The deformation and mixing of several Ni/Al powders under shock wave loading: effects of initial configuration
The deformation and mixing of several Ni/Al powders under shock wave loading: effects of initial configuration
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DOI：
10.1088/0965-0393/22/2/025018
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发表时间：
2014-03
影响因子：
1.8
通讯作者：
R. Austin;D. McDowell;D. Benson
中科院分区：
文献类型：
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作者：
R. Austin;D. McDowell;D. Benson
在无机粉末混合物中超快化学反应的激波引发需要将反应物混合在激波前沿内或激波后不久。因此，粒子变形的细节对于理解导致这些系统冲击起爆的事件序列至关重要。众所周知，粉末的初始构型(即混合物的组成和颗粒形态)对冲击波加载下的混合程度有很大影响。然而，由于所涉及的时间和长度尺度的原因，在冲击压缩实验中很难完全解决这种混合行为。本文在颗粒水平上对六种不同的Ni/Al粉末的冲击波变形和混合进行了有限元模拟研究。由于整个混合物的反应性取决于反应物界面面积的比量和在这些界面处诱导的条件，因此重点关注所形成的Ni/Al界面。分析揭示了(I)基于反应物界面面积形成的粉末的等级排序，(Ii)Ni/Al界面生成速率的标度关系，以及(Iii)在一定冲击应力范围内Ni/Al界面温度和位错密度的分布特性。结果表明，当压实粉末被反射波重新锁定时，颗粒速度差倾向于在Ni/Al界面上发展。速度差异源于聚集体的异质性，并被假设为驱动碎裂过程，从而在亚微秒的时间尺度上实现超快反应。
The shock wave initiation of ultra-fast chemical reactions in inorganic powder mixtures requires the reactants to be blended within the shock front or shortly behind it. As such, the details of particle deformation are crucial to understanding the sequence of events leading up to the shock initiation of these systems. It is known that the initial configuration of a powder (i.e. the mixture composition and particle morphology) can have a significant effect on the degree of mixing that is achieved under shock wave loading. However, it is difficult to fully resolve this mixing behaviour in shock compression experiments due to the time and length scales involved. In this work, the shock wave deformation and mixing of six distinct Ni/Al powders are studied at the particle level using finite element simulation. Attention is focused on the Ni/Al interfaces that are formed since overall mixture reactivity depends on the specific amount of reactant interfacial area and on conditions induced at those interfaces. The analysis reveals (i) a rank ordering of the powders based on reactant interfacial area formation, (ii) a scaling relation for the rate of Ni/Al interface production and (iii) the distributed nature of Ni/Al interface temperature and dislocation density over a range of shock stress. Finally, it is shown that particle velocity differentials tend to develop across Ni/Al interfaces when the compacted powders are reshocked by reflection waves. The velocity differentials stem from the heterogeneity of the aggregates and are hypothesized to drive fragmentation processes that enable ultra-fast reactions on a sub-microsecond time scale.