高温下奥克托今单晶冲击响应数值计算

为研究奥克托今(HMX)单晶在高温下的冲击响应，发展了基于热激活和声子拖曳位错滑移机制的非线性热弹黏塑性模型。该模型可再现平板撞击实验中HMX单晶Hugoniot弹性极限(HEL)的热硬化效应。通过定量分析声子散射和辐射阻尼对热硬化效应的影响，可研究373 K、423 K高温下受冲击HMX单晶位错滑移机制演变以及相关热力学响应。结果表明：随着初温由300 K升 高至423 K，声子散射和辐射阻尼效应增强导致声子拖曳系数增大，使可移动位错黏性摩擦增强，平均位错速度由2 237 m/s减小至1 537 m/s，进而产生较低的塑性剪应变率和较高的流动应力，引起HMX单晶HEL的热硬化效应；剪切模量随着初温升高变化较小(约1.0 GPa)，导致辐射阻尼对热硬化效应的贡献小于声子散射。

Numerical Calculation of Thermodynamic Response of Shocked HMX Single Crystal at Elevated Temperatures

A nonlinear thermoelastic-viscoplastic model is developed for studying the thermodynamic response of octogen (HMX) single crystal at elevated temperatures, in which the thermal activation and phonon drag dislocation glide regime are considered. The proposed model can reproduce the thermal hardening behavior of Hugoniot elastic limit (HEL) of HMX single crystal in plate impact experiment. The effects of phonon scattering and radiation damping on the thermal hardening behavior are quantitatively analyzed to investigate the evolution of dislocation glide regime and the thermodynamic response at 373 K and 423 K. It is found that the thermal hardening behavior of HEL of HMX single crystal is due to the increase in phonon scattering and radiation damping with the initial temperature from 300 K to 423 K. The phonon drag coefficient is increased to strengthen the viscous friction of mobile dislocation. Therefore, the average dislocation velocity decreases from 2 237 m/s to 1 537m/s, which leads to slower plastic shear strain rate and higher flow stress. The shear modulus changes slightly with the increase in temperature (about 1.0 GPa), thus the contribution of radiation damping to thermal hardening is less than that of phonon scattering.