Influence of shaped charge structure parameters on the formation of linear explosively formed projectiles

The research of LEFP (linear explosive forming projectile) is of great value to the development of new warhead due to its excellent performance. To further improve the damage ability of the shaped charge warhead, a special shell overhanging structure was designed to increase the charge based on the traditional spherical charge, in which case the crushing energy of LEFP could be guaranteed. LS-DYNA was used to simulate different charge structures obtained by changing the number of detonation points, the length of shell platform, the radius of curvature and the thickness of liner. The RSM (response surface model) between the molding parameters of LEFP and the structural parameters of charge was established. Based on RSM model, the structure of shaped charge was optimized by using multi-objective genetic algorithm. Meanwhile, the formation process of jet was analyzed by pulsed X-ray photography. The results show that the velocity, length-diameter ratio and specific kinetic energy of the LEFP were closely related to the structural parameters of the shaped charge. After the optimization of charge structure, the forming effect and penetration ability of LEPP had been significantly improved. The experimental data of jet velocity and length were consistent with the numerical results, which verifies the reliability of the numerical results.     

Effects of module number and firing condition on charge thermal safety in gun chamber

Thermal safety of modular charge which is fed into and retained in the chamber after gun fires consecutively is first investigated with cook-off method.A two-dimensional cook-off model of modular charge in gun chamber is established and the cook-off process of modular charge in gun chamber is numerically simulated.Then the effects of module number and firing condition on charge thermal safety are evaluated by researching the cook-off response characteristics of modules.The results show that,under conditions of different module numbers the cook-off responses all occur on the module closest to the boundary of missile,and the single-base propellants located at the inner surface of cartridge ignite first.When the number of loaded module changes from 1 to 6,the cook-off response temperatures vary little,only in a small range of 478.1 K-482.4 K.The cook-off response times decrease logarithmically in the range of 211.2 s-166.7 s with the increasing length of residual air gap in gun chamber.The simulation results are well matched with the experimental data.Furthermore,different firing conditions have great influence on the cook-off response time,minor influence on the initial response position and little in-fluence on the response temperature.Under the three conditions of consecutive 32 launches with 5 rounds/min,43 launches with 1 round/min,and 41 launches with different firing frequencies,the cook-off response temperatures are 479.2 K,481.1 K and 479.9 K respectively and the response times are 709.2 s,211.2 s and 214.4 s respectively.The response position is near the middle area of the inner cartridge surface in the former condition and near the right area in the latter two conditions.     

圆柱壳振动声辐射Jacobi-Ritz时域半解析法及特性分析

针对圆柱壳结构瞬态声振特性分析研究不足,结合Newmark-β积分法和Kirchhoff时域边界积分方程,提出一种圆柱壳受迫振动声辐射Jacobi-Ritz时域半解析法。基于一阶剪切变形理论和微元法思想,建立了圆柱壳振动声辐射分析模型,采取Jacobi多项式和Fourier级数表示轴向和周向位移容许函数,基于Rayleigh-Ritz法和Newmark-β积分法计算圆柱壳的受迫振动时域响应,在此基础上,基于Kirchhoff积分方程求解辐射噪声时域响应,分析圆柱壳受迫振动声辐射特性。与有限元方法/边界元方法数值结果对比表明,该方法具备收敛性好、精度高等优点,圆柱壳结构声振响应峰值随边界条件的刚度变弱存在左移现象,振动声辐射响应随厚度的增加呈现下降趋势;当随机载荷峰值频率与结构固有频率接近时,结构声振响应出现强特征线谱。     

层流介质中金属板腐蚀电位分布研究

为了研究流动介质中产生的静电场,结合电化学和流体力学相关知识建立层流介质中金属板模型,利用贝塞尔函数展开及其逆运算推导出在三层介质中基于点电荷模型的腐蚀电位解析表达式,同时计算出金属板产生的电场。运用推导出的解析表达式计算出在流动介质中任意场点处金属板随不同流速产生的腐蚀电位,并通过实验验证结果的正确性。结果表明,对层流条件下电化学反应产生的电流密度所建模型的结果与实验测量数据吻合度较高,同时电场分布也会随着流体流速及层流方向上长度的变化而发生变化。     

航空自导深弹和磁探仪攻潜模型与仿真

针对反潜巡逻机使用磁探仪和自导深弹的攻潜效能研究,提出了一种基于蒙特卡洛法的计算模型。在建立攻潜坐标系的基础上,给出了连投深弹射击深度的定义;结合磁探仪定位原理,提出了基于峰值追踪的定位目标和连投攻击的方法,仿真结果表明该方法能够提高命中概率;给出了目标分布和连投深弹的散布模型,依据攻潜过程和命中判定条件,进行了攻潜效能的计算;仿真分析了影响攻潜效能的主要因素,并研究了投弹间隔的确定方法。     

基于探雷信息的火箭深弹炸雷效能研究

针对火箭深弹传统炸雷方式中存在的盲目性、危险性及耗弹量大等问题,提出了火箭深弹与探雷声纳协同定点炸除水雷的方法,建立了基于随机模拟的火箭深弹炸雷效能评估模型。实例解算结果表明,火箭深弹对水雷毁伤概率随着射距的增加而增大;在同一射距下,毁伤概率随射向与探测方向夹角的增加而增大,但在最优(大)夹角附近毁伤概率变化不大。通过该模型能有效解算出火箭深弹对水雷的毁伤效果,进而得到最优射击诸元和最大毁伤概率,对火箭深弹炸雷技术实施提供了理论基础。     

燃烧室前缘扩张角对旋转爆震冲压发动机的影响

针对圆柱形隔离段-燃烧室构型的旋转爆震冲压发动机,开展了总温为860 K、马赫数为2的来流条件下的直连式试验,探讨了燃烧室前缘扩张角(θ=30°,45°,60°,90°)对爆震波传播特性、工况范围及压力分布的影响。结果表明:当燃烧室前缘扩张角为90°时,燃烧模态均为爆燃燃烧;随着扩张角的减小,燃烧模态将会向锯齿波和混合模态(包含单波阶段)转换。当燃烧室前缘扩张角为30°时,旋转爆震的自持工况范围最宽且燃烧室压力最高;同时,随着燃烧室前缘扩张角减小,实现混合模态的当量比下限降低。此外,分析了燃烧模态对来流的影响,发现:锯齿波/混合模态燃烧室内存在的周期性高频压力扰动会使隔离段内的激波串位置前移;混合模态对超声速来流的影响最为显著。     

紊流时输油管道油流静电带电计算研究

对紊流条件下输油管道内油流静电带电的计算进行了研究。在合理简化紊流扩散系数和油流速度的基础上,推导出油内有关油流带电的电荷输运方程的解析解,并且根据该解析解导出了冲流电流计算公式。该计算公式同时适用于所有电导率范围内液体介质冲流电流的计算。最后利用文中推出的计算公式对一实验油道的油流带电进行了计算,结果显示公式得到的值和实验值非常吻合。     

无限大均匀介质中电荷间的相互作用力

本文对无限大均匀介质中电荷的受力情况进行了分析.分析结果表明无限大均匀介质中两个自由的点电荷之间的相互作用力服从介质中的库仑定律.     

关于设置高校学生辅导员专业的思考

新时期党的思想政治工作对高校学生辅导员工作提出更高的要求。设立辅导员专业 ,实现辅导员职业化 ,建立一支高素质的辅导员队伍 ,是高校改革与发展的必然趋势。