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含孔洞炸药晶体HMX冲击响应的分子动力学模拟OACSTPCD

Molecular Dynamic Studies on the Shock Responses of Energetic Crystal HMX with Cylindrical Voids

中文摘要英文摘要

动载荷下炸药晶体缺陷与热点形成的关联是当前含能材料领域的研究热点之一,理解热点形成机制及其对炸药起爆和感度的影响对于炸药安全性评估和研制安全弹药至关重要.本研究采用ReaxFF反应力场和分子动力学方法,对含圆柱形孔洞的炸药单晶奥克托金(HMX)在冲击载荷下的动态响应进行了研究,并探究了孔洞尺寸和双孔洞的影响.结果表明,冲击载荷下孔洞的塌缩过程分为3个阶段,即孔洞上游的塑性变形、上游原子向孔洞中心和下游运动形成流动原子、流动原子与下游碰撞.热点形成的主要机制是流动原子与下游碰撞使得动能转换为热能导致温度快速升高.热点的高温诱发了局部化学反应,HMX分子中N—NO2键断裂生成NO2是主要的初始反应机制.圆柱形孔洞的塌缩过程和热点形成机制与球形孔洞是相似的,但圆柱形孔洞的汇聚效应更弱、形成的流动原子速度更低,导致热点温度显著降低、化学反应更弱.此外,圆柱形孔洞在塌缩过程中在其周围形成了剪切带,这在球形孔洞中没有出现.随着孔洞尺寸的增大,流动原子的速度提高、剪切带变宽、热点温度升高且面积增大,进而引发了更剧烈的化学反应.对于沿冲击方向排布相距一个孔洞半径的双孔洞,孔洞塌缩过程与单孔洞是类似的,但由于冲击波在传过上游孔洞后压力有所降低,导致下游孔洞在塌缩过程中形成的流动原子速度更小、热点温度更低.本研究有助于深入理解晶体缺陷对炸药热点形成与起爆机理的作用,为宏观理论建模提供物理机制与规律认识.

The relationship between crystal defects and hotspots formation of explosives under dynamic loading is a hot research topic in energetic materials.Understanding the mechanism of hotspots formation and its role in the ignition and sensitivity of high explosives are of great importance due to the needs of safety assessment of explosives and developing insensitive munitions.In this work,the ReaxFF reactive force field and molecular dynamics method were applied to investigate the dynamic responses of single crystal cyclotetramethylene tetranitramine(HMX)explosive with cylindrical voids under shock loading.Moreover,the ef-fect of void size and double voids were studied.It is found that the shock induced collapse of voids includes three stages,name-ly,the plastic deformation on the upstream of the void,the movement of upstream atoms towards the centerline and the down-stream of the void forming flowing atoms,and the collision of flowing atoms on the downstream.The main mechanism of hot-spots formation is the collision of flowing atoms on the downstream that transforms kinetic energy into thermal energy leading to rapid temperature rise.The high temperature of hotspots initiates local chemical reactions,and the breaking of N—NO2 bond in HMX molecule with NO2 formation is the principal initial reaction mechanism.The void collapse process and hotspots formation mechanism of cylindrical void is similar to spherical void,while the convergence effect is weaker and the velocity of formed flowing atoms is lower for cylindrical void,resulting in significantly low hotspot temperature and weak chemical reactions.Be-sides,the collapse of cylindrical void forms shear bands around,which was not observed for spherical void.With the increase of void size,the velocity of flowing atoms goes up,the shear bands are wider,and the hotspot temperature is higher and hotspot area is larger,leading to more violent chemical reactions.For the sample with two voids that are aligned along the shock direc-tion with a distance of void radius,the collapse of voids is similar to single void.The shock pressure reduces when the shock wave propagates through the upstream void due to the reflected rarefaction wave.Therefore,the velocity of the flowing atoms formed during the collapse of the downstream void is smaller,and the temperature of the second hotspot is lower.The current findings are beneficial to comprehend the effects of crystal defects on hotspots formation and subsequent ignition of explosives and can provide physical mechanism and laws cognition to construct macro-theoretical models.

周婷婷;楼建锋

北京应用物理与计算数学研究所,北京 100094

武器工业

炸药孔洞热点化学反应分子动力学

explosivevoidhotspotchemical reactionmolecular dynamics

《含能材料》 2024 (001)

65-75 / 11

10.11943/CJEM2023167

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