Preliminary discussion on the ignition mechanism of exploding foil initiators igniting boron potassium nitrate

Exploding foil initiator(EFI)is a kind of advanced device for initiating explosives,but its function is unstable when it comes to directly igniting pyrotechnics.To solve the problem,this research aims to reveal the ignition mechanism of EFIs directly igniting pyrotechnics.An oscilloscope,a photon Doppler velocimetry,and a plasma spectrum measurement system were employed to obtain information of electric characteristics,impact pressure,and plasma temperature.The results of the electric characteristics and the impact pressure were inconsistent with ignition results.The only thing that the ignition success tests had in common was that their plasma all had a relatively long period of high-temperature duration(HTD).It eventually concludes that the ignition mechanism in this research is the microconvection heat transfer rather than the shock initiation,which differs from that of exploding foil initiators detonating explosives.Furthermore,the methods for evaluating the ignition success of semiconductor bridge initiators are not entirely applicable to the tests mentioned in this paper.The HTD is the critical parameter for judging the ignition success,and it is influenced by two factors:the late time discharge and the energy of the electric explosion.The longer time of the late time discharge and the more energy of the electric explosion,the easier it is to expand the HTD,which improves the probability of the ignition success.

Recent progress in the research on magnesium and magnesium alloy foils:A short review

Magnesium and magnesium alloy foils have great potential for application in battery anodes,electromagnetic shielding,optics and acoustics,and biology because of their excellent specific damping,internal dissipation coefficients,magnetic and electrical conductivities,as well as high theoretical specific capacity.However,magnesium alloys exhibit poor deformation ability due to their hexagonal close-packed crystal structure.Preparing magnesium and magnesium alloy foils with thicknesses of less than 0.1 mm is difficult because of surface oxidation and grain growth at high temperatures or severe anisotropy after cold rolling that leads to cracks.Numerous methods have been applied to prepare magnesium alloy foils.They include warm rolling,cold rolling,accumulative roll bonding,electric plastic rolling,and on-line heating rolling.Defects of magnesium and magnesium alloy foils during preparation,such as edge cracks and breakage,are important factors for consideration.Herein,the current status of the research on magnesium and magnesium alloy foils is summarized from the aspects of foil preparation,defect control,performance characterization,and application prospects.The advantages and disadvantages of different preparation methods and defect(edge cracks and breakage)mechanisms in the preparation of foils are identified.

Purification of copper foils driven by single crystallization

High-purity copper(Cu) with excellent thermal and electrical conductivity, is crucial in modern technological applications, including heat exchangers, integrated circuits, and superconducting magnets. The current purification process is mainly based on the zone/electrolytic refining or anion exchange, however, which excessively relies on specific integrated equipment with ultra-high vacuum or chemical solution environment, and is also bothered by external contaminants and energy consumption. Here we report a simple approach to purify the Cu foils from 99.9%(3N) to 99.99%(4N) by a temperature-gradient thermal annealing technique, accompanied by the kinetic evolution of single crystallization of Cu.The success of purification mainly relies on(i) the segregation of elements with low effective distribution coefficient driven by grain-boundary movements and(ii) the high-temperature evaporation of elements with high saturated vapor pressure.The purified Cu foils display higher flexibility(elongation of 70%) and electrical conductivity(104% IACS) than that of the original commercial rolled Cu foils(elongation of 10%, electrical conductivity of ~ 100% IACS). Our results provide an effective strategy to optimize the as-produced metal medium, and therefore will facilitate the potential applications of Cu foils in precision electronic products and high-frequency printed circuit boards.

Study on theoretical model for electrical explosion resistivity of Al/Ni reactive multilayer foil

Al/Ni reactive multilayer foil(RMF)possesses excellent comprehensive properties as a promising substitute for traditional Cu bridge.A theoretical resistivity model of Al/Ni RMF was developed to guide the optimization of EFIs.Al/Ni RMF with different bilayer thicknesses and bridge dimensions were prepared by MEMS technology and electrical explosion tests were carried out.According to physical and chemical reactions in bridge,the electrical explosion process was divided into 5 stages:heating of condensed bridge,vaporization and diffusion of Al layers,intermetallic combination reaction,intrinsic explosion,ionization of metal gases,which are obviously shown in measured voltage curve.Effects of interface and grain boundary scattering on the resistivity of film metal were considered.Focusing on variations of substance and state,the resistivity was developed as a function of temperature at each stage.Electrical explosion curves were calculated by this model at different bilayer thicknesses,bridge dimensions and capacitor voltages,which showed an excellent agreement with experimental ones.

Effect of Surface Roughness on Lubrication Performance of Bump-Type Gas Foil Bearings

Taking bump-type gas foil bearings as the research object,a deformation model of bump foil and a thin-plate finite element model of top foil were proposed.By solving Reynolds equation and energy equation,the pressure distribution and the temperature distribution of gas films in foil bearings were obtained.Further,a numerical method for calculating the lubrication performance of gas foil bearings with considering the surface roughness was proposed.With a specific example,effects of the surface roughness on the bearing lubrication performance were parametrically studied.The results indicate that rougher journal surface can lead to larger fluctuation of the lubrication performance,while surface roughness of top foil has few effects on the fluctuation.Moreover,the mean values of performance parameters almost remain constant at different values of surface roughness.

Methods of controlled formation of instabilities during the electrical explosion of thin foils

The results of a study of the electrical explosion of aluminum foils with an artificial periodic surface structure created by laser engraving are presented.Experiments were carried out on pulsed high-current generators BIN(270 kA,300 kV,100 ns)and KING(200 kA,40 kV,200 ns)with Al foil of thicknesses 16 and 4μm,respectively.Images of the exploded foils were recorded by point projection radiography in the radiation from hybrid X-pinches.It is found that the application of an artificial periodic structure to the foil leads to a much more uniform and well-defined periodic structure of the exploded foil.Images recorded in the UV range using a microchannel-plate-intensified detector show that the radiation from a surface-modified foil is more uniform along the entire length and width of the foil than that from a foil without modification.

Experimental and numerical studies of titanium foil/steel explosively welded clad plate

Ti/Fe clad plate had attracted extensive attention because of its important application. In order to reduce the titanium layer thickness, the explosive welding of TA1 titanium foil to Q235 steel plate was carried out. The interfacial bonding performance was analyzed by micromorphology analysis and mechanical property test, and the formation process of interfacial wave and molten block in the vortex was simulated by smoothed particle hydrodynamics(SPH) method. The results showed that salt as pressure transfer layer used in explosive welding could play a good buffer effect on the collision between flyer and base layers. Regular waveforms were formed on the bonding interface, and the titanium foil/steel clad plate exhibited good welding quality and bonding property. The crest of the observed interfacial wave moved 200 μm from the beginning to the final formation, and it was important of jet on the formation of interfacial waveform. The interface was mainly bonded in the form of molten layer, and the grains near the interface were streamlined. Molten block containing intermetallic compounds and metal oxides appeared in the vortex of wave crest.

基于流固耦合的箔片气体轴承动态特性分析

基于有限元软件ANSYS Workbench,建立箔片气体轴承在可压缩流体介质中运动的有限元模型,采用6DOF动网格计算方法对轴承的运动状态进行流固耦合数值模拟,探讨了不同转速和波箔片结构参数(波箔片的长度比、高度以及厚度)对轴承动态特性的影响规律。仿真结果表明:转速增加,轴承的承载能力增加,但稳定性有所下降,更容易发生失稳现象;选取波箔片的长度比在1~1.5之间、厚度为0.16 mm,既可以保证轴承具有较高的刚度,同时又能获得较大的阻尼;波箔片高度与轴承动态特性成反比关系。将仿真结果与试验结果进行对比,验证了仿真计算方法的正确性和有效性。同时本文的研究为优化波箔片结构,改善轴承动态特性,提高轴承运行稳定性提供理论依据。

电爆炸金属桥箔早期过程中电磁-热-力多物理场耦合建模与分析

金属桥箔的电爆炸过程对电炮、冲击片雷管等的性能影响极为关键。这一过程中物质性质变化、几何构型和动力学过程非常复杂,早期的大量理论模拟工作均采用极为简化的物理模型。为此,建立了描述爆炸箔早期行为的三维电磁-热-固体力学耦合求解全物理模型,模拟爆炸箔在大电流加载下的早期受热膨胀过程,并对早期膨胀过程中桥箔上的磁场、电流、温度等演化进行分析,观察到电流在构型和电阻率两种因素影响下的角扩散和线扩散现象,模拟得到的桥区温度场分布与参考文献中的实验图像及模拟结果定性符合。

金属桥箔电爆炸驱动飞片过程数值模拟研究

为研究金属桥箔电爆炸等离子体驱动飞片全过程中飞片的性能特征和影响规律,建立了金属桥箔电爆炸驱动飞片全过程的多相流数值计算模型,并进行了数值模拟计算.计算中,利用了相变分数描述金属桥箔由固相到等离子体相的相态转变,采用了考虑粒子数目变化及粒子间库仑作用的高温高压等离子体状态方程描述电爆炸等离子体的形成和运动行为,采用了动网格模型描述飞片的运动.将计算结果与实验结果进行对比分析,计算得到的飞片速度值与实验值的误差小于5%,表明计算模型的准确性较好.基于该计算模型,对总面积相同的双体阵列桥箔和单体桥箔电爆炸等离子体驱动飞片过程进行了数值模拟,计算结果表明,由于阵列桥箔电爆炸过程中等离子体和冲击波的叠加汇聚作用,提高了能量转化效率,使得等离子体及冲击波流场对飞片的驱动力增加,从而提高了飞片的速度.等离子体流场对飞片表面的烧蚀厚度约为0.1μm,飞片的完整性较好.

某直列式点火器双路瞎火故障分析与改进

针对某直列式点火器在低温点火试验中出现的双路冲击片点火管瞎火问题,进行了故障定位及原因分析,提出了改进措施并对其有效性进行了试验验证。结果表明:造成双路瞎火故障的原因是点火器转接件焊点异常处的气体间隙弧光放电;提出将2个回路的触发信号时间间隔调整为50μs,按照HB 7262航空产品电装工艺的相关规定细化电装工艺,增加对能量传输通道的介质耐压检测等改进措施。验证试验表明采取改进措施后,消除了弧光放电现象,点火器内的2个爆炸箔表面均有明显的电爆炸痕迹。

硫脲对电解高性能双面光锂电铜箔性能的影响

为研究硫脲质量浓度对铜箔表面形貌、结构、性能以及电解液电化学行为的影响,以磷铜板为阳极,以硫脲(TU)、羟乙基纤维素(HEC)、聚乙二醇(PEG-1000)和聚二硫二丙烷磺酸钠(SPS)作为组合添加剂,采用自制旋转电镀装置以直流电沉积法在TAl钛辊上制备电解铜箔,并利用扫描电子显微镜、铜箔拉伸强度试验仪以及电化学分析等方法,重点考察了组合添加剂中TU对铜箔表面形貌和物理性能的影响。结果表明:在组合添加剂体系中TU具有较强的极化作用,可以抑制铜核的生长,使铜箔结晶更细致,有效地起到光亮和整平作用并提高铜箔力学性能,且组合添加剂间表现出较好的协同效应。在高性能锂电铜箔的制备过程中,可通过适当调整电解液中硫脲的加入量来改善电解铜箔的各项性能。

融合设备状态和产品要求的电解铜箔制造工艺参数优化

针对当前电解铜箔制造工艺参数的优化仅考虑产品要求的问题,提出了一种融合设备状态和产品要求的电解铜箔制造工艺参数优化方法。首先,为辨识铜箔制造中工艺、设备与产品参数之间的非线性关系,建立了基于神经网络的“工艺-设备”与产品参数的映射模型,并通过构建当前生产模式与历史生产模式的相似性度量方法,确定当前工艺参数的优化初始点;然后,基于所建立的映射模型、设备状态和产品要求构建多目标约束函数,并利用遗传算法优化工艺参数,获得同时满足设备状态和产品要求的最佳工艺参数。企业的生产验证表明:相较于仅考虑产品要求的工艺优化方法,所提方法优化后的工艺参数能在相同的设备状态下获得质量更好的产品,在常温/高温抗拉强度、常温/高温延伸率和树脂剥离强度这5项关键指标上,分别提升了6.1 MPa、6.1 MPa、1.9%、0.7%和0.22 N/mm,生箔制备和表面处理的生产效率也提高了2.65%和7.5%,能够有效保证并提高铜箔的质量和生产效益。

Cu对铝/钢CMT熔钎焊接头界面区组织的影响研究

采用冷金属过渡方法,以AlSi5焊丝为填充金属,在5052铝合金和镀锌钢板之间添加铜箔片进行搭接熔钎焊,使用扫描电子显微镜结合能谱分析和拉伸试验机对接头的界面区组织与性能进行研究。结果表明,未加入铜箔时,界面区组织主要由FeAl_(3)金属间化合物组成;铜箔的加入使得界面区组织中新生成了CuAl_(2)金属间化合物,同时改善了Zn在界面区的分布。Zn固溶于Al中,一定程度上抑制了Fe-Al金属间化合物产生。加入铜箔后的试样断裂位置发生改变,接头的承载能力与未加入铜箔的相近。

电容屏破损缺陷局部放电过程规律特征及仿真分析

油纸电容式变压器套管因性能好、成本低而被广泛采用。当电容屏存在边缘破损工艺缺陷时易发生局部放电,进而会改变油纸绝缘性能,缩短套管使用寿命,严重时危及电网设备安全运行。为研究电容屏破损局部放电过程变化规律,明确放电发展阶段,该文搭建了缺陷套管放电实验模型分析局放过程中相位谱图、放电量等参数发展规律,并基于实验规律及流体漂移扩散理论、固体双极电荷传输理论,建立了末屏缺陷针板沿面放电过程仿真模型,结合仿真中电荷形态变化、放电时间及油纸界面电荷密度分布对电容屏破损放电过程进行阶段划分:放电初始阶段,铝箔尖端电荷聚集发生电晕放电;放电发展阶段,尖端处带电粒子在电场作用下向油纸发展,小部分达到油纸界面产生沿面放电;放电破坏阶段,经过长时间沿面放电进入油纸发生预击穿,电场强度更大使带电粒子能量更高,冲击油纸表面造成油纸表面纤维素断裂炭化形成通道。仿真结果与实验结论相对应,证明了仿真的有效性。该文的研究成果进一步阐明了油纸套管电容屏工艺缺陷局部放电的过程及机理。

气浮空气循环机密封轴向气动力研究

针对传统空气循环机双侧高速转子端的轴向力理论经验公式精度偏低,数值计算耗时长的问题,建立包含双侧高速转子的窄缝间隙计算域几何模型,并通过试验校核了模型的准确性。对含双侧高速转子的窄缝间隙内部流场进行数值计算,探讨窄缝间隙对轴向气动力的作用规律,并对传统机械轴向气动力的计算公式进行修正,提出适用于气浮ACM轴向气动力计算公式。结果表明:提出的公式在压气机端的最小误差由原来的59%降低到13%,最大误差由原来的261%降低到75%,在涡轮端最小误差由原来的63%降低到2%,最大误差由原来的98%降低到8%,表明修正后轴向气动力公式减小了轴向力的计算误差,因此提出的公式更加适用于气浮空气循环机的轴向气动力计算。

陇南大堡子山遗址秦动物纹金箔饰片考论

文章以陇南大堡子山遗址秦动物纹金箔饰片为研究对象,着重分析其构图形式及典型特征。从多元动物纹饰概览入手,详细列举了鸱枭纹、兽面纹、虎纹等动物形象,从纹饰状貌、形象组构、典型特征溯源等角度再现古之工匠造物中的设计智慧,用大历史观视角真实还原秦国工匠对草原文化元素中动物纹饰装饰母题典型特征选取及设计创新。

高质量双零铝箔生产常见问题分析

简述了国内高质量双零铝箔生产状况,并对双零铝箔生产中影响产品质量的因素,如铝箔坯料质量、生产工艺选择、人员操作施工等进行了分析,从铝箔坯料控制、轧制工艺选择、轧制油选配、热处理工艺、工作环境及相对湿度等方面,探讨了如何降低针孔数量,减少双零铝箔轧制的废品率,旨在提高国内双零铝箔产品质量。

Web知识规则提取的FOIL算法改进

将一阶学习的 FOIL 算法应用到 Web知识规则的提取是当前学习 Web知识所普遍采用的方法 .本文在 FOIL算法的基础上进行了改进 ,提出了基于网页间联系的新的路径学习算法 。

不同真空包装材料对酱肉产品理化及微生物性质的影响

为研究不同包装材料对酱肉贮藏期间品质的影响,以聚酯/铝/聚乙烯(PET/AL/PE)铝箔和聚酯/聚乙烯(PET/PE)透明薄膜为包装材料,对四川酱肉进行真空包装,测定酱肉在常温贮藏过程中水分活度、过氧化值、丙二醛含量、pH值、亚硝酸盐含量、色泽、质构特性及菌落总数的变化。结果表明,真空铝箔包装相较于真空透明包装可延缓酱肉脂质的氧化并加快亚硝酸盐的降解,对维持酱肉的硬度、弹性、咀嚼性和内聚性有显著效果,并对抑制微生物的繁殖有显著作用。