齿轮轮齿接触分析的分解算法

提出了齿轮轮齿接触分析算法——分解算法。传统的轮齿接触分析方法求啮合点时需要求解含5个非线性方程的方程组，求解性差；齿面接触和边缘接触的数学模型不同，需要分别进行求解，求解过程复杂。轮齿接触分析算法——分解算法，提出了瞬时共轭啮合线的概念，可有效分离传动误差，得到啮合点、瞬时接触线，求啮合点时非线性方程的个数由5个减少为2个。分解算法建立的数学模型也适用于边缘接触分析，算法简单、有效、适应性强。以一对弧齿锥齿轮为例, 对比分析了传统方法和分解算法, 结果表明: 齿面部分的印痕是一致的，传动误差幅值相差0.3″；边缘接触部分的印痕存在少许差异。      

Method for utilizing PIV to investigate high curvature and acceleration boundary layer flows around the compressor blade leading edge

Particle Image Velocimetry (PIV) is a well-developed and contactless technique in experimental fluid mechanics, but the strong velocity gradient and streamline curvature near the wall substantially limits its accuracy improvement. This paper presents a data processing procedure combining conventional PIV and newly developed Mirror Interchange (MI) based Interface-PIV for the measurement of the boundary layer parameter development in the blade leading edge region. The synthetic particle images are used to analyze the measurement errors in the entire procedure. Overall, three types of errors, namely the errors caused by the Window Deformation Iterative Multigrid (WIDIM) algorithm, the discrete data interpolation and integration, and the wall offset uncertainty, comprise the main measurement error. Specifically, the errors due to the discrete data interpolation and integration and the WIDIM algorithm comprise the mean bias, which can be corrected through the error analysis method proposed in the present work. Meanwhile, the errors due to the WIDIM algorithm and the wall offset uncertainty contribute to the measurement uncertainty. Computational fluid dynamics-based synthetic particle flows were generated to verify the newly developed PIV data processing procedure and the corresponding error analysis method. Results showed that the data processing method could improve the accuracy of PIV measurements for boundary layer flows with high curvature and acceleration and even with significant flow separation bubbles. Finally, the data processing method is also applied in a PIV experiment to investigate the boundary layer flows around a compressor blade leading edge, and several credible boundary flow parameters were obtained.     

临近空间飞艇保形升空过程热运动特性研究

为了掌握双气囊临近空间飞艇升空过程中因保形需要而导致的复杂的热运动特性，文章建立了飞艇升空过程中的热平衡模型与运动模型，对某双气囊飞艇的保形升空过程进行仿真研究，获得了临近空间飞艇升空过程中轨迹与温度的变化规律。结果表明：临近空间飞艇保形升空时，升空速度呈现先降低后升高的变化趋势；受升空过程中氦气囊膨胀对外做功的影响，内部气体“过冷”现象明显，“过冷”最高可达20K；当飞艇升至驻空高度附近时，内部气体温度快速上升；受净浮力影响，飞艇的升空时间与充气质量呈反比；受夏至日太阳辐射投影面积的影响，飞艇升空过程中俯仰角越大，虽然阻力系数减小，但辐射得热降低，造成整体升空时间增加；气囊超压设置越大，飞艇升空时间越长。研究成果对临近空间飞艇的升空与运行控制具有一定的指导作用。     

A physically-based representative stress methodology for predicting stress rupture life of Ni-based DS superalloy

Smooth and three types of U-shape single-edge notched plate specimens adopted to experimentally investigate stress rupture behavior of Ni-based Directionally Solidified (DS) superalloy at 850 °C exhibit notch weakening effect and multi-source cracking initiation near the notch root. However, stress rupture behavior of smooth and V-shape notched round bars at 1040 °C revealed by Li et al indicates notch strengthening effect and creep micro-holes originating mostly from the central portion. A combined creep-viscoplastic constitutive model is employed to analyze the distribution of stress, strain and stress Triaxial Factor (TF) near the notch root. The different stress distribution and creep restraint between asymmetric notched plate specimens and symmetric notched round bars are the main reasons for the corresponding failure mechanism. Meanwhile, a good qualitative relationship exists between TF value and stress rupture life of notched specimen. Especially, the area with maximum TF value (TF_max) is highly consistent with creep damage initiation region. Hence, based on the distribution characteristics of the initial tensile loading, a representative stress method independent of time -changing creep load at the location of TF_max is conducted for life prediction. The predicted results of both smooth and notched plate specimens and round bars agrees well with the experimental results.     

破损安全设计在民用飞机襟翼运动机构中的应用

后缘襟翼是现代民用飞机的关键增升装置，运动机构是其重要的支撑结构。根据后缘襟翼运动机构特点和损伤容限要求，提出了破损安全设计要求和不同类型的破损安全结构应用场景。基于裂纹扩展方法和主、副结构裂纹独立扩展的原则，给出了不同类型破损安全结构的裂纹扩展曲线、检查门槛值和重复检查间隔的确定方法；针对主流铰链襟翼和滑轨襟翼运动机构的传力和连接特点，从主、副结构的相对位置出发提出了同位结构和异位结构的分类方式，从结构特点出发提出了平板结构和铰链结构的分类方式，给出运动机构破损安全设计流程，并提出了典型富勒襟翼滑轨等待破损安全最小设计间隙确定方法，对民用飞机的研制具有重要意义。     

电弧风洞上的翼前缘烧蚀试验

介绍在CAAA的FD04电孤风洞上进行的翼前缘防热材料烧蚀试验结果.试验模型由高温陶瓷制成,后掠角53°,高75 mm,长55 mm,前缘半径2 mm,对称截面半锥角为5°.试验设备包括20 MW电弧加热器、混合室、矩形超声速喷管、试验段、轨道模拟系统及真空系统等.使用的矩形超声速喷管的马赫数为3.6,以3个台阶的轨道模拟翼前缘热环境,试验时间为77.0 s.试验结果表明高温陶瓷具有优良的抗烧蚀性能,两件试验模型在试验过程中均未出现破损现象,试验还得到了翼前缘模型试验过程中的内部温度响应.     

Damage sensitivity of a wing-type leading edge structure impacted by a bird

On the windward side of an aircraft, the components with higher probability of impact with birds are the wing-type leading edge structures, such as the wing and tail. A study on the damage sensitivity of a wing-type leading edge structure under bird strikes was presented in this paper. First, a bird strike test was carried out on a wing. The principles of the bird strike test equipment and method were introduced in detail, including the bird strike test system, bird projectile production process and data acquisition system. The dynamic strain measurement results, the high-speed camera videos, and the final deformation and damage morphology observations of the structure were obtained. Based on the coupled Smooth Particle Hydrodynamics (SPH) - Finite Element Method (FEM), the commercial software PAM-CRASH was used to simulate the process of a bird strike with the wing. The good agreement between the finite element simulation results and the experimental results shows that the calculation method and the numerical model presented in this paper were reasonable. On this basis, wing-type leading edge structures can be designed by adding triangular support. The bird strike resistances of an original structure and improved structure were studied by numerical simulation. The calculated results show that the improved wing-type leading edge structure is less damaged than the original structure under bird strike. The improved leading edge structure satisfied the anti-bird strike airworthiness requirements, as the thickness of the triangular support was 1.2 mm, and the weight of the structure was reduced by 0.87 kg compared with the original structure. This indicated that the bird strike resistance of the improved structure is better than that of the original structure, and the improved design of the wing-type leading edge structure presented in this paper is reasonable.     

A Review of the Attachment Line Instability for Hybrid Laminar Flow Control

This paper focuses on the investigation of the attachment line instability for Hybrid Laminar Flow Control （HLFC）, one of the most promising drag reduction technologies for modern transport aircraft respect to high Reynolds numbers and large sweep angles. The attachment line instability also plays an important role during laminar turbulent transition control and HLFC design on a swept wing. The overview of historical research is presented and knowledge gaps are pointed out as the conclusion.     

基于UAV的空地协同任务卸载策略研究

随着各行业对大批量信息处理需求的增加，移动边缘计算（Mobile Edge Computing， MEC）技术应运而生。而在陆地障碍较多、MEC服务器搭载不便的情况下，研究了一种无人机（Unmanned Aerial Vehicle， UAV）中继辅助用户卸载任务到基站的场景。针对该场景，提出了一种基于博弈论的最优任务卸载方法，通过联合优化任务卸载比例和卸载策略使得系统时延最小化。由于这两个变量之间相互耦合，因此将原优化问题转化为两个子问题求解。首先，在确定策略的情况下，证明了系统时延最小值存在的条件，得到了用户的最优卸载比例闭合解。然后，将原优化问题转化为任务分配问题，并建立博弈论模型。在证明了该模型存在纳什均衡（Nash Equilibrium，NE）的前提下，经过多次迭代，求解得到基于时延最小的用户任务卸载策略集。仿真结果表明：上述方法有效降低了全局计算时延，在时效性上优于其他一些常见的卸载方法。     

隐身飞机机身侧棱电磁散射特点分析

隐身飞机机身侧棱是侧向重要散射源,研究其电磁散射特点具有重要意义。建立机身侧棱分析模型,采用多层快速多极子算法(MLFMM)进行计算,获得雷达散射截面(RCS)沿水平面方位角的分布数据;构建RCS峰值、波峰宽度、旁瓣均值三维度评价方法,基于该方法分析机身侧棱电磁散射的极化特性和频率特性;针对棱边长度、棱边尖劈角、棱边厚度三项关键几何参数,建立变参数模型并通过仿真研究RCS对几何参数的敏感性。结果表明:RCS峰值对棱边长度及棱边尖劈角比较敏感,波峰宽度对频率比较敏感,旁瓣均值对频率及棱边尖劈角比较敏感。