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利用MTS材料试验机和分离式Hopkinson压杆实验装置,对锻造后经930℃下退火2h的纯铁材料进行压缩实验,测定纯铁在准静态条件(10-3s-1~100s-1)和高应变率(650s-1~8500s-1)下的应力-应变曲线。实验结果表明,纯铁是应变率敏感材料,纯铁在高应变率条件下,具有应变率增强、增塑以及应变强化效应,高应变率下的塑性变形过程中产生的绝热升温对材料具有热软化作用。基于Johnson-Cook(J-C)本构模型,引入绝热温升软化项对模型进行修正,通过实验数据拟合得到了纯铁的动态塑性本构关系,模型计算结果和实验结果证明,该模型可以较好地预测纯铁在高应变率下的塑性流动应力。
The pure iron was annealed at 930 ℃ for 2h after forging by MTS material testing machine and split Hopkinson pressure bar experimental apparatus. The pure iron was tested under quasi-static conditions (10-3s-1 ~ 100s-1) and Stress-strain curves at high strain rates (650s-1 to 8500s-1). The experimental results show that the pure iron is a strain rate sensitive material. The pure iron has the effect of increasing strain rate, plasticizing and strain strengthening under high strain rate condition. The adiabatic temperature rise during plastic deformation under high strain rate has the effect of heat Softening effect. Based on the constitutive model of Johnson-Cook (JC), the model is modified by adiabatic temperature rise softening and the dynamic plastic constitutive relation of pure iron is obtained by fitting the experimental data. The calculation results and the experimental results show that the model can compare Good prediction of plastic flow stress of pure iron at high strain rates.