NAK80塑料模具钢本构关系的试验研究

利用电子材料拉伸试验机、热模拟试验机和分离式Hopkinson压杆系统对NAK80塑料模具钢在较宽温度范围(25~600℃)和不同应变率(700~5 000 s-1)条件下的力学特性开展了系列的试验研究。结果表明:室温下,NAK80塑料模具钢流变行为对应变率不敏感;相同应变率下(10-2s-1),其屈服强度和流变应力随温度升高而下降,且高温下热软化效应明显,导致屈服后应变增加而应力下降。以试验数据为基础,拟合了Johnson-Cook模型,利用该模型对不同温度和不同应变率下NAK80塑料模具钢的流变应力进行预测,与试验数据对比表明,拟合的Johnson-Cook模型能够较好的描述NAK80塑料模具钢的流变行为。

Constitutive model of plastic mould steel NAK80

The mechanical property of plastic mould steel NAK80 was studied on the electronic material tensile test system,the thermal simulation testing machine and the Split Hopkinson Pressure Bar over a wide range of temperatures(25 to 600 ℃) and strain rates(700 to 5 000 s-1).Experiments show that the flow behaviors are not sensitive to strain rates at ambient temperature;the yield strength and flow stress decline with the temperature increasing at the same strain rate of(10-2 s-1);However,under high temperature,the stress declines with the strain increasing after yielding because of the prominent thermal-softening effect.Base on the experiments,the Johnson-Cook model was fitted,and the model was used to predict the flow behaviors of plastic mold steel NAK80 at different temperature and different strain rates.The comparisons between models and the experiments show the fitted Johnson-Cook model can well describe the flow behaviors of plastic mould steel NAK80.