钛合金EJM加工中超声辅助作用研究

本文致力于研究钛合金在应用超声辅助（UA）进行电解液喷射加工（EJM）时的表现。钛合金进行EJM加工时,工件表面易生成钝化层进而导致加工效率降低。本文分别对应用氯化钠（NaCl）电解液和硝酸钠（NaNO3）电解液的超声辅助钛合金EJM加工效果进行研究,通过分析比较常规EJM加工以及功率一定,频率分别为25,68,135kHz的三种超声辅助EJM加工所得钛合金样槽的表面氧化物百分比、深宽比、表面粗糙度和微观形貌,论证了UA在钛合金EJM加工中的具体作用,为改进钛合金EJM加工的质量与效率提供了新的思路与方法。     

TC6钛合金激光喷丸纳米组织特性及热稳定性研究(英文)

应用Nd:YAG高功率激光器对TC6钛合金试样进行了激光喷丸,对部分强化试样623K真空保温10h。应用原子力显微镜(AFM)、扫描电镜(SEM)、电子背散射电镜(EBSD)、X射线衍射(XRD)、透射电镜(TEM)等设备对试样强化层形貌和纳米组织进行检测,采用显微硬度计进行显微硬度测量。测试结果表明:TC6钛合金激光喷丸表面完整性好,未在表面引入微裂纹,表面粗糙度较传统表面强化低;激光喷丸后距离表面200μm范围内α相在冲击波作用下压缩伸长,α相和β相细化,保温后SEM测试显示强化层组织和强化层深度未发现明显变化;强化后衍射峰变宽,说明强化层发生剧烈塑性变形导致晶粒细化,并留有残余应变,未发现新的衍射峰说明强化过程中没有发生相变;强化后TC6钛合金表层产生纳米晶,保温后强化层位错密度降低,纳米晶晶界更加清晰,未发现纳米晶长大;激光喷丸硬度影响层达500μm,表面硬度提高12.2%,保温后表面显微硬度降低10HV0.5,硬化深度未发现变化。以上研究表明,TC6激光喷丸纳米组织和显微硬度在623K温度下具有较好的热稳定性,有利于提高钛合金的抗疲劳、抗磨损和抗应力腐蚀的性能,从而突破了美国规范AMS2546中关于钛合金只能在589K温度下应用的限制。     

六西格玛管理方法在民用飞机维修手册编写过程中的应用

以某型民用飞机的维修手册(AMM)为案例,分析了其编写过程中存在的质量问题。针对此问题,在AMM编写过程中引入并实施了六西格玛管理方法,并用MINITAB软件对各步骤进行统计分析,结果表明六西格玛管理方法可提升AMM的编写质量。     

六自由度电动平台电动缸附加运动误差量化分析

六自由度电动平台通过六个电动缸的协调伸缩和旋转运动,结合上下铰链的两自由度转动,实现上平台在三维空间的六自由度运动.由于电动缸通过螺旋副实现缸杆的直线运动,其直线运动与旋转运动之间存在螺旋关系,因此缸杆相对于缸筒的被动转动会引起缸杆的附加直线运动,从而对六自由度电动平台的位姿精度产生影响.针对六自由度电动平台进行了运动学分析.在此基础上进一步计算了电动缸在平台运动过程中产生的被动螺旋附加运动,并对该运动引起的误差进行了量化分析.仿真结果表明,在六自由度电动平台运动过程中产生的被动螺旋附加运动误差达到毫米数量级,将会对平台的位姿精度产生显著影响.对于高精度运动平台来说,必须研究补偿算法对其进行补偿.     

微型导弹蒙特卡洛打靶仿真研究

导弹在实际作战飞行中,由于环境因素和系统误差的影响,其姿态和弹道的参数与理想弹道的参数存在偏差.对一种微型导弹在飞行中受到的多种随机干扰因素进行分析,给出了各种干扰因素的处理方法,建立了导弹六自由度弹道蒙特卡洛打靶仿真模型.通过蒙特卡洛计算机打靶仿真,对导弹的命中精度进行研究,验证了仿真模型的准确性和仿真方法的有效性.     

Modelling and design of wing tip devices at various flight conditions using a databased aerodynamic prediction tool

A design study of wing tip devices at high and low speeds is described. The basis of the design study is an equivalent drag approach containing both aerodynamic drag gain and structural weight penalty. A comprehensive parameter study is carried out using a rapid aerodynamic prediction tool named Lift and Drag Component Analysis (LIDCA). Adding to an available lifting-line method a databased module for airfoil data is employed that uses results of two-dimensional flow simulations by multidimensional interpolation. Detailed validation studies of the method at high lift and high speed have demonstrated good accuracy. RANS computations of the selected wing tip designs confirm the predicted benefits at cruise condition. The results of the most effective wing tip designs are analysed at both flight conditions. Finally, options for improving the performance at take-off are suggested.     

Depeaking – economic optimization of air traffic systems

More than half of all flights in and out of Frankfurt International Airport are conducted by Lufthansa airlines, as it is one of their two major hubs. The so called hub and spokes systems allow airlines to bundle major passenger flows via connecting flights across the in- and outbound traffic. The reliability of these transfer connections, and specifically the arrival punctuality at the hub airports are crucial to the economics of the daily operation.Since Frankfurt International Airport has lately been one of the most congested airports in Europe, delays (in particular arrival delays) have increased quite significantly throughout the last years. To compensate for additional queueing time in the arrival processes, the scheduled block times inbound Frankfurt were continuously adjusted upwardly keeping the arrival punctuality (and thereby the connection reliability) close to stable. The two disadvantages of this approach have been the decrease in aircraft productivity and over-deliveries in peak hours, which in turn induce either additional block time delay or ground delay programs inbound Frankfurt.This paper introduces an iterative stochastic-simulation approach that models the vicious circle of lengthening block times and increased over-deliveries. In a second step it quantifies the operational and economical effects of depeaking the schedule and illustrates the overall growth potentials for the depeaked operation of the airport. The schedule was successfully implemented in Frankfurt in summer 2004.     

电子束熔化成形Ti-6Al-4V钛合金研究进展和应用现状

电子束熔化成形技术(EBM)具有成形速度快、能量利用率高和真空环境无污染等优点,适合于Ti-6Al-4V钛合金的制备,在航空航天、生物医疗等领域得到广泛应用。然而,EBM成形Ti-6Al-4V钛合金构件仍然存在的内部孔隙、粗糙的表面和残余拉应力等缺陷,严重影响了成形件的疲劳性能。通过工艺参数的优化及后处理工艺,如热等静压和表面处理等,可以显著改善EBM成形件的疲劳性能。综述了EBM成形Ti-6Al-4V钛合金的成形工艺、微观组织、力学性能和典型的应用现状。重点讨论了影响疲劳性能的因素,并总结了一些提高疲劳性能的后处理方法。最后对EBM技术未来的发展前景进行了展望。     

一种氧杂蒽酮类海洋抗污损天然产物振动光谱的理论研究

基于 Gaussian 09W软件包,采用 DFT-B3LYP方法,研究了 1种来源于红树林未知真菌的海洋抗污损天然产物——6,8-di-O-methyl versiconol。先用 3-21G基组,再用 6-311G基组计算了分子的最稳定构型及其前线分子轨道分布。分析稳定构型发现,以蒽二酮为主体的分子是 1个三维非平面的结构,并且分子内部形成了 1个大的 π共轭体系。在最稳定构型的基础上,用同样的理论方法和 6-311G基组计算了该分子的红外振动频率及拉曼光谱频率,根据红外和拉曼光谱的振动频率特点,将红外光谱和拉曼光谱分成 3个区域,讨论了 2种光谱在各区域的特征峰的位置、振动特点、振动模式等,为氧杂蒽酮类海洋抗污损天然产物分子的振动光谱检测和分子结构的鉴定,提供了光谱解析方面的理论依据。     

Impact of emissions from anthropogenic sources on satellite-derived reflectance

The present study deals with the impact of extensive anthropogenic activities associated with festivities and agricultural crop residues burning in the Indo-Gangetic Plains (IGP) on satellite-derived reflectance during November 2007. Intense smoke plumes were observed in the IRS-P4 OCM satellite data over IGP associated with agricultural crop residue burning during the study period. Terra-MODIS AOD and CALIPSO LIDAR backscatter datasets were analysed over the region to understand the spatial and temporal variation of the aerosol properties. Ground-based measurements on aerosol optical properties and black carbon (BC) mass concentration were carried out during 7–14 November 2007 over urban region of Hyderabad, India. Top of the Atmosphere (TOA) reflectance estimated from IRS-P4 Ocean Color Monitor (OCM) data showed large variations due to anthropogenic activities associated with crop residue burning and fireworks. Atmospheric corrections to OCM satellite data using 6S radiative transfer code with inputs from ground and satellite measurements could account for the variations due to differential aerosol loading. Results are discussed in this paper.