【摘要】 为了研究镍基高温合金GH4720Li在高应变率下的动态力学性能，利用分离式霍普金森压杆（SHPB）对材料进行了温度范围为20～1 000℃,应变率为10～5 000 s^-1的单轴热压缩试验，获得了不同温度不同应变率下材料的应力应变曲线。结果表明：在相同的试验温度条件下，GH4720Li合金在高、低2种应变率条件下表现出了不同的动态力学性能。在低应变率(10 s^-1)条件下，GH4720Li合金的应力值随着温度的升高而降低；在高应变率(1 000 s^-1,5 000 s^-1)条件下，GH4720Li合金的应力值在特定温度（400～800℃）随着温度的升高而升高。结合已获得的试验数据，通过数值拟合的方法对原始Johnson-Cook（J-C）本构方程进行了修正，以满足GH4720Li合金在高应变率下应力的变化规律。通过线性相关系数和平均误差对修正的J-C本构方程精度进行了验证。结果显示：修正的J-C本构方程与试验数据吻合良好，可以大幅度提高J-C本构方程对GH4720Li合金在大应变率范围下的拟合精度。更多还原

【Abstract】 In order to study the dynamic mechanical properties of nickel base superalloy GH4720Li at a high strain rate, this paper carries out uniaxial thermal compression tests to the materials with a Split Hopkinson Pressure Bar（SHPB） in a temperature range of 20 ℃ to 1 000 ℃ and a strain rate range of 10 s^-1 to 5 000 s^-1. The stress-strain curves of the materials at different temperatures and different strain rates are obtained. The results show that under the same test temperature, GH4720Li alloy shows different dynamic mechanical properties at a high and a low strain rates. At a low strain rate(10 s^-1), the stress value of GH4720Li alloy decreases with the increase of temperature. Under the condition of a high strain rate(1 000 s^-1 or 5 000 s^-1), the stress value of GH4720Li alloy increases with the increase of temperature in a specific temperature range（400 ℃ to 800 ℃）. Combined with the obtained test data, the original Johnson-Cook（J-C） constitutive equation is modified by the numerical fitting method to meet the stress variation law of GH4720Li alloy at a high strain rate. The accuracy of the modified J-C constitutive equation is verified by linear correlation coefficient and mean error. The results show that the modified J-C constitutive equation is in good agreement with the experimental data, which can greatly improve the fitting accuracy of the J-C constitutive equation to the GH4720Li alloy in a large range of strain rates.更多还原