HB-2 high-velocity correlation model at high angles of attack in supersonic wind tunnel tests

Responding to a need for experimental data on a standard wind tunnel model at high angles of attack in the supersonic speed range, and in the absence of suitable reference data, a series of tests of two HB-2 standard models of different sizes was performed in the T-38 trisonic wind tunnel of Vojnotehnickˇi Institut(VTI), in the Mach number range 1.5–4.0, at angles of attack up to+30°. Tests were performed at relatively high Reynolds numbers of 2.2 millions to 4.5 millions(based on model forebody diameter). Results were compared with available low angle of attack data from other facilities, and, as a good agreement was found, it was assumed that, by implication, the obtained high angle of attack results were valid as well. Therefore, the results can be used as a reference database for the HB-2 model at high angles of attack in the supersonic speed range, which was not available before. The results are presented in comparison with available reference data, but also contain data for some Mach numbers not given in other publications.     

简论高校实验课程的改革

实验教学是高等院校教学过程的一个重要环节,应建立新型的实验室管理模式,从开放实验室和改革教学方法两个方面出发,阐述了实验课程改革的必要性。     

任务教学法在ESP阅读教学中的应用

以实证研究的方法来检验任务教学法在ESP阅读课程中的实际教学效果。实验对象是48名大三本科生,为期11周的任务教学法对比实验教学,通过对两组被试者的阅读能力的各项测试结果进行组内对比和不同组对比,分析表明任务教学法能够显著提高学生的阅读能力及其ESP学习的兴趣。     

Photolytic behaviour of methane at Lyman-α and 248 nm: Studies in the frame of a simulation program of Titan’s atmosphere (S.E.T.U.P.)

This paper first describes briefly some of the forefront global simulations of Titan’s atmosphere that have been carried out up to now. In these experiments, an initial gaseous mixture of N₂/CH₄ is submitted to a single energy source and the retrieved gas and/or solid phase(s) is/are analyzed by different techniques.     

《机械制造技术》课程特点与现场教学

《机械制造技术》课程具有很强的综合性和实践性、教学难度大的特点。教学中要以理论教学和现场教学相结合的方法，以提高教学效率和质量。同时要正确选择课题、设计合适的教学方法是改革现场教学的主要措施。     

A practical nonlinear robust control approach of electro-hydraulic load simulator

This paper studies a nonlinear robust control algorithm of the electro-hydraulic load simulator （EHLS）. The tracking performance of the EHLS is mainly limited by the actuator＇s motion disturbance, flow nonlinearity, and friction, etc. The developed controller is developed based on the nonlinear motion loading model. The problems of the actuator＇s disturbance and flow nonlinearity are considered. To address the friction problem, the friction model of the loading motor is identified experimentally. The friction disturbance is compensated using the obtained friction model. Therefore, this paper considers the main three factors comprehensively. The developed algorithm is easy to apply since the controller can be obtained just with one step back-stepping design. The stability of the developed algorithm is proven via Lyapunov analysis. Both co-simulation and experiments are performed to verify the effectiveness of this method.     

Review on signal-by-wire and power-by-wire actuation for more electric aircraft

The huge and rapid progress in electric drives offers new opportunities to improve the performances of aircraft at all levels:fuel burn,environmental footprint,safety,integration and production,serviceability,and maintainability.Actuation for safety-critical applications like flight-controls,landing gears,and even engines is one of the major consumers of non-propulsive power.Conventional actuation with centralized hydraulic power generation and distribution and control of power by throttling has been well established for decades,but offers a limited potential of evolution.In this context,electric drives become more and more attractive to remove the natural drawbacks of conventional actuation and to offer new opportunities for improving performance.This paper takes the stock,at both the signal and power levels,of the evolution of actuation for safety-critical applications in aerospace.It focuses on the recent advances and the remaining chal lenges to be taken toward full electrical actuation for commercial and military aircraft,helicopters,and launchers.It logically starts by emphasizing the specificity of safety-critical actuation for aero space.The following section addresses in details the evolution of aerospace actuation from mechanically-signaled and hydraulically-supplied to all electric,with special emphasis on research and development programs and on solutions entered into service.Finally,the last section reviews the challenges to be taken to generalize the use of all-electric actuators for future aircraft programs.     

超硬铝合金整体精车加工成型壳体及其轴压稳定性研究

本文首先简要讨论了飞行器壳体采用超硬铝合金材料、整体精车加工成型设计出优点，它对小尺寸再入飞行器设计有重要意义和应用价值。接着对超硬铝合金ＬＣ４整体精车加工成型壳体进行较详细的研究。给出了六个试件的轴压试验结果，并用小样件统计方法进行了统计分析。试验结果表明：与过去试件的试验结果相比，临界应力系数提高近一倍。散布度明显减小。对临界应力系数给出的强度变差系数值和概率下限值可供设计使用。     

横向振动下螺栓连接失效及影响因素研究

针对螺栓连接结构在横向振动下的失效问题进行试验研究,首先,对比相同条件下普通螺母与防松螺母的失效过程,结果表明普通螺母仅出现松动失效,而防松螺母会先出现部分松动,再因螺栓根部疲劳断裂而完全失效。同时在不同类型防松螺母中,Hard-lock螺母和施必牢螺母防松效果明显优于其他防松螺母。其次,考察拆卸次数、振动频率、幅值等因素对螺栓连接失效的影响规律,发现多次拆卸会改变普通螺母的失效形式;相对于振动频率,振动幅值和预紧力对螺栓失效的影响较大。     

考虑流固耦合效应的航空发动机风扇叶片应力数值模拟与试验测量研究

航空发动机风扇转子在高压比、高转速、高负荷的级环境中工作时,存在叶片固体域与流体域之间强烈的耦合作用。针对风扇工作中的流固耦合问题,采用基于流固耦合的数值模拟方法对风扇叶片的结构特性进行模拟,研究考虑流固耦合效应前后叶片结构特性的变化。通过风扇转子加减速试验测量叶片表面测点应力变化,并将数值模拟与试验测量结果进行了对比分析。分析结果表明：考虑流固耦合效应后叶片表面的受力情况变化较大,导致叶片表面的应力与变形分布产生较大的变化;仅考虑离心力作用的计算方法得到的应力值与试验测量值误差最大达到50%,而考虑流固耦合效应的计算值误差在10%左右;考虑叶片流固耦合效应得到的应力分布更满足实际工程应力与强度分析要求。