湍流度对飞行器模型大迎角气动特性影响的初步研究

本文简要地阐述了在西北工业大学低(变)湍流度风洞中进行的湍流度对某战斗机简化模型在大迎角时气动特性影响的实验研究以及对实验结果的分析.实验的湍流度为:0.02%,0.10%和0.15%.实验结果表明,湍流度对大迎角时气动特性的影响是不可忽视的,并且表现出十分复杂的特性.对于不同的迎角,湍流度对实验结果有明显不同的影响.当迎角小于20°时,湍流度对试验结果的影响不大.但当迎角大于20°时,湍流度的影响是显著的.     

三维编织细编穿刺炭/炭复合材料拉伸与压缩性能及试件尺寸效应研究

通过对三维编织细编穿刺炭/炭复合材料的Z向和XY向进行的拉伸、压缩宏观实验,观测了不同载荷形式下和不同几何尺寸的试件的破坏模式和断口形貌,得到了材料在拉伸、压缩载荷下不同的破坏机理及材料的力学性能与试件几何尺寸的相关性。研究表明,材料Z向拉伸破坏时为平断口,XY向拉伸破坏时为台阶状断口,压缩载荷作用下Z向和XY向都为与受力方向成45°的剪切型破坏,Z向和XY向的压缩强度随试件的几何尺寸的变化具有相同的变化趋势,但Z向变化趋势较XY向更明显。所获结论为进一步进行该材料的刚度和强度预报以及强度准则的建立奠定了必要的实验基础。     

Design and experimental study of a new flapping wing rotor micro aerial vehicle

A three-wing Flapping Wing Rotor Micro Aerial Vehicle (FWR-MAV) which can perform controlled flight is introduced and an experimental study on this vehicle is presented. A mechanically driven flapping rotary mechanism is designed to drive the three flapping wings and generate lift, and control mechanisms are designed to control the pose of the FWR-MAV. A flight control board for attitude control with robust onboard attitude estimation and a control algorithm is also developed to perform stable hovering flight and forward flight. A series of flight tests was conducted, with hovering flight and forward flight tests performed to optimize the control parameters and assess the performance of the FWR-MAV. The hovering flight test shows the ability of the FWR-MAV to counteract the moment generated by rotary motion and maintain the attitude of the FWR-MAV in space; the experiment of forward flight shows that the FWR-MAV can track the desired attitude.     

神舟飞船防热大底钻孔工艺技术研究

神舟飞船防热大底主要为玻璃钢蜂窝夹层结构,制孔时在较大装夹力下容易产生弹性变形。针对装夹变形导致孔位置精度难以保证的问题进行工艺优化改进,对工装结构、装夹方式、工艺流程及钻孔设备进行了优化。试验结果表明,采取低应力装夹方式、减少翻转次数、使用数控加工设备等措施能有效提高钻孔精度。     

Drilling load modeling and validation based on the filling rate of auger flute in planetary sampling

Some type of penetration into a subsurface is required in planetary sampling. Drilling and coring, due to its efficient penetrating and cuttings removal characteristics, has been widely applied in previous sampling missions. Given the complicated mechanical properties of a planetary regolith, suitable drilling parameters should be matched with different drilling formations properly. Otherwise, drilling faults caused by overloads could easily happen. Hence, it is necessary to estab-lish a drilling load model, which is able to reveal the relationships among drilling loads, an auger's structural parameters, soil's mechanical properties, and relevant drilling parameters. A concept for the filling rate of auger flute (FRAF) is proposed to describe drilling conditions. If the FRAF index under one group of drilling parameters is less than 1, this means that the auger flute currently removes cuttings smoothly. Otherwise, the auger will be choked with compressed cuttings. In dril-ling operations, the drilling loads on the auger mainly come from the conveyance action, while the drilling loads on the drill bit primarily come from the cutting action. Experiments in one typical lunar regolith simulant indicate that the estimated drilling loads based on the FRAF coincide with the test results quite well. Based on this drilling load model, drilling parameters have been opti-mized.     

带止裂筋整体翼梁结构的破损安全分析与试验

为了研究带止裂筋整体翼梁结构的裂纹扩展特性,采用ANSYS有限元软件对裂纹尖端应力强度因子进行数值计算,对缩比试验件进行疲劳裂纹扩展试验,当裂纹扩展到止裂筋前时进行剩余强度试验。结果表明:在梁缘条和蒙皮断裂情况下,止裂筋能够降低梁腹板上的应力强度因子幅值,对裂纹扩展起到拟制作用,其能够承担较大的静载荷从而实现破损安全设计,但是用止裂筋阻止疲劳裂纹扩展的效果并不显著;与梁弯曲产生的正应力相比,腹板上的剪应力不足以驱动Ⅱ型裂纹扩展。     

Numerical simulation and transonic wind-tunnel test for elastic thin-shell structure considering fluid–structure interaction

Aerodynamic force can lead to the strong structural vibration of flying aircraft at a high speed. This harmful vibration can bring damage or failure to the electronic equipment fixed in aircraft. It is necessary to predict the structural dynamic response in the design course. This paper presents a new numerical algorithm and scheme to solve the structural dynamics responses when considering fluid–structure interaction(FSI). Numerical simulation for a free-flying structural model in transonic speed is completed. Results show that the small elastic deformation of the structure can greatly affect the FSI. The FSI vibration tests are carried out in a transonic speed windtunnel for checking numerical theory and algorithms, and the wind-tunnel test results well accord with that of the numerical simulation. This indicates that the presented numerical method can be applied to predicting the structural dynamics responses when containing the FSI.     

Operational modal analysis via image based technique of very flexible space structures

Vibrations represent one of the most important topics of the engineering design relevant to flexible structures. The importance of this problem increases when a very flexible system is considered, and this is often the case of space structures. In order to identify the modal characteristics, in terms of natural frequencies and relevant modal parameters, ground tests are performed. However, these parameters could vary due to the operative conditions of the system. In order to continuously monitor the modal characteristics during the satellite lifetime, an operational modal analysis is mandatory. This kind of analysis is usually performed by using classical accelerometers or strain gauges and by properly analyzing the acquired output. In this paper a different approach for the vibrations data acquisition will be performed via image-based technique. In order to simulate a flexible satellite, a free flying platform is used; the problem is furthermore complicated by the fact that the overall system, constituted by a highly rigid bus and very flexible panels, must necessarily be modeled as a multibody system. In the experimental campaign, the camera, placed on the bus, will be used to identify the eigenfrequencies of the vibrating structure; in this case aluminum thin plates simulate very flexible solar panels. The structure is excited by a hammer or studied during a fast attitude maneuver. The results of the experimental activity will be investigated and compared with respect to the numerical simulation obtained via a FEM-multibody software and the relevant results will be proposed and discussed.     

深凹露天矿通风风洞研制与模拟实验

本文扼要阐述了开展露天矿通风研究、尤其是进行实验室风洞物理模拟研究的必要性。对露天矿通风模拟风洞的研制作了简介,指出了本风洞所具有的特点。文中介绍了最近完成的二项风洞模拟实验:对大冶露天矿深部开采风流结构及其污染物扩散净化能力进行了模拟研究,发现该矿具有比较独特的三维风流结构;对大爆破后靠自然风力稀释烟尘蘑菇云团所需的停工通风时间,分别完成了以风速 U_0和炸药量 A 为单因素变量的两组试验,揭示了通风时间与地表风速 U_0、炸药量 A_0的本质联系,推导出了通风时间的计算式。