Dynamic mechanical behaviors of high-nitrogen austenitic stainless steel under high temperature and its constitutive model
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摘要: 在293~873 K的环境下，采用分离式霍普金森杆装置对高氮钢试样进行了102~103 s-1应变率下的动态加载实验。结合准静态实验结果，分析了应变率和温度对材料塑性流动特性的影响。结果表明：高氮钢的动态力学行为具有很强的应变率敏感性和温度敏感性。当应变率达到400 s-1或更高时，流动应力随应变率的增加显著升高；在同一应变率下，流动应力随温度的降低明显升高。研究了温度和应变率耦合效应对材料塑性行为的影响，得出温度软化效应在高氮钢高温动态塑性变形中起主导作用。基于经典的Johnson-Cook（J-C）模型，通过对实验数据的分析，得出了高氮钢材料的修正J-C本构方程，经验证修正J-C方程预测结果与实验结果吻合。Abstract: Mechanical tests of high-nitrogen austenitic stainless steel (HNS) were performed at strain rates of 102-103 s-1 generated by a split Hopkinson bar apparatus and under different temperatures from 293 K to 873 K. The influences of strain rate and temperature on the plastic flow stress of HNS were analyzed by comparing the dynamic tests with quasi-static tests. The results show that the dynamic mechanical behavior of HNS is significantly sensitive to strain rate and temperature; the flow stress increases rapidly when strain rate exceeds 400 s-1; and at the same strain rate, the flow stress increases as temperature decreases. The coupling effect of strain rate and temperature on the plastic deformation behavior of HNS was investigated. The results indicate that the thermal softening effect plays a key role in the dynamic plastic deformation process of HNS. Based on the classical Johnson-Cook constitutive model, a modified Johnson-Cook constitutive model was given which can describe the dynamic mechanical behavior of HNS properly.
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图 2 不同应变率下材料的真实应力应变曲线
Figure 2. True stress-strain curves of HNS at different strain rates
图 5 不同温度加载下材料的真实应力应变曲线
Figure 5. True stress-strain curves of HNS at different temperature
图 6 高温实验中温度、应变率对屈服应力的影响
Figure 6. Influence of temperature and strain rate on yield stress from high temperature tests
表 1 Chemical composition of the as-received high-nitrogen austenitic stainless steel
Table 1. Chemical composition of the as-received high-nitrogen austenitic stainless steel
Element Mass fraction/% N 0.88 Mn 19.28 Ni 2.01 Cr 19.32 Mo 0.0001 Cu 0.031 W 0.005 C 0.03 
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