Off-Optimum Cure of Aerospace Epoxy Adhesives

Four epoxy film adhesives used in aircraft manufacture and repair have been examined to establish the effect of deviation from the cure cycle specified by the manufacturer. In addition to the variation of the cure cycle, two surface preparations of the aluminium adherends (chromic acid etch or grit blast followed by silane treatment) were evaluated. Thermal analysis was used to examine the cure envelope of the adhesive, and its extent of cure and glass transition temperature. The adhesive properties were assessed by shear strength (in both single lap joints and in Iosipescu configuration), durability (Boeing wedge test) and chemical resistance to selected aggressive fluids. The sensitivity of the performance of a particular adhesive to offoptimum cure conditions depends on its composition and needs to be determined, not predicted.     

Tracking control and robustness analysis for planar vertical takeoff and landing aircraft under bounded feedbacks

We study feedback tracking problems for the planar vertical takeoff and landing (PVTOL) aircraft dynamics, which is a benchmark model in aerospace engineering. We provide a survey of the literature on the model. Then we construct new feedback stabilizers for the PVTOL tracking dynamics. The novelty of our work is in the boundedness of our feedback controllers and their applicability to cases where the velocity measurements may not be available, coupled with the uniform global asymptotic stability and uniform local exponential stability of the closed‐loop tracking dynamics and the input‐to‐state stable performance of the closed‐loop tracking dynamics with respect to actuator errors. Our proofs are based on a new bounded backstepping result. We illustrate our work in a tracking problem along a circle. Copyright © 2011 John Wiley & Sons, Ltd.     

AI-Li/SiCp composites and Ti-AI alloy powders and coatings prepared by a plasma spray atomization (PSA) technique

There has been increasing use of Al-Li alloys in the aerospace industry, due mainly to the low density and high elastic modulus of this material. However, the problem of low ductility and fracture toughness of this material has limited its present application to only weight- and stiffness-critical components. Development of Al-Li/ceramic composites is currently being investigated to enhance the service capabilities of this material. The Ti-Al alloy is also of interest to aerospace-type applications, engine components in particular, due to its attractive high-temperature properties. Preparation of fine powders by plasma melting of composite feedstock and coatings formed by plasma spraying was carried out to examine the effect of spray parameters on the microstructure and properties of these materials. Characterization of the powders and coatings was performed using the scanning electron microscope and image analyzer. Examination of the plasma-sprayed powders and coatings has shown that in the Al-Li/SiC composite there is melting of both materials to form a single composite particle. The SiC reinforcement was in the submicron range and contributed to additional strengthening of the composite body, which was formed by a cold isostatic press and consolidated by hot extrusion or hot forging processes. The plasma-sprayed Ti-Al powder showed four categories of microstructures: featureless, dendritic, cellular, and martensite-like.     

跨音压气机转子多目标气动优化设计

采用基于雷诺平均N-S方程的全三维流场模拟程序和基于多目标遗传算法的数值优化程序,对跨音压气机转子NASA Rotor37进行了优化设计。对所开发的三维N-S方程求解程序进行了实验验证,完善了多目标遗传算法与响应面方法相结合的具有全局寻优能力的优化程序,以总压比和绝热效率最大为设计目标,应用该优化方法对NASA Rotor37进行考虑中弧线和厚度分布的多目标气动优化设计。结果表明:在满足流量约束的条件下,绝热效率提高了0.7%,总压比提高了0.66%,并且优化设计时间大幅减小。     

Examination of superplastic forming combined with diffusion bonding for titanium: Perspective from experience

Superplastic forming (SPF) combined with diffusion bonding (DB) has been used successfully for the fabrication of titanium aerospace hardware. Many of these applications have been for military aircraft, whereby a complex built-up structure has been replaced with monolithic parts. Several methods for applying the two- and four-sheet titanium SPF/DB processes have been devised, including the welding of sheets prior to forming and the use of silk-screened stop-off (yttria) to prevent bonding where it is undesirable. Very little progress has been made in the past few years toward understanding and modeling the SPF/DB process using constitutive equations and data by laboratory testing. Concerns that engineers face in designing for fatigue life, acceptable design loads, and damage tolerance are currently being studied, but the database is very limited. This is a summary of past work found in the literature and forms the foundation for additional research. This paper was presented at the International Symposium on Superplasticity and Superplastic Forming sponsored by the Manufacturing Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium was organized by Daniel G. Sanders, The Boeing Company.     

飞机铝合金型材结构FSW焊接

提出了搅拌摩擦焊接（Friction Stir Welding,FSW）技术的3个基本要素,对铝合金型材FSW焊接件在航空结构中的几个典型应用进行了分析.并简要介绍了中国搅拌摩擦焊中心在铝合金型材搅拌摩擦焊接方面的研究成果.中国搅拌摩擦焊中心的研究表明,采用搅拌摩擦焊技术焊接铝合金能够得到比较满意的接头强度.     

A globally asymptotically stabilizing trajectory tracking controller for fully actuated rigid bodies using landmark‐based information

In this paper, we address the problem of designing a control law based on sensor measurements that provides global asymptotic stabilization to a reference trajectory defined on the . The proposed control law is a function of the angular velocity, of vector measurements characterizing the position of some given landmarks, and of their rate of change. We provide sufficient conditions for the existence of synergistic potential functions on SO(3) which are pivotal in the generation of a suitable hybrid control law. We also provide sufficient conditions on the geometry of the landmarks to solve the given problem. Finally, the proposed solution is simulated and compared with a continuous feedback control law. Copyright © 2014 John Wiley & Sons, Ltd.     

数字孪生增强的领域自适应航天器多余物检测

由于标注数据的短缺,对航天器多余物进行在线检测受到了较大的限制。文章研究了多余物的物理特性,在航天器的数字孪生系统中构建相应的多余物模型,提出了一种结合数字孪生技术增强的跨域自适应航天器多余物检测方法。该方法通过数字孪生技术获取航天器的实时数据,并借助于历史标注数据中的相似结构,以跨域自适应技术辅助实时在线推理的进行。设计了一种新型的跨域自适应模型,该模型采用共享网络结构以及门控机制,从而在复杂任务中更有效地挖掘先验知识,实现了跨域自适应技术与数字孪生技术的有机结合,以实现更高效、准确和实时的预测。此种方法可以全面地检测航天器各个部件的多余物状态。     

航天发射任务组织指挥工作相关问题研究

加强新形势下航天发射任务组织指挥能力建设是满足我国当前高密度多样化发射任务要求的重要内容。分析了航天发射任务组织指挥工作的建设需求,在此基础上对航天发射任务组织指挥工作需要解决的关键问题进行了查找和反思,提出新形势下组织指挥工作的总目标以及建设的原则,同时针对存在的问题给出相应的建议和改进措施。