基于刚柔耦合的坦克炮发射动力学仿真分析

炮口扰动是影响坦克炮射击精度的重要因素，为研究弹丸出炮口瞬间的炮口扰动规律，基于多体动力学与有限元方法构建了坦克刚柔耦合的全车动力学仿真模型，该模型考虑了身管的柔性特性，对身管进行了模态分析，得到了身管的模态中性文件。通过仿真，对比了后坐部分最大后坐位移与最大后坐速度的试验值与仿真值，对刚柔耦合模型的仿真结果进行了验证。在此基础上，分析了刚性身管和柔性身管对炮口扰动的影响，结果表明：考虑身管柔性特性的刚柔耦合模型能够有效提高坦克炮射击仿真精度。     

The strategic purpose of individual augmentee officers for junior partners in multinational military operations

ABSTRACT

This article examines the strategic purpose of Individual Augmentee Officers (IAOs) for junior partners in multinational military operations through an exploratory case study of Danish IAOs in Iraq and South Sudan between 2014 and 2017. IAOs are individual officers who are moved from their normal functions to be seconded to other units of the armed forces of their own or another country or an international institution. The study concludes that IAOs function as strategically important, yet not necessarily indispensable, supplements to military contingents in several ways: making tangible contributions to the overall mission (contributing), gaining access to information, knowledge, and experience (learning), and lobbying decision-making processes within mission headquarters (lobbying). The usefulness of IAOs depends on whether the junior partner has specific interests and a significant presence in the theatre and whether the mission is conducted as a UN mission, a NATO mission, or an ad hoc coalition.     

Numerical simulation of dynamic large deformation and fracture damage for solid armature in electromagnetic railgun

The design of solid armature of railgun should take full account of its operating conditions and material properties because the armature is subjected to dynamic loading conditions and experiences a complicated electrical, thermal and mechanical process in the interior ballistic cycle. In this paper present, we first introduced a multi-physical field model of railgun, followed by several examples to investigate the launching process. Especially, we used the explicit finite element method, in which material nonlinearity and geometric nonlinearity were accounted, to investigate the deform behaviors of solid armature. The results show that the dynamic mechanical process of armature is dependent on the armature geometry, material and exciting electric current. By the numerical simulation, the understanding of the fracture mechanism of solid armature was deepened.     

The modern naval fortress: an additional sea denial option for coastal states

As fixed facilities, naval fortresses seem unlikely to be important in a sea denial strategy which is usually about mobility, but new defence technologies and the changing geostrategic environment may revive the concept of the fortress. Extended ranges of anti-ship means allow onshore firepower to engage enemies over distance, even beyond the economic exclusive zones where most maritime territorial disputes occur. In the face of size limits on missile warheads that constrain their destruction of hardened targets, various active and passive defence technologies against missiles can enhance the survivability of onshore fortresses. Furthermore, onshore locations give fortresses the advantage of being unsinkable and able to accommodate greater energy and firepower capacity in contrast to vessels, as well as other mobile platforms. The onshore nature of fortresses also gives a different political meaning to being attacked, for the clear violation of sovereignty, as opposed to vessels and aircraft in a disputed space. However, the fact those fortresses are not invincible means cooperation with other existing capabilities still necessary. The case of Vietnam demonstrates how fortresses could strengthen the inferior defence capability of a coastal state vis-à-vis. a stronger sea power.     

电磁轨道发射器动态发射过程的数值模拟

针对电磁轨道发射器动态发射过程的数值模拟问题,基于矢量磁位A和时间积分标量电位V,采用节点单元法,并选择运动坐标系描述运动问题,推导出动态发射下的电磁轨道发射器三维涡流场有限元离散方程。结合温度场控制方程,建立电磁轨道发射器的三维电磁-温度耦合有限元模型。针对一个电磁轨道发射器动态发射问题,对模型进行数值模拟,得到了动态发射下轨道及电枢的温度场分布特点及发射器电感梯度随时间的变化规律。计算结果表明,模型计算出的脉冲电流峰值、出口电流大小、出口速度等参数均与试验结果吻合较好,验证了所开发的有限元程序代码的正确性。     

AR模型仿真相关高斯序列的阶数选择

采用模型仿真相关高斯序列,具有灵活性强、效率高的优点,但如何选择合适的阶数一直是模型谱估计中的关键问题.比较了四种信息量准则和修正的Levison递推方法确定阶数的优缺点,并讨论了采样点数对阶数选择和仿真结果的影响.通过选择合适的信息量准则和采样点数来确定模型阶数,可以有效地仿真功率谱服从高斯谱、n次方谱和指数谱等多种谱形的相关高斯序列,大大降低了仿真过程的计算量.     

加筋板在横向撞击下的吸能特性研究

运用非线性有限元分析方法,对不同撞击工况下加筋板的碰撞损伤过程进行了分析。加筋板结构采用理想弹塑性的材料模型,不计入应变率对材料强化的影响,在忽略接触面的摩擦等因素影响的前提下,考虑加筋板结构在刚性体碰撞下的变形过程,从而探讨加筋板结构的动态响应特点。研究结果表明,加筋板的吸能特性与撞击因素有一定的关系。非线性动态计算采用MSC/DYTRAN程序完成。     

脉冲功率电源连续发射水冷模拟负载

针对脉冲功率电源连续循环放电吸能需求,提出一种1.9 MA级循环脉冲功率水冷模拟负载方案。考虑水冷负载与实际电磁发射负载的相似性要求,提出4×8钢管阵列组成的电阻网络,可方便实现电源不同组合方式的放电考核;针对1.9 MA级电流产生的脉冲电磁力可能引起水冷模拟负载损坏的问题,建立水冷模拟负载三维有限元分析模型,进行电磁力计算和结构分析,保证水冷模拟负载稳定性;利用热网络法对模拟负载在循环脉冲模式下的强迫风冷却、自然冷却和去离子水冷却等方式进行了温升分析。结果表明:模拟负载采用钢管内通去离子水冷却效果最好,循环放电时温度可以恢复到初始状态,最高温度62.5℃,满足连续放电实验的需求。利用提出的方法设计一台水冷模拟负载样机并进行了连续2次1.9 MA放电研究,试验结果与理论分析吻合较好,负载结构运行稳定,从而验证了理论分析的正确性。     

基于椭圆曲线群上的零知识证明

通过研究椭圆曲线群,给出基于其上的2个零知识证明方案,这2个方案均使得甲方向乙方宣称自己拥有某种信息,并通过互动证明使其确信具有该信息,但同时还未泄漏该信息。     

发动机隔热缸套热强度有限元分析

针对低散热发动机存在的热负荷状况,分析了非稳态导热有限元计算的特点:运用经验公式求出了发动机燃烧室部件燃气侧的传热边界条件;运用有限元法对隔热部件进行了热强度分析。计算结果表明:热负荷和热应力增大是造成隔热件可靠性降低的主要因素之一。