增减材复合制造内部缺陷的涡流检测

涡流检测（ECT）技术具有非接触、无需耦合剂、检测灵敏等特点，适用于加工环境较为特殊的增减材复合制造（ASHM）中。本文建立了无缺陷半无限大试样内部涡流分布的解析模型，开展了预制人工缺陷的钛合金增材试样检测实验，研究了ECT深度与激励频率、提离量之间的关系。理论分析与实验结果均表明，内部缺陷较深时，低激励频率条件下缺陷产生的电抗增量信号较大，不同提离量下的电抗增量信号相差不大，因此检测位置较深的内部缺陷时可采用较低的激励频率并适当提高提离量。在本文实验条件下，ECT最佳激励频率为90 kHz；提离量增加到0.97 mm时，有效检测深度略有减小。这一结论可为ECT技术与ASHM的集成提供理论依据。     

Active Aerothermoelastic Control of Hypersonic Double-wedge Lifting Surface

Designing re-entry space vehicles and high-speed aircraft requires special attention to the nonlinear thermoelastic and aerodynamic instability of their structural components. The thermal effects are important since temperature environment brings dramatic influences on the static and dynamic behaviors of flight structures in supersonic/hypersonic regimes and is likely to cause instability, catastrophic failure and oscillations resulting in structural failure due to fatigue. In order to understand the dynamic behaviors of these ＂hot＂ structures, a double-wedge lifting surface with combining freeplay and cubic structural nonlinearities in both plunging and pitching degrees-of-freedom operating in supersonic/hypersonic flight speed regimes has been analyzed. A third order piston theory aerodynamic is used to estimate the applied nonlinear unsteady aerodynamic loads. Also considered is the loss of torsional stiffness that may be incurred by lifting surfaces subject to axial stresses induced by aerodynamic heating. The aerodynamic heating effects are estimated based on the adiabatic wall temperature due to high speed airstreams. As a recently emerging technology, the active aerothermoelastic control is aimed at providing solutions to a large number of problems involving the aeronautical/aerospace flight vehicle structures. To prevent such damaging phenomena from occurring, an application of linear and nonlinear active control methods on both flutter boundary and post-flutter behavior has been fulfilled. In this paper, modeling issues as well as numerical simulation have been presented and pertinent conclusions outlined. It is evidenced that a serious loss of torsional stiffness may induce the dynamic instability; however active control can be used to expand the flutter boundary and convert unstable limit cycle oscillations （LCO） into the stable LCO and/or to shift the transition between these two states toward higher flight Mach numbers.     

建立在“情档合一”体制下的科技工作管理架构

在情档合一体制下,科技工作管理架构应当是:文献管理与档案管理高度融合,这是技术基础的融合;情报研究与档案研究相辅相成,这是灵魂所在;顶层管理与中层管理一线贯串,这是组织保障。     

发动机顶盖的数控加工

分析了某型号发动机顶盖组件的数控加工工艺,介绍了保证零件加工质量和加工效率的途径,针对数控加工中存在的变形、加工硬化、程序及测量等难点,提出了解决方案,为数控加工提供了有益的方法。     

Reloading partly recovers bone mineral density and mechanical properties in hind limb unloaded rats

Skeletal unloading results in decreased bone formation and bone mass. During long-term space flight, the decreased bone mass is impossible to fully recover. Therefore, it is necessary to develop the effective countermeasures to prevent spaceflight-induced bone loss. Hindlimb Unloading (HLU) simulates effects of weightlessness and is utilized extensively to examine the response of musculoskeletal systems to certain aspects of space flight. The purpose of this study is to investigate the effects of a 4-week HLU in rats and subsequent reloading on the bone mineral density (BMD) and mechanical properties of load-bearing bones.     

特征定量识别的航天精密伺服机构轴承运行可靠性评估方法及应用

滚动轴承是航天精密伺服机构中的关键运动副,其可靠性常作为表征伺服机构寿命的重要指标。针对航天精密伺服机构的复杂载荷、极端环境与具体轴承个性问题,本文开展基于特征定量识别的航天精密伺服机构轴承动态可靠性评估方法及其应用研究。采用自适应标准多小波定量识别机构关键轴承运行状态特征,基于降半正态分布函数构建关键轴承运行状态特征与其隶属可靠度的映射关系,建立轴承运行状态信息的可靠性评估模型,为精密伺服机构轴承可靠性评估缺乏大样本数据和当下产品可靠度难以真实评价的工程难题开辟新途径。工程实例表明:该方法可以有效揭示试验台轴承外圈损伤所引起的运行可靠性降低的原因,并成功应用于评估某型航天精密伺服机构轴承运行状态。     

基于模态综合法的含间隙折叠舵面动态特性分析

基于模态综合法对含间隙折叠舵面的非线性动态特性进行了研究。首先根据折叠舵面的结构特性建立含铰链连接的有限元模型，并采用双协调自由界面模态综合法对折叠舵面的有限元模型进行降阶。其次对不含间隙的折叠舵面进行扫频和模态实验，检验有限元模型及其降阶动力学模型的精度，并基于模型修正得到铰链的等效线性连接刚度。最后将等效线性连接刚度和间隙值进行组合，得到不同间隙下铰链的非线性连接刚度，完成含间隙折叠舵面的非线性动力学模型建立。基于非线性动力学模型对含间隙折叠舵面进行数值扫频，计算结果与实验扫频结果吻合良好，验证了所建立非线性动力学模型的精度及其在含间隙折叠舵面非线性动态特性分析中的可行性。     

深空网干涉测量数据对嫦娥五号定轨能力分析

针对嫦娥五号探测器(CE-5)开展基于深空网测量数据的定轨能力分析.首先从测量原理分析了深空网VLBI数据的误差源,然后利用CE-5的精密轨道评估了 VLBI数据的误差,最后基于实测数据与协方差分析理论,分析UXB与VLBI数据的定轨能力.结果表明:转移阶段,单独利用深空网测量数据可以获取优于1 km的转移轨道精度,标...     

基于知识本体的资源管理平台框架设计与实现

针对大量领域信息资源缺乏有效内容分析这一问题,设计、开发了通过构建领域本体来充分发掘信息资源之间内在关系,实现信息资源增值服务的原型系统.首先构造了服装知识本体CO(Costume Ontology)用来表示服装领域知识.利用CO对被管信息资源进行语义描述,在描述数据库的基础上,实现基于语义的信息检索.讨论了服装知识本体的建模过程,本体的形式化表示以及存储方式.实验系统采用J2EE架构,开发了存储组件、语义查询接口组件、语义分析组件和语义推理组件.通过使用资源描述框架RDF,实现被管信息资源到知识本体层的映射.通过语义分析和语义推理,可以充分利用信息资源之间的关系实现相关信息资源检索与语义融合.     

利用真空热试验进行轨道卫星污染研究

利用北京卫星环境工程研究所拥有的各种规模的空间环境模拟器在进行真空热试验时,测量卫星表面返回质量流密度和发射质量流密度,通过加文(GarWin)方程组来确定轨道卫星的污染预估,从而解决了当前型号研制中污染控制的问题.