Homogeneous dislocation nucleation in cyclotrimethylene trinitramine under shock loading
Homogeneous dislocation nucleation in cyclotrimethylene trinitramine under shock loading
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DOI：
10.1063/1.3305630
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发表时间：
2010-03-15
影响因子：
3.2
通讯作者：
Sewell, Thomas D.
中科院分区：
文献类型：
--
作者：
Cawkwell, M. J.;Ramos, K. J.;Sewell, Thomas D.
用大尺度分子动力学模拟方法研究了垂直于（111）面的激波在含能分子晶体环三亚甲基三硝胺（RDX）中的传播。当Rankine-Hugoniot冲击压力大于1.3 GPa时，Burgers矢量为0.16[010]的部分位错环在（001）面上均匀形核。对（001）广义层错能面的[010]截面作为沿着[001]方向施加的压力的函数的计算表明，由部分位错环包围的层错由于应力诱导的分子构象变化而呈现亚稳态。此外，对准二维（111）取向单晶进行的大规模分子动力学模拟显示了具有“驰振”塑性波的两波弹塑性响应。我们提出均匀位错成核的开始解释了最近实验中观察到的宏观（111）取向RDX单晶的弹塑性响应的突然变化，引起了异常的塑性硬化。
The propagation of shock waves normal to (111) in the energetic molecular crystal cyclotrimethylene trinitramine (RDX) has been studied using large-scale molecular dynamics simulations. Partial dislocation loops with Burgers vector 0.16[010] are nucleated homogeneously on (001) at Rankine-Hugoniot shock pressures greater than 1.3 GPa. Calculations of the [010] cross-section of the (001) generalized stacking fault energy surface as a function of applied pressure along [001] reveals that the stacking fault enclosed by the partial dislocation loops is rendered metastable by a stress-induced change in molecular conformation. Furthermore, large-scale molecular dynamics simulations performed on quasi-two-dimensional (111)-oriented single crystals show a two-wave elastic-plastic response with a "galloping" plastic wave. We propose that the onset of homogeneous dislocation nucleation accounts for the abrupt change in the elastic-plastic response of macroscopic (111)-oriented RDX single crystals observed in recent experiments by giving rise to an anomalous plastic hardening.