涡轮叶片流固耦合协作优化方法

针对结构和流场相互影响的流固耦合多学科设计问题,提出一种耦合量曲面拟合的协作优化方法。其特点是用曲面函数拟合结构-流场界面耦合量(温度、气压和变形)的空间分布,并用曲面拟合参数的一致性代替原有耦合量界面分布的学科一致性。涡轮叶片的算例表明:曲面拟合函数可以表征结构和流场界面的耦合量;用拟合参数的一致性代替界面直接耦合是可行的;该协作优化方法是可以用来解决流固耦合多学科优化设计问题的。     

Dynamics in the Phobos environment

The dynamical environment on and about the Martian moon Phobos is explored. This planetary moon provides a unique dynamical environment in the solar system, being subject to extreme tidal forces and having a characteristically non-spherical shape. Further, it is not in a fully circular orbit, meaning that it has librations that arise from its eccentricity, contributing to a periodic forcing environment. Thus, to plan and implement missions in the vicinity of and on Phobos will require these considerations be taken into account. In this paper the latest published models of the Phobos shape and dynamics are used to characterize its dynamical environment in close proximity orbit about the body, for motion across its surface and for controlled hovering motion in its vicinity. It is found that surface motion is subject to a number of “speed limits” that can cause a moving vehicle to leave the surface and to possibly escape the moon and enter orbit about Mars. In terms of orbital stability, the existence of libration orbit families are characterized down to the surface using an exact potential, and the known stable QSO orbits are shown to be associated with families of stable quasi-periodic orbits.     

纤维表面处理对PBO/ 环氧界面性能的影响

为提高PBO纤维/环氧树脂的剪切强度,采用聚合物涂层法对PBO纤维进行表面改性。通过NOL环复合材料层间剪切强度测试,研究不同浓度的表面涂层处理液、不同浸渍工艺对复合材料层间剪切强度的影响。结果表明:PBO纤维表面经不同涂层处理液处理后,层间剪切强度均高于未经表面处理的;当PBO纤维经过以涂层A为一浴浸渍液、涂层B为二浴浸渍液的两次浸渍工艺处理后,层间剪切强度最高,比未经表面处理的提高了61%。     

Influences of milling and grinding on machined surface roughness and fatigue behavior of GH4169 superalloy workpieces

Surface topography of superalloy GH4169 workpieces machined by milling and grinding is different significantly. Meanwhile, surface roughness, as one of the main indicators of machined surface integrity, has a great influence on the fatigue behavior of workpieces. Based on analyzing the formation mechanism and characteristics of surface roughness utilizing different machining processes and parameters, the machined surface roughness curve can be decoupled into two parts utilizing frequency spectrum analysis, which are kinematic surface roughness curve and stochastic surface roughness curve. The kinematic surface roughness curve is influenced by machining process,parameters, geometry of the cutting tool or wheel, the maximum height of which is expressed as R'_z.By subtracting the kinematic part from the measurement curve, the stochastic surface roughness curve and its maximum height R'_zcan be obtained, which is influenced by the defects of cutting tool edge or abrasive grains, built-up edges(BUE), cracks, high frequency vibration and so on. On the other hand, the results of decoupling analysis of surface roughness curves indicate that Raand Rz values of milling GH4169 are 2–5 times and 1–3 times as high as those of grinding, while R'_zvalue of milling is 13.85%–37.7% as high as that of grinding. According to the results of fatigue life tests of specimens machined by milling and grinding, it can be concluded that fatigue behavior of GH4169 decreases with the increase of R'_zmonotonically, even utilizing different machining processes.     

Feasibility study of creep feed grinding of 300M steel with zirconium corundum wheel

The ultrahigh strength 300M steel has been commonly used in the manufacture of aircraft landing gear and rotor shaft parts due to its excellent mechanical properties. Creep feed grinding is one of the essential operations during the whole component manufacturing processes. In this work, the feasibility of creep feed grinding of 300M steel by using the hard zirconium corundum wheel was theoretically and experimentally evaluated. A variety of responses including grinding forces, temperature fields...     

磁暴期间的地磁导航精度分析

地磁导航是无源自主导航技术研究的新方向. 分析了地磁导航的基本原理, 描述了典型磁暴过程, 并针对地磁导航在磁暴环境中的适用性进行了研究. 在采用曲面样条方法对实测地磁场数据建立观测模型的基础上, 结合广义卡尔曼滤波方法讨论了磁暴不同阶段对地磁导航精度造成的影响. 分别采用理论典型磁暴数据以及实测磁暴数据进行仿真, 仿真结果表明, 在磁暴的初相、恢复相的中后时段以及中等强度以下的磁暴全过程仍然可以采用地磁来进行导航定位, 导航精度在200 m以内, 满足飞行器中程制导的精度要求.      

航空航天用钛合金表面工程技术研究进展

钛合金以其高比强度、低密度等优点,被广泛应用于航空航天零件中.然而,钛合金也存在硬度低、耐磨性差、高温氧化抗力差等弱点,表面应力集中敏感导致的疲劳问题也较突出,需利用表面工程技术克服磨损、腐蚀和疲劳3大问题.介绍了近10年来钛合金耐磨涂层、抗氧化涂层与抗疲劳表面改性技术的研究进展,并对技术发展趋势进行了展望,为表面工程...     

C─8587A型多参数表面粗糙度测量仪参数运算软件分析

介绍了C-8587A型多参数表面粗糙度测量仪各项参数的定义、测量、数学模型、流程控制、功能特点，用单片机实现仪器的各项功能，利用宏汇编语言的编程技巧得以实现，表现了仪器的优越性。     

钛合金高压气瓶表面裂纹程序载荷谱试验的结果和分析

本文介绍两个带有疲劳表面裂纹的钛合金高压气瓶在程序载荷谱下的试验结果,并对它作了简单的分析。结果表明,即使气瓶具有“最大可能出现”的表面裂纹,它在公路运输及地面贮存保压过程中也是安全的。利用我们推导的表面裂纹半经验公式,参考NASA的K_(TH)/K_I实验数据,估计了在使用载荷作用下,气瓶在水介质中贮存保压较长时间裂纹不产生扩展的临界尺寸。     

Grinding behavior and surface appearance of（TiC_p＋ TiB_w）/Ti-6Al-4V titanium matrix composites

（TiCp＋ TiBw）/Ti-6Al-4V titanium matrix composites（PTMCs） have broad application prospects in the aviation and nuclear field. However, it is a typical difficult-to-cut material due to high hardness of the reinforcements, high strength and low thermal conductivity of Ti-6Al-4V alloy matrix. Grinding experiments with vitrified CBN wheels were conducted to analyze comparatively the grinding performance of PTMCs and Ti-6Al-4V alloy. Grinding force and force ratios, specific grinding energy, grinding temperature, surface roughness, ground surface appearance were discussed. The results show that the normal grinding force and the force ratios of PTMCs are much larger than that of Ti-6Al-4V alloy. Low depth of cut and high workpiece speed are generally beneficial to achieve the precision ground surface for PTMCs. The hard reinforcements of PTMCs are mainly removed in the ductile mode during grinding. However, the removal phenomenon of the reinforcements due to brittle fracture still exists, which contributes to the lower specific grinding energy and grinding temperature of PTMCs than Ti-6Al-4V alloy.