长杆射弹侵彻三种混凝土靶的实验研究

为了研究钻地武器的侵彻性能,在57mm口径的气炮上发射长杆射弹对三种靶体进行模拟侵彻实验。靶体为水泥砂浆石靶、钢纤维混凝土靶和含单层密排刚玉球的钢纤维混凝土靶。实验结果表明,弹头形状对侵彻深度有明显影响;当长杆射弹和撞击速度都相同时,与侵彻钢纤维混凝土靶相比,含单层密排刚玉球的钢纤维混凝土靶中的侵彻深度大约降低了11%,而水泥砂浆石靶中的侵彻深度增加了12%。     

Partial penetration of annular grooved projectiles impacting ductile metal targets

Changing and optimizing the projectile nose shape is an important way to achieve specific ballistic performance. One special ballistic performance is the embedding effect, which can achieve a delayed high-explosive reaction on the target surface. This embedding effect includes a rebound phase that is significantly different from the traditional penetration process. To better study embedment behavior, this study proposed a novel nose shape called an annular grooved projectile and defined its interaction process with the ductile metal plate as partial penetration. Specifically, we conducted a series of low-velocity-ballistic tests in which these steel projectiles were used to strike 16-mm-thick target plates made with 2024-O aluminum alloy. We observed the dynamic evolution characteristics of this aluminum alloy near the impact craters and analyzed these characteristics by corresponding cross-sectional views and numerical simulations. The results indicated that the penetration resistance had a brief decrease that was influenced by its groove structure, but then it increased significantly-that is, the fluctuation of penetration resistance was affected by the irregular nose shape. Moreover, we visualized the distribution of the material in the groove and its inflow process through the rheology lines in microscopic tests and the highlighted mesh lines in simulations. The combination of these phenomena revealed the embed-ment mechanism of the annular grooved projectile and optimized the design of the groove shape to achieve a more firm embedment performance. The embedment was achieved primarily by the target material filled in the groove structure. Therefore, preventing the shear failure that occurred on the filling material was key to achieving this embedding effect.     

有限水深Kelvin源格林函数及其导数的快速计算

应用线性船舶水动力学理论,将有限水深Kelvin移动兴波源格林函数分解成3部分:简单Rankine源集合、局部扰动项和波函数项。对各部分在亚临界和超临界航速时的快速计算分别作了讨论,其中对计算费时的局部扰动项采用了复数中的最陡下降积分法,加快了计算速度,进而引出各部分偏导数的计算。最后,比较了格林函数的差分值与偏导数值,计算了薄船兴波阻力与表面兴波,讨论了不同面元网格划分的收敛性,证实了亚临界、超临界航速兴波分别以横波、散波为主。     

蒙皮材料静电起电影响因素实验研究

为有效减小静电放电对飞行器的影响,设计蒙皮材料静电起电地面模拟实验平台．利用该平台对某型蒙皮材料进行静电起电实验研究,得到材料摩擦起电电位随时间的变化规律,并研究接触面积、相对速度、环境温度和相对湿度对材料静电起电电位最大值的影响,通过拟合曲线得到：相对湿度对静电起电电位的影响最大,相对速度次之,接触面积和环境温度对起电电位的影响相对较小．     

面向突防效能的超声速巡航导弹总体设计技术初步研究

防御系统技术的不断发展,对超声速巡航导弹设计提出了新的需求.针对以“性能”为核心的设计不能满足超声速巡航导弹设计新需求的问题,初步探讨了面向突防效能的超声速巡航导弹总体设计技术.分析了国内外导弹武器设计技术的发展,指出设计技术向着以“效能为核心”的设计方向发展;提出了面向效能的设计理念,分析指出面向效能的设计是以追求满意设计为目标的优化设计;在新的设计理念指导下提出了面向突防效能设计的技术框架,主要说明了面向突防效能的超声速巡航导弹设计框架、效能基础、技术基础、基本模式以及几项关键技术等.     

弹丸对钢管混凝土结构冲击效应的数值模拟

为将模块化设计钢管混凝土结构用于防御工事的构建,进行20 mm口径弹丸垂直侵彻混凝土结构和不同钢管混凝土结构的数值模拟,对比不同结构的抗冲击性能,分析钢管混凝土结构抗冲击性能提高的机理.结果表明,正六边形钢管混凝土结构抗冲击性能良好,兼容了金属和混凝土材料的优点,克服了混凝土材料的脆性以及金属材料容易发生局部屈曲的缺点,为防御工事结构的改进提供了理论基础和参考依据.     

传导冷却高温超导磁体热输运参数反演识别

在传导冷却高温超导磁体系统中,超导磁饼热导率以及磁饼与导冷体之间的界面热阻是影响热输运的主要因素,也是传导冷却超导磁体系统热设计的难点。为了获得准确的热导率和界面热阻参数,根据Levenberg-Marquardt算法提出通过表面测温确定传导冷却超导磁体热输运参数的反演识别方法。搭建低温实验数据测试平台,建立高温超导磁饼三维各向异性热传导模型。利用反演算法对传导冷却Bi2223高温超导磁体在40~76K温区的各向异性热导率与界面热阻进行反演识别,并分析测温误差对识别结果的影响。研究成果将为超导磁体热输运参数的获取提供一种新思路。     

电磁发射装置电-磁-热场分布的分析与仿真

为探讨电磁发射过程中出现的热烧蚀现象,构建了电磁发射及电接触层接触电阻的模型,推导出电-磁-热场耦合方程,采用有限元数值计算方法得到了在脉冲电流激励下,轨道和电枢间电流密度、磁感应强度及温度的分布图。计算过程表明:电磁发射过程实际是电-磁-热场的耦合过程,接触电阻是造成电磁发射热损耗的主要原因之一,接触电阻使得轨道和电枢接触表面区域的电流密度极大,容易造成轨道材料的烧蚀。     

Is South Africa's 20 years of democracy in crisis? Examining the impact of unrest incidents in local protests in the post-apartheid South Africa

This article assesses South Africa's 20 years of democracy, which has frequently been bedevilled by local protests. This article is particularly interested in those unrest incidents that have been distinct for one reason or another. In South Africa, the surge in local unrest incidents is often linked to police behaviour, which has become increasingly militant and brutal when quelling protests. While the right to protest is constitutional, the damage caused during protest action can be immense owing to acts of violence. Protestors' resorting to violent protest action is often linked to increased frustrations as a result of the government's inability to live up to the expectations of marginalised and poor communities. While this article draws primarily on existing scholarly debates focusing on social protests, the primary objective is to examine the impact of unrest incidents on local protests in post-apartheid South Africa. The article further argues that ‘spaces’ for participation in local governance should be created so that citizens can become architects of development and their own future.     

化学键合胶凝材料抗硫酸盐侵蚀性能

采用浸-烘循环的方法模拟干湿循环交替环境进行新型化学键合胶凝材料抗硫酸盐加速侵蚀试验.侵蚀溶液为质量浓度为5％的硫酸钠溶液,一组试验采用全浸-烘循环,另一组试验采用半浸-烘循环.在经受30×N(N=1,2,3,4,5)次循环后,测定试件的强度耐蚀系数和质量损失率,以此评价化学键合胶凝材料抗硫酸盐侵蚀性能.试验结果表明:半浸-烘循环的侵蚀比全浸-烘循环的侵蚀严重;在经受150次侵蚀循环后,试件外观无严重破损,质量不减反增,强度也不降低,说明化学键合胶凝材料具有优良的抗硫酸盐侵蚀性能.