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.%为解决高温高压环境下Johnson-Cook(J-C)本构模型不再适用于Ti-6Al-4V合金切削有限元仿真的问题,建立了基于重结晶的修正J-C本构模型,它可以体现出高速切削Ti-6A1-4V合金时的应力回落现象.首先,利用霍普金森压杆试验测得了Ti-6A1-4V的应力-应变数据,利用变量分离法拟合出修正J-C本构模型,该模型可以反映材料发生相变时应力-应变曲线的变化趋势,并能很好地逼近压杆试验数据曲线.然后,以AdvantEdge FEM有限元软件为平台,采用回退映射应力积分算法编写子程序,将该修正本构模型和J-C本构模型导入有限元系统,并对这2种本构模型进行有限元仿真.仿真结果对比表明:在相同的切削条件下,当温度超过850℃时,修正本构模型体现出流动应力急剧下降的现象,下降幅度为46.7％,而J-C本构模型的流动应力下降平缓,仅下降了11％,说明修正本构模型更贴近高速切削Ti-6A1-4V合金时的高温与高冲击环境.
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