On the Adjusting of the Dynamic Coefficients of Tilting-Pad Journal Bearings

This paper gives a theoretical and experimental contribution to the problem of active modification of the dynamic coefficients of tilting-pad journal bearings, aiming to increase the damping and stability of rotating systems. The theoretical studies for the calculation of the bearing coefficients are based on the fluid dynamics, specifically on the Reynolds equation, on the dynamics of multibody systems and on some concepts of the hydraulics. The experiments are carried out by means of a test rig specially designed for this investigation. The four pads of such a bearing are mounted on four flexible hydraulic chambers which are connected to a proportional valve. The chamber pressures are changed by means of the proportional valve, resulting in a displacement of the pads and a modification of the bearing gap. By changing the gap, one can adjust the dynamic coefficients of the bearing. With help of an experimental procedure for identifying the bearing coefficients, theoretical and experimental results are compared and discussed. The advantages and the limitation of such hydrodynamic bearings in their controllable form are evaluated with regard to application on the high-speed machines.     

铜合金表面激光熔覆研究现状

为了提高铜合金的表面耐磨性能,激光熔覆技术已被用于铜合金的表面处理;总结了铜合金表面激光熔覆的特点,评述了铜合金表面熔覆材料体系的研究现状和激光熔覆技术工艺,分析了熔覆层的表面性能,阐明了铜合金表面激光熔覆存在的主要问题和相应改进途径,并提出了今后的研究方向。     

Distribution patterns and morphology of sensilla on the apical segment of the antennae and palpi of Hydradephaga (Coleoptera: adephaga).

The sensilla on the terminal antennomere of selected Hydradephagans (Coleoptera) are modified in several distinct ways as compared to the sensilla on the terminal antennomere of Geadephagans (Coleoptera). There are no long sensilla of any type on antennae of Hydradephagans, the sensilla are either short, peg-like sensilla that may be recessed in the antennal surface or they are multiporous plate-like sensilla. Multiporous plate-like sensilla have not been found on the antennae of Geadephagans. A pit sensillum occurs on the antennae of one family, Gyrinidae, in the Hydradephaga whereas it is found on the antennae of several species from the families of Geadephaga. The sensilla on the terminal antennomere of Hydradephaga are often grouped into sensory fields that could be located on a particular area of the antennomere. Sensory fields are also located on the apices of the maxillary and labial palps and the most unique sensory fields occur in the Noteridae. The maxillary palpal apex of Hydrocanthus oblongus (Noteridae) is bifurcate and a sensory field with several types of sensilla is at the apex of each branch. The terminal labial palpomere is greatly enlarged and has a long, slender sensory field at the apex and a secondary sensory field on a thumb-like projection. The sensilla on the palpal apices are more diverse and complex in form as compared to the sensilla on the palps of Geadephaga. The most complex sensillum has a cuticular collar and a dome that is divided into six or seven triangular sections. The dome may be opened or closed and a peg-like sensillum with a very wide apical pore is situated beneath the dome.     

精密丝杠加工误差数学模型分析

分析了热变形和残余应力对精密丝杠加工误差的影响 ,建立了精密丝杠温度分布和热变形数学模型 ,提出了基于能量守恒定律、采用平均线膨胀系数的丝杠热变形简化计算方法。分析了磨削残余应力对精密丝杠尺寸变化的长期影响及计算方法。     

Effects of Blade Number on Characteristics of Centrifugal Pumps

The blade number of impeller is an important design parameter of pumps,which affects the characteristics of pump heavily.At present,the investigation focuses mostly on the performance characteristics of axis flow pumps,the influence of blade number on inner flow filed and characteristics of centrifugal pump has not been understood completely.Therefore,the methods of numerical simulation and experimental verification are used to investigate the effects of blade number on flow field and characteristics of a centrifugal pump.The model pump has a design specific speed of 92.7 and an impeller with 5 blades.The blade number is varied to 4,6,7 with the casing and other geometric parameters keep constant.The inner flow fields and characteristics of the centrifugal pumps with different blade number are simulated and predicted in non-cavitation and cavitation conditions by using commercial code FLUENT.The impellers with different blade number are made by using rapid prototyping,and their characteristics are tested in an open loop.The comparison between prediction values and experimental results indicates that the prediction results are satisfied.The maximum discrepancy of prediction results for head,efficiency and required net positive suction head are 4.83%,3.9% and 0.36 m,respectively.The flow analysis displays that blade number change has an important effect on the area of low pressure region behind the blade inlet and jet-wake structure in impellers.With the increase of blade number,the head of the model pumps increases too,the variable regulation of efficiency and cavitation characteristics are complicated,but there are optimum values of blade number for each one.The research results are helpful for hydraulic design of centrifugal pump.     

LQY-800压缩机的机体结构可靠性优化设计

对垃圾压缩机中所常用的LQY-800型压缩机的机体结构设计进行了研究.针对垃圾压缩机的工作特点,分析了机体设计要求;根据机体的受力特性对底板进行了相关的设计和计算;根据流体力学原理对机体倾斜方案进行了分析和相关计算;对机体的尺寸和结构强度进行了详细的设计和计算,以满足垃圾压缩机整体的可靠性要求.     

Dynamic characteristics analysis and vibration experiment of Upper-time of Flight Counter (U-ToFC)

The dynamic characteristic parameters of Up-time of Flight Counter (U-ToFC) are important for research of structure optimization and reliability. However, the current simulation is performed based on homogenous material and simplified constraint model, the correct and reliability of results are difficult to be guaranteed. The finite element method based on identification of material parameters is proposed for this investigation on dynamic analysis, simulation and vibration experiment of the U-ToFC. The structure of the U-ToFC is complicated. Its’ outside is made of aluminum alloy and inside contains electronic components such as capacitors, resistors, inductors, and integrated circuits. The accurate material parameters of model are identified difficultly. Hence, the parameters identification tests are performed to obtain the material parameters of this structure. On the basis of the above parameters, the experiment and FEA are conducted to the U-ToFC. In terms of the flight acceptance test level, and two kinds of joints condition between the U-ToFC and fixture are considered. The natural frequencies, vibration shapes and the response of the power spectral density of the U-ToFC are obtained. The results show simulation which is based on parameters identification is similar with vibration experiment in natural frequencies and responses. The errors are less than 10% . The vibration modes of simulation and experiment are consistent. The paper provides a more reliable computing method for the dynamic characteristic analysis of large complicated structure.     

Effect of transfer medium on wear rate of groove seals of centrifugal pumps

The effect of various liquids (oil, water) transferred by centrifugal pumps on the wear rate of their groove seals is studied and the findings are analyzed. The transfer medium was shown to significantly influence the wear rate. The liquid effect can be both positive and negative depending on the metal used to make the components of the groove seal. The wear of the groove seal is low if alloys based on copper are used. To the contrary, the wear increases if groove seals are made of steel, which may be due to the specific physicochemical processes.     

温度对电液伺服阀的影响分析

分析了环境温度对电液伺服阀滑阀零件尺寸以及配合间隙的影响,不同初始温度下阀内流场分布和温度分布。还分析了液压油的高低温特性,温度对永磁体、导磁体的影响。     

WMPS系统软件设计

基于西门子“WinCCV5．0”组态软件平台，设计开发了动态监控程序，在计算机上实现监控整个系统的设备运行状况，同时进行参数设定等功能。采用现场总线技术和共享内存方式成功地解决了设备间的通讯问题，介绍了上位机和下位机的软件编程的方法和技巧。     

CFD investigation of the influence of volute geometrical variations on hydrodynamic characteristics of circulator pump

Improper design of volute geometry can be the main cause that leads to unsteady pressure pulsation and radial force in pumps. Therefore, it is important to understand the influence of volute geometrical parameters on hydrodynamic characteristics of pump and the mechanism. However, the existing studies are limited to investigate the influence of only one or two volute geometrical parameters each time, and a systematic study of the influence of the combinations of different volute geometrical parameters on the pump’s hydrodynamic characteristics is missing. In this paper, a study on the understanding of the influence of volute geometrical variations on hydrodynamic characteristics of a high speed circulator pump by using computational fluid dynamics(CFD) technology is presented. Five main volute geometrical parametersD3,A8,a0,j0 andRt are selected and 25 different volute configurations are generated by using design of experiments(DOE) method. The 3D unsteady flow numerical simulations, which are based on the SSTk-w turbulence model and sliding mesh technique provided by CFX, are executed on the 25 different volute configurations. The hydraulic performance, pressure pulsation and unsteady radial force inside the pump at design condition are obtained and analyzed. It has been found that volute geometrical parametersD3 andA8 are major influence factors on hydrodynamic characteristics of the pump, whilea0,j0 andRt are minor influence factors. The minimum contribution from bothD3 andA8 is 58% on head, and maximum contribution from bothD3 and A8 is 90% on pressure pulsation. Regarding the pressure pulsation intensity, two peaks can be found. One is in the tongue area and the other is in the diffusor area. The contributions are around 60% from tongue and 25% from diffusor, respectively. The amplitude of pressure pulsation has a quadratic polynomial functional relationship with respect toD3/D2 andA8/A10, and fluctuating level of radial force has a quadratic polynomial functional relationship with respect toD3/D2. While for the other volute parametersa0,j0 andRt, no special function has been found related to pressure pulsation and radial force. The presented work could be a useful guideline in engineering practice when designing a circulator pump with low hydrodynamic force.     

一种BCH码编译码器的软件实现

BCH码是迄今为止所发现的一类很好的线形纠错码类。它的纠错能力很强，特别在短和中等码长下．其性能很接近于理论值，由于BCH码性能优良．结构简单，编译码设备也不太复杂，使得它在实际使用中受到工程技术人员的欢迎。本文根据BCH码的编译码原理介绍了一种BCH码——[15，7]码的编译码器的软件实现。该软件在VC 6．0的环境下编译完成．以文件的形式实现的．可以直接应用于PC机．因此在远程抄表，电力线通信等通讯方面都有应用参考价值。     

蛋形耐压壳设计与分析

基于蛋壳几何学特性,开展了蛋形耐压壳结构设计与性能分析。根据鹅蛋形状扫描、宏观尺寸统计试验,研究蛋壳圆度、体积、表面积及蛋形系数分布规律,建立体积方程、表面积方程及蛋形函数;设计了4 km水深蛋形耐压壳,并定量分析其安全性、储备浮力、空间利用率、水动力学特性等性能;采用正交试验,研究长轴、短轴、厚度对蛋形耐压壳性能影响规律。结果表明,鹅蛋壳为高度对称结构,其蛋形系数符合均值为0.69的正态分布;蛋形耐压壳具有良好的综合性能,其中厚度是影响强度的重要因素,长轴次之,短轴最小;长轴是影响屈曲的重要因素,厚度次之,短轴最小;厚度是影响浮力系数重要因素,短轴次之,长轴影响最小;长轴是影响空间利用率的重要因素,短轴次之,厚度影响最小;水动力学特性主要受短轴影响。     

表面横向波形点接触弹流动压性能的研究

物体的表面结构形态在有些场合下对润滑状况有重要的影响作用.本文研究了考虑表面粗糙度的点接触问题的特点,建立了点接触的分析模型和接触物体表面的横向波形数学模型,应用多网格重积分方法求解了在给定条件下其与时间相关的弹流动压性能的解.主要分析了表面横向波形的点接触的润滑性能,揭示了油膜压力、油膜厚度在油膜接触区上随参数变化的特征和规律.     

恒电位仪研究现状及基于恒电位仪的电化学检测系统的应用

介绍了恒电位仪的基本结构及其工作原理；分析了恒电位仪电位控制误差问题；从溶液电阻的角度阐述了恒电位仪的研究现状；简介了基于恒电位仪的电化学检测系统的应用；对恒电位仪的发展前景进行了展望。     

Morphological modelling of three‐phase microstructures of anode layers using SEM images

A general method is proposed to model 3D microstructures representative of three‐phases anode layers used in fuel cells. The models are based on SEM images of cells with varying morphologies. The materials are first characterized using three morphological measurements: (cross‐)covariances, granulometry and linear erosion. They are measured on segmented SEM images, for each of the three phases. Second, a generic model for three‐phases materials is proposed. The model is based on two independent underlying random sets which are otherwise arbitrary. The validity of this model is verified using the cross‐covariance functions of the various phases. In a third step, several types of Boolean random sets and plurigaussian models are considered for the unknown underlying random sets. Overall, good agreement is found between the SEM images and three‐phases models based on plurigaussian random sets, for all morphological measurements considered in the present work: covariances, granulometry and linear erosion. The spatial distribution and shapes of the phases produced by the plurigaussian model are visually very close to the real material. Furthermore, the proposed models require no numerical optimization and are straightforward to generate using the covariance functions measured on the SEM images.     

数控机床可靠性技术现状和研究进展

数控机床是装备制造业的工作母机,其可靠性技术目前已成为制约行业发展的关键共性技术。主要对我国数控机床可靠性技术的研究进展进行综合评述。论述数控机床的可靠性建模技术、故障分析技术、可靠性设计技术和可靠性试验技术的研究历程和技术进展,介绍数控机床关键功能部件可靠性台架试验设备的技术状况。在肯定数控机床可靠性技术取得明显进展的基础上,分析指出研究工作存在的问题和不足,并对数控机床可靠性技术研究的动态和热点进行论述。从产品可靠性技术自身的发展规律和行业需求的角度对数控机床可靠性的技术发展愿景进行了展望。     

On the wear resistance of high-speed steels

The wear resistance of cast and strained high-speed steels are evaluated and compared, and the regularities of variations in their structure and properties depending on the austenitizing temperature are described. The impact of modification on the wear resistance of tungsten-molybdenum high-speed steels has been studied. Data on the steels with improved wear resistance are reported     

Nondestructive Testing of Mechanical Properties of Rolled Steel (Review): 2. Testing of Ductile Properties

The results of the first studies that established a correlation between impact ductility and coercivity are considered in this review. The data of studies on the search for the factors that encourage or inhibit this correlation are analyzed. The methods based on estimation of the coercivity, which ensure increased reliability of nondestructive testing of rolled steel with a tendency toward brittle fracture, are discussed. The experimental data on nondestructive tests of impact ductility carried out using a sharp notch are analyzed.__________Translated from Defektoskopiya, Vol. 41, No. 5, 2005, pp. 53–76.Original Russian Text Copyright © 2005 by Bida.     

混合轴承柔性转子系统稳定性研究

用数值解方法分析了多腔混合轴承的动态特性。对于典型的毛细管节流４腔轴承计算了在各种设计参数下的线性化的刚度系数和阻尼系数,从而得到了轴承相应的刚度和稳定性速度阈值,指出了动压效应对这两者的负面影响。讨论了转子柔性对自激涡动的作用,提出了在设计转子混合轴承系统中实用的确定稳定性阈值的方法。