微波星及空间碎片高速撞击航天器风险度分析

给出了微流量及空间碎片高速撞击航天器风险分析的方法,并采用风险分析软件,以柱状近地轨道航天器为例,对不同防护结构方案、航天器的飞行姿态、防护屏的厚度以及航天器的运行时间等因素对航天器不发生穿孔损伤的影响进行了分析,给出了分析的结果。     

介质材料带电对二次电子发射影响的研究

航天器充放电效应故障大多都会引起卫星灾难性事故,对航天器在轨安全运行产生较大的影响。二次电子发射系数是决定卫星表面带电速率和充电平衡电位水平的重要材料特征参数。研究介质材料表面带电对二次电子发射影响的理论模型,分析表面正电位激发和负电位阻挡效应,并给出计算结果,为航天器充放电效应数值模拟和防护设计提供数据支持。     

空间环境防护型薄膜评述

空间环境的复杂性和特殊性对航天器的使用寿命和性能造成严重威胁。提高航天器表面材料抵抗空间环境作用的能力一直是空间技术开发工作的重点关注问题。目前,表面薄膜技术已被广泛应用在航天器热控涂层、光学器件等方面的空间防护。针对航天器在空间原子氧环境、空间等离子体环境、空间污染环境中的空间环境效应问题,详细介绍了相应空间环境防护薄膜的研究现状及主要制备方法。在地面空间模拟实验和飞行试验成果的基础上,对这些防护薄膜的空间环境适应性进行了分析,总结了空间环境防护薄膜应具备的综合性能,提出复杂型薄膜的开发和空间环境防护薄膜标准评价体系的建立是今后研究的重点。     

近地轨道航天器微流星及空间碎片风险度分析研究

以单防护屏防护结构为例,根据描述其防护性能的撞击极限方程,微流量及空间碎片环境数学模型,建立了航天器结构的有限元分析模型,进行了航天器在微流星及空间碎片环境下风险度的初步分析,其结论可供工程实践参考。     

聚合物材料表面原子氧防护技术的研究进展

聚合物材料具有质量轻、强度高等优点, 常被用作航天器表面的复合结构基材。原子氧是低地球轨道空间中成分含量最高的粒子之一, 对暴露在航天器表面的聚合物材料易形成大通量、高能量轰击, 造成其表面氧化侵蚀和质量损失, 使聚合物材料的性能发生不同程度的衰退, 也是导致航天器件可靠性降低、工作寿命缩短的主要环境因素。本文对当前国内外通用的几种聚合物材料表面原子氧防护技术进行了整理归纳, 其中表面化学改性方法结合了体材改性和常用防护涂层的优点, 得到的有机/无机复合改性防护层具有较好的综合防护性能。文中分析了近年来由计算模拟法开展原子氧与表面防护材料相关作用机理的研究, 指出采用计算模拟结合试验的研究方法, 有可能从本质上揭示复合改性层与原子氧的作用机理, 从而促进原子氧防护材料与防护技术的研究发展。     

探月充电环境及效应研究综述

在探月过程中航天器与各种等离子体环境相互作用,使航天器表面和内部材料出现充放电效应,从而影响航天器的工作性能、使用寿命、工作可靠性等。结合国外探测数据,分析了探月任务的奔月、环月和落月过程中可能遭遇的等离子体环境和可能出现的充放电问题,对科学探测载荷性能参数的设定、航天器充放电防护设计具有一定的参考价值。     

动态子结构法在航天工程中的应用研究EI北大核心CSCD

以载荷分析为主要内容,概述动态子结构法在航天工程中的应用。首先采用约束子结构模态综合法与超单元法进行全箭级器箭耦合载荷分析,给出器箭界面加速度条件、运载器和航天器的内部载荷;然后介绍采用航天器基础激励方法与超单元法,依据全箭级器箭耦合载荷分析给出的器箭界面加速度条件,进行航天器级的载荷二次分析,给出航天器的内部载荷,可以证明载荷二次分析所得航天器的内部载荷结果与全箭级器箭耦合载荷分析结果一样。由此说明航天器级载荷二次分析获得结果是可信的,也就是说全箭级器箭耦合载荷分析与航天器级载荷二次分析流程是合理的、可靠的。     

考虑贮箱液体晃动的复杂航天器分离动力学分析

考虑空间微重力环境下贮箱燃料的晃动行为,采用耦合的欧拉-拉格朗日(coupled Eulerian-Lagrangian, CEL)方法,建立了航天器和液体燃料的分离动力学模型,通过航天器分离动力学及流固耦合动力学分析,解决了贮箱燃料液体晃动对航天器分离姿态的影响问题,给出了液体晃动对航天器产生的干扰力和力矩,对比了考虑液体晃动和假设贮箱液体为刚体得到航天器分离姿态的差异,不同液面高度对航天器分离姿态、干扰力和力矩的影响情况,分析结果为弹簧分离机构的优化设计和分离安全性设计提供参考,同时提高了航天器在轨姿态控制设计的可靠性。     

空间环境下航天器部件密封性能评价方法研究

从航天器密封部件的密封种类和泄漏原理,特别是橡胶密封圈的泄漏原理出发,分析了经高真空、高低温、空间辐照等空间环境对航天器密封性能的影响,给出了采用泄漏检测技术作为密封性能评价的方法。重点介绍了基于现有漏率性能评价方法而研制的几种航天器部件密封性能评价装置以及在现有评价装置上开展的部分航天器部件密封性能试验及研究情况。     

填充空心球/铝基复合材料结构的超高速撞击损伤特性研究

针对人类航天活动在空间中积累的大量空间碎片严重威胁在轨运行航天器安全,急需开发具有优良防护性能的新材料防护结构问题,初步研究填充空心球/铝基复合材料Whipple防护结构的撞击特性,获得相关撞击损伤数据,与填充实心铝板的Whipple防护结构进行对比,并评估空心球/铝基复合材料作为一种航天器防护材料的可行性。     

Modeling of electromagnetic shield dynamics

The object of this work is the development of the algorithm making possible the modeling of electromagnetic shield dynamics. The analysis of the field distribution and the synthesis of the models defining the field have been carried out for the following configurations: a) shield of spherical symmetry and b) flat shield.     

数量工程技术在南京长江隧道工程中风险 辨别及事故防范的应用研究

以南京长江隧道工程为背景,提出了基于数量工程技术的风险提示及事故防范方法,即运用数值仿真方法,借助超级计算机的并行计算能力,建立盾构机进出洞,盾构机穿越长江大堤及穿越江中最浅覆土层,两台盾构机同时施工影响,盾构机穿越复合土层等工程关键问题的数量分析模型。基于该模型,对地表沉降过大、盾构机姿态偏移、开挖面失稳等工程风险进行了提示;分析了风险产生的机理、后果;提出了事故防范的措施,评价和验证了防范措施的有效性和合理性。     

水下隧道盾构法施工安全风险评估探讨

随着地铁、公路等交通隧道的不断发展,隧道往往穿越江河湖泊等水体,大直径泥水平衡盾构广泛应用于水下隧道施工。大直径盾构施工风险高、控制难度大,加上水下施工不确定因素多,风险因素具有不断动态变化的特点,使得施工过程中存在较大的风险。风险评估越来越多的应用于水下隧道施工安全管理中。文章介绍了大直径泥水盾构的几个特点,并对这几个特点引起风险增大的机理进行了分析,针对风险评估常用的几中方法中存在的不足,提出了一种改进的指数法,给出了该方法的评估流程及基本计算模型,并将该方法初步应用于某水下隧道施工风险评估。该方法能够适应风险因素的变化,并且不拘泥于真实概率,通过进一步的细化和完善,能够更好地适用于水下隧道施工安全风险评估。     

盾构进出洞全方位风险控制冻结加固技术

在含水复杂的地质条件下采用水平冻结法进行盾构进出洞施工,可以通过延长（加深）水平冻结外圈冻结深度,使冻结加固体全方位包裹并超过盾构机本体,利用外圈冻结孔的维护冻结,将盾构推进过程中形成的微小流水通道中的泥土冻结成为冻土,封闭流水通道,较为有效地防止了流水、涌砂现象的发生。利用长距离水平钻孔防喷接驳器,简单方便地解决了在已施工完毕的端头井内长距离钻孔的难题。工程实践证明,全方位风险控制冻结加固技术在复杂地质条件下盾构进出洞施工中,简单易行,安全可靠,值得推广应用。     

Instantaneous liquid release from a rail tanker: the influence of noise shields on pool shape and pool size

In the Netherlands, the Betuweline is a dedicated freight railway. It will, among other things, be used for transportation of all kinds of hazardous materials from the Port of Rotterdam to the German Hinterland and vice versa. The line is approximately 150 km long. Alongside the line, more than 100 km noise shields have been constructed. The question is how, and to what extent, this noise shield will affect the pool shape and size of an instantaneous release of a flammable liquid, such as liquefied petroleum gas (LPG). In case of an instantaneous release of liquid from a rail tanker (50 m(3)), both risk analysts and emergency responders use a circular pool shape of about 600 m(2) would result. To assess the influence of a noise shield, a full scale test was conducted on an already constructed part of the Betuweline. A rail tanker was filled with 50 m(3) red-colored environmentally safe liquid. The liquid was instantaneously released. A very peculiar pool shape actually results due to the presence of a noise shield. A zone between the rails and the noise shield (2m wide and 90 m long) is within 2-3 min filled with 15 cm of liquid. The total pool size area was about 750 m(2). Both shape and size deviate substantially from the traditional figures. These insights are both relevant to emergency responders for disaster abatement purposes and to risk analysts for effective modeling purposes. The Dutch Ministry of Transport is examining possible strategies to deal with these results. The results of this study are based upon one single instantaneous release test. In addition, it is valuable to find out what the pool shape and size would be in case of a continuous release from the rail tanker near a noise shield.     

集液器端盖爆破试验后开裂原因分析

采用化学成分分析、宏观和微观检验等方法对集液器端盖经爆破试验后发生开裂的原因进行了分析,并对原因分析的结果进行了验证。结果表明:端盖R角处存在拉应力产生渗铜现象以及锡铜合金共化物(IMC)的生成与老化是开裂的主要原因。并提出了预防端盖开裂的措施。     

Dynamic magnetic shield for the CLAS12 central TOF detector photomultiplier tubes

The Central Time-of-Flight detector for the Jefferson Laboratory 12-GeV upgrade is being designed with linear-focused photomultiplier tubes that require a robust magnetic shield against the CLAS12 main 5-T solenoid fringe fields of 100 mT (1 kG). Theoretical consideration of a ferromagnetic cylinder in an axial field has demonstrated that its shielding capability decreases with increasing length. This observation has been confirmed with finite element analysis using POISSON model software. Several shields composed of coaxial ferromagnetic cylinders have been studied. All difficulties caused by saturation effects were overcome with a novel dynamical shield, which utilizes a demagnetizing solenoid between the shielding cylinders. Basic dynamical shields for ordinary linear-focused 2-in. photomultiplier tubes were designed and tested both with models and experimental prototypes at different external field and demagnetizing current values. Our shield design reduces the 1 kG external axial field by a factor of 5000.     

Computational analysis of a sandwich shield with free boundary inserted fabric at high velocity impact

In this paper, a novel hybrid composite shield to protect space structures from hypervelocity impact of micrometeoroid and space debris is proposed. The finite-element model of the proposed shield was constructed and finite-element analysis was conducted to approximate the energy absorption rate. Before the final model analysis, analysis of each component including the aluminum plate (front plate), PMMA plate (rear plate), and intermediate layer of fabric was performed, verifying the finite-element model of each component. The material properties used in the analysis were predicted material property values for high strain rates. The analysis results showed that, other than the fabric, the energy absorption rate of each component was in agreement. Afterwards, the finite-element model of the hybrid composite shield was constructed, where it was analyzed for the constrained and unconstrained fabric boundary condition cases. Through the finite-element analysis, the fiber pullout mechanism was realized for the hybrid shield with free boundary inserted fabric, and it was observed that this mechanism led to energy absorption increase.