仿蝙蝠折叠扑翼机构设计与分析

基于对蝙蝠飞行方式的研究,提出了一种仿蝙蝠扑翼飞行器设计方案,并且通过单一原动件驱动,既实现了拍动和折叠的耦合协调运动,又提高了系统的单位质量功率系数.设计的对称双翼拍动机构能保证左右翅膀同步运动,为飞行器的平稳飞行提供了保证.采用凸轮机构来控制翅翼的伸展和收缩,通过调整凸轮外轮廓线和初始相位角可以控制蝙蝠翅翼的折叠状况.拍动机构和翅翼折叠机构的协调耦合,可以实现翅翼空间运行轨迹的规划.建立了翅膀拍动和折叠的数学模型,在此基础上编写了仿真程序,仿真结果达到了预期的目标.     

Robust Non-Wetting PTFE Surfaces by Femtosecond Laser Machining

Nature shows many examples of surfaces with extraordinary wettability, which can often be associated with particular air-trapping surface patterns. Here, robust non-wetting surfaces have been created by femtosecond laser ablation of polytetrafluoroethylene (PTFE). The laser-created surface structure resembles a forest of entangled fibers, which support structural superhydrophobicity even when the surface chemistry is changed by gold coating. SEM analysis showed that the degree of entanglement of hairs and the depth of the forest pattern correlates positively with accumulated laser fluence and can thus be influenced by altering various laser process parameters. The resulting fibrous surfaces exhibit a tremendous decrease in wettability compared to smooth PTFE surfaces; droplets impacting the virgin or gold coated PTFE forest do not wet the surface but bounce off. Exploratory bioadhesion experiments showed that the surfaces are truly air-trapping and do not support cell adhesion. Therewith, the created surfaces successfully mimic biological surfaces such as insect wings with robust anti-wetting behavior and potential for antiadhesive applications. In addition, the fabrication can be carried out in one process step, and our results clearly show the insensitivity of the resulting non-wetting behavior to variations in the process parameters, both of which make it a strong candidate for industrial applications.     

基于智能夹层的复合材料柔性蒙皮变形测量研究

探索变体机翼蒙皮拉伸变形测量的可行性,对波纹式复合材料蒙皮的变形测量方法进行研究。通过新配方制作了波纹式蒙皮试件,对其进行力学拉伸试验,分析蒙皮的力学性能。制作模块化的智能夹层,对安装在蒙皮上的智能夹层输出特性进行测试,并与直接粘贴在蒙皮表面的应变片输出特性进行对比分析。结果表明:通过新配方制作的柔性蒙皮线弹性范围达到0~7%;在蒙皮线弹性范围内智能夹层能有效测得应变数据,其应变灵敏系数相对于应变片由2.08降至1.84;由应变反推的蒙皮伸长量与实际伸长量较吻合。     

不同杀菌条件对软包装肉鸡鸡翅感官品质的影响

对比分析了相同杀菌值F=6 min下,不同杀菌温度(115、121、127℃)对软包装肉鸡鸡翅品质及感官的影响。试验结果表明,相同的环境升温时间6 min,达到相同的杀菌值F=6 min时,115、121、127℃的恒温时间分别为35、15、11 min,降温时间分别为12.5、13.5、15.5 min。杀菌温度对鸡翅色泽、质构TPA、剪切力的影响显著(P<0.05);杀菌温度越高,L*、b*值越大,而a*越小;不同杀菌温度处理后鸡翅的TPA与剪切力的变化具有协同性,127℃处理后的鸡翅剪切力值及硬度、弹性、咀嚼性等指标值最大。感官分析比较得出,不同杀菌温度处理后的鸡翅之间气味和滋味差异不大,而高温短时鸡翅外观更好,咀嚼性、弹性更高,总体口感更佳。因此,鸡翅的高温短时杀菌,不仅效率高,且色泽好,剪切力高,对鸡翅品质破坏小。     

Antifatigue properties of dragonfly Pantala flavescens wings

The wing of a dragonfly is thin and light, but can bear high frequent alternating stress and present excellent antifatigue properties. The surface morphology and microstructure of the wings of dragonfly Pantala flavescens were observed using SEM in this study. Based on the biological analysis method, the configuration, morphology, and structure of the vein were studied, and the antifatigue properties of the wings were investigated. The analytical results indicated that the longitudinal veins, cross veins, and membrane of dragonfly wing form a optimized network morphology and spacially truss‐like structure which can restrain the formation and propagation of the fatigue cracks. The veins with multilayer structure present high strength, flexibility, and toughness, which are beneficial to bear alternating load during the flight of dragonfly. Through tensile‐tensile fatigue failure tests, the results were verified and indicate that the wings of dragonfly P. flavescens have excellent antifatigue properties which are the results of the biological coupling and synergistic effect of morphological and structural factors. Microsc. Res. Tech. 77:356–362, 2014. © 2014 Wiley Periodicals, Inc.     

复杂地层条件下导向钻进法用三翼扩孔钻头最优切削角计算

分析了用三翼钻头在复杂地层条件下导向钻进法的力学性质 ,推导了计算不同岩石的最优切削角公式 ,并得出常见岩石的最优切削角值 ,提出了优化反向扩孔钻头结构形式的方法 ,为导向钻进法反向扩孔施工达到最优钻进提供了必要的力学计算依据。     

激光波前功率谱密度与焦斑旁瓣的关系

基于波前功率谱密度(PSD)的定义,分析了采用功率谱密度方法研究中频波前畸变与焦斑旁瓣关系的可行性。由于任意形状的波前畸变都可以由不同空间频率的正弦函数叠加组成,以正弦函数波前为例进行功率谱密度分析和远场分析。分析表明,当中频波前畸变的幅度满足一定条件时,远场二级以上的衍射非常低,可以忽略不计,此时波前功率谱密度与焦斑旁瓣具有非常好的相似性,并且这种相似性仅与中频波前畸变的幅度有关,与空间频率无关。最后还用数值模拟的方法验证了这个结论对叠加后的结果仍然成立。研究结果可以用于设计满足惯性约束聚变(ICF)驱动器打靶对焦斑旁瓣要求的光学元件中频段波前畸变指标。     

遗传算法用于飞机机翼参数的优化设计

提出采用遗传算法这一智能优化处优化设计飞机机翼参数，根据飞机飞行任务的要求建立综合优化指标，在此基础上提出采用遗传算法进行飞机主要设计参数优化的基本步骤，并以具体飞机机翼参数的优化为例仿真计算，研究表明，对比传统的优化方法遗传算法是一种十分有效的优化方法，遗传算法因不要求优化对象的数学模型连续，而具有更宽的适用范围，同时遗传算法还具有易于采用并行算法实现的优点。     

A wrinkle in flight: the role of elastin fibres in the mechanical behaviour of bat wing membranes

Bats fly using a thin wing membrane composed of compliant, anisotropic skin. Wing membrane skin deforms dramatically as bats fly, and its three-dimensional configurations depend, in large part, on the mechanical behaviour of the tissue. Large, macroscopic elastin fibres are an unusual mechanical element found in the skin of bat wings. We characterize the fibre orientation and demonstrate that elastin fibres are responsible for the distinctive wrinkles in the surrounding membrane matrix. Uniaxial mechanical testing of the wing membrane, both parallel and perpendicular to elastin fibres, is used to distinguish the contribution of elastin and the surrounding matrix to the overall membrane mechanical behaviour. We find that the matrix is isotropic within the plane of the membrane and responsible for bearing load at high stress; elastin fibres are responsible for membrane anisotropy and only contribute substantially to load bearing at very low stress. The architecture of elastin fibres provides the extreme extensibility and self-folding/self-packing of the wing membrane skin. We relate these findings to flight with membrane wings and discuss the aeromechanical significance of elastin fibre pre-stress, membrane excess length, and how these parameters may aid bats in resisting gusts and preventing membrane flutter.     

一种变后掠翼导弹弹道快速优化方法

变后掠翼导弹弹道优化问题是一个复杂的多变量优化问题;为了获得变后掠翼导弹飞行弹道,利用Radau伪谱法求解了同时满足路径约束和终端约束条件下的射程最远弹道轨迹;选取后掠角和攻角作为优化控制变量,并通过采取一系列实时性保证策略提高算法的计算效率;仿真结果表明:该方法能够快速优化出满足性能指标和约束条件的弹道轨迹;研究结果可为变后掠翼导弹在线重构的实现提供有益参考。