单轴压缩下U75V钢动态力学行为及其修正J-C本构模型

Dynamic mechanical behavior of U75V steel under uniaxial compression and its modified J-C constitutive model

采用材料试验机(MTS-880/25T)和温度控制的霍普金森压杆装置研究了U75V钢在25~700℃和0.0003~8000 s-1应变率下的力学行为进行了单轴压缩实验研究,获得了U75V钢在高温、高应变率动态压缩条件下的应力-应变曲线。利用Johnson-Cook模型对U75V钢动态塑性本构进行拟合,获得了其本构模型参数,发现U75V钢在500~700℃温度范围具有动态应变时效现象。对在2500 s-1应变率及不同温度下霍普金森杆撞击实验的试样组织进行观察,并对其发生动态应变时效的原因进行了分析和讨论。通过引入动态应变时效临界温度Tc和强化系数λ,对经典J-C模型进行了修正。结果表明,修正后的J-C模型参数可以在25~700℃和2500~8000 s-1应变率范围内准确描述U75V钢的动态力学行为。

The mechanical behavior of U75 V steel at 25-700 ℃ and strain rate of 0.0003-8000 s-1 was studied by means of a material testing machine(MTS-880/25 T) and a temperature controlled Hopkinson compression bar device, and the stress-strain curves of the U75 V steel under dynamic compression at high temperature and high strain rate were obtained. Based on the experimental data, the Johnson-Cook model was used to fit the dynamic plastic constitutive model of the U75 V steel, and the parameters of the constitutive model were obtained. It was found that the U75 V steel had dynamic strain aging phenomenon in the temperature range of 500-700 ℃. The microstructure of the Hopkinson impact test specimens at different temperatures and strain rate of 2500 s-1 was observed and the causes of dynamic strain aging were analyzed and discussed. The classical J-C model was modified by introducing the critical temperature of dynamic strain aging Tc and the strengthening coefficientλ. The results show that the modified J-C model parameters can accurately describe the dynamic mechanical behavior of the U75 V steel at 25-700 ℃ and strain rate of 2500-8000 s-1.