Johnson-Cook(J-C)material constitutive model is inaccurate for machining simulation of titanium alloy with high temperature and heavy impact. In this study
a modified constitutive model of Ti-6Al-4V alloy based on recrystallization was established considering the phenomenon of stress decline during machining. High-temperature SHPB(Split Hopkinson Pressure Bar)test was conducted to determine the true flow stress-strain relationship of Ti-6Al-4V alloy. With the SHPB test data
the modified constitutive model was developed by the variable separation method. The flow stress decreased significantly at the temperatures higher than the recrystallization temperature in the modified constitutive model
showing a good agreement with experimental results. A subroutine was then coded and embedded in the finite element simulation software AdvantEdge FEM with the return mapping stress integration algorithm. Finite element simulations for both J-C constitutive model and the modified constitutive model were performed. The result shows that the simulated stress decreases in J-C model and the modified model at 850 ℃ by 11% and 46.7%
respectively
indicating the modified constitutive model is more suitable for the condition of high temperature and heavy impact in machining titanium alloy.
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references
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