不锈钢上的铬硅原位化学气相沉积

用原位化学气相沉积方法在不锈钢上同时沉积铬硅扩散涂层已获得成功，涂层表面约含２７％铬和４％硅，试验钢渗层厚度分别达到１３０μｍ和２００μｍ。渗后试样在１ＮＨ２ＳＯ４溶液中有很好的耐蚀性，在３．５％ＮａＣｌ水溶液中的点蚀电位得到提高，抗氧化性也有明显提高。     

基于隧道效应的纳米级轮廓仪

介绍了一种利用量子力学中隧道效应原理工作的纳米级轮廓仪．它可对直径为１３０ｍｍ的光盘、磁盘等较大工件表面直接进行测量，扫描范围为１×１～１４０×１４０μｍ２，Ｘ，Ｙ方向扫描步长为１～８００ｎｍ可调，横向分辨率达几个纳米，纵向分辨率优于１ｎｍ．利用该装置已测得精密光栅、精磨祥块、金刚石镜面车削等表面的纳米级形貌．     

旋转CVI制备陶瓷基复合材料碳界面层

用旋转ＣＶＩ工艺，通过优化工艺参数，在低压（５ｋＰａ）、高温（１１００℃）、高Ｃ３Ｈ６ 浓度（６２．５ｖｏｌ％ ）以及３．５ｍ ｍ ·ｍ ｉｎ－ １ 碳布旋转线速度条件下，在二维碳布上快速制备了厚度均匀（０．２５μｍ ）、表面规整的致密热解碳界面层。实验结果表明：沉积温度对界面层表面状况有较大的影响；采用减压法与优化沉积炉结构与几何尺寸，能有效防止高温高Ｃ３Ｈ６ 浓度下炭黑的形成。     

铝合金在模拟SO2污染大气环境中的腐蚀行为

采用扫描电镜(SEM/EDX)、增重法、傅立叶变换红外光谱(FTIR)和X射线衍射研究铝合金1060、铝合金2A12和7A04分别在表面沉积与未沉积70μg/cm2氯化钠条件下在含50×10-6SO2(50ppm)污染大气环境中的腐蚀行为和规律,并测试三种材料力学性能的变化。研究结果表明,随试验时间的延长,铝合金表面腐蚀产物不断增多,腐蚀增重符合指数衰减规律Δm/A=B Dexp(-t/k),抗拉强度和延伸率呈下降趋势;表面腐蚀产物形貌呈团状或圆团状,并不断向外扩展延伸,呈现不均匀的凹凸形貌;铝合金在50ppm SO2污染大气环境中腐蚀产物少,腐蚀增重较少,表面腐蚀产物主要为氧化铝和硫酸铝;而表面沉积70μg/cm2NaC l的铝合金在模拟50ppm SO2污染大气环境中腐蚀产物明显增多,腐蚀增重大,力学性能下降幅度大,二氧化硫和氯化钠的协同作用明显促进铝合金的腐蚀,腐蚀产物主要为氧化铝、铝的硫酸盐和铝的氯化物。     

不同状态NiCrAlY涂层组织结构的研究

对ＤＤ２镍基单晶材料表面上采用阴极电弧镀（ＡＰＤ）方法获得ＮｉＣｒＡｌＹ防护涂层的原始涂层、扩散处理涂层、塑变涂层以及塑变后时效处理涂层等的表面与内部的相结构进行了试验研究。结果表明,厚度约１３０μｍ的涂层中主要由Ｎｉ３Ａｌ基体（有序或无序）、简单立方ＮｉＡｌ和Ｃｒ三种物相构成,但不同状态的涂层由不同的相结构组成,且沿着涂层深度有着各自不同的分布;塑变使扩散处理析出的ＮｉＡｌ新相又发生回溶,而在高温（１１００℃）下对塑变涂层时效处理后,ＮｉＡｌ相又重新析出。     

两种模具材料对热等静压TC4 显微组织的影响

研究了A3钢和GH1131高温合金两种材料作为模具对TC4钛合金HIP组织的影响。结果表明在HIP过程中,A3钢模具对有效应力传递的阻碍作用较大,设计HIP用A3钢模具时应避免深型腔结构,GH1131模具对有效应力传递的影响较小。受元素互扩散的影响,两种模具材料在HIP过程中均污染了TC4材料表面,A3钢模具对合金的影响层较薄,但使材料形成了波浪形的粗糙表面;GH1131对成形材料的影响层厚度>100μm。为了获得高精度的无污染表面,TC4合金HIP净成形时两种模具均需要进行表面处理,形成与TC4兼容的保护层。     

关于脉冲硬质阳极氧化方法修复铝合金零件尺寸的研究

采用正交试验方法,以HB/Z237—1993《铝及铝合金硬质阳极氧化工艺》的槽液配方为基础,研究了对2D70铝合金进行脉冲硬质阳极氧化能得到的膜层厚度;将其应用于超差铝合金零件修复,使相对于图纸要求超差70μm以内的铝合金零件可以修复到合格尺寸继续使用,避免了零件报废,节约了修理成本。     

兆声波精密微电铸设备及相关工艺研究

兆声波具有高声强、低空化、声流扰动的特点,将其应用于电化学沉积领域有着明显的优势。设计了一种贴片式双向兆声辐照的兆声波反应器,组合其他功能模块,制作了一款集成化的兆声精密电铸设备。以铜基底上镍的电沉积过程为研究对象,考察了不同兆声波作用形式对铸层厚度均匀性及表面形貌的影响,对比了无兆声作用、单侧兆声作用、双侧交替兆声作用下的电铸层厚度均匀性及电铸层表面形貌。电铸完成后,镍铸层的平面度值分别为:无兆声15.03μm、单侧兆声15.36μm、双侧兆声10.91μm。单侧兆声振动产生的驻波条纹及偏向推积现象影响了铸层的厚度均匀性及表面形貌。双侧交替兆声辐照克服了单侧兆声作用存在的偏向推积问题。相对于无兆声作用及单侧兆声作用,双侧兆声辅助电沉积获得了更均匀的电铸层厚度以及更好的沉积层表面形貌。     

通过非对称电极实现IPMC单向弯曲

针对常规对称电极的离子聚合物-金属复合材料(IPMC)在交流信号的作用下仅能够产生往复摆动这种单一运动形式对其开发利用的限制,通过在传统IPMC铂电极表面的一侧镀铜制备出非对称电极IPMC,实现了IPMC的单向弯曲。利用扫描电镜对样品铂电极层表面镀铜的厚度观察,结果显示在IPMC电极一侧分别电镀1.01μm、2.59μm、3.80μm铜层;通过激光位移传感器对样品末端的位移进行测试,结果表明,在正弦电压信号的激励下,非对称电极的IPMC有单向弯曲的趋势,当镀铜层厚度达到3.80μm,即铜层厚度与铂层厚度之比达到2.06时,IPMC正向最大位移与负向最大位移相差5倍,单向弯曲的趋势明显,且倾向于向更厚的铂铜复合镀层方向弯曲。     

新型复合材料π 型接头弯曲性能

针对传统复合材料π型接头层间性能薄弱的问题,提出一种新型复合材料π型接头结构,并通过预浸料-RTM成型方法制备出具有不同底板厚度的复合材料接头。对复合材料π型接头与同尺寸的铝合金接头进行了弯曲试验,试验结果表明,底板厚度为6 mm复合材料接头弯曲强度优于铝合金接头、弯曲刚度与铝合金接头相当,而底板厚度为8 mm的复合材料接头弯曲强度逊于铝合金接头、弯曲刚度与铝合金接头相当。     

The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow

This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig.Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine.Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air.Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows(Re up to 5×106 and Rez up to 2×105).Two different builds have been tested.The most significant difference between these two build configurations is the size of the annular gap between the(non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method.The velocity measurements were made using a two component,LDA system.The heat transfer results from the discs show differences between the two builds.This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity.There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig.For the narrow annular gap,there is an increase of non-dimensional tangential velocity V/Ωr with radial location to solid body rotation V/Ωr=1.For the wider annular gap,the non-dimensional velocities show a decrease with radial location to solid body rotation.      

Research on Auto-detection for Remainder Particles of Aerospace Relay Based on Wavelet Analysis

Aerospace relay is one kind of electronic components which is used widely in national defense system and aerospace system. The existence of remainder particles induces the reliability declining, which has become a severe problem in the development of aerospace relay. Traditional particle impact noise detection (PIND) method for remainder detection is ineffective for small particles, due to its low precision and involvement of subjective factors. An auto-detection method for PIND output signals is proposed in this paper, which is based on direct wavelet de-noising (DWD), cross-correlation analysis (CCA) and homo-filtering (HF), the method enhances the affectiv-ity of PIND test about the small particles. In the end, some practical PIND output signals are analysed, and the validity of this new method is proved.     

Preparation of Highly Dispersed Antimony-doped Tin Oxide Nano-powder via Ion-exchange Hydrolysis of SnCl4 and SbCl3 and Azeotropic Drying

Antimony-doped tin hydroxide colloid precipitates have been synthesized by hydrolysis of SnCl4 and SbCl3 using: (1) an ion-exchange hydrolysis to remove chlorine ions, and (2) isoamyl acetate as an azeotropic solvent to obviate water. The obtained dried powder is of high dispersivity without any need for further grinding. The size and dispersivity of the final particles are investigated with the aid of TG-DTA, BET, XRD and TEM. After having calcined, the antimony-doped tin oxide nanopowder possesses a tetragonal rutile structure with high dispersivity, uniform particles and low hard agglomeration.     

Effects of Mo on the Microstructure and Hydrogen Sorption Properties of Ti-Mo Getters

The effects of Mo on the microstructure evolution, porosity and hydrogen sorption properties of Ti-Mo getters are investigated in this work. The results show that the addition of Mo prolongs the densification process of Ti-Mo getters and results in a significant amount of sintered pores. With the Mo content increasing, the porosity of getters firstly increases reaching the maximum value as it at- tains about 7.5wt.%, and then drops. At the room temperature, the hydrogen sorption property of getters increases progressively with the Mo content increasing, but the tendency is not very clear before its content lies below 2.5wt.%. When the Mo content achieves about 7.5wt.%, the hydrogen sorption property proves to be the best. The discussion is made about the above mentioned phenomena inclusive of hydrogen sorption properties of getters under different activation conditions (from 500-750 ℃).     

超声速燃烧数值模拟中的湍流与化学反应相互作用模型

高精度数值模拟有助于理解超声速湍流燃烧中湍流与化学反应的相互作用,可为发动机燃烧室等工程应用设计提供可靠的预测模型。除直接数值模拟外,目前在湍流燃烧应用中使用的大涡模拟和雷诺平均Navier-Stokes模拟均需要借助模型模化发生在湍流小尺度上的流动与化学反应过程对湍流大尺度运动的影响。现有的湍流与化学反应相互作用模型大致可分为:火焰面类模型和概率密度函数类模型,2类模型在不同的应用中各自具有优势和局限性。此外,现有模型大都基于低马赫数燃烧,而超声速燃烧中通常会伴随快速混合、局部熄火和再着火以及激波等复杂过程,这为发展其中的湍流与化学反应相互作用模型提出了更多的挑战。     

适于低轨卫星IP网络的单核共享树组播算法(英文)

为了解决低轨卫星IP网络中现有典型源组播算法的信道资源浪费问题,本文提出了一套单核共享树组播算法,即核心群合并共享树(CCST)和加权核心群合并共享树(w-CCST)算法。CCST 算法包括动态近似中心(DAC)选核方法和核心群合并组播路径构建方法。DAC方法专为周期、规律运动的低轨卫星网络提出,不需要复杂的星上计算。在核心群合并方法中,以核节点作为初始核心群,通过核心群和剩余组成员的最短路径方法逐步扩展直至整棵组播树构建完成,从而使得组播树的树代价最小,大大提高了网络的带宽利用率和组播传输效率。w-CCST 算法中所提出的加权因子可以调整树代价和端到端传播时延之间的折衷程度,因此,可以通过调整加权因子来适度增大树代价、降低端到端传播时延以支持某些端到端时延要求苛刻的实时组播业务。最后,与低轨卫星 IP 网络中典型算法进行了性能比较,仿真结果说明,CCST 算法的平均树代价比其它算法显著降低,w-CCST 算法的平均端到端传播时延小于 CCST 算法。     

Jet Vectoring Control Using a Novel Synthetic Jet Actuator

A primary air jet vectoring control system with a novel synthetic jet actuator (SJA) is presented and simulated numerically. The results show that, in comparison with an existing traditional synthetic jet actuator, which is able to perform the duty of either “push” or “pull”, one novel synthetic jet actuator can fulfill both “push” and “pull” functions to vector the primary jet by shifting a slide block inside it. Therefore, because the new actuator possesses greater efficiency, it has potentiality to replace the existing one in various appli- cations, such as thrust vectoring and the reduction of thermal signature. Moreover, as the novel actuator can fulfill those functions that the existing one can not, it may well be expected to popularize it into more flow control systems.     

Nonlinear Adaptive Slewing Motion Control of Spacecraft Truss Driven by Synchronous V-gimbaled CMG Precession

The slewing motion control of a truss arm driven by a V-gimbaled control-moment-gyro (CMG) is a nonlinear control problem. The V-gimbaled CMG consists of a pair of gyros that must precess synchronously. The moment of inertia of the system, the angular momentum of the gyros and the external disturbances are not exactly known. With the help of feedback linearization and recursive Lyapunov design method, an adaptive nonlinear controller is designed to deal with the unknown items. Performance of the proposed controller is verified by simulation.     

An SOR Implicit Time-accurate Scheme in Calculating Unsteady Flows

A new time-accurate marching scheme for unsteady flow calculations is proposed in the present work. This method is the combination of classical Successive Over-Relaxation (SOR) iteration method and Jacobian matrix diagonally dominant splitting method of LUSGS. One advantage of this algorithm is the second-order accuracy because of no factorization error. Another advantage is the low computational cost because the Jacobian matrices and fluxes are only calculated once in each physical time step. And, the SOR algorithm has better convergence property than Gauss-Seidel. To investigate its accuracy and convergency, several unsteady flow computa- tional tests are carried out by using the proposed SOR algorithm. Roe’s FDS scheme is used to discritize the inviscid flux terms. Un- steady computational results of SOR are compared with the experiment results and those of Gauss-Seidel. Results reveal that the numerical results agree well with the experimental data and the second-order accuracy can be obtained as the Gauss-Seidel for unsteady flow computations. The impact of SOR factor is investigated for unsteady computations by using different SOR factors in this algorithm to simulate each computational test. Different numbers of inner iterations are needed to converge to the same criterion for different SOR factors and optimal choice of SOR factor can improve the computational efficiency greatly.