Investigation of system parameters towards safer impact based shock-to-detonation transition in a novel laser driven flyer plate prototype

Laser driven flyer plate technology offers improved safety and reliability for detonation of explosives in industrial applications ranging from mining and stone quarrying to the aerospace and defense industries.This study is based on developing a safer laser driven flyer plate prototype comprised of a laser initiator and a flyer plate subsystem that can be used with secondary explosives.System parameters were optimized to initiate the shock-to-detonation transition(SDT)of a secondary explosive based on the impact created by the flyer plate on the explosive surface.Rupture of the flyer was investigated at the mechanically weakened region located on the interface of these subsystems,where the product gases from the deflagration of the explosive provide the required energy.A bilayer energetic material was used,where the first layer consisted of a pyrotechnic component,zirconium potassium perchlorate(ZPP),for sustaining the ignition by the laser beam and the second layer consisted of an insensitive explosive,cyclotetramethylene-tetranitramine(HMX),for deflagration.A plexiglass interface was used to enfold the energetic material.The focal length of the laser beam from the diode was optimized to provide a homogeneous beam profile with maximum power at the surface of the ZPP.Closed bomb experiments were conducted in an internal volume of 10 cm^(3) for evaluation of performance.Dependency of the laser driven flyer plate system output on confinement,explosive density,and laser beam power were analyzed.Measurements using a high-speed camera resulted in a flyer velocity of 670±20 m/s that renders the prototype suitable as a laser detonator in applications,where controlled employment of explosives is critical.

Theoretical Model for Calculating Electric-Power Curves Depicting Accelerated Flyer by Exploding Foil

A theoretical model for calculating electric-power curves of small-size foil during its electrical explosion is given.This technique is based on temperature dependence of foil conductivity.After taking into account the energy conversion of the foil explosion,the power-time curve is applied to the hydrodynamic code.One-dimensional numerical simulations of electric-explosion driving flyers are performed using this code.Calculated flyer velocities lie within ±8% of experimental data from Lawrence Livermore National Laboratory （LLNL）,and simulated history curves of flyer velocities coincide well with those measured using velocity interferometer system for any reflector （VISAR）,indicating a helpful work for design optimization of slapper detonators.

CALCULATION AND MEASUREMENT OF DYNAMIC EXPANSION OF ROVING FLYER

Roving flyer is an important part of roving frame. Its dynamic expansions affect the quality of rove greatly. The expansions are calculated by means of the general program SAP84 based on finite element method in this paper. Its measuring principle and usage are also described. The results of calculating and measuring are identical. The method presented in the paper is effective for studying the properties of roving flyer.

Method of Testing the Flyer Sensitivity of Explosives

By means of Mylar flyer shock explosives driven by electric gun, the method of testing the flyer initiation sensitivity of explosives is studied, and some experiments are done. The experimental results show that the test method established is correct, which is very important and instructive to study and evaluate the safety and reliability of explosives. For the moment, the test should be researched and discussed further..

Swiss Innovation Week 2019:Home of Drones,the New High Flyer of Swiss Industry

Following the successful Swiss Innovation Week(SIW)held in July 2018,the Embassy of Switzerland in China launches its 2nd edition from 12 to 14of June 2019.With Swiss drones as the brand-new theme,Switzerland’s drone ecosystem and innovation in the field of flying robots were present.According to various rankings,Switzerland is one of the most innovative countrie s in the world and also one of the most competitive co untries.

Retail Brand Building Through Promotional Communication： A Study That Focuses on Category Killers Promotional Flyers

Strong competition in retail distribution and the development of new purchasing options for the consumer generate a growing need to strengthen the retailers＇ brand image using all the communication elements, with promotional flyers being one of the most important ways to do this. Promotional flyers make-up 5.1% of the money spent on communication and rank third place in terms of importance for retailers. The aim of this investigation work is to focus on analysing the utility of a promotional tool, such as a flyer, to fulfil a strategic objective, like creating a retail brand image, within a modern dynamic sector that is growing fast, such as Category Killers. Two sources of information have been used to carry out the research. On the One hand, a survey conducted on those responsible for the definition and execution of the promotional plan, and on the other hand, the accumulation and analysis of all the flyers issued into the market thought-out a year by those retailers which belong to this format, in order to conduct a study of seven defined image indicators. This information has been largely analyzed using multidimensional scaling method and chi-square test. As a result, we have managed to gather the differential elements in flyers execution between those retailers that prize the communications of image attributes and those retailers which concentrate on communicating price. The first group makes greater use of promotional theme related flyers, and shows greater differentiation in both product assortment and the depth of the range being communicated.

英孚发布创意英语教材High Flyers

为进一步激发7至9岁儿童学习英语的主动性,英孚教育发布了由多国教育人士共同创作的创意教材。近日,《留学》应邀参加英孚教育在北京召开的媒体体验会,亲身感受了一套为7-9岁儿童量身定做的英语教材。这套名为"High Flyers"的教材研发历时三年,由多国教育界人士共同参与创作完成。英孚教育青少儿英语执行副总裁白皎宇告诉《留学》,High Flyers教材及课程引入了个性鲜明的动画人物,加入了多个实用的对话情景。

Experimental Study on the Small Flyer Initiating Behavior of Fine-grained Explosives

The initiating behavior of fine-grained explosives by small flyer is studied. The diameter of small flyer in this device is 1mm. The test results indicate that the granularity of explosives has great effect on its flyer initiating sensitivity.The flyer initiating sensitivity of the fine-grained explosives is higher and the critical initiating energy is lower than that of common explosives. For common explosive, the flyer initiating sensitivity increases as the density is reduced. But for the fine-grained explosive, the test results are exactly opposite.

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.

环境温度对TATB/RDX传爆药起爆及驱动性能的影响

为了获得环境温度对TATB/RDX传爆药起传爆性能及驱动性能的影响特性,采用激光多普勒测速技术及瞬态太赫兹波多普勒干涉测速技术,对TATB/RDX传爆药在隔层起爆条件下的起爆、传播及驱动性能开展实验研究,获取了-45~70℃温度环境中TATB/RDX传爆药的到爆轰距离、爆轰反应区时间宽度、爆轰传播速度及驱动飞片的飞行速度曲线。结果表明:TATB/RDX传爆药的到爆轰距离及爆轰反应区时间宽度随环境温度的降低均近乎呈线性增长趋势;爆轰传播速度随环境温度的降低而逐渐提高;驱动飞片的速度随环境温度的变化特性在飞片主体-层裂层融合前后存在明显不同。

装药过载环境力等效模拟实验技术研究

为解决装药安全可靠性能实验成本高、强过载环境测试难度大等瓶颈问题,以等效模拟弹体侵彻钢板时内部装药过载环境力为目标,基于数值模拟方法,设计了装药过载环境力等效模拟实验装置,并开展了等效模拟实验,突破了同时满足加载压力大于1 GPa和脉冲宽度大于100μs的技术难点。结果表明,弹丸侵彻钢板时装药受到的过载为正弦波单脉冲。在装置中采用波形调整器不仅能够调控加载到待测药表面的波形,还能对压力的衰减产生大幅影响。随着波形调整器厚度的增大,加载在待测药表面的压力逐渐减小,脉冲宽度显著增大;随着飞片厚度增大,飞片获得的驱动速度逐渐减小,加载在待测药表面的压力明显减小,脉冲宽度变化不明显。装药过载环境力模拟装置形成的脉冲特征值与弹丸侵彻钢靶过程的数值模拟结果对比,超压峰值误差最高为5.71%,脉宽误差最高为14.8%,均低于15%,验证了用该装置模拟弹体侵彻钢靶时装药加载状态的等效性。

Plastic deformation behavior of a Cu-10Ta alloy under strong impact loading

In this work,a Cu-10Ta alloy with a copper to tantalum mass ratio of 9:1 is prepared using powder metallurgy technology.Physical properties of the alloy,including density,microstructure,melting point,and constant-volume specific heat,are tested.Via the split Hopkinson pressure bar(SHPB)and flyerplate impact experiments,the relationship between equivalent stress and equivalent plastic strain of the material is studied at temperatures of 298-823 K and under strain rates of 1×10^(-3)-5.2×10^(3)s^(-1),and the Hugoniot relationship at impact pressures of 1.46-17.25 GPa and impact velocities of 108-942 m/s is obtained.Evolution of the Cu-10Ta microstructure that occurs during high-strain-rate impact is analyzed.Results indicate that the Cu-10Ta alloy possesses good thermal stability,and at ambient temperatures of up to 50%its melting point,stress softening of less than 15%of the initial strength is observed.A modified J-C constitutive model is employed to accurately predict the variation of yield strength with strain rate.Under strong impact,the copper phase is identified as the primary source of plastic deformation in the Cu-10Ta alloy,while significant deformation of the high-strength tantalum particles is less pronounced.Furthermore,the longitudinal wave speed D is found to correlate linearly with the particle velocity u upon strong impact.Analysis reveals that the sound speed and spallation strength of the alloy increase with increasing impact pressure.

Applicability limits of the DAX test in plastic bonded explosives

The Disc Acceleration e Xperiment(DAX)is one of the most recent experimental methods of performance characterization of new energetic materials.A cylindrical explosive charge accelerates a thin metallic disc and its velocity is measured continuously using photonic Doppler velocimetry.The detonation velocity is measured simultaneously.The DAX test can be used to obtain the Chapman-Jouguet(CJ)detonation pressure and to describe detonation products expansion using reduced amount of explosive.A series of DAX tests was performed at various charge diameters and disc thicknesses with Semtex 1 A plastic bonded explosive and sensitized nitromethane.The DAX-like evaluation was also applied to previously measured data of Semtex 1A and A-IX-1 explosives.The optimum disc thickness is determined by the disc to explosive mass ratio of 0.01-0.08.The repeatability of the Semtex 1 A detonation pressure results is about four times lower compared to the pressed and liquid explosives.

Research on the quasi-isentropic driving model of aluminized explosives in the detonation wave propagation direction

Taking CL-20(Hexanitrohexaazaisowurtzitane)-based aluminized explosives with high gurney energy as the research object, this research experimentally investigates the work capability of different aluminized explosive formulations when driving metal flyer plates in the denotation wave propagation direction.The research results showed that the formulations with 43 μm aluminum(Al) powder particles(The particle sizes of Al powder were in the range of 2~43 μm) exhibited the optimal performance in driving flyer plates along the denotation wave propagation direction. Compared to the formulations with Al powder 13 μm, the formulations with Al powder 2 μm delivered better performance in accelerating metal flyer plates in the early stage, which, however, turned to be poor in the later stage. The CL-20-based explosives containing 25% Al far under-performed those containing 15% Al. Based on the proposed quasi-isentropic hypothesis, relevant isentropy theories, and the functional relationship between detonation parameters and entropy as well as Al reaction degree, the characteristic lines of aluminized explosives in accelerating flyer plates were theoretically studied, a quasi-isentropic theoretical model for the aluminized explosive driving the flyer plate was built and the calculation methods for the variations of flyer plate velocity, Al reaction degree, and detonation product parameters with time and axial positions were developed. The theoretical model built is verified by the experimental results of the CL-20-based aluminized explosive driving flyer plate. It was found that the model built could accurately calculate the variations of flyer plate velocity and Al reaction degree over time. In addition, how physical parameters including detonation product pressure and temperature varied with time and axial positions was identified. The action time of the positive pressure after the detonation of aluminized explosives was found prolonged and the downtrend of the temperature was slowed down and even reversed to a slight rise due to the aftereffect reaction between the Al powder and the detonation products.

The interaction between a shaped charge jet and a single moving plate

Reactive armour is a very efficient add-on armour against shaped charge threats.Explosive reactive armour consists of one or several plates that are accelerated by an explosive.Similar but less violent acceleration of plates can also be achieved in a completely inert reactive armour.To be efficient against elongated jets,the motion of the plates needs to be inclined against the jet such that a sliding contact between the jet and the plates is established.This sliding contact causes a deflection and thinning of the jet.Under certain circumstances,the contact will become unstable,leading to severe disturbances on the jet.These disturbances will drastically reduce the jet penetration performance and it is therefore of interest to study the conditions that leads to an unstable contact.Previous studies on the interaction between shaped charge jets and flyer plates have shown that it is mainly the forward moving plate in an explosive reactive armour that is effective in disturbing the jet.This is usually attributed to the higher plate-to-jet mass flux ratio involved in the collision of the forward moving plate compared to the backward moving plate.For slow moving plates,as occurs in inert reactive armour,the difference in mass flux for the forward and backward moving plate is much lesser,and it is therefore of interest to study if other factors than the mass flux influences on the protection capability.In this work,experiments have been performed where a plate is accelerated along its length,interacting with a shaped charge jet that is fired at an oblique angle to the plate’s normal,either against or along the plate’s velocity.The arrangement corresponds to a jet interacting with a flyer plate from a reactive armour,with the exception that the collision velocity is the same for both types of obliquities in these experiments.The experiments show that disturbances on the jet are different in the two cases even though the collision velocities are the same.Numerical simulations of the interaction support the observation.The difference is attributed to the character of the contact pressure in the interaction region.For a backward moving plate,the maximum contact pressure is obtained at the beginning of the interaction zone and the contact pressure is therefore higher upstream than downstream of the jet while the opposite is true for a forward moving plate.A negative interface pressure gradient with respect to the jet motion results in a more stable flow than a positive,which means that the jet-plate contact is more stable for a backward moving plate than for a forward moving plate.A forward moving plate is thus more effective in disturbing the jet than a backward moving plate,not only because of the higher jet to plate mass flux ratio but also because of the character of the contact with the jet.

冲击片雷管换能界面轴向距离能量耗散失效分析

为提高冲击片雷管作用的一致性和可靠性,针对因材料表面小型突起导致接触面不平整的装配问题,从换能界面能量耗散的角度对装配结构中两种轴向距离所产生的影响进行了探究。通过不同电压下的发火试验及感度试验,验证和分析两种轴向距离对冲击片雷管作用过程的影响。结果表明:加速膛-桥箔轴向距离会导致电爆能量的径向散失,进而影响了飞片冲击药柱端面能量的大小并引起聚酰亚胺薄膜的撕裂拉伸,随着轴向距离的持续增加,爆炸桥箔逐渐失效;加速膛-药柱轴向距离会影响飞片飞行的平稳程度以及撞击药柱速度,随着轴向距离增加,飞片飞行距离增长,到达药柱端面的速度降低且不一致,导致起爆药柱的稳定性降低,轴向距离应控制在0.3mm以内。

集成化Al膜爆炸箔起爆器的制备与性能研究

为了提高爆炸桥箔的换能效率以及爆炸箔起爆系统的起爆能力,采用Al膜作为爆炸箔金属桥膜,开展了集成化Al膜爆炸箔起爆器的制备工艺研究。对桥区尺寸为0.2~0.4 mm、厚度为5~8μm的Al桥电爆炸性能进行测试,并在此基础上测试了驱动飞片速度。研究结果表明:200 W溅射功率、20 sccm氩气流速是制备Al膜的最佳工艺条件;1 000 V电压条件下,厚度为6μm、桥区尺寸为0.35 mm×0.35 mm的桥箔电爆炸时爆发功率最大,相比相同输入能量的Cu桥,爆发功率提高14.3%,电能沉积率提高9.63%;桥区尺寸在0.2~0.4 mm时,飞片速度随桥区尺寸的增大而逐渐减小,桥区厚度为7μm时飞片速度最大,1 000 V充电电压下达到4 100 m·s^(-1),高出Cu桥7.89%。

MEMS集成爆炸箔芯片的发火性能研究

为了实现高速飞片输出和爆炸箔起爆器(Exploding Foil Initiator, EFI)低能发火,依据EFI工作原理,进行Cu桥箔电热仿真、PC(聚氯代对二甲苯)飞片冲击作用参数计算和SU-8加速膛结构确定。基于结构设计参数,采用微机电系统(Micro-Electro-Mechanical System, MEMS)工艺实现了爆炸箔芯片一体化批量制备,并开展了MEMS集成爆炸箔芯片的桥箔电爆特性、飞片实时速度和冲击起爆性能测试。结果表明:基于小尺寸桥箔结构在较低放电电压下就能够获得较高的飞片速度,并且在加速膛口飞片速度达到峰值速度的96%以上;冲击起爆HNS-IV药柱的最低发火条件为0.22μF/1 100 V,实现了EFI低能发火。

加速膛参数对换能元飞片速度的影响

飞片速度是冲击片雷管能否可靠起爆的一个关键因素,为了深入研究加速膛参数对飞片速度的影响,分别通过实验和数值模拟方法对飞片速度的影响因素进行分析。采用磁控溅射技术设计制备了一种膜层厚度为0.5/0.5/2μm,尺寸为0.15 mm×0.15 mm的TiW/Ni/Au复合薄膜爆炸箔。在激励条件为0.1μF、1200 V下,选用密度为1.45 g·cm^(-3),厚度为25μm的聚酰亚胺飞片,利用光子多普勒速度测试技术测量了不同加速膛参数的飞片速度。研究结果显示:在相同孔径条件下,当加速膛厚度分别为0.3,0.4,0.5,0.6 mm时,随着加速膛厚度的增加,飞片速度先增后减,在厚度为0.4 mm时达到最高值;在相同厚度条件下,当加速膛孔径分别为0.15,0.23,0.3,0.35,0.45 mm时,飞片速度随孔径增加而降低,其中孔径为0.15 mm时速度最高;此外,在相同孔径和厚度下,飞片经过聚酰亚胺和陶瓷两种材质的加速膛测试得到的速度变化趋势和数值相近,而聚酰亚胺具有较高的强度和韧性,成本更低,因此可替代陶瓷作为加速膛材料。同时采用数值模拟方法重新拟合了适用于TiW/Ni/Au复合薄膜的飞片速度经验公式,验证结果表明,计算结果与实验数据的偏差均在2.5%以内。

降低粗纱断头,提高生产效率

为了降低粗纱断头,提高生产效率,分析因棉网破洞破边、过棉通道挂花等前纺工序导致的粗纱断头原因及应对措施,详述通过粗纱捻系数、粗纱伸长率、专件器材及牵伸部件、工艺设计与上机合格率、机架水平、设备运行、温湿度、设备清洁、操作水平等方面控制断头的要点,总结在生产中采取跟踪处理、捻度调整等攻关措施后的具体效果。指出:降低粗纱断头率应坚持从多维度出发,全面优化生产流程;日常生产中应做好设备维护、精准工艺参数、加强人员培训、注重前后工序协同等工作,为提高纱线质量和生产效率打好基础。