Fields-Backofen and a Modified Johnson-Cook Model for CP-Ti at Ambient and Intermediate Temperature

The flow stress behavior of commercial pure titanium (CP-Ti) was studied by uniaxial tension tests at temperatures ranging from 283 to 573 K and strain rates from 0.000 05∼0.005 s−1. The tensile properties of CP-Ti was investigated to determine the quantitative variation of the strain rate sensitivity and the strain hardening with temperature. The results show that the strain rate sensitivity of CP-Ti at 283∼423 K is not obvious and strain hardening index increases with temperature at 353∼573 K. A mathematical model using an updated Fields-Backofen (FB) equation based on temperature changing was established to describe the plastic flow stress behavior of CP-Ti. Meanwhile by considering the coupled effects of strain, strain rate and temperature, a modified Johnson-Cook (JC) model were proposed to predict the flow behavior. Compared with the original JC model, the modified JC model shows better agreement with the experimental stress, which validates the accuracy of the modified model describing the plastic flow stress of CP-Ti.