and temperature effects was presented by fitting the true stress-strain curves of Ti-6Al-4V alloy over a wide range of strain-rates (0.0005-0.05s^-1) and temperatures (923-1023K). The Forming Limit Curve (FLC) of Ti-6Al-4V alloy at 973K was measured by conducting the hemispherical dome test with specimens of different widths. The forming limit prediction model of Ti-6Al-4V alloy, which takes strain-rate and temperature sensitivity into account, was predicted based on Marciniak and Kuczynski (M-K) theory along with Von Mises yield criterion. The comparison shows that the limit strain decreases with temperature lowering but strain-rate increasing. The comparison between theoretical analysis and experiment of FLC verifies the accuracy and reliability of the proposed methodology, which considers the strain-rate and temperature effects, to predict limit strains in the positive minor strain region of Forming Limit Diagram (FLD).