SHPB实验考虑绝热变形和端面摩擦的修正方法

采用高温分离式霍普金森压杆(SHPB)实验技术对GH4169高温合金进行测试,获得了材料在高应变率下的温度敏感性，并拟合了Johnson-Cook本构模型的参数。结合数值计算方法对压缩实验中试件内部的应力、应变以及温度的分布建立了一个半经验的数学模型并提出了一种新的参数修正方法,将端面摩擦效应、绝热变形升温效应与SHPB实验结果进行解耦。实验结果表明:温度越高，GH4169高温合金的屈服强度以及流动应力越小。并且在SHPB实验中GH4169高温合金存在明显的绝热变形升温效应和端面摩擦效应,导致实验结果并不能真实反映材料的硬化特性。通过对原始Johnson-Cook本构方程的硬化项乘以1.2的修正系数,发现修正后的本构参数准确反映了材料在高应变率下的应力应变特性。 

Correction method of SHPB experiment considering adiabatic deformation and interfacial friction effects

GH4169 super alloy was tested using high temperature split Hopkinson pressure bar (SHPB) technique. The temperature sensitivity of the material under high strain rates was obtained and the parameters of Johnson-Cook constitutive model were fitted. A semi-empirical model was established to describe the distribution of stress, strain and temperature inside the specimen during compression based on the numerical calculation method. Then a new method for correcting the constitutive parameters was put forward to decouple the interfacial friction effect and adiabatic deformation from the result of SHPB experiment. The experimental results showed that the yield strength and flow stress of GH4169 super alloy decreased with the increase of temperature. And it was confirmed that adiabatic deformation and interfacial friction effect obviously affected the accuracy of SHPB experiment, thus the results can not reflect the work hardening properties of the material. After multiplying the hardening term by the correction factor of 1.2, the modified constitutive parameters accurately reflected the stress-strain characteristics of the material under high strain rates.