高应变率下TC4-DT钛合金的动态力学性能及塑性本构关系Dynamic mechanical property and plastic constitutive relation of TC4-DT Ti alloy under high strain rate

为研究TC4-DT钛合金的动态力学性能及其本构关系，在1000~8000 s^-1应变率范围内，利用分离式Hopkinson压杆试验装置对该材料进行动态压缩试验，得到高应变率下的真实应力-应变曲线。结果表明：高应变率时TC4-DT钛合金材料存在应变率增强、增塑以及应变强化效应，其流变应力表现出较强的应变率敏感性。通过微观组织观察，发现高应变率变形时出现绝热剪切带是材料流变应力急剧减小的主要原因。改进Johnson-Cook本构模型中的温度项，利用试验数据对TC4-DT钛合金在高应变率下的动态塑性本构关系进行拟合，得到室温下该材料的动态塑性本构方程，模型计算结果和试验结果证明该模型可以更好地预测TC4-DT钛合金高应变率下的塑性流变应力。

The dynamic compression experiments of TC4-DT Ti alloy were performed at a range of strain rate from 1000 s^-1 to 8000 s^-1 by high split Hopkinson pressure bar for investigating its dynamic mechanical property and constitutive relation, and the true stress-strain curves under high strain rates were obtained. The results show that the true flow stress of TC4-DT is sensitive to the strain rates and TC4-DT has strain rate strengthening, plasticity-increasing and strain work-hardening. The observation of cross-section microstructure of deformed sample reveals that the adiabatic shear band is responsible for the rapid reduction of flow stress when TC4-DT was deformed at high strain rate. Based on the Johnson-Cook constitutive model, with new temperature item, the dynamic constitutive model of TC4-DT was obtained by fitting the experimental results. The comparison between the calculated curves and experimental results shows that the present dynamic constitutive model can make a better prediction of the plastic flow stress.

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