可变形定向破片战斗部在不同展开模式下的性能数值模拟

为使战斗部具有多种定向毁伤模式并实现一定程度上的可控毁伤,提出了一种扇形装药的可变形定向破片战斗部,该战斗部可实现轴向展开和侧向展开2种模式。采用AUTODYN软件进行破片场的数值模拟。首先,基于战斗部单元体分析获得了距离轴心25 mm处的最佳起爆点位置;其次,对整个战斗部进行分析,在轴向展开模式下分析了轴向展开角度对破片飞散速度、破片数目和破片空间分布的影响,发现轴向展开角在60°～75°范围内毁伤效果较佳;最后,在侧向展开模式下分析了整个战斗部的破片速度和破片空间分布情况,结果表明破片具有明显的定向飞散特性。     

基于数值计算结果的破片战斗部威力仿真方法

建立了包含数值方法和分析方法的威力仿真方法。考虑数值计算的规模和复杂度，采用爆轰计算获得初始时刻破片场，利用分析方法描述破片飞散和破片作用目标的过程。采用该威力仿真方法，实现了对破片场形成、破片飞散、破片作用目标的全过程描述。数值计算采用LS-DYNA软件，为了获得战斗部初始时刻破片场，开发了接121处理程序。利用分析方法，建立了破片飞散和破片毁伤性能评估模型，飞散模型中考虑空气阻力等因素的影响，破片毁伤性能评估模型中采用THOR方程预估破片剩余速度、剩余质量和最大穿透厚度，从而获得破片弹道、破片威力参数和破片对靶板的毁伤效果。通过对虚拟靶板上命中破片进行统计，计算出破片命中靶板密度分布和破片飞散角分：布，完成破片战斗部威力仿真试验。在威力仿真方法的基础上，建立了系统仿真模型（图1）。采用面向对象的Visual Studio．NET编程语言，实现威力仿真软件的编码。     

预制破片冲击起爆裸炸药的理论分析

为了研究球形、圆柱形和正多棱柱形预制破片冲击起爆裸炸药的规律,利用Mathcad软件,基于Held高能炸药冲击起爆u2 d判据进行了理论计算与分析,着重比较了破片的质量、密度、形状、长径比、棱数等对冲击起爆裸炸药特性的影响,并与AUTODYN的仿真结果进行了比较。结果表明:对于球形破片,直径一定时,破片密度增大,质量增加,起爆能力增强;相同材料和直径的球形破片与长径比为1的圆柱形破片相比,圆柱形破片的起爆能力优于球形破片。对于圆柱形和正棱柱形破片,密度和质量一定时,随着长径比的增加,破片的起爆能力下降;正棱柱破片的棱数增加时,起爆能力降低,当棱数趋于无穷时,效果趋近于相应的圆柱形破片。     

起爆方式对复合战斗部毁伤输出的影响

为了进一步提高复合战斗部的毁伤输出效率,基于一种可形成聚能侵彻体、预制破片和自然破片3种毁伤元的破甲杀伤复合战斗部结构,应用LS-DYNA数值仿真软件,研究了起爆点位置、起爆直径和起爆点数量对复合战斗部各毁伤元成型和能量输出的影响,讨论了实现战斗部毁伤威力可调的技术路径。结果表明:起爆点距药型罩越远、数量越多、起爆直径越大,由药型罩形成的聚能侵彻体的头部速度越高,头尾速度差和长径比越大,速度增益最高可达50%,可以实现爆炸成型弹丸(EFP)到聚能杆式侵彻体(JPC)转换;在装药内部轴线阵列多点起爆时,聚能侵彻体的成型基本仅与离药型罩最近的起爆点有关。对于预制破片,装药高度60 mm(P2)处起爆速度最快,增加起爆点数量和增大起爆直径可以有效提高预制破片的最高速度,但整体上最低速度仍在600 m/s上下波动,变化并不显著。对于壳体形成的自然破片,以平均速度来表征时,整体变化并不明显,速度增益不足10%,但合理的起爆方式可使壳体断裂形成的自然破片更均匀,有利于调整破片质量分布。通过控制起爆方式可在一定程度上实现复合战斗部毁伤威力可调,但对于破片速度的调控仍需进一步研究。     

破片式战斗部破片与冲击波相遇位置研究

为研究破片式战斗部爆炸后破片和冲击波两种毁伤元的相遇位置,先通过ANSYS/LS-DYNA对破片式战斗部的爆炸过程进行数值计算,再通过试验的方法测量破片和冲击波相遇位置,验证了数值计算方法的合理性。在此基础上,分析了装填系数、破片质量、爆速和爆热对相遇位置的影响。结果表明:随着装填系数、破片质量、爆速和爆热的增加,相遇位置减小;装填系数增加31%,相遇位置距爆炸中心的距离减小11.5%;单枚破片质量增加1倍,相遇位置距爆炸中心的距离减小2.4%。     

序贯起爆参数对定向战斗部毁伤效能的影响

为提高定向战斗部的毁伤效能,明确序贯起爆参数对定向战斗部毁伤效能的影响,运用LS-DYNA有限元程序,采用破片速度差累加和飞散角累加的方法,研究了不同序贯起爆参数下破片初始威力参数,利用毁伤概率法,计算了不同序贯起爆参数下战斗部对地面军用车辆的毁伤效能。结果表明:起爆线个数和起爆线夹角主要影响破片速度大小,起爆延时时间主要影响破片速度大小和飞散角正负占比。相对于偏心一线和三线序贯起爆,偏心两线序贯起爆在落高为7～9 m时有7.5～25.0 m²的毁伤面积。当起爆线夹角由30°增大到120°,落高为4～8 m时,战斗部对地面军用车辆的毁伤面积降低3.9%～60.3%。序贯起爆的延时时间由零增加到0.75倍的相邻起爆点间爆轰波传播时间,落高为4～8 m时,战斗部的毁伤面积增加8.4%～87.2%。当起爆方式采用偏心两线序贯起爆,起爆线夹角取30°～60°,延时时间取0.50～0.75倍的相邻起爆点间爆轰波传播时间时,破片战斗部对地面军用车辆目标具有较好的毁伤效能。     

扇形复合装药驱动破片定向飞散的数值模拟

利用LS-DYNA软件对扇形单一装药和复合装药驱动破片的作用过程进行了数值模拟,得到预制破片的初速及分布规律,并对不同起爆方式和复合装药参数的扇形装药结构破片驱动特性进行了计算分析。结果表明:数值模拟计算值与试验结果吻合较好,相对于单一装药结构,复合装药能使破片飞散更为集中,且破片的总动能提高了12%以上;通过改变起爆方式和复合装药参数,破片的综合毁伤效能可进一步增强。     

切割式双模战斗部毁伤元成型及侵彻钢靶特性研究

 基于60 mm弧锥结合罩爆炸成型弹丸（EFP）装药,设计了一种在药型罩前适当位置安装可抛掷的十字形网栅的切割式双模战斗部结构,其具有生成单个EFP或者多爆炸成型弹丸（MEFP）的功能;根据目标属性,可选择性地改变战斗部的毁伤元成型模式,实施最有效的打击。利用LS-DYNA程序,对两种模式毁伤元成型及侵彻45钢靶过程特性进行了数值模拟,模拟结果与地面静爆实验结果吻合较好。研究表明,该战斗部形成的单个EFP能贯穿25 mm厚45钢靶,可有效打击重装甲目标;经网栅切割后能形成5片具有一定质量和方向性、可贯穿6 mm厚45钢靶的EFP破片,显著提高了对轻装甲目标的毁伤概率。     

高压气体载荷下预制破片与空气冲击波的运动关系

冲击波与破片的运动关系直接决定两者对目标的联合毁伤效果,采用有限体积方法和网格自适应技术,对高温高压气体载荷作用下圆形刚体破片的运动规律、冲击波的衰减规律以及两者的运动关系进行了数值模拟研究。结果表明,高温高压气团形成的冲击波与破片作用发生反射和透射,在破片前后形成的压力差是导致其加速的主要原因。在破片数量一定的情况下,破片距离高温高压气团中心越远,初速越小。当破片与高温高压气团中心的间距相同时,破片数量越多,初速越大。同时研究发现,冲击波与刚体球存在复杂的追逐关系:当初速较大时,破片和冲击波相遇两次;初速减小时,二者相遇一次;初速进一步减小时,二者不能相遇。冲击波与刚体球破片的前后关系将会影响它们对目标的毁伤是否存在耦合关系。     

非金属壳体低附带战斗部实验与破片飞散分析

为了研究低附带战斗部的非金属破片飞散特性,结合某低附带杀伤战斗部静爆威力实验,对战斗部爆炸产生的非金属破片初速以及速度衰减情况进行了分析。基于能量守恒得到了包含壳体结构和材料强度因素的破片初速公式;基于破片在空气中飞行运动情况的分析,通过对球形破片阻力公式和等效面积进行修正,得到了非金属自然破片的速度衰减规律。所得结果较好地解释了战斗部静爆实验中的破片终点效应情况,亦可为该类战斗部破片毁伤效应评估提供一种分析方法。     

AFM investigation of films based on UV-solidified powder oligoesterdimethacrylate compositions

The morphology, supramolecular structure, and thermal behavior of powder coatings based on UV-solidified oligoesterdimethacrylate powder compositions with and without reactive coreactant bis-styrenated urethane prepared on different substrates have been studied using atomic-force microscopy, X-ray phase analysis, and differential scanning calorimetry. It was found that addition of the reactive coreactant in powder compositions results in homogenization of structure and morphology of coatings and increase in their glass transition temperatures by more than 10 K. The character of their morphology depends also on the conditions of film formation and substrate material. Unmodified coatings formed on a steel substrate exhibit an anisotropic structure, in contrast to the coatings prepared on the PTFE substrate, which are isotropic and represent a homogeneous polymer matrix containing aggregates formed by inclusions of nanoand microdimensions.     

液相混合铋系超导前驱粉体工艺研究

本研究采用溶胶凝胶颗粒包覆技术，将钙铜离子均匀包覆在2212颗粒表面，通过适当的热处理，使包覆层转变为Ca2CuO3 CuO相，同时确保2212相结构稳定，从而获得了均匀混合的装管前驱粉体．详细研究了钙铜溶胶体系的胶凝工艺，2212悬浮体系的稳定性以及Ca2CuO3成相温区等工艺参数，并利用XRD，SEM等分析手段，研究了粉体的粒度分布，形貌，相组成及其均匀性．     

拉曼高光谱成像系统中光在奶粉层的穿透深度研究

拉曼高光谱成像技术不仅可以获取样本的空间分布信息,图像上每个像素点还包括了完整的光谱信息,因其信息量丰富的特点已在食品安全检测方面得到了应用。本研究探索拉曼高光谱成像系统中光在奶粉层中的穿透深度,以及采集参数和奶粉类型对穿透深度的影响。实验选取均匀奶粉层样品放置于厚度为5 mm的三聚氰胺样本之上,检测奶粉层厚度为0.8～4.0 mm时的三聚氰胺特征峰强度,以此评估光在奶粉层中的穿透性和信号衰减情况。结果显示当奶粉层厚度一定时,随着激光功率变大,拉曼特征峰值随之增加,此外更长的曝光时间也可以使拉曼信号得到增强。在激光功率不小于2 W且曝光时间不小于500 ms时,光在全脂奶粉层的穿透深度可达4 mm。奶粉层厚度在0.8～4.0 mm范围内,穿透奶粉层的拉曼信号随着奶粉层厚度增加呈指数式衰减。在激光功率为8 W、曝光时间为1 000 ms的条件下,光在全脂、低脂和脱脂奶粉层的穿透深度均达到了4 mm。在相同测量厚度下,通过脱脂奶粉层接收的拉曼信号弱于通过全脂和低脂奶粉层接收的拉曼信号强度。研究结果为拉曼高光谱检测中奶粉样品的前处理提供了有益参考。     

PTFE/Al反应材料的力学性能研究

 反应材料是一种由冲击引发的新型含能材料,对其力学性能的研究是其广泛应用的一个重要前提。在室温下,利用万能试验机和改进的摆锤冲击试验机对聚四氟乙烯/铝（PTFE/Al）系列反应材料的拉伸和冲击性能进行了实验研究。随着Al含量的增加,反应材料的密度和燃烧热升高,拉伸强度呈先升高后降低的趋势,在Al含量为6%左右时达到最大值36.1 MPa,与计算结果较符合。推测反应材料的损伤过程为变形、开裂和反应3步。Al含量的增加导致反应材料试样的冲击韧性先升高后降低,在Al含量为40%左右时达到最大值72.06 J/cm²。随着Al含量的增加,材料的反应难度增加,反应自持性降低。     

The effect of powder preparation method on the corrosion and mechanical properties of TiN-based coatings by reactive plasma spraying

TiN-based composite coatings with and without the addition of Cr were deposited by reactive plasma spraying (RPS) in air. Both sintered and mixed powder of Ti and B₄C were used for the RPS process. A thermodynamic model was firstly used to estimate the complicated phase composition of composite coatings prepared by RPS. The phase composition, structures and properties of TiN-based coatings were investigated using XRD, SEM and a Vickers microhardness tester. The results show that the phases in TiN-based coatings do not generate according to priority of Gibbs free energy value due to non-equilibrium reactive course during thermal spraying. The coating deposited using sintered Ti and B₄C powder is composed of two main phases (TiN and TiN_0.3), two minor phases (Ti₂O₃ and TiB₂), and a small fraction of TiC phase. The composition of the coating deposited using the mixed powder with Cr added is predominantly in the TiN and TiB₂ phases, a smaller phase fraction of Ti₂O₃ and TiO₂, and some unreacted Cr. The Vickers microhardness of the coating deposited using sintered powder is higher than that of using mixed powder. The composite coating deposited using mixed powder with the addition of Cr shows superior corrosion resistant to that using sintered powder when tested in 3.5 wt.% NaCl electrolytic solution.     

A multi-step reaction model for ignition of fully-dense Al-CuO nanocomposite powders

A multi-step reaction model is developed to describe heterogeneous processes occurring upon heating of an Al-CuO nanocomposite material prepared by arrested reactive milling. The reaction model couples a previously derived Cabrera-Mott oxidation mechanism describing initial, low temperature processes and an aluminium oxidation model including formation of different alumina polymorphs at increased film thicknesses and higher temperatures. The reaction model is tuned using traces measured by differential scanning calorimetry. Ignition is studied for thin powder layers and individual particles using respectively the heated filament (heating rates of 10³–10⁴ K s^?1) and laser ignition (heating rate ～10⁶ K s^?1) experiments. The developed heterogeneous reaction model predicts a sharp temperature increase, which can be associated with ignition when the laser power approaches the experimental ignition threshold. In experiments, particles ignited by the laser beam are observed to explode, indicating a substantial gas release accompanying ignition. For the heated filament experiments, the model predicts exothermic reactions at the temperatures, at which ignition is observed experimentally; however, strong thermal contact between the metal filament and powder prevents the model from predicting the thermal runaway. It is suggested that oxygen gas release from decomposing CuO, as observed from particles exploding upon ignition in the laser beam, disrupts the thermal contact of the powder and filament; this phenomenon must be included in the filament ignition model to enable prediction of the temperature runaway.     

粉末颗粒气力加注特性实验研究

粉末发动机是以粉末颗粒为燃料的新型发动机,具有多次起动和推力调节的功能.粉末加注是粉末发动机实验组织过程中的重要环节.本研究通过搭建粉末供应系统开展粉末气力加注实验,研究对比了集粉箱加注位置、流化气量对粉末气力加注特性的影响.考虑了供粉过程中储箱内粉末堆积密度的动态变化,并建立了相应的计算方法,同时还采用控制系统理论揭示了储箱内粉末堆积密度的变化规律.结果表明:在相同条件下,较大的流化气量有利于加注过程稳定,但集粉箱加注率较低;气力加注方式下集粉箱内的粉末堆积密度大于储箱内初始堆积密度;采用较小的流化气量与集粉箱壁面切向加注方式有利于提高粉末粒径分布均匀性;集粉箱壁面切向加注方式下,流化气量较小时储箱内粉末的堆积密度是先增大后减小,且堆积密度最终值小于初始值,而流化气量较大时,储箱内粉末的堆积密度是先增大后减小再增大后减小,且堆积密度最终值大于初始值;储箱内粉末堆积密度的动态变化过程类似于欠阻尼二阶系统,流化气量较小时系统阻尼系数较小,而流化气量较大时系统阻尼系数较大,且是一个变阻尼过程.     

Deuterium-tritium fuel impact ignition in the presence of degenerate plasma

The impact ignition model is proposed based on the collision of a deuterium-tritium (DT) layer accelerated to high velocities in a conical target. Simple mechanism, low cost, high coupling efficiency, and lack of the need for Petawatt laser pulses are the prominent advantages of this model. However, an increase in the productivity of this ignition mechanism is an important issue. In this regard, in this paper, the idea of impact ignition using the plasma degeneracy mechanism has been investigated. For this purpose, first, the ignition energy gain and stopping power of the DT beam in pure and impure fuels, by employing both degenerate and non-degenerate plasmas, have been examined numerically. Then, in order to assess the penetration depth and range of the incident beam, simulations have been carried out using a three-dimensional (3D) Monte Carlo code for two states of degenerate and non-degenerate pre-compressed pure fuel. The results imply that the state of degeneracy causes an increase by about 63% in the energy gain of impact ignition. In addition, the degeneracy condition leads to an approximate enhancement of 60% in the energy deposition of the pure fuel and about 67% for the impure fuel, with a mixed density ratio of 1.5%; therefore, the range and penetration depth decrease significantly in comparison to the non-degenerate one. This can be indicative of the increasing efficiency of impact ignition conditions in the presence of degenerate plasma. The results of the range for the pure fuel have also been confirmed by a 3D Monte Carlo simulation code.     

Desensitizing nano powders to electrostatic discharge ignition

Electrostatic discharge (ESD) is a main cause for ignition in powder media ranging from grain silos to fireworks. Nanoscale particles are orders of magnitude more ESD ignition sensitive than their micron scale counterparts. This study shows that at least 13 vol. % carbon nanotubes (CNT) added to nano-aluminum and nano-copper oxide particles (nAl + CuO) eliminates ESD ignition sensitivity. The CNT act as a conduit for electric energy and directs electric charge through the powder to desensitize the reactive mixture to ignition. For nanoparticles, the required CNT concentration for desensitizing ESD ignition acts as a diluent to quench energy propagation.     

An experimental investigation on spray, ignition and combustion characteristics of biodiesels

Spray, ignition and combustion characteristics of biodiesel fuels were investigated under a simulated diesel-engine condition (885 K, 4 MPa) in a constant volume combustion vessel. Two biodiesel fuels originated from palm oil and used cooking oil were used while JIS#2 used as the base fuel. Spray images were taken by a high speed video camera by using Mie-scattering method to measure liquid phase penetration and liquid length. An image intensifier combined with OH filter was used to obtain OH radical image near 313 nm. Ignition and combustion characteristics were studied by OH radical images. Biodiesel fuels give appreciably longer liquid lengths and shorter ignition delays. At low injection pressure (100 MPa), biodiesel fuels give shorter lift-off lengths than those of diesel. While at high injection pressure (200 MPa), the lift-off length of biodiesel fuel originated palm oil gives the shortest value and that of biodiesel from used cooking oil gives the longest one. Air entrainment upstream of lift-off length of three fuels was estimated and compared to soot formation distance. This study reveals that the viscosity and ignition quality of biodiesel fuel have great influences on jet flame structure and soot formation tendency.