An Assessment of Joint Rigidity with Ultrasonic Wave Energy

A modular satellite design has been proposed in order to enable rapid deployment of satellites. The design would allow panels with common functions to be manufactured and tested long before a new satellite is needed. Once the satellite is assembled, a quality assessment of the connections between panels would need to be performed before the craft is deemed flight worthy. This paper reports on an investigation on the feasibility of using transmitted wave energy for joint rigidity assessment. The experimental setup and methods will be presented. Experiments were conducted on a joint between two aluminum plates consisting of a dry aluminum-to-aluminum connection, similar to possible panel-to-panel connections that could be used as part of a modular satellite design. Comparisons were made between wave energy transmission and a mechanical assessment of the joint rigidity. Results show excellent correlation between joint rigidity and energy transmission, demonstrating the feasibility of the using wave energy transmission amplitudes to inspect metal-to-metal dry connections.     

Design and qualification of the AMS-02 flight cryocoolers

Four commercial Sunpower M87N Stirling-cycle cryocoolers will be used to extend the lifetime of the Alpha Magnetic Spectrometer-02 (AMS-02) experiment. The cryocoolers will be mounted to the AMS-02 vacuum case using a structure that will thermally and mechanically decouple the cryocooler from the vacuum case. This paper discusses modifications of the Sunpower M87N cryocooler to make it acceptable for space flight applications and suitable for use on AMS-02. Details of the flight model qualification test program are presented.AMS-02 is a state-of-the-art particle physics detector containing a large superfluid helium-cooled superconducting magnet. Highly sensitive detector plates inside the magnet measure a particle’s speed, mass, charge, and direction. The AMS-02 experiment, which will be flown as an attached payload on the International Space Station, will study the properties and origin of cosmic particles and nuclei including antimatter and dark matter.Two engineering model cryocoolers have been under test at NASA Goddard since November 2001. Qualification testing of the engineering model cryocooler bracket assembly including random vibration and thermal vacuum testing was completed at the end of April 2005. The flight cryocoolers were received in December 2003. Acceptance testing of the flight cryocooler bracket assemblies began in May 2005.     

四面体构架式可展天线展开过程控制及测试

为了减小展开过程中天线节点的速度、加速度以及天线对星体的冲击力,对四面体构架式可展天线进行展开过程动力学分析,并提出一种通过施加主动力来控制展开过程的方法．设计加工了口径为2 m的天线模型,在此模型的基础上,就所提出的控制方法进行试验测试.测试采用非接触式计算机视觉测量系统,通过自编MATLAB程序对视频跟踪所得数据进行处理和分析,得到展开过程中天线节点的速度和加速度.试验结果表明,通过所施加的控制方法,有效地减小了天线节点在展开过程中的速度、加速度,从而降低了天线对星体的冲击力,验证了控制方法的可行性．     

真空测试计量技术及其航天应用

真空测试计量技术是确保载人航天、探月工程、北斗导航等重大航天工程顺利实施的重要基础。围绕计量发展和航天发展建设对真空测试计量提出的新任务、新要求,真空测试计量发展在深度、广度及维度上表现出强劲的态势。近年来,围绕国家重大战略需求,瞄准真空测试计量技术核心科学问题,开展了面向航天应用的真空测试计量原始创新研究,实现了由真空中性气体测试计量向空间电推进真空等离子体测试、卫星充放电真空模拟测试、真空环境下空间计量等交叉领域的拓展,并在月球样品采样、飞船交会对接、空间守时原子钟研制、卫星平台升级换代、卫星安全防护等应用中发挥了至关重要的作用。     

氧化剂对炸药水中爆炸能量输出结构的影响

为了研究氧化剂对炸药爆炸能量输出结构的影响,采用水中爆炸试验方法研究了高氯酸铵(AP)对炸药水中爆炸冲击波的影响。试验结果表明,在炸药中添加AP,可以调整炸药爆炸能量输出结构,降低炸药水中爆炸冲击波的压力衰减速度,提高炸药水中爆炸冲击波冲量。通过等质量替换试验发现,AP在试验所用的炸药体系中释放的能量高于黑索今(RDX),试验结果可为炸药配方精细化设计及水中兵器毁伤设计提供指导。     

基于悬吊法和气浮法的多自由度微重力模拟展开试验系统研究

为满足三维空间展开机械臂在进行地面微重力模拟展开试验时对多维度、多自由度、高精度展开轨迹和高卸载效率的要求,通过对当前成熟的微重力模拟展开试验方法进行分析总结,设计了一种基于悬吊法和气浮法的多自由度微重力模拟展开试验系统。首先,对所设计的多自由度微重力模拟展开试验系统进行结构设计和原理分析;然后,将多自由度微重力模拟展开试验系统应用于某三维空间展开机械臂的三维轨迹微重力模拟展开试验。结果表明该三维空间展开机械臂展开过程稳定可靠,且微重力模拟展开试验系统对机械臂产生的气浮运动摩擦阻力、垂直方向阻力波动量和展开方向附加阻力均很小,卸载效率高于95%,满足高精度和高卸载效率的展开要求。研究结果可为多自由度空间可展开机构地面模拟展开试验系统的深入研究提供一定的参考。     

Built-in online and offline test of airborne digital systems

This paper studies the effects of both online and offline test during flight critical missions where safety is a major issue. The online test, in this context, is a test performed on a digital airborne system during some specified windows in time while it is still performing its intended task. An offline test is a test that is performed on the digital system once it is taken offline because of a suspected failure. Both the online and the offline tests are performed during flight. The difference between the two is that the offline test can be made more effective than an online test due to the longer amount of time available for testing. Moreover, the offline test may be designed to have diagnosis and repair capability built in. Upon successful repair, the faulty processor may be reconfigured back into the system. Even though both tests are important, we show that the online test is more important than the offline test in enhancing the mission reliability. This is a counter-intuitive result since system repairs are conducted offline.     

重力梯度稳定卫星伸展动力学研究

针对重力梯度卫星姿态控制系统的设计需求,本文首先推导了卫星姿态和重力梯度杆伸展的耦合动力学方程,其中重力梯度杆伸展动力学方程是根据其结构特点利用能量方法建立的。最后以“清华一号”卫星为算例进行了数值仿真计算,在不同初始条件下,得到了重力梯度杆伸展过程中杆长和三个姿态角的变化规律。探讨了保证重力梯度杆伸展后卫星姿态能正确捕获所需的条件。     

装配式混凝土框架节点基本性能研究进展

提出了一种新型的钢筋连接器——可调组合钢筋连接套筒,并基于此组装了一套耗能连接件。对耗能连接件开展了轴向的低周往复加载试验,验证了其荷载传递的可靠性以及优异的耗能性能。将耗能连接件内置于装配式混凝土框架梁端底部,提出了一种带可更换耗能钢棒的单侧屈服梁柱节点(REDB-SYBC)。对试件开展拟静力试验研究,分析节点的损伤分布、破坏形态、滞回特性、耗能能力等抗震性能。试件滞回曲线稳定饱满无捏缩,抗震性能良好。试验结果表明：新型节点单侧屈服的变形模式减少了楼板的变形与损伤,充分发挥了梁底连接件的耗能能力,其主要损伤及破坏均发生在梁底耗能钢棒上,实现了损伤集中的设计目标以及“强柱弱梁”的抗震设计原则;利用新型连接套筒的内部空间即可实现耗能钢棒的更换,经过更换和修复后的节点各项抗震性能与初始节点基本相当。     

带可更换耗能钢棒的装配式混凝土单侧屈服梁柱节点抗震性能试验研究

提出了一种新型的钢筋连接器——可调组合钢筋连接套筒,并基于此组装了一套耗能连接件。对耗能连接件开展了轴向的低周往复加载试验,验证了其荷载传递的可靠性以及优异的耗能性能。将耗能连接件内置于装配式混凝土框架梁端底部,提出了一种带可更换耗能钢棒的单侧屈服梁柱节点(REDB-SYBC)。对试件开展拟静力试验研究,分析节点的损伤分布、破坏形态、滞回特性、耗能能力等抗震性能。试件滞回曲线稳定饱满无捏缩,抗震性能良好。试验结果表明：新型节点单侧屈服的变形模式减少了楼板的变形与损伤,充分发挥了梁底连接件的耗能能力,其主要损伤及破坏均发生在梁底耗能钢棒上,实现了损伤集中的设计目标以及“强柱弱梁”的抗震设计原则;利用新型连接套筒的内部空间即可实现耗能钢棒的更换,经过更换和修复后的节点各项抗震性能与初始节点基本相当。     

The development of a test specification to determine the rollover protection of passengers in light commercial vehicles fitted with canopies

In this paper, a basic test specification is proposed to assess the structural integrity of a canopy that covers the load-area of a light commercial vehicle (LCV) used to carry passengers in the rear. The proposed test specification is a first step towards improving the safety of these passengers during rollover accidents. Different test methods were evaluated for applicability, ease of use and financial implications. The mass and geometric characteristics of three different one-ton LCVs were experimentally obtained and used to determine the minimum lateral velocity that will result in a rollover should a tripping mechanism be encountered. These velocities, in conjunction with other published data, were used to determine the energy required for a pendulum qualification test. It was decided that 7.7 kJ of energy delivered by a pendulum travelling between 4 and 7 m/s just prior to impact would be the most representative load case. A finite element analysis (FEA) of the proposed impact test on a specimen canopy was completed. Thereafter, the actual pendulum impact test was conducted to demonstrate the applicability of the proposed test procedure as well as the correlation with the FEA. It was shown that both FEA and actual testing are viable qualification procedures and that they can in fact be used to reliably assess the strength of the canopy. Finally, the outline of a test specification was developed and proposed, which can be used by national regulatory institutions to assess the structural integrity of commercially manufactured canopies.     

《卫星力控振动试验的模型简化原理分析》

航天器振动环境试验的首要目标,是为了发现航天器在结构动力学设计方面存在的问题,防止在发射过程中由于严酷的振动环境导致发射任务失败。在常规航天器的振动测试中,振动台台面的加速度输入是按照加速度规范进行控制的,将飞行环境中实际测量得到的加速度峰值的进行包络,这种测试方法会在卫星或飞船的固有频率处产生较大的过试验现象。为此,NASA从1993年以来,推行“力限振动试验（force limited vibration testing）”技术,即采用振动台加速度和界面力进行“双控”,以降低过试验的危害。但是,由于真实飞行时的星箭界面力无法通过实际测量得到,因此,通过对星箭界面的计算模型、实验获得的模态参数、以及从实测界面加速度等条件下获得界面力数据的研究成为FLVT技术研究的核心内容。本文通过星箭耦合系统的动力学模型,利用子结构模态综合法推导出界面动力学响应以及界面力与界面加速度的关系式。然后根据子结构各阶主模态在特定频率区间内的特性,对动力学模型进行简化,并对NASA文献中的“复杂二自由度模型”进行了理论证明和误差分析。     

飞行参数记录系统测试简介

飞行参数记录系统是重要的机载设备,本文应用功能测试法,对飞行参数记录测试系统进行了设计,实现了对飞参系统的测试,故障覆盖率高。该测试方法对其它飞参系统的测试具有推广价值。     

A novel accelerated moisture absorption test and characterization

Moisture plays a significant role in influencing the mechanical behavior and long-term durability of composites. With the current available testing techniques the time required for environmental qualification of polymer composites can be on the order of several years and any interruption in the test can result in a significant cost and schedule penalty. Because of these long environmental conditioning times there is a strong desire to accelerate the process to advance environmental qualification of materials for use in commercial and military aerospace structures. An accelerated humidity test technique has been developed where moisture ingression was obtained by increasing the pressure in the test chamber. A hygrothermal humidity chamber was used in combination with D₂O water to subsequently characterize the diffusion of D₂O in a carbon/epoxy composite using Nuclear Reaction Analysis (NRA). Moisture content was also measured as a function of through-thickness depth using NRA. The accelerated technique decreased the time to saturation by 80% as compared to conventional diffusion without pressure. Moisture uptake from both conventional and accelerated diffusion exposures followed typical Fickian diffusion response.     

压电陶瓷弯曲元法测试土样弹性剪切模量

在动三轴仪基础上开发研制了压电陶瓷弯曲元相结合的测试系统。利用该系统测试了钱塘江粉土的弹性剪切模量,并与共振柱试验结果相对比,两者非常相近。本文还用Hardin和Richart经验公式对钱塘江粉砂土的试验结果拟合,也取得了很好的结果,从而证明了该系统的可靠性。压电陶瓷弯曲元是一种很有发展前途和应用前景的试验手段,值得在理论和实验中进一步研究。     

Recent Progress of HTS Microwave Applications in Satellite Receiver, Meteorological Radar, Mobile Communication and Radio Astronomy

The applications of high-temperature superconductor (HTS) filters or subsystems to radio astronomy, the third generation (3G) mobile communications, meteorological radar, and satellite are introduced. A wideband HTS filter for the Miyun 50-m radio telescope in Beijing was presented, and a novel resonator and a new style interleaved coupling structure were proposed for the design of the wideband filter. An HTS transceiver subsystem was constructed. A field trial in commercial TD-SCDMA base station network was carried out in Beijing and remarkable improvements were achieved for RF performance in both transmitting and receiving chains. A demonstration HTS meteorological radar station was set up in Beijing and it showed great enhancements in sensitivity and anti-interference ability in urban area wind profile measurements. An experimental HTS microwave receiver front end for satellite applications had been constructed and passed all the space qualification tests. As a payload of an experimental satellite, it was ready for launch.     

空间卷曲折叠管充气控制展开动力学研究

充气展开管是大型空间充气展开结构的基本支撑部件,该文针对柔性卷曲折叠管,采用刚体平面运动理论分析了有无阻尼控制的展开过程,并提出了分段式充气控制体积有限元模型,模拟了空间环境下卷曲折叠管的展开动力学。最后对卷曲折叠管在阻尼控制下进行了充气展开测试,试验结果与数值模拟结果相一致。这表明:采取一定控制展开的卷曲折叠管能作为空间充气展开结构的控制展开方式;数值模拟是有效的,可为空间环境下的展开过程提供一定依据。     

Analysis of the Effectiveness of the Method of Qualification Tests for Satellite Communications Earth Stations

Measurement Techniques - We analyze the effectiveness of the qualification test method for communications satellite earth stations, implemented using a multi-user distributed measurement control...     

列车-轨道时变系统横向振动能量随机分析方法

根据大量客、货车构架实测蛇行波及德国高速机车轮对横向摇摆力的测试资料,基于随机振动理论模拟出一般车速及高速构架人工蛇行波,分别以构架人工蛇行波及前苏联规律性的竖向不平顺函数为横向及竖向激振源,对列车－轨道时变系统横向随机振动进行计算。计算结果与实测结果的接近验证了本文方法的可行有效性。     

基于区间与概率的星载网状天线展开可靠性分析

针对大型星载网状天线展开过程的特点,该文采用区间与概率混合可靠性分析方法对星载网状天线的展开过程可靠性进行了分析和评估。首先,建立了星载网状天线的展开失效树模型,并对失效树模型中各底事件进行了归类;其次,将关键底事件中所涉及到的不确定量视其特点描述为随机变量或区间变量,并利用混合可靠性模型分析方法获得了相应底事件的失效概率;再者,制作了2 m口径试验天线与典型试验展开机构样件,通过试验获得了天线展开过程中伸缩杆滑动的失效概率,进而得到了星载网状天线总的展开失效概率和展开可靠度;最后,对基本底事件进行了重要度分析,找出了可能导致星载网状天线展开失效的薄弱环节。