利用交变旋转磁场去除叶片气膜孔毛刺的试验研究

对航空发动机叶片采用电火花打出气膜冷却孔后产生的毛刺,用传统的加工方法难以去除,利用交变旋转电磁场带动微细磁针旋转与气膜冷却孔发生碰撞可有效去除叶片气膜冷却孔的毛刺。从理论上分析了磁力研磨法的工作原理、磁力研磨过程中磁针的运动方式以及影响磁力研磨加工效率的因素,并对气膜冷却孔进行磁力研磨抛光试验;采用3D超景深显微镜观察叶片气膜冷却孔研磨前后表面微观形貌的变化。试验结果表明:利用磁力研磨法可以有效去除叶片气膜冷却孔的毛刺,使表面形貌得到改善,满足工件的使用要求。     

基于HIFiRE-2 超燃发动机内流道的激波边界层干扰分析

为了研究高超声速流激波边界层干扰特性， 选取HIFiRE-2 （The Hypersonic International Flight Research Experimentation 2）项目的高超声速流道为研究对象，采用k-棕SST 模型在无燃油工况下模拟计算地面试验过程，所得计算结果 与试验结果接近。在此基础上，分析激波边界层干扰过程、流动分离现象及入口马赫数对气动热影响。结果表明：随着入口马赫数增 大，激波角变小，激波强度提高，在尾喷管中激波反射次数减少；随着入口速度增大，边界层分离区范围变小，回流区的位置逐渐向 下游移动；加入气动耗散项后，流场的温度有一定升高，最大温升约为50 K。     

Acoustic measurements of models of military style supersonic nozzle jets

Modern military aircraft jet engines are designed with variable-geometry nozzles to provide optimal thrust in different operating conditions, depending on the flight envelope. How- ever, acoustic measurements for such nozzles are scarce, due to the cost involved in making full- scale measurements and the lack of details about the exact geometries of these nozzles. Thus the present effort at Pennsylvania State University （PSU） in partnership with GE Aviation and the NASA Glenn Research Center is aiming to study and characterize the acoustic field produced by supersonic jets issuing from converging-diverging military style nozzles, and to identify and test promising noise reduction techniques. An equally important objective is to develop methodology for using data obtained from small- and moderate-scale experiments to reliably predict the full-scale engine noise. The experimental results presented show reasonable agreement between small-scale and medium-scale jets, as well as between heated jets and heat-simulated ones.     

变截面加筋板尺寸-布局一体化设计

为了提高加筋板结构的开口补强效率,文中提出了一种新型变截面加筋构型。通过丰富加筋结构层级,有效抑制了开口引发的失稳变形扩展,从而提高了结构的承载能力。在优化设计中,为了合理缩减设计变量的数目,文章采用函数变量来分别描述加筋层级与布局的变化规律。进而基于代理模型,实现了尺寸-布局一体化设计。最后,与等尺寸、等布局优化方法及等布局、尺寸余弦分布的优化方法的结果进行对比,凸显了文中所提出的一体化设计方法的简洁与有效。     

ATP弹性体的制备及其热分解特性和机理研究

以ATP为粘合剂、N-100为固化剂制备出ATP弹性体,并进行了性能表征.采用DSC/TG-FTIR-MS联用技术、高压DSC技术和热裂解快速扫描傅里叶变换红外技术(RSC/FITR),研究了叠氮类粘合剂ATP弹性体热分解过程,获得了ATP弹性体的热反应动力学参数,并提出了可能的分解机理.结果表明,ATP弹性体的热分解...     

Effects of dry/wet ratio and pre-immersion on stress corrosion cracking of 7050-T7451 aluminum alloy under wet-dry cyclic conditions

The stress corrosion cracking (SCC) behavior and mechanism of 7050-T7451 aluminum alloy under wet-dry cyclic conditions were investigated. Slow strain rate tests (SSRTs) and electrochemical tests were used to study the effects of dry/wet ratio (DWR) and pre-immersion on SCC. Fracture and side surface characterizations were observed by scanning electron microscopy (SEM). The results demonstrate that SCC susceptibility decreases with an increase of the DWR. With an increase of the pre-immersion time, both continuous pre-immersion (CP) and wet-dry cyclic pre-immersion (WDP) samples are more sensitive to SCC, and the cracking mode in the SCC fracture region is intergranular. Furthermore, the effect of WDP on SCC is greater than that of CP when the total time immersed in solution before an SSRT is the same with each other. In fact, each single wet-dry cycle can be divided into three processes with respect to the change of solution on samples’ surface. Volatilization of water on the surface results in an increase in solute concentration, thus accelerating corrosion.     

考虑内压影响的加筋柱壳高效屈曲优化

针对运载火箭贮箱结构,基于渐近均匀化法建立考虑内压的非等厚筋条的加筋壳承载力快速计算方法。首先,采用渐近均匀化法获得加筋单胞的等效刚度阵,进而基于瑞利-里兹法计算考虑内压的整体失稳载荷,并基于板壳理论发展了加筋柱壳的蒙皮和筋条局部失稳载荷计算方法。此外,基于自适应代理模型优化方法,开展了考虑多种失效模式的加筋柱壳承载力最大化设计,以最优设计为例,分析了内压对加筋柱壳整体失稳载荷的影响规律。     

WHAT DRIVES BUSINESS AND LEISURE AIR PASSENGER TRANSPORT DEMAND

The back-propagation neural network ( BPN ) is used to explore what the most influential variables are to drive business and leisure air passenger travel from Japan to Taiwan.The variables are systematically identified , evaluated and analyzed in detail.The results reveal that some factors affect both leisure and business air passenger transport , and the others only affect one of them.Flights from Tokyo to Taipei and average hotel rate in Taiwan are the two most important factors for forecasting the demand of leisure air passenger transport , while variables related to business activities have more effect on the demand forecast of business air passenger transport.By using BPN , a forecasting model that considers actual market segments is established , and the results show that it is an accurate tool to forecast air transport demand.     

Prospects of Global Navigation Satellite System (GNSS) reflectometry for geodynamic studies

Innovative processing of satellite radar altimetry over solid Earth has been successfully applied for observing geodynamic process of glacial isostatic adjustment over the former Laurentide Ice Sheet in the present-day Hudson Bay land region. In this contribution, a simulation is conducted to study the prospects of the applications of space-/airborne and land-based Global Navigation Satellite System (GNSS) reflectometry to synoptically observe global-scale geodynamic processes with a vertical accuracy of ∼2 mm/yr.     

悬浮月尘的遮挡模型

探月活动中,月表的尘埃会对太阳翼等光电器件的工作效率造成严重影响.基于附着月尘的遮挡模型,从立体空间的角度分析了悬浮月尘对工作器件的遮挡,提出了悬浮月尘的单粒度遮挡模型,利用月尘的平均粒度可计算在指定立体空间内,定量月尘造成的遮挡量;引入月尘的粒度分布函数,提出了悬浮月尘的多粒度遮挡模型,能够计算已知粒度分布函数的月尘在指定立体空间内造成的遮挡量;通过设计悬浮月尘遮挡的仿真实验,分别利用3种不同粒度大小的月尘进行实验,实验数据与悬浮月尘的单粒度、多粒度遮挡模型的理论计算值都较好吻合,实验结果证实了悬浮月尘遮挡模型的正确性与可靠性.