夹芯复合材料圆柱壳在静水压力下的承载能力试验

为研究极限复合材料圆柱壳在静水压力下的损伤现象和机理,首先基于钢制耐压壳比重大以及声学和磁学性能差的缺点,提出了使用夹芯复合材料圆柱壳作为潜水器耐压壳的新型结构形式;然后,采用试验研究,比较了两种模量芯材的夹芯复合材料圆柱壳结构在静水压力下的承载能力;最后,根据两种壳体的特点,设计了两种不同的试验方案进行试验,得到了壳体的失效载荷,并通过应变片测定了壳体复合材料表层上相应测点在试验过程中的应变数据。得到以下结果:HW-S01壳体受到屈曲效应的破坏,而HW-055壳体由于局部复合材料应力过载而失效;HW-S01壳体的试验失效荷载为1.34 MPa,HW-055壳体的失效载荷为11.2 MPa。试验结果表明:该夹芯复合材料圆柱壳有能力承受超过1 000 m水深的静水压力,可以对大潜深潜水器全复合材料耐压壳的设计研究提供参考。     

带有损伤凹陷的环肋圆柱壳应力和稳定性分析

为探寻局部受损伤潜艇结构的承载能力,以出现较大损伤变形的环肋圆柱壳舱段结构为研究对象,"涡形凹陷"作为损伤变形的典型形状,运用MSC/NASTRAN软件计算了这种结构在静水外压作用下的应力分布和失稳临界压力。结果表明:带有损伤凹陷的环肋圆柱壳与完好状态环肋圆柱壳相比,最大应力值提高,失稳临界压力值下降,应力的改变对环肋圆柱壳承载能力的影响更大;相同凹陷幅度下,损伤凹陷中心在肋骨位置时,对圆柱壳应力状态和稳定性的影响最为恶劣。肋骨分别采用梁单元或壳单元两种建模方式时,得出的应力和失稳临界压力变化规律一致,采用梁单元建模得出的肋骨应力偏安全。     

分布载荷作用下多铁性圆柱复合材料的断裂分析

针对多铁性圆柱复合材料因其外表面上存在不同类型的轴向分布载荷而出现的界面裂纹问题,建立了断裂力学分析模型。首先利用分离变量法和无穷级数法推导出该模型的Cauchy奇异积分方程组,然后利用Lobatto-Chebyshev配点法离散该方程组为代数方程组,进而得到裂纹尖端应力强度因子(Stress Intensity Factor,SIF)的数值解。通过对数值结果的分析得到:在不同类型的分布载荷作用下,压电层厚度以及分布载荷大小是影响裂纹尖端SIF的主要因素。该研究结果可为此类复合材料在实际工程应用中的防断裂优化设计提供理论参考。     

冲击波载荷作用下固支正交各向异性薄板挠度特性分析

根据能量原理,采用层合板理论和薄板大变形理论,对四边固支的矩形正交铺层的纤维增强复合材料薄板在爆炸冲击波作用下的弹性大变形进行理论分析,得到了层合板的最大挠度计算公式。有限元数值模拟计算表明,理论计算结果与有限元数值模拟的结果吻合较好,因此该方法可用来对复合材料板在弹性范围内的最大挠度进行预测,同时认为根据薄板的最大挠度,可以计算板的应力(应变)分布和复合材料板失效时的爆炸载荷。     

具有初始挠度的环肋圆柱壳在静水外压作用下的应力分析

本文讨论了壳板初挠度对环肋圆柱壳在静水外压作用下应力分布的影响,用理论分析的方法预报了有初挠度壳体中的应力。通过对涡型初挠度的讨论,建立了初挠度范围因子的概念,提出了具有普遍意义的初挠度数学模型,并且用线性小挠度理论对具有非轴对称初挠度的弹性环肋圆柱壳进行了求解并与SAPV计算结果进行了比较。理论分析表明,初桡度范围对壳体应力也有较大的影响,外凸和内凹初挠度对壳体应力的影响是不同的。因此,应该综合讨论初挠度幅值、范围以及凸凹形式对环肋圆柱壳壳体应力的影响。     

无约束自由体有限元分析中的准静态法

在对某水下无约束航行体进行有限元静力分析的时候,由于无法限定结构的自由度而使刚度矩阵奇异,从而导致求解失败。为了解决这一问题,采用强迫约束法和准静态法(惯性释放)对此航行体进行了有限元静力对比计算,结果表明:用强迫约束法对水下航行体进行静力分析时,在施加强迫约束的部位出现了严重的应力集中现象,应力最大值为1.25×106Pa,应力集中使得整个结构的应力分布与实验数据相差较大,可认为计算结果错误;采用惯性释放法对其进行静力分析时,应力最大值为3.27×105Pa,整个结构的应力分布合理,与实验数据一致,计算结果正确。     

不同锥-柱连接结构舱段力学特性对肋骨初挠度敏感度研究

为给不同锥-柱连接结构加工时的偏差控制提供参考,根据类圆柱壳结构肋骨初挠度测量经验,建立了数学模型描述单根肋骨初挠度沿周向的形态变化,并将其施加到有限元模型中;分析了锥-柱结合壳、厚板削斜过渡环以及锥-环-柱结合壳应力、舱段弹性失稳压力以及极限载荷对肋骨初挠度敏感度的差异。得到结论如下:锥-环-柱结合壳较锥-柱结合壳及厚板削斜过渡环,其内表面纵向应力抵抗肋骨初挠度不利影响的安全裕度更大;含锥-环-柱结合壳或厚板削斜过渡环的舱段弹性失稳压力对肋骨初挠度的敏感度相当;肋骨初挠度控制在规范允许上限值的3倍以内时,含不同凸型锥-柱连接结构舱段的极限载荷对肋骨初挠度均不敏感。     

焊接过程对焊接残余应力及残余变形的影响

采用热弹塑性有限元法 ,对直通焊和多人同时分段焊两种焊接过程的平板对接焊时焊接应力变形和圆柱壳板环缝的焊接变形进行比较 ,认为多人同时分段焊较直通焊无论在降低焊接残余应力还是焊接残余变形都具有非常显著的效果     

带有消声瓦的潜艇耐压壳的稳态振动和横向应力

采用混合分层理论和Ressiner混合变分原理,在壳的厚度方向取二次插值函数来描述位移沿厚度方向的变化规律;采用三次和四次插值函数来描述横向应力沿厚度方向的变化,线形处理筋条的变形,推导出粘弹加筋层合圆柱壳的动力学方程和协调方程组,并采用拉普拉斯变换,得出简支粘弹加筋层合圆柱壳稳态振动的响应解。对于自由阻尼层合圆柱壳,所给出的振动频率和结构损耗因子与解析解吻合良好.结果表明,较高的层间横向正应力是引起潜艇消声瓦脱落的主要因素,而采用较高模量的粘弹性阻尼材料将降低层间横向应力的幅值.     

安静型夹芯复合材料舵设计及其力学性能分析

通过对夹芯复合材料各层材料的选择,以及夹芯复合材料舵壳的结构设计,提出了夹芯复合材料舵的设计方案和制作工艺。并利用有限元方法计算了复合材料舵壳在流体压力作用下的应力和变形,以及在瞬态载荷作用下舵壳的振动响应。计算结果表明,夹芯复合材料舵壳满足结构的强度和刚度的要求,同时振动水平与钢舵比较有很大的改善。     

Terrorism,insurgency, kidnapping,and security in Africa's energy sector

Energy continues to serve as the bedrock of modern economies and the main driver of modern society. For Africa, the production and supply of energy resources such as crude oil, natural gas, uranium, coal, biomass, biofuels and other renewables are an important source of employment, rents, taxes, royalties and profits. This sector brings in several tens of billions of dollars of revenue annually. The production and delivery of such resources, however, depend on critical infrastructures such as pipelines, refineries, processing plants, terminals, rigs, electrical energy pylons, substations, pump stations, vessels, and tankers. These infrastructures have been attacked by terrorists, insurgents, vandals and saboteurs, all of whom see them as targets against which to register their grievances and extract concessions from the state. This paper is a chronological account of some of the documented incidents of terrorism, insurgency, kidnapping, destruction, sabotage, and human casualties suffered in the oil and gas sectors in Africa between 1999 and 2012. It is based on data extracted from the databases of the RAND Database of World Terrorism Incidents and the University of Maryland's Global Terrorism Database (GTD).     

Helping hands: civil–military cooperation and Italy's military operation abroad

In the Post-Bipolar Era the growing complexity of the military operations requires a new approach for the resolution of international crises. Since the end of the Cold War, peace support operations (PSO) have become the mainstay and principal occupation of most Western armies. At the same time, Italy has been one of the most important actors in such an area. The article focuses on the cooperation between military and civil components (a process called CIMIC) as a key variable in the Italian PSOs. We will analyse in detail the main lessons learned from past military interventions as well as the general context in which new tendencies are taking place. The maintaining of a minimum security frame becomes essential to fulfil activities ‘collateral’ to the mission: reconstructing services and infrastructure, food distribution, water and medication, law and order, de-mining, training of local forces, and supporting local institutions. These are the main tasks to obtain thrust and support from the population.     

Tacit support for terrorism: The rapprochement between the USSR and Palestinian guerrilla organizations following the 1967 war

This article demonstrates the inconsistent and wavering Soviet attitude towards national liberation movements in general and the Palestinian organizations in particular. Until the late 1960s, the Soviets viewed these organizations with suspicion, hesitating to engage in political dialogue with them. However, in the 1970s, political and military events in the region, as well as modifications in the Kremlin's Cold War strategies, led to a general shift towards the Middle East in Soviet foreign policy. Soviet leaders showed increased willingness to provide certain Palestinian organizations with arms with which to conduct terrorist activities against Israeli, pro-Israeli, Jewish and Western targets. The article explores the complex relations between Palestinian organizations and the USSR in the field of international terror. The study also exposes and analyzes the nature and content of Soviet–Palestinian arms dialogues and transactions. It provides clear evidence that Soviet policymakers and other luminaries were fully informed of, and sometimes directly involved in, these transactions and dialogues at the highest levels.     

A1 Qaeda and the radical Islamic challenge to western strategy

The September 11 global crisis prompted by the attacks on the World Trade Center and the Pentagon raises major questions concerning the nature and trajectory of terrorism in the post-Cold War global order. Hitherto, terrorism has been largely debated by analysts at the level of nation states. Terrorist and insurgent movements have also been largely anchored in nationalist and ethnic power bases even when they have sought to mobilise a transnational ideological appeal on religious or class grounds. There have been a few exceptions to this pattern such as the alliance between the German Baader-Meinhof group and the Japanese Red Army Faction, but even such international alliances as this did not, until at least the 1980s, presage anything like a global terrorist network necessitating a global strategic response. This study examines terrorism and global strategic responses.     

Helping hands: external support for the KNU insurgency in Burma

This article analyses to what extent the Burmese KNU insurgency made use of external support from states, refugees, and diasporas. Based on extensive fieldwork it is concluded that support from neighbouring states and refugees has for years kept the Karen rebellion alive. Western countries perceived forms of resistance to the illegitimate Burmese regime as just and have therefore played a crucial role in the continuation of conflict in Karen State. It is important that policymakers and donors as well as executing organizations continue to reflect critically on the way they exercise their work.     

基于GTST-DMLD-ESD的装备RMS建模仿真

装备的RMS是装备的重要设计参数,是影响战备完好和保障能力的关键因素.引入GTST-DMLD作为主要建模工具,建立起装备系统的RMS描述模型,以ESD为补充和扩展,对维修过程进行建模.并以GTST-DMLD-ESD模型作为装备RMS仿真的核心,对装备RMS仿真模型的总体框架进行了研究,并对各模块进行了较为详细的探讨.     

Cyber sheiks and grassroots jihadis: the war in Syria and the devolution of the Bosnian Salafi communities

ABSTRACT

What was the scope of the Bosnian jihadi participation in the war in Syria? Did the Bosnian volunteers tend to join one particular faction? Why did the Bosnian youngsters decide to join the holy war in the Levant? Was this an organized and hierarchical process or was this a grassroots movement? Last, were all the Salafis in Bosnia supportive of this dynamic or did this process cause internal frictions? These are some of the questions that this research will try to answer.     

Country survey XVI the defence sector in the economy of a declining superpower: Soviet Union and Russia, 1965-2001

The Soviet Union was able to develop a large military-industrial complex and become the world's second superpower despite deficiencies in its centrally planned economy because defence was given high priority status and special planning, rationing and administrative mechanisms were used to attain national security objectives. However, in the period 1976-85 the effectiveness of priority protection diminished and defence institutions experienced more of the problems typical of the shortage economic system. The heavy defence burden also created growing difficulties for the civilian economy. The attempts by the Gorbachev government to reform the defence sector and improve defence-economic relationships during perestroika (1985-91) uniformly failed. For most of the transition period, the Russian military-industrial complex has been adversely affected by its low priority status, cuts in defence spending, instability of the hybrid politico-economic system, and negative growth of the economy. The armed forces and defence industry have been reduced in size and their outputs of military services and equipment have fallen to low levels. Nevertheless, the Russian armed forces still have over one million troops, significant stocks of sophisticated conventional weapons, and a large nuclear arsenal. The government of President Putin has raised the priority of the defence sector, increased real defence spending, and adopted ambitious plans to revive Russian military power. It is likely, though, that tight resource constraints will hamper efforts to reform the armed forces and to upgrade weapons. By 2010 Russia will be an important, but not dominant, military power in Eurasia.     

Traffickers,terrorists, and a ‘new security challenge’: Russian counternarcotics strategy and the Federal Service for the Control of the Drugs Trade

The collapse of the Soviet Union precipitated the massive expansion of drug use and trade in Russia. The country now has one of the largest populations of injecting drug users in the world and has become the largest single-country market for Afghan heroin. In 2003 the Federal Service for the Control of the Drugs Trade was created to coordinate a comprehensive counternarcotics strategy appropriate to the scale of this threat. The service continues to face a number of challenges in its early stages of development. However, it has made considerable advances in improving responses to large-scale organised crime and in building international cooperation.