Effect of flexibility on unsteady aerodynamics forces of a purely plunging airfoil

Introducing flexibility into the design of a vertically flapping wing is an effective way to enhance its aerodynamic performance. As less previous studies on the aerodynamics of vertically flapping flexible wings focused on the lift generated in a wide range of angle of attack·a 2D numerical simulation of a purely plunging flexible airfoil is employed using a loose fluid–structure interaction method. The aerodynamics of a fully flexible airfoil are firstly studied with the flexibility and angle of attack. To verify whether an airfoil could get aerodynamic benefit from the change in structure, partially flexible airfoil with rigid leading edge and flexible trailing edge were further considered. Results show that flexibility could always reduce airfoil drag while lift and lift efficiency both peak at moderate flexibility. When freestream velocity is constant, lift is maximized at a high angle of attack about 40° while this optimal angle of attack reduces to 15° in drag-balanced status. The airfoil drag reduction, lift augmentation as well as efficiency enhancement mainly attribute to the passive pitching other than the camber deformation. Partially deformed airfoil with the longest length of moderate flexible trailing edge can achieve the highest lift. This study may provide some guidance in the wing design of Micro Air Vehicle (MAV).     

计算机与航空先进制造技术

信息化、柔性化、智能化是21世纪先进制造技术的基础，本文对此做了介绍，并对发展我国航空先进制造技术提出了建议。     

一种带帆板挠性的控制系统分析和设计

分析了一种卫星太阳帆板结构挠性对姿态控制系统稳定性影响的问题;给出了带挠性的控制系统仿真与设计方法。试验结果表明,通过合理的设计可以减小挠性对卫星姿态稳定性的影响,提高系统的控制精度。     

带单侧裂纹楔梁动力特性研究

由于裂纹存在引起构件局部柔度的变化,本文用线弹性断裂力学理论导出裂纹所释放的应变能,由Ｃａｓｔｉｇｌｉａｎｏ 定理得出局部柔度矩阵诸元素,据此来修正楔形梁的刚度矩阵,借助梁有限单元法,求解带裂纹楔形梁的动力特性,并对裂纹相对深度、裂纹位置、梁的长宽比、宽厚比、厚度斜度等几何因素对固有频率的影响进行了数值研究和相应的振动响应试验     

柔性空间飞行器的振动抑止控制

本文提出了一种带有柔性附件的卫星的振动主动抑止方法,给出了能抑止任意阶振动谐波的条件.作为举例,分析了太阳帆板的转动控制,在使帆板平稳旋转的同时,还使卫星姿态稳定无振.     

Survey of mission evolution and flexibility in the Space Shuttle program

Given the diversity of missions it has accomplished and the myriad of adaptations it has undergone, the US Space Shuttle is widely regarded as a highly flexible space vehicle. With the Shuttle’s upcoming 2011 retirement, it is instructive to survey the history of this vehicle’s flexibility for the insights it can provide to the design and characterization of flexibility in future space systems. Data are presented on the evolution of mission requirements over time for 120 missions performed by the Space Shuttle over a period of some 27 years. Distinct trends in the time domain – as well as their causes – are identified and discussed, and early manifest plans from 1982 serve as a confirmation that these trends were not originally anticipated. Eight examples are then presented of engineering modifications that allowed the Shuttle to adapt and accommodate these requirement changes. Several additional instances of Shuttle flexibility are explored, such as post-Columbia disaster modification, upgrade programs and derived vehicles, and one case in which flexibility was inhibited by an early design decision.     

柔性AgNWs/ITO/WO3薄膜的制备及其电致变色性能

文摘为适应电致变色领域越来越丰富的柔性化需求,解决柔性基底上直接制备电致变色薄膜性能不佳的问题。以聚对苯二甲酸乙二醇酯(PET)/银纳米线(AgNWs)为基底,采用室温直流反应磁控溅射制备了氧化铟锡(ITO)/氧化钨(WO_3)薄膜,研究了AgNWs/ITO复合电极的光电性能以及PET/AgNWs/ITO/WO_3薄膜的电致变色性能。结果表明,通过加镀ITO过渡层,克服了PET/AgNWs/WO_3薄膜存在的着色不均匀、单次循环后性能迅速衰退等问题。最终获得了透过率调制为57.4%(550 nm处)、69.6%(1 000 nm处),着褪色响应时间分别为10.4 s和9.9 s,相应的着褪色效率分别为27.79 cm~2/C和40.45 cm~2/C的高性能柔性电致变色薄膜。薄膜在超过500次循环稳定测试以及2 000次弯折测试后仍能保证较高的透过率调制,展现出了在柔性电致变色领域的巨大应用潜力。     

层状Ti3C2Tx/水性聚氨酯复合双层薄膜的制备及电磁屏蔽性能

采用交替真空抽滤制备Ti_3C_2T_x MXene/WPU复合双层薄膜,用扫描电子显微镜(SEM)和透射电子显微镜(TEM)表征了微观形貌,X射线衍射仪(XRD)测试了晶体结构,通过矢量网络分析仪测试了电磁屏蔽性能。结果表明,可以通过超声离心制备出少层Ti_3C_2T_x;复合双层薄膜具有高韧性、高导电性以及优异的电磁屏蔽性能,表面电阻为3.57Ω;电磁屏蔽性能结果表明,MWPU_(3:1)的复合薄膜屏蔽性能为37.9 dB。在X波段与K波段,MWPU_(3:1)复合薄膜性能较为优异,且复合薄膜是吸收型电磁屏蔽材料。