Long-rod penetration： the transition zone between rigid and hydrodynamic penetration modes

Long-rod penetration in a wide range of velocity means that the initial impact velocity varies in a range from tens of meters per second to several kilometers per second. The long rods maintain rigid state when the impact velocity is low, the nose of rod deforms and even is blunted when the velocity gets higher, and the nose erodes and fails to lead to the consumption of long projectile when the velocity is very high due to instantaneous high pressure. That is, from low velocity to high velocity, the projectile undergoes rigid rods, deforming non-erosive rods, and erosive rods. Because of the complicated changes of the projectile, no well-established theoretical model and numerical simulation have been used to study the transition zone. Based on the analysis of penetration behavior in the transition zone, a phenomenological model to describe target resistance and a formula to calculate penetration depth in transition zone are proposed, and a method to obtain the boundary velocity of transition zone is determined. A combined theoretical analysis model for three response regions is built by analyzing the characteristics in these regions. The penetration depth predicted by this combined model is in good agreement with experimental result.     

Microstructure and corrosion behaviour of gas tungsten arc welds of maraging steel

Superior properties of maraging steels make them suitable for the fabrication of components used for military applications like missile covering, rocket motor casing and ship hulls. Welding is the main process for fabrication of these components, while the maraging steels can be fusion welded using gas tungsten arc welding(GTAW) process. All these fabricated components require longer storage life and a major problem in welds is susceptible to stress corrosion cracking(SCC). The present study is aimed at studying the SCC behaviour of MDN 250(18% Ni) steel and its welds with respect to microstructural changes. In the present study, 5.2 mm thick sheets made of MDN 250 steel in the solution annealed condition was welded using GTAW process. Post-weld heat treatments of direct ageing(480 C for 3 h), solutionizing(815 C for 1 h) followed by ageing and homogenizing(1150 C for 1 h) followed by ageing were carried out. A mixture of martensite and austenite was observed in the microstructure of the fusion zone of solutionized and direct aged welds and only martensite in as-welded condition. Homogenization and ageing treatment have eliminated reverted austenite and elemental segregation. Homogenized welds also exhibited a marginal improvement in the corrosion resistance compared to those in the as-welded, solutionized and aged condition. Constant load SCC test data clearly revealed that the failure time of homogenized weld is much longer compared to other post weld treatments, and the homogenization treatment is recommended to improve the SCC life of GTA welds of MDN 250 Maraging steel.     

Analysis of Micro-scale Flame Structure of AP/HTPB Base Bleed Propellant Combustion

A complex multiple flame stracture is formed dining the combustion of AP/HTPB base bleed propellant. The AP monopropellant flame is concentrated in a thin zone above the burning surface of AP mystal to maintain seK-sustained decomposition. Due to the low temperature near the burning surface, the diffusion between the decomposition products of AP and the pyrolysis products of HTPB occurs, and a partly pre-mixed diffusion flame stracture-leading edge flame （LEF） is formed. The effects of pressure, chemical reaction rate and AP particle size on diffusion flame structure in the ravage from 20 arm to 100 ann are discussed. The Peclet number increases from 6.64 at 20 ann to 21.91 at 100 ann when AP particle size is 140 μm. The high temperature zone is blown away from the burning surface because the convective transport rate increases with the increase in Peclet number. The chemical reaction rate is enhanced and the diffusion mixing is hlhibit ed as Damkolfler nunlber increases. The chemical heat release is more concentrated axed the chemical reaction zone becomes nan＇ow when Damkolfler nunlber changes from 330 at 20 ann to 4700 at 100 atm. When AP particle diameter is decreased to 60 μm, the diffusion time scale is reduced due to the reduced diffusion length scale. So the diffusion mLxing is enhanced a more pre-mixed flame is formed. The burning rate increases because the more pre-mixed     

字母趣谈轻武器(D)——随意中学英文术语(4)

DROP SHOT软铅弹。DROP OFBULLET弹道降,the vertical distance abullel has fallen under the influence ofgravity,during its flight(弹头飞行时受重力影响垂直下降的高度)。DROP ATHEEL枪托底板(抵肩部)下降量,thevertical distance between the line of sightand the top edge of the butt or heel. 对于“non-disposable weapon”,在     

Evolution of Approaches to Safe Handling of Explosives

On definition, nuclear weapons (NW) containing fissile and explosive materials are dangerous in terms of radiation release and explosion. In Russia, the problems of nuclear safety of ammunition during accidents are solved by so-called “one-point safety” with use of physical and design scheme of the primary unit.     

Research on Radial Friction Welding of 30 mm Shell＇s Band

A new radial friction welding technology of 30 mm shell＇s band is introduced.Bands are assembled to shell bodies without notches by using the process.The width of heat-affected zone（HAZ） is small,and the microstructure on steel side is incomplete quenching while that on cooper side is grain refining.The shear-strength of joint exceeds 200 MPa.The result of firing test indicates that radial friction welding can satisfy the assembly requirements of shell bands.     

Influence of A1203 particles on the microstructure and mechanical properties of copper surface composites fabricated by friction stir processing

The influence of three factors, such as volume percentage of reinforcement particles （i.e. A1203）, tool tilt angle and concave angle of shoulder, on the mechanical properties of Cu-A1203 surface composites fabricated via friction stir processing was studied. Taguchi method was used to optimize these factors for maximizing the mechanical properties of surface composites. The fabricated surface composites were examined by optical microscope for dispersion of reinforcement particles. It was found that A1203 particles are uniformly dispersed in the stir zone. The tensile properties of the surface composites increased with the increase in the volume percentage of the A1203 reinforcement particles. This is due to the addition of the reinforcement particles which increases the temperature of recrystallization by pinning the grain boundaries of the copper matrix and blocking the movement of the dislocations. The observed mechanical properties are correlated with microstructure and fracture features.     

字母趣谈轻武器D——随意中学英文术语(3)

“dis-”(词头),表示“分离”、“解除”、“取消”、“否定”等意。Distance距离,如Distance from face of Bolt head toLocking surface of locking piece(弹底窝平面到闭锁支撑面之间的距离)。Disassemble,分解,拆除,武器术语中也有的用“Dismantle"。 DISPERSION散布,a scattered pattern of shots fired from the same gun withsame firing data(同一武器同一射击诸元     

Research on Pulse Radiation Characteristics of Leaf-like Ultra Wide Band Antenna

A new kind of ultra wideband antenna, which consists of a leaf-like dipole and a dielectric block, is proposed and analyzed. The dielectric block is attached in parallel with the dipole near its feed point. Thus, the near field is attracted to the side where the dielectric block is located. It leads to a focusing effect of the energy in the far zone. The finitedifference time-domain （FDTD） method combined with the perfectly matched layers （PML） technique is used in the simulation of the antenna radiation characteristics. The research shows that, with proper dielectric loading and 50 Ωfeeding line, the bandwidth of the antenna can be up to 6.5 GHz, from 3.5 GHz to 10 GHz with VSWR （voltage standing wave ratio） less than 2.5.     

Numerical Simulation of Particle/Matrix Interface Failure in Composite Propellant

Interface debonding between particle and matrix in composite propellant influences its macroscopic mechanical properties greatly. For this, the laws of interface cohesive damage and failure were analyzed. Then, its microscopic computational model was established. The interface mechanical response was modeled by the bilinear cohesive zone model. The effects of interface properties and particle sizes on the macroscopic mechanical behavior were investigated. Numerical simulation of debonding damage evolution of composite propellant under finite deformation was carried out. The debonding damage nucleation, propagation mechanism and non-uniform distribution of microscopic stress-strain fields were discussed. The results show that the finite element simulation method based on microstructure model can effectively predict the trend of macroscopic mechanical behavior and particle/matrix debonding evolution process. It can be used for damage simulation and failure assessment of composite propellants.     

让暴风雨来得更猛烈些吧!

正当世界脱去了冷战的思维,经济又实用的护卫舰便开始大行其道。挪威的"南森"级、西班牙的F-100型、德国F-124型"萨克森"级、法国的FREMM、日本的19DD,一艘艘耀眼登场。它们用先进的设计理念、强大的综合性能以及简洁优雅的外形,对着昔日的海上强国大吐其槽。不过,斯拉夫民族都有着海燕般的情怀。沉寂多年后推出了22350型"戈尔什科夫"级护卫舰,集远程区域防空(反导)、中远程区域反潜、远程突击和对岸火力支援等能力于一身,在苏俄历史上首次实现了各方面作战能力的均衡。它用自信和骄傲大声叫喊着:让暴风雨来得更猛烈些吧!     

更高更快更强--记全国国防科技工业劳动模范四九七厂科研所戴涌同志

他不是职业运动员,更不是奥运健将,但他在自己的科技职业生涯中,追求并实践着“更高、更快、更强”的奥运精神,在平凡中追求卓越,把自己所做的每一件事都争取做     

我国烟花爆竹生产工艺装备现状及发展趋势

概述国内烟花爆竹行业生产现状,针对该行业仍处于手工作业向机械化生产过渡的生产模式,分析现行工艺装备存在的问题,提出安全可靠、高效高质、多工位自动化的发展方向,以及需要重点解决的制约性技术难题。该研究可为下一步突破各项关键技术提供参考。     

献身求实勤奋创新--记优秀青年科技工作者石晓辉教授

石晓辉教授,重庆工学院副院长,1963年10月生,1985年毕业于清华大学汽车工程系汽车专业,同年考入重庆大学攻读硕士学位。1994年12月博士毕业后在重庆工学院任教,先后任该院汽车研究所所长、车辆工程系副主任、机械系主任、副院长等职,兼任重庆市科技     

海上测控任务指挥显示优化策略及应用

针对现阶段海上测控任务指挥显示系统存在的不足,提出一种集数据、图形和状态结构显示为一体的智能化显示策略。首先设计了指挥显示优化策;其次详细阐述一种基于状态控件的策略实现方法,并举例设计和开发几种典型的状态控件,将状态码控件应用于具体的数据显示,最后通过实例对优化策略的实现进行详细的演示和验证。验证结果表明:该方法能形象直观地表现全局性关键信息,加强对航天器遥外测信息异常状态的实时分析及预警显示等控制,为同类系统建设奠定技术基础。     

基于多光谱与显著性的红外弱小目标融合检测

基于多光谱与显著性,提出一种红外弱小目标融合检测算法。该算法旨在将从多光谱探测器获得的同一场景的多光谱图像信息组合到一起,利用它们在时空上的相关性及信息上的互补性,提高系统的检测性能。采用一种新的基于人类视觉注意机制的显著性方法,该方法能够快速准确找到图像中的显著性区域;将目标看作一类,背景和干扰点看作另一类,选取离差平方和准则,使类内距离最小,类间距离最大;训练出融合参数,得到融合后的显著性图像。通过设定的门限值二值化,可以看出该融合方法能很好地将目标与背景分开,从而检测出目标。     

火炸药理化实验室危害辨识与防护

火炸药理化分析检测对象是含能材料和火炸药制品,具有燃烧、爆炸的危险性;火炸药自身固有的燃爆危险性,决定了其理化分析的特殊性,必须采取有针对性的防护措施;分析了火炸药理化分析检测过程中存在的危害因素及其产生的途径,并从安全技术和安全管理角度提出了相应的对策措施。     

基于PROFIBUS和MCGS的汽车检测线研发

基于PROFIBUS和MCGS将汽车安全检测线进行了技术改造和升级,应用AVR单片机开发了DI、DO和AI数据处理模块,采用PROFIBUS工业现场总线技术降低了开销,减少了为分布式输入/输出设备所进行的电缆布线,应用MCGS开发了友好的人机交互界面,并采用软件补偿的方法提高了检测的精度.     

科学技术与持续发展--学习陈云同志"一五"时期的经济发展观

作为国家第一个一年计划的主要制定者与实施者，陈云同志的诸多经济主张、理论观点、工作方法及具体实践精神在“一五”期间发挥了重大作用，并最终形成了以科学技术与持续发展为中心的经济发展观思想，这一思想在我国后来长期的经济建设中都起着重要的指导作用。     

对羟基苯基五唑及其衍生物的合成与稳定性

以对氨基苯酚及其衍生物为原料,在-45℃下合成了一系列芳基五唑,通过核磁和质谱分析对其结构进行了表征。研究了取代基的位置及数目对芳基五唑化合物稳定性的影响,运用电喷雾离子化串联质谱分析了不同裂解能量下(10,60 e V)芳基五唑的裂解途径,并讨论了芳基五唑的稳定性与产生N~-_5之间的关系。结果表明,在这一系列化合物中,间位和对位被供电基取代的3,5-二甲基-4-羟基苯基五唑稳定性最好,同时在高裂解能量(60 e V)轰击下切断C—N键产生N~-_5的能力也最强。