高强高导铜-铬-锆合金的铸态显微组织

采用光学显微镜、场发射扫描电镜及其附带的能谱仪研究了高强高导Cu-0.8Cr-0.2Zr合金的铸态显微组织以及合金中形成的铬锆相。结果表明:合金铸态显微组织为粗大的柱状晶;铬主要以未溶相、初生相、次生相存在于合金中,未溶相以块状存在于晶内,粗大的初生相以颗粒链状形式分布在晶界上,次生相以小颗粒弥散均匀分布于基体内部;锆主要以共晶的α+Cu5Zr形式呈长条状分布于晶界上和以次生相的形式弥散均匀分布于基体内部;合金中还存在少量层片状的铜铬锆三元共晶组织。     

机械合金化结合冷压烧结制备铜-锆合金的组织与性能

采用机械合金化结合冷压烧结的方法制备了不同锆含量的铜-锆合金,用X射线衍射仪和扫描电镜等对制备的复合粉体进行了表征,并研究了球磨时间、烧结温度和保温时间、锆含量等因素对合金电阻率、硬度及抗弯强度的影响.结果表明:随着球磨时间的延长,复合粉体的主衍射峰强度逐渐降低,而铜-锆金属间化合物的衍射峰强度逐渐增加,颗粒由片状转变为近球状,而烧结后制得合金的电阻率和硬度逐渐升高;提高烧结温度和保温时间可以使合金的导电性能提高,但硬度下降;随着锆含量的增加,合金的电阻率、硬度及抗弯强度均不断增加.     

8-羟基喹啉锆的制备及摩擦学性能研究

以8-羟基喹啉和硝酸锆为原料在乙醇-水溶液中合成一种亮黄色的锆配合物,并用元素分析、XRD、红外等分析手段对其结构进行表征。结果表明,锆配合物为Zr(C9H6NO)4,是一个晶体结构的物质。用MRS-10A型四球机测试Zr(C9H6NO)4在液体石蜡中的摩擦学性能,结果表明,Zr(C9H6NO)4能显著改善液体石蜡的抗磨性能,提高液体石蜡的极压性能,Zr(C9H6NO)4质量分数为0.1%时可使磨斑直径降低24%,质量分数为0.2%时可使承载能力提高29%。采用SEM和EDS分析磨损表面形貌和元素组成,其抗磨作用机制为:在摩擦亚表面形成摩擦扩散层,使得摩擦表面的润滑状态得到明显的改善。     

磁控共溅射制备锆-硅-氮复合薄膜的显微组织与性能

通过磁控共溅射方法制备了一系列不同硅含量的锆-硅-氮复合薄膜;采用能谱仪、X射线衍射仪、扫描电镜和微力学探针等对复合薄膜进行了表征;研究了薄膜中硅、锆原子比对复合薄膜的显微组织、高温抗氧化性能和力学性能的影响。结果表明：随着硅含量的增加,复合薄膜的ZrN（111）、（220）晶面衍射峰逐渐消失,呈现ZrN（200）择优取向;同时其性能逐渐提高,当硅、锆原子比为0．030时可获得最大硬度和最大弹性模量,分别为37．8GPa和363GPa;进一步增加硅含量,复合薄膜向非晶态转化,而薄膜的硬度和弹性模量迅速降低,抗氧化温度显著提高。     

锆溶胶的制备、稳定及氧化锆粉体的特性

以氧氯化锆为前驱体,采用溶胶-凝胶法快速制备锆溶胶,凝胶后经煅烧制得氧化锆粉体,分析了锆溶胶的制备、稳定和氧化锆粉体的特性。结果表明：随着H_2O_2与ZrOCl_2·8H_2O摩尔数的比值m的增大,锆溶胶形成所需的pH值也逐渐增大;m为4～6,且pH值为3～4．5时,所得的溶胶最稳定;随m值的增大,凝胶干燥后氧化锆粉体粒径减小,分布变窄;m为4时,氧化锆粉体的平均粒径为21．4μm。粉体在450℃热处理时有四方相ZrO_2析出,随着温度升高,四方相ZrO_2结晶趋于完整,并开始析出少量单斜相;900℃时亚稳态四方相大部分转化成单斜相;1020℃时转变完成,此时得到粉体粒径在100nm左右。     

集成铁电器件中的关键工艺研究

对集成铁电器件中的关键工艺进行了研究,采用改进的溶胶-凝胶(Sol-Gel)法制备了高品质、(110)择优取向的锆钛酸铅(PZT)铁电薄膜,成功的利用离子束刻蚀(IBE)、反应离子刻蚀(RIE)和湿法腐蚀方法对PZT薄膜进行了刻蚀加工,采用正胶剥离和干法刻蚀工艺实现了金属铂(Pt)电极图形,为集成铁电器件的实现提供了良好的工艺基础.     

锆的核应用与我国锆材加工技术

简述了锆的核性能与应用,从各关键技术环节评述了我国锆材加工的现状,说明我国的锆材加工能力可以满足国家核电发展的需要。当前应加快实现海绵锆原料的生产,建立完整的锆产业链。     

锆冷却器焊接技术

针对锆冷却器制造过程中焊接难点，对锆板以及管与管板的焊接进行试验研究，为锆设备的国产化提供了重要技术保障。     

基于原子晶格为参照标度的纳米计量技术

纳米检测和纳米计量是一项正在发展的科学技术,文中介绍了利用双探头扫描隧道显微镜与原子力显微镜系统,作纳米计量的技术。     

锆对输电铝合金蠕变行为的影响

研究了锆对铝导线蠕变变形与蠕变裂纹扩展的影响。结果表明，经530℃×1．5h固溶处理及250℃×48h时效后冷拔成形，锆在铝合金中以弥散细小第二相形式存在，能有效地阻碍蠕变变形，抑制蠕变裂纹的扩展。     

高速动车组减振器载荷特征研究

减振器的主要功能是提供阻尼力以衰减和抑制车辆系统振动,对高速动车组动力性能有十分重要的影响。既有研究主要将减振器处理为阻尼力以研究车辆系统动力性能,极少从动力学和结构可靠性角度关注减振器自身承受的载荷。制作某型高速动车组转向架抗蛇行减振器、轴箱减振器、二系横向和垂向减振器测力元件,在大同-西安高速线路上测试并获得该型动车组运行过程中四种减振器载荷引起的应变信号。对测试数据进行处理和分析,获得高速动车组运行工况下四种减振器载荷的时间历程,分析减振器载荷的时域和频域特征。采用雨流计数法统计减振器载荷峰谷值和频次,获得不同速度等级下载荷分布。结果表明,高速动车组抗蛇行减振器载荷最大、二系横向减振器载荷最小。轴箱减振器相对速度最大、二系横向减振器相对速度最小。减振器载荷总体上呈正态分布,而且一般有列车运行速度越高减振器载荷越大。列车正线行驶时曲线半径对轴箱减振器、二系垂向减振器以及二系横向减振器载荷影响不明显,列车速度和线路小半径曲线对抗蛇行减振器载荷影响明显。     

应用于万能铣床的自动滚齿系统设计

介绍了一种在万能铣床上实现滚齿加工的自动化系统。该系统以单片机作为核心控制单元,利用光电编码器采集滚刀及工件转速信息,通过控制器控制工件与滚刀比例同步运转,从而实现铣床上的滚齿加工。其软件设计采用了PID算法,根据所测滚刀转速对工件转速进行实时偏差调节,从而保证了滚刀与工件恒定的转速比关系。实践证明,本系统工作稳定、可靠,能很好地满足中小型机械加工企业齿轮加工的要求。     

韧性材料的几种断裂形式及判据讨论

考察几种韧性材料的复合型断裂试验过程，用传统强度理论思想认定启裂位置与启裂方向，通过对不同物理机制的断裂形式变化规律的研究，判定韧性材料的主要断裂形式有三类，以空穴成核、扩张、聚合为主导机制的正拉断，和以局部剪切带形成、发展为主导机制的两种不同类型的剪切断裂。局部大塑性变形的出现在材料内引起损伤，空穴的聚合或局部剪切带的出现仅发生在载荷达到某一临界值时。导致材料断裂发生的根本因素，是危险点上某应力参数达到了材料的断裂临界值，以此对不同断裂形式的断裂判据进行讨论，提出新的韧性断裂判据。     

Reliability prediction of the fatigue life of a crankshaft

Crankshaft, the core element of the engine of a vehicle, transforms the translational motion generated by combustion to rotational motion. Its failure will cause serious damage to the engine so its reliability verification must be performed. In this study, the S-N data of the bending fatigue limit of a crankshaft are derived. To evaluate the reliability of the crankshaft, reliability verification and analysis are performed. For the purpose of further evaluation, the bending test of the original crankshaft is carried out, and failure mode analysis is made. The appropriate number of samples, the applied load, and the test time are computed. On the basis of the test results, Weibull analysis for the shape and scale parameters of the crankshaft is estimated. Likewise, the B10 life under 50% of the confidence level and the MTTF are exactly calculated, and the groundwork for improving the reliability of the crankshaft is laid. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Do-Hyun Jung received his B.S. and M.S. degrees in Mechanical Engineering from Ajou University in 1988 and 1990, respectively. He then obtained his Ph.D. degree from Changwon National University in 2006. Dr. Jung is currently an Adjunct Professor at the School of Mechanical Engineering of Sunmoon University, Korea. He also manages the Reliability Application Research Center of the Reliability Division of KATECH. Dr. Jung’s fields of study include fatigue, reliability, and remanufacturing issues.     

基于力的存在性与可行性的夹紧力变向增量递减规划算法

根据工件的静力平衡条件与工件-装夹元件之间接触力的方向约束,建立工件装夹方案的力学模型。进一步结合线性规划技术,构建力的存在性分析模型及其求解方法,实现夹紧力是否有解的判断。针对夹紧力有解这一条件,由装夹方案力学模型与线性规划技术推导出力的可行性分析模型及其判断标准,实现给定的夹紧力是否合理的判断。考虑夹紧力的取值范围,以一定步长正向从最小值开始取值,根据当前值与上一次取值之间可行性的差异,确定下一次取值的步长及其方向;若可行性相同则以相同步长继续正向取值,否则以一半步长、反向取值,直至步长的绝对值在阈值范围之内,构建夹紧力变向增量递减的规划算法。该算法将连续型的夹紧力设计问题转化为离散型,不仅利于计算机实现夹紧力的自动化设计,而且还适合于形状复杂的工件。     

The study on pressure oscillation and heat transfer characteristics of oscillating capillary tube heat pipe

In the present study, the characteristics of pressure oscillation and heat transfer performance in an oscillating capillary tube heat pipe were experimentally investigated with respect to the heat flux, the charging ratio of working fluid, and the inclination angle to the horizontal orientation. The experimental results showed that the frequency of pressure oscillation was between 0.1 Hz and 1.5 Hz at the charging ratio of 40 vol.%. The saturation pressure of working fluid in the oscillating capillary tube heat pipe increased as the heat flux was increased. Also, as the charging ratio of working fluid was increased, the amplitude of pressure oscillation increased. When the pressure waves were symmetric sinusoidal waves at the charging ratios of 40 vol.% and 60 vol.%, the heat transfer performance was improved. At the charging ratios of 20 vol.% and 80 vol.%, the waveforms of pressure oscillation were more complicated, and the heat transfer performance reduced. At the charging ratio of 40 vol.%, the heat transfer performance of the OCHP was at the best when the inclination angle was 90°. the pressure wave was a sinusoidal waveform, the pressure difference was at the least, the oscillation amplitude was at the least, and the frequency of pressure oscillation was the highest.     

Non-singular tool path planning by translating tool orientations in C-space

This paper discusses the singular problem in five-axis machining of freeform surfaces. At first, the generating mechanism of the singularities is studied on the unit sphere in the P-system. Then a new method is developed to avoid the singularities by translating the tool orientations in the configuration-space (C-space) at the time just after the initial cutter locations have been generated for a cutter contact (CC) trajectory on the surface. The tool orientation vectors of the initial cutter locations are projected onto the C-space, forming the orientation polyline. In the C-space, a taper circle is defined. The singularities are detected by contact checking between the orientation polyline and the taper circle. Once they contact, the orientation polyline is translated by a minimum translating vector to avoid the contact. The minimum translating vector is picked on the offset polyline of the original orientation polyline. After that, the translated orientation polyline is inversed to calculate the optimized cutter locations in the P-system. The benefit of avoiding singularities at the tool path planning stage is that the original CC points on the CC trajectory are respected. The developed method is programed and tested through contrastive experiments. Results show that the optimized cutter locations can effectively avoid the singularities.     

Compensation of nonlinear dynamics for energy/phase control of hopping robot

Hopping height control is one of the difficult problems in legged control. Many kinds of research employ a leg spring for the supplement of energy, and model the robot as a spring-mass model. Feedback linearization enables to cancel the nonlinear terms theoretically. However, it is difficult to identify the nonlinear terms including the parameters precisely in the real world.This paper nominalizes the robot dynamics as the desired spring-mass system applying a disturbance observer. In order to realize the desired characteristics of the spring and the mass, the disturbance including the nonlinear terms is rejected firstly by a disturbance observer. To make the mass in the workspace as constant, the nominal inertia of the disturbance observer in the joint space is varied. Next, by adding the desired virtual elastic force, the robot dynamics is nominalized as the desired spring-mass system.Based on the nominalized spring-mass dynamics, hopping-height control using energy/phase control is implemented. While energy control is often used for hopping height control, the energy/phase control enables the hopping-height control and the spring-mass oscillation simultaneously.Constant hopping-height and stepwise hopping height are realized experimentally through the proposed control method. The simulations in the case of the ideal dynamics are also conducted for comparison.     

A Computer Code for Aerial Magnetic Soundings of Layered Media

An iterative algorithm is described to solve the inverse problem of stratified media using magnetic field data collected in aerial surveys. An airborne antenna sends downwards magnetic fields at several frequencies, and an airborne antenna detects the secondary magnetic fields. The input data for the inversion algorithm are the complex ratios between the secondary and primary magnetic fields at different frequencies. The algorithm selects one value for each unknown in ranges where the solution is likely to lie. Complex residuals between experimental and estimated data are computed. A cost function is defined as the summation of the absolute values of the real parts of the residuals added to the summation of the absolute values of the imaginary parts of the residuals. A value of the cost function is computed for the selected set of values of the unknowns. All such procedures are repeated for other sets of values of the unknowns. Such sets span the ranges of values where the solution is deemed to lie. The solution in the first iteration is the set of values of the unknowns that relates to the minimum computed value of the cost function. In each subsequent iteration, a minimization of the cost function is performed around the solution estimated in the immediately preceding iteration. The final solution relates to the minimum value of the cost function over all the iterations. The inverse problem is solved without recourse to either analytical or numerical computation of derivatives. This provides stability and simplicity to the algorithm. The MATLAB code of the algorithm is set forth. The code is assessed using field data from two aerial magnetic surveys.     

重型燃气轮机叶片离心载荷下应力特性的研究

针对重型燃气轮机叶片疲劳寿命研究的需要,通过设计和搭建的全尺寸叶片疲劳试验装置,模拟离心载荷工况下的低周疲劳试验,开展离心载荷下叶片应力分布和疲劳寿命预测的研究。该全尺寸叶片疲劳试验装置能够模拟低周疲劳中的等效离心载荷工况,为叶片试验提供必要的条件和手段。同时,对叶片进行网格划分和有限元仿真计算后,得到叶片Von mises应力分布结果,发现叶身应力最大处位于中部偏下边缘薄壁侧。然后将有限元仿真及应力试验相结合,提出叶片疲劳试验的离心载荷等效方法。在此基础上完成叶片的动应力试验,获得应力时间历程数据,并且给出离心载荷应力谱。结果表明,叶身中部边缘的应力水平最高,动应力谱幅值与频数概率的分布服从6阶麦克劳林拟合函数,用等效离心载荷疲劳寿命进行叶片寿命预测的结果是偏安全的,该结论可作为优化设计和试验研究的参考依据。