Critical interfaces in body armour systems

The ballistic performance, and behaviour, of an armour system is governed by two major sets of variables, geometrical and material. Of these, the consistency of performance, especially against small arms ammunition, will depend upon the consistency of the properties of the constituent materials. In a body armour system for example, fibre diameter, areal density of woven fabric, and bulk density of ceramic are examples of critical parameters and monitoring such parameters will form the backbone of associated quality control procedures. What is often overlooked, because it can fall into the User’s domain, are the interfaces that exist between the various products; the carrier, the Soft Armour Insert (SAI), and the one or two hard armour plates (HAP1 and HAP2). This is especially true if the various products are sourced from different suppliers.There are between 30 and 150 individual layers within a typical body armour system, and each of the interfaces between each of those layers will, in some way or another, contribute to the ballistic performance of the system. For example, consider the following interfaces/interlayers: (i) the frictional, sliding, inter-ply surfaces within a soft armour pack, and also between the pack and the carrier, (ii) the air-gaps that may develop within the soft armour pack, (iii) the interconnecting space between the soft armour pack and the hard armour plate, (iv) the nature of the interfaces between adjacent plies of a multiplied backing laminate, even in a highly compressed Ultra High Molecular Weight Polyethylene (UHMWPE) variant, (v) the interlayer between the ceramic and its substrate, within a HAP, and (vi) the geometrical fit between two hard armour plates within a stacked body armour system. This paper will provide a User-friendly overview of all such interfaces and provide unique guidance as to their criticality and influence.     

Influence of porosity distribution on nonlinear free vibration and transient responses of porous functionally graded skew plates

This article deals with the investigation of the effects of porosity distributions on nonlinear free vibration and transient analysis of porous functionally graded skew (PFGS) plates. The effective material properties of the PFGS plates are obtained from the modified power-law equations in which gradation varies through the thickness of the PFGS plate. A nonlinear finite element (FE) formulation for the overall PFGS plate is derived by adopting first-order shear deformation theory (FSDT) in conjunction with von Karman’s nonlinear strain displacement relations. The governing equations of the PFGS plate are derived using the principle of virtual work. The direct iterative method and Newmark’s integration technique are espoused to solve nonlinear mathematical relations. The influences of the porosity distributions and porosity parameter indices on the nonlinear frequency responses of the PFGS plate for different skew angles are studied in various parameters. The effects of volume fraction grading index and skew angle on the plate’s nonlinear dynamic responses for various porosity distributions are illustrated in detail.     

An energetic nano-fiber composite based on polystyrene and 1,3,5-trinitro-1,3,5-triazinane fabricated via electrospinning technique

Electrospinning is a simple technique used to fabricate polymeric nano-fibrous membranes. These nano-fibers have found a wide range of valuable applications in the biomedical field. However, it has not been utilized with solid high explosives yet. Herein, the electrospinning technique has been used to fabricate polystyrene(PS)/1,3,5-trinitro-1,3,5-triazinane(RDX) composite nanofibers. The governed electrospinning parameters, voltage, distance from the collector, flow rate, mandrel rotating speed...     

四轴超精密车床的改进坐标驱动装置

带微进给方式步进电机的PC控制轴系驱动装置可生产光学质量的表面。超精密车床可生产诸如球体和非球体之类的集合体,其表面粗糙度≤5nmRa,可用于光学装置的反光镜或空气轴承转轴的超精密零件。     

精密机床导轨的测量分析

本文提出了一个用于质量诊断的精密机床导轨分析系统。受控目标的质量评估是依据于对一个物体在选定区间内的测量形状与位置偏差来确定的。质量评估采用相关综合指标的形式:基本误差函数,综合不平行度。在对完整的支撑部件或导向部件作评估的时候,这套系统能对各部件的位置做校正。本文所描述的计算机系统能控制任何测量系统。目前的版本是控制一个测量平动与转动位移量的激光干涉仪。     

第二次世界大战和1939──1941年的共产国际

第二次世界大战是一个非常复杂和矛盾的现象。它的起源、性质、时期划分过去和现在都引起史学家们的争论,特别是“战争性质”,“正义战争”,“非正义战争”,这些概念与其说学术性的,还不如说是政治——道义上的。初次提出第二次世界大战性质和起源问题是在战争前夕和战争初期,是由一些包括共产国际领导在内的政治活动家提出的,政治家们当然不会从学术出发,而是从政治和意识形态出发。当时由季米特洛夫主持领导工作的共产国际无条件追随斯大林,季米特洛夫在给副手曼努伊里斯基的信中称斯大林为“主人”①,而斯大林首先考虑的是自己…     

用于微机器人的线切割加工的平行弹性平台

本文给出了具有四个圆形柔性铰链的平行弹性平台的研究结果,并运用材料力学和有限元分析进行了理论仿真,利用线切割加工工艺制造了几个整体式的平台。颈缩截面的厚度为20—100um。对这些结构的刚度进行了精密测量并与理论值进行了比较。这使得能够定性的分析在电加工中产生的在微米级范围内不能忽略的粗糙度和其它表面变形的影响。通过这些实验得到的结果对其它具有几个自由度的复杂柔性机构非常有用。     

反卫星武器:增长中的危险

反卫星武器的任务是,摧毁敌方武装力量的指挥控制系统和情报搜集网。这就提出一个非常重要的问题:反卫星武器的军事应用是否会加剧危机和冲突?当世界从和平时期通过危机而走向战争时,反卫星武器的任务将发生明显变化。在谈判解决危机和建立信任的过程中,卫星能为军事当局“突时”传递信息。如果外交遭到失败,同样的信息就可用之于最佳的进攻。卫星还可提供早期预警:在平时有利于消除疑虑,战时则有助于对敌方目标进行报复性打击。     

以微处理机为基础的跟踪与瞄准系统的宽频带现代控制

本文叙述多年来从事宽频带、高精度跟踪与武器瞄准控制系统开发、以至实际实现具有现代技术水平的现代控制理论与微处理机相结合的武器控制系统的一些最新研究成果。     

VR黑板——策划和训练的任务可视化

本文概述了虚拟现实(VR)在临场训练中的优点以及在进行虚拟现实设计中应注意的问题。