Delamination process in cross-ply UHMWPE laminates under ballistic penetration

Cross-ply unidirectional laminates made of ultra-high molecular weight polyethylene fibers are widely used as components of bullet-proof vests. To simulate the delamination process of the material under penetration, we constructed a numerical mechanical model, which was validated by tests using 7.62 × 39 mm rifle bullets penetrating laminates of different thicknesses. The results show that the delamination region is essentially diamond-shaped. The simulated delamination region is in good agreement with the experimental data. It is found that the delamination region increases with the compression modulus along the fiber direction. The delamination region increases when the shear strength between the fabric layers decreases;However, it is little influenced by the normal strength. The delamination region of the front face of the laminate is little influenced by the failure strain of the material and the initial velocity of the bullet. The delamination region of the back face increases with the failure strain and decreases with the initial velocity.     

A reusable planar triggered spark-gap switch batched-fabricated with PCB technology for medium-and low-voltage pulse power systems

Triggered spark-gap switch is a popular discharge switch for pulse power systems. Previous studies have focused on planarizing this switch using thin film techniques in order to meet the requirements of compact size in the systems. Such switches are one-shot due to electrodes being too thin to sufficiently resist spark-erosion. Additionally, these switches did not employ any structures in securing internal gas composition, resulting in inconsistent performance under harsh atmospheres. In this work, a novel planar triggered spark-gap switch (PTS) with a hermetically sealed cavity was batched-prepared with printed circuit board (PCB) technology, to achieve reusability with low cost. The proposed PTS was inspected by micro-computed tomography to ensure PCB techniques meet the requirements of machining precision. The results from electrical experiments demonstrated that PCB PTS were consistent and reusable with lifespan over 20 times. The calculated switch voltage and circuit current were consistent with those derived from real-world measurements. Finally, PCB PTS was used to introduce hexanitrostilbene (HNS) pellets in a pulse power system to verify its performance.     

羧酸盐对锡和铝在中性溶液中的缓蚀作用研究

分别采用交流阻抗、线性极化、动电位扫描等电化学方法初步研究了羧酸盐缓蚀剂在中性介质中对锡和铝的缓蚀作用.实验结果表明,锡和铝在中性介质中的腐蚀以点蚀为主,而该羧酸盐结构中含有羧基,对锡和铝有良好的缓蚀效果,尤其是处于最佳缓蚀浓度时.     

正交投影法的飞机效能-费用系统评价

飞机效能-费用系统评价是飞机研制早期一个非常重要的问题,需要从数个替代方案中找出所需的最优方案,然而要决定哪个方案“最优”却未必容易。TOPS IS法对与理想解距离更近可能与负理想解的距离也更近的这一类方案排序的结果并不能完全反映各方案的优劣性。针对TOPS IS法的不足,提出将基于“垂面”距离的TOPS IS法-正交投影法应用于飞机效能-费用系统评价,对其基本原理进行了解释,给出了简化的计算步骤,并在随后的实例评估中取得了良好的效果。     

基于马氏过程的目标发现率分析

针对目标发现率的变化规律问题,提出了一种从作战过程出发、基于马氏过程状态转移的研究思路.根据“侦察→信息处理与决策→火力打击”的一般作战过程,建立了状态转移方程,推导了目标发现率的解析表达式并求解之.     

BP神经网络的布撒器末端修正

针对布撤器开舱点位置解算及子弹药减速伞延时解算所需时间长的问题,引入了BP神经网络算法,建立了子弹药的数学模型和BP神经网络解算模型,并进行了布撒器末端修正的仿真分析.仿真结果表明:运用BP神经网络算法计算的结果误差较小,并且大大缩短了在线解算的时间,进一步提升了布撤器的作战效能.     

构件化雷达仿真系统的测试方法

雷达仿真系统的构件化设计具有可重用、易扩展等优势,但其软件测试方法也面临新的挑战.为了实现对构件化雷达仿真系统的有效测试,促进构件化技术在雷达仿真研究中的进一步应用,在分析了现有构件测试技术的基础上,结合雷达仿真领域的特点,提出了基于元数据的分层构件测试方法.在此基础上,分析了雷达构件元数据的基本特征并给出了XML形式的描述,建立了基于元数据的雷达仿真构件分层测试体系,实现了雷达仿真构件的自动化测试方法.最后分析了一个雷达构件测试实例,验证了该测试方法的可行性与有效性.     

基于直接数据域自适应算法的相干信号DOA估计

利用直接数据域自适应算法的稳态权值代替噪声子空间构建空间谱,构造了一种超分辨波达方向(DOA)估计方法.为了解决谱峰搜索时的伪峰问题,采用参考阵元轮换得到多组线性无关稳态权值,逼近噪声子空间,能有效去除伪峰.针对相干信号的DOA估计,进一步提出了直接数据域取对称共轭向量的解相干方法.相比子空间分解类算法,本文算法不需估计信号源数目和协方差矩阵、不需特征分解,复杂度仅为O(MP),同时能有效完成解相干处理.     

梁式转换结构的ABAQUS非线性有限元分析

为研究梁式转换结构在竖向荷载作用下应力的分布及承载力情况,运用ABAQUS软件对文献[9]中的满跨剪力墙梁式转换结构ZHL-1进行有限元分析,并将有限元计算与文献报道的试验进行结果对比。分析表明:数值模拟与试验所得极限承载力误差仅为4.17%;该结构中转换梁与上部剪力墙共同作用所产生的应力拱效应分布及变形发展全过程与试验吻合较好;引入的损伤参数可以有效体现混凝土的拉伸开裂变化和压缩破坏特征。因此,运用ABAQUS软件,结合混凝土损伤塑性模型梁式转换结构所作的非线性有限元分析结果,可以为类似的剪力墙梁式转换结构设计和试验提供参考。     

气液同轴式喷嘴雾化特性的试验

通过试验研究气液同轴直流式和气液同轴离心式喷嘴的雾化性能。研究表明:喷嘴出口扩张时可以改善喷嘴的雾化性能;气液同轴直流式和气液同轴离心式喷嘴都存在一个合适的缩进长度,在改善喷嘴雾化特性的同时对总流量影响较小;在相同条件下,气液同轴离心式喷嘴的喷雾性能要优于气液同轴直流式喷嘴的喷雾性能。