Machine tool settings for manufacture of cams with flat-face followers

A method has been developed for cam profile determination using conjugate surface theory and NC data generation for machine tools to machine cams with flat-face followers. The desired cutter location and the machine tool's form-shaping function are derived using a modified Denavit-Hartenberg notation. NC data equations are obtained by solving the machine tool's link variables through equation of its form-shaping function and the desired cutter location matrices. This methodology combines the activities of design and cam manufacturing, thus making the production process more flexible and automatic.     

从板造型工艺的优化选择

采用脱箱叠浇直浇道直接补缩工艺生产机车车辆从板铸钢件，产品的工艺出品率高，造型速度快，成本低，合格率高。从工装设计、工装制作、造型、合箱、熔炼、浇注、清砂到后期打磨交库，每个工序都体现出采用此工艺方案的优点。该方案的选择是我厂在铸造生产实践中工艺选用的一个亮点。对于铁路机车车辆配件生产中的效率提高和成本节约积累了一定的经验。     

Leader Followers多机器人编队控制方法

提出一种Leader-Followers多机器人编队控制方法。该方法利用距离-角度(l-φ)控制方案,仅利用跟随机器人(Followers)观测(Leader)领航机器人的纯角度信息,并利用无迹卡尔曼滤波算法对Leader-Followers多机器人系统的状态进行估计,根据状态估计结果设计了输入-输出反馈控制规律使得跟随机器人(Followers)准确跟踪(Leader)领航机器人,使多机器人快速形成编队,并确保了编队的稳定性,达到理想的编队控制效果。仿真验证了该方法的有效性。     

Graphite-like and Diamond-like Carbon Coatings with Exceptional Tribological Properties

THE PHYSICAL DEMANDS on engineeringcomponents are continually increasing whilstenvironmental controls on the use of lubricants becomemore and more restrictive.This has led to increasingdemand for high load bearing,solid lubricant coatingsthat enable engineered surfaces to rub against oneanother with reduced friction and wear.One of themost promising candidate coatings is diamond-likecarbon,DLC.However,the term DLC is used to describe a broadrange of carbon-based coatings that includes…     

对心直动滚子从动件盘形凸轮机构精确解与近似解的比较

分析和比较了对心直动滚子从动件盘形凸轮机构顶杆运动方程的近似解和精确解。推导了理想状态下对心直动滚子从动件盘形凸轮机构顶杆运动方程的精确表达式,使用Taylor级数将精确表达式展开,通过数值算例,获得了顶杆的位移、速度和加速度表达式的精确解和分别对应的一阶、二阶、三阶近似解。结果表明:只有当凸轮转动中心到圆盘中心的距离与圆盘半径加上滚子半径之和的比值较小时,对心直动滚子从动件盘形凸轮机构近似解才接近精确解;比值较大时,近似解和精确解的差别较大。     

Mechanical properties of heat treated high-strength microalloyed steels

An international seminar on problems of modern materials science held in April 1997 in Dnepropetrovsk was dedicated to the memory of Academician K. F. Starodubov. His ideas are now implemented by his students and followers. One of them is V. I. Bol'shakov, Doctor of Engineering, member of the International Engineering Academy, the Building Academy of Ukraine, and the Academy of Higher Education, Honored Scientist and Engineer of Ukraine, rector of the Dnieper State Academy of Building and Architecture, and well-known specialist in the physical metallurgy of structural steels. He celebrated his 50th anniversary in 1996. We present an article by V. I. Bol'shakov devoted to the effect of the final rolling temperature and the cooling conditions on the mechanical properties of heat-treated high-strength low-alloy steels. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 30–33, April, 1997.     

北京地区大气腐蚀及其与城市污染因素的灰色关联分析

利用灰色关联分析方法对北京地区大气腐蚀与污染物的关系进行了分析.将北京地区4个地点的A3钢、铜、铝1年和2年的大气腐蚀数据作为母函数序列，对应地点的6种污染因素在夏季及冬季的平均值作为子函数序列进行斜率关联度分析，得到污染物与北京大气腐蚀的关联顺序，与北京大气腐蚀关系最密切的污染物是夏季的SO2，其次为冬季的SO2以及冬季的微粉尘.      

Modelling of processes of thermochemical treatment of metals: traditions of Russian scientific school

Abstract

The paper is devoted to 100th anniversary of the outstanding Russian scientist professor Yuriy Mikhailovich Lakhtin – the founder of the world-famous scientific school of surface strengthening of metals and alloys. Lakhtin's scientific school is recognised for its contribution into research of processes of thermochemical treatment of metals and especially of nitriding. Today at the Department of Metal Science and Heat Treatment of MADI his followers continue the traditions of Lakhtin's scientific school. The development of technologies of surface engineering is based on complex modelling of physical processes realised by thermochemical treatment of metals. Thermodynamic models describe the interaction between metals and components of saturating atmosphere and predict phase composition of diffusion layer. Diffusion models of kinetics of saturation of metals allow us to calculate the rate of growth of diffusion layer and regulation of its depth and structure. Structural models determine quantitative dependence between parameters of structure (grain size, dispersed particles, etc.) and mechanical properties. These models allow us to estimate the level of strengthening by control of structural specifics of strengthened layer. On the basis of this complex of models, new efficient technologies of surface strengthening are developed.     

Effects of Leptothrix discophora on the potential behavior of stainless steel

Biofilm formation and electrochemical behavior of stainless steel have been studied in well water, in tap water and in water taken from fire extinguishing system. Some of the waters have been modified by adding manganese ions as well as in some cases acetate and yeast extract as a nutrient. Manganese oxidizing bacteria Leptothrix discophora has been used in these studies. To eliminate crevices in the specimen holder and to simulate reasonably well the conditions in fire‐extinguishing systems where the water is stagnant most of the time, a tape test arrangement with very slow flowing rate has been used in most of these studies. Also specimens with heat tint areas produced by heating inductively a small section of the specimen under flowing argon shielding gas were used in these studies. The results of these tape tests show that manganese oxidizing bacteria are able to increase the potential of both the base material (stainless steel UNS S30400) and of specimens with heat tint areas in well water, in tap water and in water taken from fire extinguishing system. Manganese oxidizing bacteria are also able to increase the cathodic reaction and thus enhance the initiation of corrosion. However, the increase of potential is not alone enough to start the corrosion. In these tests corrosion was initiated only in the specimens with heat tint areas in one of the waters taken from fire extinguishing system. No corrosion was detected in the specimens exposed to the well water or to the tap water used in these tests.     

Comparison of arc stability and variability of geometry of welds obtained by MIG/MAG and FCAW processes

Despite their similarity, the MIG/MAG and Tubular Electrode processes display particular features with regard to arc stability and variability in the characteristics of the beads. Thus, selection of one of these processes for a specific application will have to consider how these particular features affect the quality of the welds. To support this choice, the present study aimed to investigate how changing the average current affects the stability and regularity of metal transfer in welds carried out with constant voltage and pulsed current and compare the variability in the geometry and dilution of these welds. To achieve these aims, automatic welding was carried out, with steel ABNT 1020 as base metal and wire AWS ER70S-6 and AWS E71T-1 as filler metals. Besides the welds with variation in the average current, the tests involved determination of the parameters for occurrence of stable short circuiting, drop and pulsed transfer. The results showed that the voltage that gives the highest stability in short circuiting transfer is independent of the welding speed and increases with the wire speed, and also showed that welds made with hollow wire displayed greater variability compared to solid wire.     

The inhibitive effect of extraneous ion addition on stress corrosion cracking of alpha-brass

The addition of ammonium chloride, cobalt sulphate, cesium sulphate and ethylene diamine to a Mattsson solution and the addition of ammonium sulphate to the Pugh solution have been found to produce an inhibitive effect on the stress corrosion cracking of alpha-brass in these solutions. Ammonium chloride and ammonium sulphate additions affect the tarnish formation on the specimen as well as the cracking pattern. Electrochemical polarization studies have also been carried out with these two additives. The observations have been explained in the light of adsorption of these ionic species at selected sites on the metal surface and their possible interference with the cathodic reactions.     

Advancing the industrial aluminum process: 20th century breakthrough inventions and developments

In connection with the 125th anniversary of the Hall-Héroult process this year, we will review the most important progress that has been made in the twentieth century. What were the most significant improvements in this period, and which scientists and engineers came up with the ideas for these improvements? In this paper we will try to answer these questions. We will highlight the major technological breakthroughs and mention those people who played important roles in the development of these improvements.     

Nb-Ni-Ti体系氢分离合金膜的结构和渗氢性能研究

开展了Nb-Ni-Ti体系氢分离合金膜的结构和渗氢性能研究。采用XRD、SEM分析膜片的相结构和组织特征,利用Devanathan-Stachurski双电解池法测定膜片的氢扩散系数,考察膜片厚度、成分和结构组织对其氢扩散系数的影响。实验结果表明:氢分离膜的氢扩散系数均随膜片厚度的增加而增大。制备的Nb-Ni-Ti体系合金膜都具有两相结构,即先析出相(bcc-Nb(Ni,Ti)固溶体)和共晶相(bcc-Nb(Ni,Ti)+β2-NiTi),个别成分点有少量的第三相NiTi2生成。膜片成分和组织结构对氢扩散系数影响显著,当合金中先析出固溶体相比例增加时,合金中的氢扩散系数也随着增大,而Ni,Ti含量的变化引起共晶相变化,NiTi相及NiTi2相都不同程度增加了共晶相的相比例而引起氢扩散系数的降低,但同时在结构上改善了合金在吸氢膨胀过程中发生的氢脆现象。氢在Nb-Ni-Ti体系氢分离膜中的扩散系数在10-9数量级范围。     

Scattering and its role in radiography simulations

The last decade has witnessed a proliferation of various radiography simulation codes. Most of these codes emphasize on a good geometrical representation of the test object. Simulated image formation is another point emphasized by these simulators. Most of the simulators use a variety of ways to generate primary beam photon energy spectrum. Apart from these common points, the simulation codes address photon object interactions with different sophistication levels. There has not been much discussion on what constitutes adequate level of physics used in these simulators. This paper provides a brief survey of these radiography efforts and discusses approaches adapted by various simulation efforts. Along with the survey of the simulation efforts, it provides an algorithm for computing scattered photon flux and shows impact of various parameters, assumptions and approximations.     

非甾体类抗炎药与心血管疾病的研究进展

非甾体类抗炎药(NSAIDs) 是当今广泛应用的一类药物。目前许多证据表明选择性的环氧化酶-2(COX-2) 抑制剂具有不良心血管作用, 包括增加心肌梗死、中风、心衰和高血压的危险, 对有心血管病史或高心血管疾病危险者上述不良作用可能最为明显。对上述病人, 仅在没有可替代的药物时使用COX-2 抑制剂, 并使用最小的剂量和必需的最短的时间。普通的非选择性的环氧化酶(COX) 抑制剂其心血管安全性也有待更多的证据。因此, 使用NSAIDs 时要注意权衡利弊。     

Rendering wrought aluminium alloys castable by means of minimum composition adjustments

Wrought alloys have low fluidity and are prone to hot tearing, which make them difficult to cast. The presence of eutectic-forming elements in the alloy composition lessens these effects. For this reason, the constituents of casting alloys tend to include a eutectic portion. Typically, silicon is added to aluminium alloys to provide casting ability by forming the aluminium–silicon eutectic. However, the presence of silicon in aluminium alloys is associated with a number of issues that do not allow these alloys to reach their full potential. In this publication we report results of our investigation of three alternative eutectics: Al–6.1Ni, Al–1.8Fe, and Al–1.75Fe–1.25Ni. Our results indicate that these eutectics have satisfactory fluidity and resistance to hot tearing and higher strength than the aluminium–silicon eutectic. We also found that introducing these eutectic compositions into 7075 wrought alloy results in a castable composition with yield strength comparable to that of the wrought alloy.     

Atomistic simulation of stacking faults in cementite: Planes containing vector [100]

The method of molecular dynamics (MD) has been used to study γ surfaces in crystallographic planes of cementite containing Burgers vector [100]. Displacement vectors that correspond to stable stacking faults (SFs) and the energies of these SFs have been determined. The energies of unstable SFs, which characterize the tendency of the material toward plastic relaxation, have been estimated. It has been established that, in all these planes except for (013), the dislocations with the Burgers vector [100] are not split. Planes have been found that are most suitable for the slip of these dislocations. The opportunity of the propagation of stacking faults in these planes is discussed; reactions of the splitting of perfect dislocations with the Burgers vector [100] in the plane (013) have been suggested.     

Electrochemical investigation of rolled-in subsurface layers in commercially pure aluminium alloys with the micro-capillary cell technique

Rolling alters the surface properties of aluminium alloys and introduces disturbed oxide-rich subsurface layers. The presence of these layers alters the electrochemical characteristics of the aluminium surface and has an influence on its corrosion behaviour.In order to reach a better understanding of these rolled-in layers, the electrochemical behaviour of areas in the (sub)surface with and without these layers was characterised with a local electrochemical technique: the micro-capillary cell. The effect of these layers on pit initiation in a chloride containing environment was investigated by performing potentiodynamic polarisation measurements over areas including and excluding rolled-in layers and deriving the respective local breakdown potentials. GDOES was used as sample preparation method, which enabled us to compare the electrochemical behaviour at depths of 0.5 μm and 10 μm to the as-received surface. SEM/EDX + BEI was used to characterise the surface before and after the micro-electrochemical measurements. Differences in breakdown potential, as well as differences in local attack have been observed for regions including and excluding rolled-in oxides. It was concluded that areas containing rolled-in oxides exhibit lower breakdown potentials, thus indicating these areas to be more susceptible to localised attack.     

Corrosion control of steel in HCl solutions by cyanoacetamide derivatives

The corrosion inhibition of C-steel in 1 M HCl solution by cyanoacetamide derivatives was investigated using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) techniques. The results obtained from these techniques show that, the inhibition efficiency of these inhibitors increased with increase in inhibitor concentration but deceased with rise in temperature. Adsorption of these derivatives follows the Temkin adsorption isotherm. The polarization measurement showed that these inhibitors are acting as mixed-type inhibitors for both anodic and cathodic reactions. Some activated thermodynamic parameters were computed and discussed. The results obtained from the four different techniques were in good agreement. Quantum structure-activity relationships have been used to study the effect of molecular structure on inhibition efficiency of the inhibitors.     

咪唑啉缓蚀剂的合成与缓蚀性能研究

利用环烷酸及二乙烯三胺料合成咪唑啉缓蚀剂,合成产品可按沸程分为5个组分,利用红外光谱分析对产品的结构作了定性分析,并通过失重实验和自制的局部腐蚀模拟探头对合成咪唑啉的缓蚀性能进行了表征,结果表明这5个组分都具有咪唑啉环结构,且均具有良好的缓蚀性能,当使用量为5／10^6时,对Q235钢在酸性介质中的缓蚀效率最高可达93．81％,此外由于高沸点组分的分子结构中疏水基团较大,缓蚀效率也较高,实验结果还表明该产品对局部腐蚀亦有很好的缓蚀作用。