微重力模拟装置中悬吊弹簧局部模态动力学建模与试验研究

微重力模拟下的地面试验是验证隔振器能否在轨可靠工作的重要措施之一。通常采用悬吊法进行微重力模拟时,悬吊弹簧局部模态处的振动很容易引入隔振上平台。针对悬吊弹簧阻尼低,局部模态振动限制主动隔振控制性能的问题,采用PVC胶带与悬吊弹簧并联的方式提高弹簧阻尼;建立了微重力模拟装置中加胶带悬吊弹簧的连续动力学模型,对比研究纯悬吊弹簧模态振动和加胶带悬吊弹簧模态振动对隔振上平台的影响;搭建了地面试验验证系统并通过试验验证了悬吊弹簧动力学模型的准确性。试验结果表明,粘贴PVC胶带能够起到增加悬吊弹簧阻尼的效果,可以将弹簧的模态振动降低到1μg以下,从而减小模态振动对被动隔振的影响,并有效缓解模态振动对主动隔振控制性能的限制,这种状态能够更准确地反应在轨工作状态。     

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。     

外场对SiCp/AZ91D镁基复合材料组织和性能的影响

在常规条件、电磁模拟微重力场、脉冲电流场和"电磁模拟微重力+脉冲电流"复合场四种外场条件下制备出SiCp含量5wt％的SiCp/AZ91D镁基复合材料,分析测试结果表明:在常规条件下,样品晶粒粗大,β-Mg17Al12相呈现出无规律的网格状结构,新生相Mg2Si以颗粒状的初生相和树枝状的共晶相存在;在电磁模拟微重力场条...     

带有弹性介质电磁成形落料的研究

本文在自行研制的电磁成形机上利用试验方法,研究了带有传力介质的电磁成形落料的传力介质厚度、凸棋直径,搭边值及凸模安装型式等,对电磁成形落料最小放电能量的影响。所得研究结果可供实际使用参考。     

海鸥300飞机起落架着陆动力学试验研究

针对海鸥300水陆两栖飞机起落架落震试验的技术需求,研制一套用于轻型飞机起落架落震试验的动力冲击试验系统,解决了低摩擦滑道设计、机轮高速带转、跑道模拟、撞击平台设计等关键技术.结合CCAR-23-R3要求,完成了海鸥300前起落架落震调参试验、限制落震试验和储备能量吸收落震试验.结果表明,试验系统工作稳定可靠,起落架限...     

织物复合材料空间可展桁架模态试验与分析

航天器正朝着大型化、轻量化和模块化的方向发展。由织物复合材料制成的空间可展桁架结构,作为航天器的组成结构有广泛的应用前景。以一个由织物复合材料制成的空间可展桁架结构为研究对象,开展了微重力环境下的模态试验和仿真分析。结构主要由空心圆管、三角形隔板和斜加劲索组成。模态试验采用气动-电磁悬挂系统实现结构重力卸载,模拟微重力环境。仿真分析中,空心圆管由织物复合材料构成,假设为正交各向异性材料结构;三角形隔板由铺层复合材料构成,假设为各向同性材料结构;考虑斜加劲索的预应力对结构刚度及斜加劲索自身有效弹性模量的影响。最终得到的仿真结果与试验对应关系良好,对大型预应力空间可展桁架研究具有参考价值。     

形状记忆聚合物材料及其在航天器新型锁紧释放机构中的应用

综述了形状记忆聚合物的种类、驱动方式以及形状记忆聚合物复合材料,同时介绍了其在空间锁紧释放机构中的应用,分析了各种锁紧释放机构的优缺点,并讨论了基于形状记忆聚合物材料的航天器新型锁紧释放机构关键技术,包括结构设计、加热源、承载能力、地面试验技术和重复使用性等。随着智能材料的进一步发展,基于形状记忆聚合物材料的锁紧释放机构有望取代火工品锁紧释放机构。     

电磁悬浮熔炼系统的结构及其悬浮力的研究

电磁悬浮熔炼技术是伴随着对特种纯净材料的需求以及航天等高新技术中对微重力研究等而产生和发展起来的，因其重要的科学技术地位而受到关注。本文从电磁基本理论从发，对轴对称螺线锥管电磁悬浮熔炼系统的结构进行分析，得到悬浮系统几何参数与悬浮力的关系；对悬浮系统中平衡线圈的结构进行改进，计算结果表明，改进结构具有较大的悬浮力。据此研制的试验系统实现了电磁全悬浮。     

舰载机全机落震试验机翼升力模拟方法研究

舰载机全机落震试验机翼升力模拟是在实验室测试飞机着陆载荷时,给飞机动态施加飞机着陆时刻机翼升力,模拟飞机着陆真实受载,机翼升力施加是否合理是全机落震试验成功与否的关键技术。给出了全机落震试验机翼升力模拟准则,提出了一种适用于全机落震试验的模拟机翼升力加载方法。根据该方法介绍了机翼升力加载装置设计原理,并对设计的机翼升力模拟装置进行了力学性能测试。将此方法和装置应用于某型飞机全机落震试验中,分别从施加模拟机翼升力大小、飞机姿态影响、下沉速度影响和着陆能量吸收四个方面对全机落震试验机翼升力模拟方法进行验证和评估。试验结果表明,该方法符合全机落震试验升力模拟准则,可用于舰载机全机落震试验。     

非线性悬吊质量摆对输电塔减振控制的研究

针对悬吊质量摆减控制研究中小摆角线性分析的局限性,本文提出考虑悬吊质量摆大摆角非线性特性来计算结构体系动力响应的方法,将传统分析中的悬吊质量摆的线性刚度修正为非线性。以一输电塔为例,通过线性和非线性计算结果对比可知,当摆角过大时线性计算方法不满足线性小摆角条件,而非线性计算方法则可很好模拟质量摆在大摆角下的响应。通过参数分析讨论了正弦激励周期、摆长及质量比对输电塔减震率的影响。选取三条不同场地地震记录,计算输电塔附加质量摆体系的地震响应,结果表明在不同场地条件下,输电塔均具有明显的减震效果。     

The “<Emphasis Type="Italic">Daphnia</Emphasis>” Lynx Mark I Suborbital Flight Experiment: Hardware Qualification at the Drop Tower Bremen

The Drop Tower Bremen, a ground-based facility enabling research under real microgravity conditions, is an excellent platform for testing new types of experimental hardware to ensure full performance when deployed in costly and rare flight opportunities such as suborbital flights. Here we describe the “Daphnia” experiment which will fly on XCOR Aerospace Lynx Mark I and our experience from the hardware tests with the catapult system at the drop tower. The aim of the “Daphnia” experiment is to obtain data on the biological performance of daphnids and predator-prey interactions in microgravity, which are important for the development of aquatic bioregenerative life support systems (BLSS). The experiment consists of two subunits: The first unit is dedicated to predator-prey interactions, where behavioural analysis should reveal if microgravity interfere with prey (Daphnia) detection or feeding and therefore may interrupt the trophic cascade. The functioning of such an artificial food web is indispensable for a long-lasting BLSS suitable for long-duration manned space missions or Earth-based explorations to extreme habitats. The second unit is designed to investigate the impact of microgravity on gene expression and the cytoskeleton in Daphnia. Next to data collection, the real microgravity conditions at the drop tower have helped to identify the weak points of the “Daphnia” experimental hardware and lead to further improvement. Hence, the drop tower is ideal for testing new experimental hardware which is indispensable before the implementation in suborbital flights.     

钢筋混凝土筒体水塔控制爆破拆除

介绍了控制爆破拆除一个高33米,直径3．6米,壁厚0．16米钢筋混凝土薄壁筒式结构水塔的设计与施工,并对爆破倾倒过程及爆破效果进行了分析讨论。     

A Six-DOF Buoyancy Tank Microgravity Test Bed with Active Drag Compensation

Ground experiment under microgravity is very essential because it can verify the space enabling technologies before applied in space missions. In this paper, a novel ground experiment system that can provide long duration, large scale and high microgravity level for the six degree of freedom (DOF) spacecraft trajectory tracking is presented. In which, the most gravity of the test body is balanced by the buoyancy, and the small residual gravity is offset by the electromagnetic force. Because the electromagnetic force on the test body can be adjusted in the electromagnetic system, it can significantly simplify the balancing process using the proposed microgravity test bed compared to the neutral buoyance system. Besides, a novel compensation control system based on the active disturbance rejection control (ADRC) method is developed to estimate and compensate the water resistance online, in order to improve the fidelity of the ground experiment. A six-DOF trajectory tracking in the microgravity system is applied to testify the efficiency of the proposed compensation controller, and the experimental simulation results are compared to that obtained using the classic proportional-integral-derivative (PID) method. The simulation results demonstrated that, for the six-DOF motion ground experiment, the microgravity level can reach to 5 × 10^?4 g. And, because the water resistance has been estimated and compensated, the performance of the presented controller is much better than the PID controller. The presented ground microgravity system can be applied in on-orbit service and other related technologies in future.     

基于两段法及改变落球高度的硝化棉落球粘度测量

为提高落球法测量硝化棉粘度的精确性，减小因小球在落球距离内做非匀速运动造成的误差，提出了一种基于两段法及改变落球高度的精确测量方法。采用PLC、光电传感器设计实验装置，选取5种粘度的试液，获得不同落球高度的计时值，拟合数据得到适宜落球高度。对比了传统固定高度与适宜落球高度方法的测量误差。实验表明，适宜落球高度和试液粘度之间存在负相关性；粘度大于60 300 mPa·s时，落球管口处即为适宜落球高度；粘度小于60 300 mPa·s时，在适宜落球高度释放小球能减小测量误差；粘度越低误差减小效果越明显。     

The 2.5 s Microgravity Drop Tower at National Centre for Combustion Research and Development (NCCRD), Indian Institute of Technology Madras

Space missions involving humans require a better understanding of various phenomena happening in space environments. A number of experiments need to be conducted in microgravity for addressing various issues encompassing safety (primarily fire) and better understanding of fluid and material behaviour. Of the various methods used for obtaining microgravity conditions, drop towers offer ground based microgravity platform. They provide a cost effective platform for doing short duration, repeatable, high quality microgravity experiments. This paper describes key factors that influence the design of a drop tower. The salient features of 2.5 s microgravity tower set up at National Centre for Combustion Research and Development (NCCRD), IIT Madras (IITM) are discussed. Primary features of the three critical elements, namely the drop capsule, the release unit and the decelerator unit are described along with review of these elements in existing drop towers. The IITM drop tower operates in ambient atmospheric conditions to minimise the cost of operation. In order to achieve good quality microgravity levels, a dual capsule configuration is adopted. The shape of the outer capsule is arrived at by detailed transient computational fluid dynamic analysis of the drag shield under free fall condition over the drop height. A pneumatic mechanism is used for capsule release and brought to rest at the end of fall in a carefully designed decelerator unit. The decelerator unit consists of an airbag with controlled air outflow for smooth deceleration.     

2座105m高双曲线冷却塔控制爆破拆除

针对复杂环境下2座105 m 高冷却塔的结构特点和周围环境情况,采用了机械开设定向窗和减荷槽的预处理方案,之后对圈梁和人字立柱进行爆破。采用了交叉复式网路多段微差爆破,通过延期增加冷却塔倒塌时扭转撕裂时间,来减小冷却塔的塌落块度;采用双层胶皮网和草垫结合的方法有效的控制了飞石;采用开挖减震沟、敷设减震缓冲提有效降低了塌落冲击振动;特别是针对冷却塔爆破粉尘污染严重的现象,在冷却塔基础处灌入1 m 高的水,采用单药量分散小药包进行水耦合爆破,有效的降低了粉尘的危害。最后利用高速摄影分析了冷却塔倒地冲击气浪造成周边民宅受损的原因。     

降膜式蒸发器用高效传热管换热性能试验研究

通过试验对降膜式蒸发器用高效传热管的换热性能进行研究,并将其与之相对应的池沸腾换热性能进行比较.由比较数据可知:样管池沸腾换热性能均随热流密度的增大而增强,降膜蒸发性能在一定热流密度下随喷淋流量的增大而增强;在恒定热流密度和恒定喷淋流量下,光管降膜燕发性能低于池沸腾性能,强化管降膜蒸发性能高于池沸腾性能;池沸腾性能高的强化管降膜蒸发性能也强.     

用螺旋槽管强化溴化锂降膜式发生器传热传质的研究

热源温度较低时,在溴化锂吸收式制冷机或热泵中使用降膜式发生器可以改善传热传质的性能.如何用强化管对降膜式发生器的传热传质进行强化是本文所关注的.文中对螺旋槽管进行了实验,并对结果进行了分析,最后得出了结论.     

Development of a unidirectional cooling technique for synthesizing compound semiconductors in 10 m drop tower

The solidification process and structures of CdTe solidified in microgravity were studied using the unidirectional cooling apparatus in a 10 m drop tower. Since the drop tower provides 1.4 seconds of microgravity, the unidirectional cooling apparatus cools samples rapidly by cooling gas. The system adopts a Pt heater, which accurately heats samples to a maximum of 1300°C. The sample is placed in an ampoule under vacuum conditions. A flat wall in the ampoule divides the inner sealed sample from the outer open side. A nozzle blowing cooling gas is directed on to the outer wall, and cools the sample until solidification. The cooling properties were measured during CdTe solidification in microgravity. The result shows that solidification occurred between 0.9 and 1.3 seconds after release, so solidification is completed in microgravity. Optical microscope (OM) observation of the sample solidified in microgravity revealed that it produces CdTe and Te phases with segregation patterns, and the structures are ordered along the cooling direction, whereas no order is observed in the structures of the terrestrial sample solidified under 1 g.     

垂直管氨水降膜吸收传质研究

吸收器是影响氨水吸收式制冷系统的关键部件。对常用的垂直管氨水降膜吸收器进行绝热吸收模拟分析,并将模拟分析结果与实验结果进行了对比。在此基础上,通过实验进一步研究了稀溶液进口过冷和外部吸收冷却对吸收传质的影响,得到稀溶液进口过冷能够促进吸收传质的结论。结果表明:氨水吸收式制冷传质率的模拟结果与实验结果的偏差在20%以内,在冷却吸收和进口过冷的实验测试工况下,吸收传质率提高了132%。