TC4钛合金线性摩擦焊接头的冲击韧性及断口特征

在自制的XMH-160型线性摩擦焊机上利用先期试验优化的规范参数进行TC4线性摩擦焊接试验.对焊后试件进行冲击试验研究,冲击试件基本沿母材断裂.观察冲击试件的宏观和微观断口,并分析接头的金相组织.结果表明,焊缝超细晶组织所具有的高断裂应力是焊接接头冲击韧性值高于母材的主要原因.     

Better ways of getting into the space business: microeconomic reform in Australian space affairs

This personal view of trends in global space enterprise suggests that, unless they adapt and re-structure, large-scale national and regional space agencies built on traditional lines may struggle to survive, at least in the developed world. With the growing maturity of speculative private sector space initiatives, the role of traditional space agencies as project managers and mediators between providers and the market may become redundant, while in the absence of a cogent national security argument, public interest in space is no longer to be relied upon to deliver large national space budgets. Australia’s newest space mission, the FedSat scientific microsatellite, was announced at the same time as the former national space program was terminated. This process and its consequences are examined as an instance of microeconomic reform, which seeks to improve productivity and competitiveness by producing a regulatory and infrastructure environment that gives business more flexibility. Historical circumstances unique to Australia may have contributed to this change of direction, but many contributing elements also apply elsewhere. The features of the new approach are identification of public sector space needs; selecting the most suitable team from both public and private sectors to manage the project; and the acceptance of a large proportion of the risk by the proponents.     

太阳同步(准)回归轨道卫星的轨道保持方法研究

文中使用解析方法对太阳同步 (准 )回归轨道卫星动力学特性进行了研究 ,分析了非球摄动、大气阻力摄动和太阳引力谐振等主要摄动因素对太阳同步 (准 )回归轨道卫星的影响 ,并以此为依据对太阳同步 (准 )回归轨道卫星的轨道保持方法进行了探讨。定量分析结果表明 ,该方法切实可行 ,可以为轨道设计和轨道控制研究工作提供参考。     

变螺距诱导轮的气蚀性能研究

为了研究变螺距诱导轮的气蚀性能,通过试验观察了变螺距诱导轮的气蚀发展变化情况,分析了其内部的压力脉动现象。结果表明:诱导轮内的气穴随着入口压力降低,会呈现不同的气穴形态;气穴发展受流量影响,流量越大,气穴发展速度越快;诱导轮内发生了同步旋转气蚀,同步旋转气蚀也受流量影响,流量越大,同步旋转气蚀越强。     

Predicting the vulnerability of spacecraft components: Modelling debris impact effects through vulnerable-zones

The space environment around the Earth is populated by more than 130 million objects of 1 mm in size and larger, and future predictions shows that this amount is destined to increase, even if mitigation measures are implemented at a far better rate than today. These objects can hit and damage a spacecraft or its components. It is thus necessary to assess the risk level for a satellite during its mission lifetime. Few software packages perform this analysis, and most of them employ time-consuming ray-tracing methodology, where particles are randomly sampled from relevant distributions. In addition, they tend not to consider the risk associated with the secondary debris clouds. The paper presents the development of a vulnerability assessment model, which relies on a fully statistical procedure: the debris fluxes are directly used combining them with the concept of vulnerable zone, avoiding the random sampling the debris fluxes. A novel methodology is presented to predict damage on internal components. It models the interaction between the components and the secondary debris cloud through basic geometrical operations, considering mutual shielding and shadowing between internal components. The methodologies are tested against state-of-the-art software for relevant test cases, comparing results on external structures and internal components.     

基于统计分析模型的飞行器落点预报方法

目前飞行器落点预报主要采用人机交互方式进行处理,而不同人员计算出的结果存在较大差异.针对该问题,提出了一种基于四阶龙格库塔计算方法的落点预报分布式计算统计分析模型.该模型根据飞行器的运行轨迹特性和在无动力、无控制、常质量段的预报落点具有集中分布的特点,采用零假设和备择假设统计方法对预报落点过滤选择,并对有效预报落点求其数学期望值.采用实际测量数据对所提出的模型进行了可行性和有效性验证,试验结果表明,该模型不仅具有较强的实时性、稳定性,而且当飞行器运行距离在数千千米时,该方法计算出的平面位置误差仅为几十米.     

织构对TC1棒材动态冲击力学行为的影响

挤压成形是TC1棒材成形的主要手段。在挤压过程中,钛合金往往会形成织构,从而导致棒材的性能变化。本研究通过对比分析,研究了织构对动态冲击力学行为的影响。结果表明,在动态冲击过程中TC1合金出现了大量孪晶,且孪晶的数量随着冲击速度的提高而增加;0．4～0．7MPa气压气压范围内冲击时,具有强织构的冲击试样动态屈服强度变化不明显,而具有弱织构的冲击试样动态屈服强度由于位错强化有所增加,表现出了应变率正效应;当气压增高到0．9MPa,由于更多孪晶的开动,具有强、弱织构的样品都出现负的应变速率效应。     

含低速冲击损伤层压板的压缩破坏研究

对复合材料的结构损伤演化过程的研究在飞机结构设计中具有越来越重要的工程指导意义。针对含低速冲击损伤层压板的压缩分析,提出了一种考虑层间损伤的三维有限元模型,该模型通过层间节点耦合方式,将复合材料层压板各子层粘合到一起,能准确、形象的模拟层间的相互作用。同时,基于累积损伤思想开发了复合材料层压板压缩过程的损伤仿真程序,该...     

适用于软体冲击动位移测量的磁敏检测系统

介绍了一种适用于诸如飞行器鸟撞实验的软体冲击动位移检测系统，提出了用霍尔磁敏器件为位移传感元件，新型线性补偿电路为中间处理环节的高频动位移非接触式测量方法。这一测试系统被用于某型号飞行嚣雷达罩的鸟撞实验位移测量中，效果十分理想。     

着陆冲击仿真月壤本构模型及有限元建模

为建立合理的月壤有限元模型用于着陆器着陆冲击动力学仿真分析,在对已知月壤的相关力学特性参数和试验数据进行分析推理的基础上,推断出月壤屈服面在低围压条件下可能会呈现出剪切膨胀特性,而在高围压条件下则可能会呈现出塑性压缩和应变硬化特性,因此定性地选择帽盖德鲁克-普拉格（Cap Drucker-Prager,CDP）模型作为月壤本构模型。模型的参数通过月壤或模拟月壤的试验数据定量地标定。对着陆器地面着陆冲击试验进行有限元建模和仿真分析,仿真结果表明：模型参数的标定方法是合理可行的;CDP模型可以准确模拟月壤在着陆冲击载荷下的动力学响应,可用于着陆冲击动力学仿真月壤有限元建模。对月壤模型参数进行了参数分析,并评估了月壤模型参数对着陆器着陆冲击性能的影响。