机械类毕业论文外文翻译

中国地质大学长城学院本科毕业论文外文资料翻译系别：工程技术系专业：机械设计制造及其自动化姓名：刘萌萌学号： 502083262012 年 3 月 1 日外文资料翻译译文粉状的石英即受自然风化的平均微粒大小为10.4um的石英一起在行星球磨机中被磨。

经测试，在干磨及湿磨的状态下，不一样的粒度分布、特性表面面积、晶体结构、表面无定形和热特性是与被磨时间成反比的。

结果显示，干磨能导致晶体结构的无序、表面无定形和表面活力的增强同时其微粒大小跟着磨碎进度而降低，而湿的磨碎永久的降低了在这台行星球磨机中的石英粉的磨碎极限。

粉状的石英是一种在自然界被风化的硅酸盐矿物粉末，该粉末已经在广东，江西和中国的其他省中被发现。

它由于有较高的纯度，目前已经被用于橡皮，塑料性物质，复合材料如一种填隙料的材料和涂料。

但是在这些应用较小的粒度和比较高的表面化学的活度有时是必要的。

因此，自然的被风化的粉状石英的干的或更干的磨碎被认为是重要的加工阶段之一。

众所周知，干的磨碎不仅仅引起颗粒的破坏而且还有机械化学作用。

前面的因素符合多样性的颗粒大小的分布和特性的变化比表面面积。

后者以多种多样的晶体结构的形式出现，比如，制做格子变形和铸疵，无形状，组自由基，自由表面能的增强，电子的放射，等离子体的外表等等。

以上的这些变化增强了这种地表材料的活力程度和其的反应度。

但是对自然被风化的粉末的石英的试验，即关于它在干的磨碎下的机械化学作用，没有被记录。

因此，这个实验在干的磨碎下的机械化学作用的结果对粉末石英的加工和利用是十分必要的。

粉状的石英试样在一个行星的球磨机中被磨。

质点尺寸的分布, 特性的比表面的面积, 晶体构造，表面无定形等等的变化,在干的轮磨和湿的轮磨中被测试与磨碎的时间成反比。

从这些数据，干的磨碎的机械装置和其对粉末的机械化学作用被认为与不同的磨碎条件有联系。

一个实验室以回转速度400个转/每分钟 ( XPW-100 X 4)依比例决定行星的球磨机。

毕业设计(论文)外文翻译学生姓名：系别：机械工程系专业：机械设计制造及其自动化班级：学号:译文出处：Science and Technology Engl-ish for Mechanical EngineeringCasting、Forging and Welding1. CastingMetal casting is one of the oldest of all industries, both ancient and medieval history offering examples of the manufacture and use of casting. From simple axeheads poured from copper in open moulds some 5000 years age, casting in the pre-Christian world developed to a point at which elaborate bronze statuary could be produced in two-piece and cored moulds. By the end of the medieval period, decorated bronze and pewter casting had begun to be used in European church and domestic life.The widespread adoption of cast iron as engineering material awaited the success of Abraham Darby in 1790 in smelting in the coke blast furnace; this paved the way for the massive use of cast iron in construction during the years following the industrial revolution.Many foundries sprang up after the industrial revolution, the vast majority being for the manufacture of the cast iron then being used as a structural material. The quantity production of iron castings in the nineteenth century was not matched by a universal advance in quality and the engineering use of the products encountered more serious risks in a non-ductile material.Despite the skill of the molder in producing complex forms, there was little change in the metallurgical and engineering situation until the modern era brought a better understanding of the factors determining quality. With modern techniques of process control the rudimentary judgment of the operator could give way to objective measurements of metal temperature, molding material properties and other production variables. These improvements have been applied not only to cast iron but to a wide range of cast alloys.There are four basic casting methods: sand-casting, die-casting, investment-casting, and centrifugal casting.Sand-casting is the most widely used method employed in foundry. In this process, sand moulds are contained in metal molding boxes that have four sides but no top or bottom. During the molding operation the boxes are located togetherby pins so that they can be separated to remove the pattern, and replaced in the correct position before the metal is poured in. The boxes are clamped together, or the cope (top section) weighted down when pouring to prevent the cope from “floating away”from the drag (lower section) when the mould is full of molten metal. The sequence when molding the simple two-part mould to cast a bracket is illustrated as follows.At the first stage the pattern is seated on the moulding board. The pattern is covered with facing sand, which is a specially prepared sand of good quality, which can take a clean and smooth impression, and can resist the heat from the molten metal that will be in contact with it. The facing sand is backed up with molding sand, which is old facing sand from previous moulds. The molding sand is carefully rammed up so that it is fairly tight around the pattern to produce a good solid mould, yet permeable enough to allow the gases produced during casting to escape. The sand is finally leveled off.At the second stage the mould with the pattern still in position is inverted; the exposed sand lightly covered with parting sand, and the exposed pattern with facing sand.(The parting sand has no cohesion, and is introduced to permit a clean separation when the mould is opened up to remove the pattern .) The second molding box is located in position on the first box and filled with molding sand. Two or more plugs are introduced when the second box is being filled (these are removed later, leaving channels in the sand). One of these plugs is positioned to one side of the pattern. The sand is rammed up and leveled off.Now, at stage 3, to allow the pattern to be removed. This is done by screwing a bar with a threaded end into a suitable insert in the pattern, damping the sand around the pattern, and gently rapping the bar in all directions so that the pattern can be carefully withdrawn. To facilitate the removal of the pattern without scuffing the sides of the impression, all surfaces that lie in the direction of pattern removal are inclined slightly by a small amount (the draw angle).A groove called a gate is cut in the sand face to allow the channel producedby the plug that is outside the pattern to connect with the impression .The metal is poured through this channel (called the runner), and the gate prevents it from dropping straight into the impression and damaging it .The cross-section of the gate is slightly smaller than that of channel so that a full runner will always supply metal to the gate at a slight pressure.Finally, the mould is reassembled, carefully locating and securing the two sections. The top section is known as the cope, and the lower section is known as the drag. The sand in the cope is vented. These vents allow the sand to be rammed up more tightly at the earlier stages without the risk of gases being trapped in the molten metal and forming blowholes in the solid metal. A sand-feeding gate (also called a pouring or bowl) is added to make it easier to pour the metal into the runner. The molten metal is poured through the runner and the air will escape through the riser.The impression will be filled with molten metal when it is completely filled. Gases can escape through the runner and the riser, which also act as headers to supply the impression with more metal to compensate for the contraction of the metal when cooling in the molten state.2. ForgingForging is the plastic working of metal by means of localized compressive forces exerted by manual or power hammers, presses, or special forging machines. It may be done either hot or cold. however, when it is done cold, special names usually are given to the processes. Consequently, the terms“forging” usually implies hot forging done above the recrystallization temperature.Modern forging is a development form the ancient art practiced by the armor makers and the immortalized village blacksmith. High-powered hammers and mechanical presses have replaced the strong arm, the hammer, and the anvil and modern metallurgical knowledge supplements the art skill of the craftsman in controlling the heating and handling of the metal.Forge ability is the term used in the industry to denote a material relative resistance to deformation and its plasticity. While considerable disagreementexists as to precisely what characteristics the word “forge ability” should include, the term as used here is defined as the tolerance of a metal or alloy for deformation without failure, regardless of forging pressure requirements.Raw material used for forging is generally bar or billet stock hot rolled from ingots melted in open-hearth, electric arc, or vacuum arc furnace .other forms and shapes such as rolled slabs, plats, and stock produced by continuous casting techniques are occasionally used .for certain grades ,vacuum arc melting imparts better forge ability than does conventional arc melting . However, the major purpose of vacuum melting is the improvement of mechanical properties and cleanliness, not forging behavior.Equipment behavior influences the forging progress since it determines the feasibility of forging a part and affects the rate of deformation and the temperature conditions.The hammer is the most economical type of equipment for generating load and energy necessary to carry out a forging process, provided that the material being forged can support high deformation velocities. It is most commonly used hot forging equipment for repeated blows on the same workpiece and cannot be overloaded.There are various types of hammers: air-lift gravity drop hammers, power drop hammers, power drop hammers, Counterblow hammers ect. In a simple gravity drop hammer the upper ram is positively connected to a board, a belt, a chain or a piston. When forging the ram is lifted to a certain height and then dropped on the stock placed on the anvil. During the down stroke, the rain is accelerated by gravity and builds up the blow energy. The upstroke takes place immediately after the blow, the force necessary to ensure quick lift-up of the ram can be 3 to 5 times the ram weight. The operation principle of a power-drop hammer is similar to that of an air drop hammer. During the down stroke, in addition to gravity, the ram is accelerated by steam, cold air or hot air pressure. In an electro hydraulic gravity-drop hammer, the ram is lifted with oil pressure against an air cushion. The compressed air slows down the upstroke of the ram and contributes to its acceleration during the down stroke .thus; the electrohydraulic hammer also has a minor power hammer action.Press forging employs a slow squeezing action in deforming the plastic metal, as contrasted with the rapid-impact blows of a hammer. Hydraulic forging press is operated by large pistons driven by high-pressure hydraulic or hydrometric system. The squeezing action is carried completely to the center of the part being pressed, thoroughly working the entire section. These presses are the vertical type and may be either mechanically or hydraulically operated. The mechanical presses, which are faster operating and most commonly used, range in capacity from 5000 to 10000 tons.In the forging press a grater proportion of the total work put into the machine is transmitted to the metal than in a drop hammer. The machine and foundation absorb much of the impact of the drop hammer .press reduction of the metal is faster, and the cost of operation is consequently lower. most press forging s are symmetrical in shape ,having surfaces, which are quite smooth, and provide a closer tolerance than is obtained by a drop hammer .however ,drop forging can forge many parts of irregular and complicated shapes more economically. Forging presses are often used for sizing operations on parts made by other forging processes.For small forgings closed impression dies are used, and only one stroke of the ram is normally require to perform the forging operation .the maximum pressure is built up at the end of the stroke ,which forces the metal into shape .dies may be mounted as separate units, or all the cavities may be put into a single block. for small forgings individuals die units are more convenient .large ingots are now almost always forged with hydraulic presses instead of with steam hammers, since the work done by a press goes deeper. Further, the press can take a cooler ingot and can work to closer dimensions.The forging should be done at about the same temperature as rolling; the process improves the physical properties of the steel just as rolling does. In the final forging it is important not to have the steel too hot, for overheated steel will have poor mechanical properties when cooled. in heating for forging the temperature is usually judged by the eye, but where a large number of thesame patterns will be made, the pieces to be forged are heated in furnaces in which the temperature is indicated by pyrometers, and often is automatically controlled.3. weldingWelding techniques have become so versatile that it is difficult nowadays to define “welding”. Formerly welding was “the joining of metals by fusion”, that is, by melting, but this definition will no longer do. Welding was next defined as the “joining of metals by heat”, but this is not a proper definition either. Not only metals can be welded, so can many of the plastics. Furthermore several welding methods do not require heat. Every machinist is familiar with heatless welding method under some circumstances. Besides these, we can weld with sound and even with the famous laser. Faced with a diversity of welding methods that increase year by year, we must here adopt the following definition of welding:" welding is the joining of metals and plastics by methods that do not employ fastening devices”.There is also no uniform method of naming welding processes. Some processes are named according to the heat source or shielding method, other certain specialized processes are named after the type of joint produced. Examples are spot and butt welding. But an overall classification can not take account of this because the same type of joint may be produced by a variety of processes. Spot welding may be done by electric resistance, arc, or electron-beam processes and butt welding by resistance, flash or any of a number of other methods. Many welding processes are named depending on the heat applied, equipment used, and type of metal to be joined and the strength of the joint.Soldering is the process of joining two metals by a third metal to be applied in the molten state. Solder consists of tin and lead, while bismuth and cadmium are often included to lower the melting point. One of the important operations in soldering is that of cleaning the surface to be joined, this may be done by some acid cleaner. Soldering gives a satisfactory joint for light articles ofsteel, copper or brass, but the strength of soldering joint is rather less than a joint which is brazed, riveted or welded. These methods of metal are normally adopted for strong permanent joints.Pressure welding is known as the simplest method of welding two pieces of metal together. The ends of metal are heated to a while heat—for iron, the welding temperature should be about 1300℃—in a flame. At this temperature the metal becomes plastics. The ends are then presses or hammered together, and the joint is smoothed off. Care must be taken to ensure that the surfaces are thoroughly clean first, for dirt will weaken the weld. Moreover, the heating of iron or steel to a high temperature causes oxidation, and a film of oxide is formed on the heated surfaces. For this reasons, a flux is applied to the heated metal. At welding heat, the flux melts, and the oxide Particles are dissolved in it together with any other impurities which may be present. The metal surfaces are pressed together, and the flux is squeezed out from the center of the weld.Gas welding includes all the processes in which gases are used to obtain a hot flame. Those commonly used are acetylene, natural gas, and hydrogen in combination with oxygen. The maximum temperature developed by oxyhydrogen welding is 3600℉ (1980℃). Hydrogen is produced either by the electrolysis of water or by passing steam over coke. An oxyacetylene weld is produced by heating with a flame obtained from the combustion of oxygen and with or without the use of a filler metal. In most cases the joint is heated to a state of fusion, and as a rule, no pressure is used.Are welding is a process in which coalescence is obtained by heat produced from an electric arc. The electrode or filler metal is heated to a liquid state and deposited into the joint to make the weld. Contact is first made between the electrode and the work to create an electric circuit, and then, by separating the conductors, an arc is formed. The electric energy is converted into intense heat in the arc, which attains a temperature around 10 000°F (5500℃). Either direct or alternating current can be used for arc welding, direct current being preferred for most purposes. A d-c welder is simply a motor-generator set ofconstant-energy type, having the necessary characteristics to produce a stable arc. Arc welding uses commonly metal electrodes or carbon electrodes.Laser Welding is used because of laser’s high heat intensity. It can be operated in any transparent medium without contact with the workpiece, since the laser delivers its energy in the form of light. In welding, the power is delivered in pulses rather than as a continuous beam, the beam is focused on the workpiece and the intense heat produces a fusion weld. Laser welding is slow and is used only for special jobs involving small weldments. Its greatest use is found in the electronics industry.Explosion welding is a process that uses energy from the detonation of an explosive to join two pieces of metal. The explosion accelerates the pieces to a speed at which a metallic bond will form between them when they collide. The weld is produced in a fraction of a second without the addition of filler metal. This is essentially a room temperature process in that gross heating of the workpieces does not occur. The faying surfaces, however, are heated to some extent by the energy of the collision, and welding is accomplished through plastic flow of the metal on those surfaces. Welding takes place progressively as the explosion and the forces it creates advance from one end of the joint to the other. Deformation of the weldment varies with the type of joint. There may be no noticeable deformation at all in some weldments, and there is no loss of metal.译文：铸造、锻造和焊接1.铸造金属铸造是最古老的产业之一，远古时期和中世纪就有人使用和制造铸件了。

毕业设计(论文)外文资料翻译学院：机械电子工程学院专业：机械设计制造及其自动化姓名：孙明明学号： 070501504外文出处： The advantages of PLC control,filed under PLC Articles附件： 1.外文资料翻译译文；2.外文原文。

(用外文写)附件1：外文资料翻译译文PLC的控制优势任何控制系统从概念到进入工厂工作都要经历四个阶段。

PLC系统在每一个阶段都有优势。

第一阶段是设计，对工厂的需要进行研究和制定控制策略，传统的运行平台的设计和制造必须在设计进行前完成。

PLC系统仅仅需要的是一个模糊的关于机器的可能大小的想法和I/O数量的要求（多少输入和输出接口）。

在这个阶段输入和输出芯片十分便宜，所以可以内置一个很健全的备用容量，它允许用来补充遗漏项目和为未来的扩充做准备。

其次是设计。

传统的方案是，每一项工作都是“一次成型”这不可避免的造成了工程拖延和增加成本。

一个的PLC系统使用最简单的标准件螺栓连接在一起。

在这样的连接下开始编写 PLC程序（或者至少是写入详细的程序规范）。

下一阶段是安装，安装是一种繁琐和昂贵的工作，例如安装传感器、执行器、限制开关系统和主机的连接。

分布式PLC系统使用串行链路式的预编译，测试界面可以简化安装它带来了巨大的成本优势。

PLC的程序多数在这个阶段完成。

最后是调试，而这正是PLC真正的优势被发掘的部分。

没有任何设备在第一次就正常工作。

人性就是这样，总会有一些疏漏。

与传统的系统变动情况的耗时和昂贵相比，PLC的设计师提供了系的内置备用内存容量、备用I/O和一些备用多芯电缆线，多数的变动能迅速和相对便宜的完成。

另外一个好处是，所有的变化PLC都有记录，程序的调试和修改不会因为没有被记录而遗失，这是一个经常发生在常规系统中的问题。

还有一个额外的第五阶段，维护，一旦启动工作，并移交生产就产生了维护的问题。

所有设备都有缺点，大多数设备在错误的模式中度过了它们的大部分的时间。

Frictionally excited thermoelastic instability in disc brakes—Transientproblem in the full contact regimeAbstractExceeding the critical sliding velocity in disc brakes can cause unwanted forming of hot spots, non-uniform distribution of contact pressure, vibration, and also, in many cases, permanent damage of the disc. Consequently, in the last decade, a great deal of consideration has been given to modeling methods of thermo elastic instability (TEI), which leads to these effects. Models based on the finite element method are also being developed in addition to the analytical approach. The analytical model of TEI development described in the paper by Lee and Barber [Frictionally excited thermo elastic instability in automotive disk brakes. ASME Journal of Tribology 1993;115:607–14] has been expanded in the presented work. Specific attention was given to the modification of their model, to catch the fact that the arc length of pads is less than the circumference of the disc, and to the development of temperature perturbation amplitude in the early stage of breaking, when pads are in the full contact with the disc. A way is proposed how to take into account both of the initial non-flatness of the disc friction surface and change of the perturbation shape inside the disc in the course of braking.Keywords: Thermo elastic instability; TEI; Disc brake; Hot spots1. IntroductionFormation of hot spots as well as non-uniform distribution of the contact pressure is an unwanted effect emerging in disc brakes in the course of braking or during engagement of a transmission clutch. If the sliding velocity is high enough, this effect can become unstable and can result in disc material damage, frictional vibration, wear, etc. Therefore, a lot of experimental effort is being spent to understand better this effect (cf. Refs.) or to model it in the most feasible fashion. Barber described the thermo elastic instability (TEI)as the cause of the phenomenon. Later Dow and Burton and Burton et al.introduced a mathematical model to establish critical sliding velocity for instability, where two thermo elastic half-planes are considered in contact along their common interface. It is in a work by Lee and Barber that the effect of the thickness was considered and that a model applicable for disc brakes was proposed. Lee and Barber’s model is made up with a metallic layer sliding between twohalf-planes of frictional material. Only recently a parametric analysis of TEI in disc brakes was made or TEI in multi-disc clutches and brakes was modeled. The evolution of hot spots amplitudes has been addressed in Refs. Using analytical approach or the effect of intermittent contact was considered. Finally, the finite element method was also applied to render the onset of TEI (see Ref.).The analysis of nonlinear transient behavior in the mode, when separated contact regions occur, is even accomplished in Ref. As in the case of other engineering problems of instability, it turns out that a more accurate prediction by mathematical modeling is often questionable. This is mainly imparted by neglecting various imperfections and random fluctuations or by the impossibility to describe all possible influences appropriately. Therefore, some effort aroused to interpret results of certain experiments in addition to classical TEI (see, e.g.Ref).This paper is related to the work by Lee and Barber [7].Using an analytical approach, it treats the inception of TEI and the development of hot spots during the full contact regime in the disc brakes. The model proposed in Section 2 enables to cover finite thickness of both friction pads and the ribbed portion of the disc. Section 3 is devoted to the problems of modeling of partial disc surface contact with the pads. Section 4 introduces the term of ‘‘thermal capacity of perturbation’’ emphasizing its association with the value of growth rate, or the sliding velocity magnitude. An analysis of the disc friction surfaces non-flatness and its influence on initial amplitude of perturbations is put forward in the Section 5. Finally, the Section 6 offers a model of temperature perturbation development initiated by the mentioned initial discnon-flatness in the course of braking. The model being in use here comes from a differential equation that covers the variation of the‘‘thermal capacity’’ during the full contact regime of the braking.2. Elaboration of Lee and Barber modelThe brake disc is represented by three layers. The middle one of thickness 2a3 stands for the ribbed portion of the disc with full sidewalls of thickness a2 connected to it. The pads are represented by layers of thickness a1, which are immovable and pressed to each other by a uniform pressure p. The brake disc slips in between these pads at a constant velocity V.We will investigate the conditions under which a spatially sinusoidal perturbation in the temperature and stress fields can grow exponentially with respect to the time in a similar manner to that adopted by Lee and Barber. It is evidenced in their work [7] that it is sufficient to handle only the antisymmetric problem. The perturbations that are symmetric with respect to the midplane of the disc can grow at a velocity well above the sliding velocity V thus being made uninteresting.Let us introduce a coordinate system （x1; y1）fixed to one of the pads (see Fig. 1) thepoints of contact surface between the pad and disc having y1 = 0. Furthermore, let acoordinate system （x2; y2）be fixed to the disc with y2=0 for the points of the midplane. We suppose the perturbation to have a relative velocity ci with respect to the layer i, and the coordinate system （x; y）to move together with the perturbated field. Then we can writeV = c1 -c2; c2 = c3; x = x1 -c1t = x2 -c2t,x2 = x3; y = y2 =y3 =y1 + a2 + a3.We will search the perturbation of the uniform temperature field in the formand the perturbation of the contact pressure in the formwhere t is the time, b denotes a growth rate, subscript I refers to a layer in the model, and j =-1½is the imaginary unit. The parameter m=m（n）=2pin/cir =2pi/L, where n is the number of hot spots on the circumference of the disc cir and L is wavelength of perturbations. The symbols T0m and p0m in the above formulae denote the amplitudes of initial non-uniformities (e.g. fluctuations). Both perturbations (2) and (3) will be searched as complex functions their real part describing the actual perturbation of temperature or pressure field.Obviously, if the growth rate b<0, the initial fluctuations are damped. On the other hand, instability develops ifB〉0.2.1. Temperature field perturbationHeat flux in the direction of the x-axis is zero when the ribbed portion of the disc is considered. Next, let us denote ki = Ki/Qicpi coefficient of the layer i temperature diffusion. Parameters Ki, Qi, cpi are, respectively, the thermal conductivity, density and specific heat of the material for i =1,2. They have been re-calculated to the entire volume of the layer (i = 3) when the ribbed portion of the disc is considered. The perturbation of the temperature field is the solution of the equationsWith and it will meet the following conditions:1，The layers 1 and 2 will have the same temperature at the contact surface2，The layers 2 and 3 will reach the same temperature and the same heat flux in the direction y,3，Antisymmetric condition at the midplaneThe perturbations will be zero at the external surface of a friction pad(If, instead, zero heat flux through external surface has been specified, we obtain practically identical numerical solution for current pads).If we write the temperature development in individual layers in a suitable formwe obtainwhereand2.2. Thermo elastic stresses and displacementsFor the sake of simplicity, let us consider the ribbed portion of the disc to be isotropic environment with corrected modulus of elasticity though, actually, the stiffness of this layer in the direction x differs from that in the direction y. Such simplification is, however, admissible as the yielding central layer 3 practically does not take effect on the disc flexural rigidity unlike full sidewalls (layer 2). Given a thermal field perturbation, we can express the stress state and displacements caused by this perturbation for any layer. The thermo elastic problem can be solved by superimposing a particular solution on the general isothermal solution. We look for the particular solution of a layer in form of a strain potential. The general isothermal solution is given by means of the harmonic potentials after Green and Zerna (see Ref.[18]) and contains four coefficients A, B, C, D for every layer. The relateddisplacement and stress field components are written out in the Appendix A.在全接触条件下，盘式制动器摩擦激发瞬态热弹性不稳定的研究摘要超过临界滑动盘式制动器速度可能会导致形成局部过热，不统一的接触压力，振动分布，而且，在多数情况下，会造成盘式制动闸永久性损坏。

机械类英语作文模板英文回答：Introduction。

Mechanical engineering is an incredibly vast anddiverse field that encompasses the design, development, and operation of machines. It is a highly interdisciplinaryfield that draws upon principles from physics, mathematics, and materials science to create solutions to real-world problems. Mechanical engineers play a vital role in many industries, including transportation, manufacturing, energy, and healthcare.Education and Training。

To become a mechanical engineer, a strong foundation in mathematics and science is essential. Most mechanical engineers hold a bachelor's degree in mechanicalengineering from an accredited university. Some may alsochoose to pursue a master's degree or doctorate in mechanical engineering or a related field.Career Opportunities。

Mechanical engineers are in high demand across a wide range of industries. Some of the most common job titles for mechanical engineers include:Design Engineer。

附录一英文科技文献翻译英文原文：Experimental investigation of laser surface textured parallel thrustbearingsPerformance enhancements by laser surface texturing (LST) of parallel-thrust bearings is experimentally investigated. Testresults are compared with a theoretical model and good correlation is found over the relevant operating conditions. A compari-son of the performance of unidirectional and bi-directional partial-LST bearings with that of a baseline, untextured bearing ispresented showing the benefits of LST in terms of increased clearance and reduced friction.KEY WORDS: fluid film bearings, slider bearings, surface texturing1. IntroductionThe classical theory of hydrodynamic lubricationyields linear (Couette) velocity distribution with zeropressure gradients between smooth parallel surfacesunder steady-state sliding. This results in an unstablehydrodynamic film that would collapse under anyexternal force acting normal to the surfaces. However,experience shows that stable lubricating films candevelop between parallel sliding surfaces, generally because of some mechanism that relaxes one or moreof the assumptions of the classical theory.A stable fluid film with sufficient load-carryingcapacity in parallel sliding surfacescan be obtained,for example, with macro or micro surface structure ofdifferent types. These include waviness [1] and protruding microasperities [2–4]. A good literature review onthe subject can be found in Ref. [5]. More recently,laser surface texturing (LST) [6–8], as well as inletroughening by longitudinal or transverse grooves [9]were suggested to provide load capacity in parallelsliding. The inlet roughness concept of Tonder [9] isbased on ……effective clearance‟‟ reduction in the s lidingdirection and in this respect it is identical to the par-tial-LST concept described in ref.[10] for generatinghydrostatic effect in high-pressure mechanical seals.Very recently Wang et al. [11] demonstrated experimentally a doubling of the load-carrying capacity forthe surface- texture design by reactive ion etching ofSiC parallel-thrust bearings sliding in water. Thesesimple parallel thrust bearings are usually found inseal-less pumps where the pumped fluid is used as thelubricant for the bearings. Due to the parallel slidingtheir performance is poorer than more sophisticatedtapered or stepped bearings. Brizmer et al. [12] demon-stratedthepotential of laser surface texturing in theform of regular micro-dimples for providing load-carrying capacity with parallel-thrust bearings. A model of a textured parallel slider was developed and the effect of surface texturing on load-carrying capacitywas analyzed. The optimum parameters of the dimples were found in order to obtain maximum load-carrying capacity. A micro-dimple ……collective effect‟‟ was identi-fied that is capable of generating substantial load-carrying capacity, approaching that of optimumconventional thrust bearings. The purpose of the present paper is to investigate experimentally the validity of the model described in Ref. [12] by testing practical thrust bearings and comparing the performance of LST bearings with that of the theoretical predictions and with the performance of standard non-textured bearings2. BackgroundA cross section of the basic model that was analyzedin Ref. [12] is shown in figure1. A slider having awidth B is partially textured over a portion Bp =αB ofits width.The textured surface consists of multipledimples with a diameter，depth and area densitySp. As a result of the hydrodynamic pressure generatedby the dimples thesliding surfaces will be separated bya clearance depending on the sliding velocity U, thefluid viscosity l and the external load It was foundin Ref. [12] that an optimum ratio exists for the parameter that provides maximum dimensionlessload-carrying capacity where L isthe bearing length, and this optimum value is hp=1.25. It was further found in Ref. [12] that an optimumvalue exists for the textured portion a depending onthe bearing aspect ratio L/B. This behavior is shown infigure 2 for a bearing with L/B = 0.75 at various values of the area density Sp. As can be seen in the rangeof Sp values from0.18 to 0.72 the optimum a valuevaries from 0.7 to 0.55, respectively. It can also be seenfrom figure 2 that for a < 0.85 no optimum valueexists for Sp and the maximum load W increases withincreasing Sp. Hence, the largest area density that canbe practically obtained with the laser texturing isdesired. It is also interesting to note from figure 2 theadvantage of part ial-LST (a < 1) over the full LST(a = 1) forbearing applications. At Sp= 0.5, forexample, the load W at a = 0.6 is about three timeshigher than its value at a = 1. A full account of thisbehavior is given in Ref. [12].3. ExperimentalThe tested bearings consist of sintered SiC disks10 mm thick, having 85 mm outer diameter and40 mm inner diameter. Each bearing (see figure 3)comprises a flat rotor (a) and a six-pad stator (b). Thebearings were provided with an original surface finish by lapping to a roughness average Ra= 0.03 lm. Eachpad has an aspect ratio of 0.75 when its width is measured along the mean diameter of the stator. The photographs of two partial-LST stators are shown infigure 4 where the textured areas appear as brightermatt surfaces. The first stato r indicated (a) is a unidirectional bearing with the partial-LST adjacent to theleading edge of each pad, similar to the model showninfigure 1. The second stator (b) is a bi-directionalversion of a partial-LST bearing having two equal textured portions, a/2, on each of the pad ends. The lasertexturing parameters were the following; dimple depth, dimplediameter and dimple area density Sp= 0.60.03. These dimpledimensions were obtained with 4 pulses of 30 ns duration and 4 mJ each using a 5 kHz pulsating Nd:YAGlaser. The textured portion of the unidirectional bearing was a= 0.73 and that of the bi-directional bearingwas a= 0.63. As can be seen from figure 2 both thesea values should produce load-carrying capacity varyclose to the maximum theoretical value.The test rig is shown schematically in figure 5. An electrical motor turns a spindle to which an upperholder of the rotor is attached. A second lower holderof the stator is fixed to a housing, which rests on ajournal bearing and an axial loading mechanism that can freely move in the axial direction. An arm thatpresses against a load cell and thereby permits frictiontorque measurements prevents the free rotation of thishousing. Axial loading is provided by means of deadweights on a lever and is measured with a second loadcell. A proximity probe that is attached to the lowerholder of the stator allows on-line measurements ofthe clearance change between rotor and stator as thehydrodynamic effects causeaxial movement of thehousing to which the stator holder is fixed. Tap wateris supplied by gravity from a large tank to the centerof the bearing and the leakage from the bearing is collected and re-circulated. A thermocouple adjacent tothe outer diameter of the bearing allows monitoring ofthe water temperature as the water exit the bearing. APC is used to collect and process data on-line. Hence,the instantaneous clearance, friction coefficient, bearing speed and exit water temperature can be monitoredconstantly.The test protocol includes identifying a reference“zero” point for the clearance measurements by firstloading and then unloading a stationary bearing overthe full load range. Then the lowest axial load isapplied, the water supply valve is opened and themotor turned on. Axial loading is increased by stepsof 40 N and each load step is maintained for 5 minfollowing the stabilization of the friction coefficient ata steady-state value. The bearing speed and water temperature are monitored throughout the test for anyirregularities. The test ends when a maximum axialload of 460 N is reached or if the friction coefficientexceeds a value of 0.35. At the end of the last loadstep the motor and water supply are turned offandthe reference for the clearance measurements isrechecked. Tests are performed at two speeds of 1500and 3000 rpm corresponding to average sliding velocities of 4.9 and 9.8 m/s, respectively and each test isrepeated at least three times.4. Results and discussionAs a first step the validity of the theoretical modelin Ref. [12] was examined by comparing the theoretical and experimental results of bearing clearance versus bearing load for a unidirectional partial-LSTbearing. The results are shown in figure 6 for the twospeeds of 1500 and 3000 rpm where the solid anddashed lines correspond to the model and experiment,respectively. As can be seen, the agreement betweenthe model and the experiment is good, with differences of less than 10%, as long as the load is above150 N. At lower loads the measured experimentalclearances are much larger than the model predictions, particularly at the higher speed of 3000 rpmwhere at 120 N the measured clearance is 20 lm,which is about 60% higher than the predicted value.It turns out that the combination of such large clearances and relatively low viscosity of the water mayresult in turbulent fluid film. Hence, the assumptionof laminar flow on which the solution of the Reynolds equation in Ref. [12] is based may be violatedmaking the model invalid especially at the higherspeed and lowest load. In order to be consistent withthe model of Ref. [12] it was decided to limit furthercomparisons to loads above 150 N.It should be noted here that the first attempts to testthe baseline untextured bearing with the original surface finish of Ra= 0.03 lm on both the stator androtor failed due to extremely high friction even at thelower loads. On the other hand the partial-LST bearingran smoothly throughout the load range. It was foundthat the post-LST lapping to completely remove about2 lm height bulges, which are formed during texturingaround the rims of the dimples, resulted in a slightlyrougher surface with Ra= 0.04 lm. Hence, the baselineuntextured stator was also lapped to the same rough- ness of the partial-LST stator and all subsequent testswere performed with the same Ra value of 0.04 lm forall the tested stators. The rotor surface roughness remained, the original one namely, 0.03 lm. Figure 7presents the experimental resultsfor the clearance as afunction of the load for a partial-LST unidirectionalbearing (see stator in figure 4(a)) and a ba selineuntextured bearing. The comparison is made at the twospeeds of 1500 and 3000 rpm. The area density of thedimples in the partial-LST bearing is Sp= 0.6 and thetextured portion is a ¼ 0:734. The load range extendsfrom 160 to 460 N. The upper load was determined bythe test-rig limitation that did not permit higher loading. It is clear from figure 7 that the partial-LST bearing operates at substantially larger clearances than theuntextured bearing. At the maximum load of 460 Nand speed of 1500 rpm the partial-LST bearing has aclearance of 6 lm while the untextured bearing clearance is only 1.7 lm. At 3000 rpm the clearances are 6.6and 2.2 lm for the LST and untextured bearings,respectively. As can be seen from figure 7 this ratio ofabout 3 in favor of the partial-LST bearing is maintained over the entire load range.Figure 8 presents the results for the bi-directionalbearing (see stator in figure 4(b)). In this case the LSTparameters are Sp ¼ 0:614 and a ¼ 0:633. The clearances of the bi-directional partial-LST bearing arelower compared to these of the unidirectional bearingat the same load. At 460 N load the clearance for the1500 rpm is 4.1 lm and for the 3000 rpm it is 6 lm.These values represent a reduction of clearance between 33 and 10% compared to the unidirectional case. However, as can be seen from figure 8 the performance ofthe partial-LST bi-directional bearing is still substantially better than that of the untextured bearing.The friction coefficient of partial-LST unidirectionaland bi-directional bearings was compared with that ofthe untextured bearing in figures 9 and 10 for the twospeeds of 1500 and 3000 rpm, respectively. As can beseen the friction coefficient of the two partial-LSTbearings is very similar with slightly lower values inthe case of the more efficient unidirectional bearing.The friction coefficient of the untextured bearing is much larger compared to that of the LST bearings. At1500 rpm (figure 9) and the highest load of 460 N thefriction coefficient of the untextured bearing is about0.025 compared to about 0.01 for the LST bearings.At the lowest load of 160 N the values are about 0.06for the untextured bearing and around 0.02 for theLST bearings. Hence, the friction values of the untextured bearing are between 2.5 and 3 times higher thanthe corresponding values for the partial-LST bearingsover the entire load range. Similar results wereobtained at the velocity of 3000 rpm (figure 10) butthe level of the friction coefficients is somewhat higherdue to the higher speed. The much higher friction ofthe untextured bearing is due to the much smallerclearances of this bearing (see figures 7 and 8) thatresult in higher viscous shear.5. ConclusionThe idea of partial-LST to enhance performance ofthe parallel thrust bearing was evaluated experimentally.Good correlation was found with a theoretical model as long as the basic assumption of laminar flow in the fluidfilm is valid. At low loads with relatively large clearances, where turbulence may occur, the experimental clearance is larger than the prediction of the model.The performance of both unidirectional and bidirectional partial-LST bearings in terms of clearanceand friction coefficient was compared with that of abaseline untextured bearing over a load range in whichthe theoretical model is valid. A dramatic increase, ofabout three times, in the clearance of the partial-LSTbearings compared to that of the untextured bearingwas obtained over the entire load range. Consequentlythe friction coefficient of the partial-LST bearings ismuch lower, representing more than 50% reduction infriction compared to the untextured bearing.The larger clearance and lower friction make thepartial-LST simple parallel thrust bearing conceptmuch more reliable and efficient especially in seal-lesspumps and similar applicatio ns where the processfluid, which is often a poor lubricant, is the only available lubricant for the bearings.AcknowledgmentsThe authors would like to thank Mr. J. Boylan ofMorgan AM&T for providing the bearing specimensand Mr. N. Barazani of Surface Technologies Ltd. Forproviding the laser surface texturing.实验研究激光加工表面微观造型平行的推力轴承实验是研究激光处理的表面微观造型平行的推力轴承增强的某些性能。

本科毕业设计（本科毕业论文）外文文献及译文文献、资料题目：High-rise Tower Crane designed文献、资料来源：期刊（著作、网络等）文献、资料发表（出版）日期：2000.3.25院（部）：机电工程学院专业：机电工程及自动化High-rise Tower Crane designed under Turbulent Winds At present, construction of tower cranes is an important transport operations lifting equipment, tower crane accident the people's livelihood, major hazards, and is currently a large number of tower crane drivers although there are job permits, due to the lack of means to monitor and review the actual work of a serious violation . Strengthen the inspection and assessment is very important. Tower crane tipping the cause of the accident can be divided into two aspects: on the one hand, as a result of the management of tower cranes in place, illegal operation, illegal overloading inclined cable-stayed suspended widespread phenomenon; Second, because of the tower crane safety can not be found in time For example,Took place in the tower crane foundation tilt, micro-cracks appear critical weld, bolts loosening the case of failure to make timely inspection, maintenance, resulting in the continued use of tower cranes in the process of further deterioration of the potential defect, eventually leading to the tower crane tipping. The current limit of tower crane and the black box and can not be found to connect slewing tower and high-strength bolts loosening tightened after the phenomenon is not timely, not tower verticality of the axis line of the lateral-line real-time measurement, do not have to fight the anti-rotation vehicles, lifting bodies plummeted Meng Fang, hook hoists inclined cable is a timely reminder and record of the function, the wind can not be contained in the state of suspended operation to prevent tipping on the necessary tips on site there is a general phenomenon of the overloaded overturning of the whole security risks can not be accurately given a reminder and so on, all of which the lease on the tower crane, use, management problems,Through the use of tower crane anti-tipping monitor to be resolved. Tower crane anti-tipping Monitor is a new high-tech security monitoring equipment, and its principle for the use of machine vision technology and image processing technology to achieve the measurement of the tilt tower, tower crane on the work of state or non-working state of a variety of reasons angle of the tower caused by the critical state to achieve the alarm, prompt drivers to stop illegal operation, a computer chip at the same time on the work of the state of tower crane be recorded. Tower crane at least 1 day overload condition occurs, a maximum number of days to reach 23 overloading, the driver to operate the process of playing the anti-car, stop hanging urgency, such as cable-stayed suspended oblique phenomenon often, after verification and education, to avoid the possible occurrence of fatal accidents. Wind conditions in the anti-tipping is particularly important, tower cranes sometimes connected with the pin hole and pin do not meet design requirements, to connect high-strength bolts are not loose in time after the tightening of the phenomenon, through timely maintenance in time after the tightening of the phenomenon, through timely maintenance and remedial measures to ensure that the safe and reliable construction progress. Reduced lateral line tower vertical axis measuring the number of degrees,Observation tower angle driver to go to work and organize the data once a month to ensure that the lateral body axis vertical line to meet the requirements, do not have to every time and professionals must be completed by Theodolite tower vertical axismeasuring the lateral line, simplified the management link. Data logging function to ensure that responsibility for the accident that the scientific nature to improve the management of data records for the tower crane tower crane life prediction and diagnosis of steel structures intact state data provides a basis for scientific management and proactive prevention of possible accidents, the most important thing is, if the joint use of the black box can be easily and realistically meet the current provisions of the country's related industries. Tower crane safety management at the scene of great importance occurred in the construction process should be to repair damaged steel, usually have to do a good job in the steel tower crane maintenance work and found that damage to steel structures, we must rule out potential causes of accidents, to ensure safety in production carried out smoothly. Tower crane in the building construction has become essential to the construction of mechanical equipment, tower crane at the construction site in the management of safety in production is extremely important. A long time, people in the maintenance of tower crane, only to drive attention to the conservation and electrical equipment at the expense of inspection and repair of steel structures, to bring all kinds of construction accidents.Conclusion: The tower crane anti-tipping trial monitor to eliminate potential causes of accidents to provide accurate and timely information, the tower crane to ensure the smooth development of the leasing business, the decision is correct, and should further strengthen and standardize the use of the environment (including new staff training and development of data processing system, etc.).The first construction cranes were probably invented by the Ancient Greeks and were powered by men or beasts of burden, such as donkeys. These cranes were used for the construction of tall buildings. Larger cranes were later developed, employing the use of human treadwheels, permitting the lifting of heavier weights. In the High Middle Ages, harbour cranes were introduced to load and unload ships and assist with their construction – some were built into stone towers for extra strength and stability. The earliest cranes were constructed from wood, but cast iron and steel took over with the coming of the Industrial Revolution.For many centuries, power was supplied by the physical exertion of men or animals, although hoists in watermills and windmills could be driven by the harnessed natural power. The first 'mechanical' power was provided by steam engines, the earliest steam crane being introduced in the 18th or 19th century, with many remaining in use well into the late 20th century. Modern cranes usually use internal combustion engines or electric motors and hydraulic systems to provide a much greater lifting capability than was previously possible, although manual cranes are still utilised where the provision of power would be uneconomic.Cranes exist in an enormous variety of forms – each tailored to a specific use. Sizes range from the smallest jib cranes, used inside workshops, to the tallest tower cranes,used for constructing high buildings, and the largest floating cranes, used to build oil rigs and salvage sunken ships.This article also covers lifting machines that do not strictly fit the above definition of a crane, but are generally known as cranes, such as stacker cranes and loader cranes.The crane for lifting heavy loads was invented by the Ancient Greeks in the late 6th century BC. The archaeological record shows that no later than c.515 BC distinctive cuttings for both lifting tongs and lewis irons begin to appear on stone blocks of Greek temples. Since these holes point at the use of a lifting device, and since they are to be found either above the center of gravity of the block, or in pairs equidistant from a point over the center of gravity, they are regarded by archaeologists as the positive evidence required for the existence of the crane.The introduction of the winch and pulley hoist soon lead to a widespread replacement of ramps as the main means of vertical motion. For the next two hundred years, Greek building sites witnessed a sharp drop in the weights handled, as the new lifting technique made the use of several smaller stones more practical than of fewer larger ones. In contrast to the archaic period with its tendency to ever-increasing block sizes, Greek temples of the classical age like the Parthenon invariably featured stone blocks weighing less than 15-20 tons. Also, the practice of erecting large monolithic columns was practically abandoned in favour of using several column drums.Although the exact circumstances of the shift from the ramp to the crane technology remain unclear, it has been argued that the volatile social and political conditions of Greece were more suitable to the employment of small, professional construction teams than of large bodies of unskilled labour, making the crane more preferable to the Greek polis than the more labour-intensive ramp which had been the norm in the autocratic societies of Egypt or Assyria.The first unequivocal literary evidence for the existence of the compound pulley system appears in the Mechanical Problems (Mech. 18, 853a32-853b13) attributed to Aristotle (384-322 BC), but perhaps composed at a slightly later date. Around the same time, block sizes at Greek temples began to match their archaic predecessors again, indicating that the more sophisticated compound pulley must have found its way to Greek construction sites by then.During the High Middle Ages, the treadwheel crane was reintroduced on a large scale after the technology had fallen into disuse in western Europe with the demise of the Western Roman Empire. The earliest reference to a treadwheel (magna rota) reappears in archival literature in France about 1225, followed by an illuminated depiction in a manuscript of probably also French origin dating to 1240. In navigation, the earliest uses of harbor cranes are documented for Utrecht in 1244, Antwerp in 1263, Brugge in 1288 and Hamburg in 1291, while in England the treadwheel is not recorded before 1331.Generally, vertical transport could be done more safely and inexpensively by cranes than by customary methods. Typical areas of application were harbors, mines, and, in particular, building sites where the treadwheel crane played a pivotal role in the construction of the lofty Gothic cathedrals. Nevertheless, both archival and pictorial sources of the time suggest that newly introduced machines like treadwheels or wheelbarrows did not completely replace more labor-intensive methods like ladders, hods and handbarrows. Rather, old and new machinery continued to coexist on medieval construction sites and harbors.Apart from treadwheels, medieval depictions also show cranes to be powered manually by windlasses with radiating spokes, cranks and by the 15th century also by windlasses shaped like a ship's wheel. To smooth out irregularities of impulse and get over 'dead-spots' in the lifting process flywheels are known to be in use as early as 1123.The exact process by which the treadwheel crane was reintroduced is not recorded, although its return to construction sites has undoubtedly to be viewed in close connection with the simultaneous rise of Gothic architecture. The reappearance of the treadwheel crane may have resulted from a technological development of the windlass from which the treadwheel structurally and mechanically evolved. Alternatively, the medieval treadwheel may represent a deliberate reinvention of its Roman counterpart drawn from Vitruvius' De architectura which was available in many monastic libraries. Its reintroduction may have been inspired, as well, by the observation of the labor-saving qualities of the waterwheel with which early treadwheels shared many structural similarities.In contrast to modern cranes, medieval cranes and hoists - much like their counterparts in Greece and Rome - were primarily capable of a vertical lift, and not used to move loads for a considerable distance horizontally as well. Accordingly, lifting work was organized at the workplace in a different way than today. In building construction, for example, it is assumed that the crane lifted the stone blocks either from the bottom directly into place, or from a place opposite the centre of the wall from where it could deliver the blocks for two teams working at each end of the wall. Additionally, the crane master who usually gave orders at the treadwheel workers from outside the crane was able to manipulate the movement laterally by a small rope attached to the load. Slewing cranes which allowed a rotation of the load and were thus particularly suited for dockside work appeared as early as 1340. While ashlar blocks were directly lifted by sling, lewis or devil's clamp (German Teufelskralle), other objects were placed before in containers like pallets, baskets, wooden boxes or barrels.It is noteworthy that medieval cranes rarely featured ratchets or brakes to forestall the load from running backward.[25] This curious absence is explained by the high friction force exercised by medieval treadwheels which normally prevented the wheel from accelerating beyond control.目前，塔式起重机是建筑工程进行起重运输作业的重要设备，塔机事故关系国计民生、危害重大，而目前众多的塔机司机虽然有上岗证，由于缺少监督和复核手段，实际工作中违规严重。

学号： 06406322常州大学毕业设计（论文）外文翻译（2010届）外文题目Five-axis milling machine tool__ kinematic chain design and analysis译文题目五轴铣削机床运动链设计与分析外文出处 International Journal of Machine Tools & Manufacture42 (2002) 505–520学生毛伟学院怀德学院专业班级机制061 校内指导教师朱伟专业技术职务讲师校外指导老师专业技术职务二○一○年三月五轴铣削机床运动链设计与分析E.L.J. BohezDepartment of Design and Manufacturing Engineering, Asian Institute of Technology, P.O. Box 4, KlongLuang, 12120 Pathumthani, Thailand摘要：五轴数控加工中心目前已成为相当普遍的机床。

大多数机床的运动学分析是建立在直角笛卡儿坐标系基础上的。

本文根据理论上可能的自由度组合对机床的可行性概念设计和实际应用状况进行了分类，定义了一些有用的定量参数，如工作空间的影响因素，机床空间的使用效率，空间定位指数和角度定位指数。

分析比较了每种类型的优缺点，给出了选择和设计机床的相关标准。

简要讨论了基于Steward平台的新型机床，这种机床最近工程中已得到广泛应用。

关键词：五轴联动，机床，运动链，工作空间，数控系统，旋转轴1.导言机床的主要设计规范应遵循下列原则：* 运动学应提供一部分方向和工具的位置足够的灵活性。

* 定位准确和定位速度尽可能高。

* 定位准确性尽可能高的。

* 工具和工件变化快速。

* 保护环境。

* 节省材料。

机床轴的数目通常是指自由度的数目，机器上的幻灯片独立控制的议案。

标准轴建议用右手坐标系统，机床轴线与Z轴一致。

AxeBot Robot: The Mechanical Design for an Autonomous Omni directional Mobile RobotTiago P. do Nascimento, Augusto Loureiro da Costa, Cristiane Correa Paim Post-graduation Program in Electrical EngineeringUniversidade Federal da BahiaSalvador, Bahia, Brasiltiagopn@, augusto.loureiro@ufba.br, cpaim@ufba.brAbstractThe AxeBot robot‟s mechanical design, a fully autonomous mobile robot, for the RoboCup Small Size League, is presented in this paper. The AxeBot robot uses three omnidirectional wheels for movement and is equipped by a shooting device for shooting the ball in different directions. Once the AxeBot robot is a fully autonomous mobile robot all the sensors, engines, servos, batteries, and the computer system, must be embedded on. The project can be separated in four different parts: the chassis design, the wheel design, the shooting device design and the overall assembly which makes a shell design possible to cover the whole robot. The AxeBot mechanical design brings up a new chassis concept for three wheels omnidirectional robot, also present a new shooting device, and finally present AxeBots prototype assembly.1. IntroductionThe RoboCup Initiative is an international research group whose aims are to promote the fields of Robotics and Artificial Intelligence. A standard challenge, a soccer match performed by autonomous robot teams, was proposed in 1996 [1]. Initially with three different leagues 2D: Robot Soccer Simulation league, Small Size Robot league, and Middle Size Robot league. Nowadays these leagues have been increased up to: Four-Legged League, Humanoid League, Middle Size League, RoboCup Junior Soccer, Small Size League, Soccer Simulation, Standard Robot League. Also, another challenge, the RoboCup Rescue was proposed in 1999 to show that the result from the robot soccer research could be directly applied on a real world problem like a disaster rescue made by robots. Through the integration of technology and advanced computer algorithms, the goal of RoboCup is to build a team of humanoid robots that can beat the current World Cup champions by the year 2050. The AxeBot uses three omnidirectional wheels, positioned on a circle with an angle of 120o among each wheel, to move in different directions. Three Maxxon A-22 motors are used to drive the omnidirectional wheels, one motor per wheel. These motors are controlled by two Brainstem Moto 1.0 and a cascade controller made to control the robot trajectory [2] [3]. The AxeBot also holds a shooting device to kick the ball in different directions, a Vision System with a CMUCam Plus and GP202 Infra-red sensor [4], a embedded Computer System based on StrongArm, called StarGate Kit and a IEEE 802.11 wireless network card. This work presents the mechanical project to enclose these equipments into an fully autonomous omnidirectional robot calledAxeBot. The complete AxeBot dynamics and kinematics model can be found in [5], this model was used to specify some mechanical parameter, like the wheel diameter.2. The ChassisThe chassis of the robot is the frame to which all other components can be attached, directly or indirectly. Therefore the chassis must be strong enough to carry the weight of all parts when the robot is in rest o in movement. The chassis has to withstand the forces on it, caused by the acceleration of the robot as well. Another important requirement of the chassis is that it fixes all components in a stiff way, so that there will be small relative displacements of the components within the robot, during acceleration and deceleration. This is particular important for the three driving motors, which are positioned on the ground plane with an angle of 120o between each motor. The performance of the control of the robot is dependent on a precise and stiff placement of the motors [6]. The chassis has to be strong enough also to withstand a collision of the robotagainst the wall or against another robot, with the highest possible impact velocity that can occur. Finally the chassis has to be built with the smallest amount of material. At first to reduce the costs, and to minimize the total weight of the robot. Less weight requires less power to accelerate. So with the same motors, less weight gives you more acceleration. This is of course only true, when all the power generated by the motors can be transferred, via the wheels, to the ground. In other words, the wheels must have enough traction that there will be no slip between the wheels and the ground [7].2.1. MaterialFiberglass was used to build the chassis. This choice is purely financial, because the material is not expensive (although it is strong) and there is no need to hire a professional constructor. The building of all the chassis (six in total) can be done by the team members themselves. Only the moulds have to be built by a professional. The upper and lower chassis can be made using one mould that can be adjusted to produce the different chassis.2.2. DesignThe primary goal of the design is the fixation of the motors in the desired positions. Therefore a ground plate with 3 slots for the motors is modeled. At the front side each motor can be attached to the chassis. At the rim of the ground plate an edge is attached to give the chassis more torsion stiffness. This edge can also be used for attaching other components of the robot, like the covering shell. Also there is a cutout to create space for the shooting device of the robot. In section 5 the design of this device will be discussed. However no final design will be presented and therefore we stick with this assumption that the shooting device needs these cutouts. All edges are rounded, because this will make the construction of the easier part. The final part, the lower chassis, is shown in the figure below. This part is modeled in Solid Edge. To get a stiffer and stronger chassis, a second chassis part, the upper chassis, is modeled. This is almost an exact copy of the first part, only now there are 3 cutouts that provide more space for placing the components of the robot. These cutouts also save some material and therefore weight. The both parts are This sandwich construction gives thewhole chassis more stiffness, and so the total thickness of both the chassis can probably be lower than using one chassis part.Figure 1: Lower chassisFigure 2: Upper and lower chassis attached to each other2.3. Chassis mouldTo build these parts, a mould was made. This is just a negative of the actual robot parts. In figure 3 the mould of the upper chassis. To change this mould in the mould for the lower chassis, where the ground plate does not have holes, the indicated pieces (with white stripes) and the not indicated left piece (symmetric to the most right part) should be lowered 4 mm. For the upper and lower chassis, the basis mould is exactly the same. Only piece one and two are different for the two chassis, the motor piece and the shooting system piece are the same.Figure 3: Chassis mould3. WheelsThe AxeBot robot is equipped with three wheels positioned on a circle with an angle of 120°among attached to each other as shown in the picture below.each wheel. These wheels have to enable the omnidirectionality of the AxeBot robot. This means that the wheels have to be able to let the robot make two translational movements (in x and y-direction, see figure 4) without rotating the robot around its z-axis (the axis perpendicular to the y and x-axis, that is rotation in figure 4). The wheels have also to enable a rotation of the total robot around the z-axis.Figure 4: AxeBot wheels positionsNevertheless, the wheels have to be as small and light as possible to minimize weight and moment of inertia but still remain usable and manageable. The wheels are based on an existing design of an omnidirectional wheel from the Cornell Robot 2003 [8]. Figure 5 shows an exploded view the final version of a wheel. The two shells are connected to each other by screws and hold every part on the right place. The hub is also attached to the shells by screws. The hub is mounted on the output axle of a motor by a screw to transfer the rotational output of a motor to the wheel. The rings of the rollers are in contact with the floor. A roller can rotate around its roller axle.As mentioned above, the wheel has to enable two translations (x and y, see figure 4) without rotating around its z-axis. The whole wheel ensures one translation by rotating around the output shaft of the motors while the rollers ensure the other translation. Combining these translations on a proper way a robot can move anywhere in a plane or make a rotation.3.1. RingThe ring is the only part of the wheel that is in contact with the floor. Note that a wheel can also be in contact with the floor by two rings. To obtain maximum grip (no slip) the Cornell Robot 2003 team first developed rollers without rings. The rollers had sharp edges to cut into the carpet of the football fieldfor maximum grip. This however ruined the carpet and rubber rings were added in the design to obtain maximum grip without ruining the carpet. The rings are circular with a circular profile.Figure 5: Exploded view of the wheelTherefore the rubber rings are also used for the AxeBot 2006. Rubber rings can be bought in several sizes and since they are highly elastic it wasn‟t difficult to find a ring of a right size. Since there are more than one …right sizes‟ and the geometry of the ring is that simple, no technical drawing of the ring was made.3.2. RollerThe geometry of the rollers may not restrict the rotation of the roller and should enable the placement of the rubber ring, without the ring falling off. This can be easily obtained (see drawings). The only problem is friction with their axles and with the shells.The geometry of the rollers can influence the friction with the shells and the friction with its roller axle. To minimize the possibility of wear on the contact area between the roller and the roller axle, this contact area should be as big as possible.When the torque of the motor is transferred through a roller to the ground (driving the robot), the roller that is on the ground is pressed against the shells. It will occur often that, in this situation, the desired driving direction also requires a rotation of the roller (then the summation of the two translational movements will results in the desired driving direction). The rotating roller is, in this situation, pressed against the shells which, in some cases, can result in wear of the roller and or the shells. This depends on the material of the roller, the material of the shell, the magnitude of the force which presses the surfaces on each other (in this case it is the torque of the motor) and the geometry of both contact surfaces. Only the materials and geometry can be chosen in the design process of the wheels.A small contact area results in low friction but possible wear of one of the two surfaces and though materials have to be used to avoid wear. A large contact area will not cause wear but will result in a large friction force. An optimum for the contact area and the materials has to be found. The geometry has to be machinable also. Problems that are mentioned above did not occur with the design of the rollers of the Cornell Robot 2003. Therefore the same geometry for the rollers is used for the AxeBot.The Cornell Robot 2003 team designed a wheel with 15 rollers that worked very well. Therefore also 15 rollers are used in each wheel of the AxeBot 2006.The prototypes of the wheels of the Cornell Robot 2003 first had Delrin rollers to minimize friction and weight. Delrin is a kind of plastic which is used with moving contact surfaces because of its low friction coefficients with other materials. After a few test with the prototype robot it became clear that the Delrin-rollers easily broke with a collision. Therefore the Cornell Robot 2003 was equipped with aluminum rollers. These were strong enough to withstand collisions and aluminum has a low density (compared to other metals).However, during other prototype tests of the Cornell Robot 2003 team some aluminum residue built up on the steel rollers axles. The Cornell Robot 2003 did not encounter problems due to the wearing of the aluminum rollers, but to optimize the design of the AxeBot wheels this problem was solved.To avoid wearing of the aluminum rollers other material for the axles can be used or the rollers can be made of a tougher material. After a few calculations it became clear that roller axles of Delrin (to reduce the friction) are strong enough (see the section about the axles), but it is not possible to produce thin bars of Delrin. Therefore steel axles are used, the same material as the roller axles of the Cornell Robot 2003.So to avoid wear of the rollers a more though material than aluminum has to be used for the rollers. Steel is more though and an easily obtainable and cheap material. Adisadvantage of steel compared to aluminum is its higher density. This will increase the moment of the inertia which …costs‟ more torque of the motor. The total moment of inertia of a wheel with steel rollers is 1.39×10−4kgm2 and the moment of inertia of a wheel with aluminum rollers is 1.30×10−4kgm2. Using steel rollers instead of aluminum rollers would increase the moment of inertia by 7 this increase is neglectable small and steel rollers can be used.Concerning friction, using steel rollers and steel axles is also better than using aluminum rollers and steel axles since the friction-coefficient between steel and steel is lower than that between steel and aluminum. A lubricant can also be used to even more reduce friction.3.3. Roller axleAs mentioned above, the use of Delrin for the roller axles was investigated since it would reduce the wear of the aluminum rollers. In a static situation was calculated whether Delrin axles of 2.4 mm diameter would be strong enough. This was also done in a dynamical situation (dropping the robot on the floor and landing on one roller), but without using a Finite Element Method this did not result in realistic results. When the total weight of 3.5 kg of one AxeBot 2006 would completely be on one roller axle this would result in a shear stress in the axle.In this situation the shear stress can be calculated by dividing the force on the axle (due to the weight of the AxeBot) by the area of the shear plane. The area of the shear plane is of course the area of a circle with a radius similar to the radius of the axles. Note that the weight of the AxeBot has to be divided by two since there are two shear planes in one axle.The magnitude of the shear stress would be 3.8 MPa. Delrin starts to plastically deform in due to shear at around 44 MPa. Statically, Delrin axles would be strong enough.However, this calculation was not necessary it became clear that it is not possible to produce Delrin bars of 2.5 mm (diameter). Therefore steel axles will be used (aluminum axles would result in more friction). To reduce friction, the axles were coated with a lubricant like carbon. Lubricants like carbon are easily available.The Cornell robot team 2003 documentation does not mention problems of wear of their polycarbonate shells due to their steel roller axles. As one can be read further down this section, the shells of the AxeBot wheels will be made of aluminum or polycarbonate. The coefficient of friction between aluminum (shells) and steel (axles) and between polycarbonate (shells) and steel (axles) are of equal sizes (about 0.45 [-]). Also, the geometry of the wheels of the Cornell robot and the AxeBot are almost the same. Therefore it is most likely that wearing due to friction will not be a problem with steel roller axles and polycarbonate or aluminum shells.Production the axles can easily be made out of a steel bar. Depending on the available diameters of steel bars, the diameter of the axles could be adjusted. The edges of the axles are rounded to avoid sharp corners.3.4. HubThe hub connects the wheel to the axle of the motor. A M2-bolt can be used for this purpose, the hole in the hub where this bolt will be placed is dimensioned 1.5 mm indiameter so screw thread can be made to fit in the M2-bolt. The hub is connected to the shells by three M3-screws. Corresponding holes of 2.5 mm will be made in the hub and the shells. The geometry of the hub can be changed to facilitate the production process. The hub can be made out of aluminum or polycarbonate, both light materials. To investigate the option (and price) of injection moulding the hub out of polycarbonate a sketch of a design for a mould has been made.3.5. ShellsAlmost the all geometry of the shells of the Cornell Robot 2003 is used. Only little changes in the slots for the rollers of the axles have been made to facilitate the production process of the shells. In the section about the production of the shells a different design for the slots of the axles is presented to make the production of the shells easily.The shells can be made out of aluminum or a though, light plastic like polycarbonate. The Cornell Robot had shells of polycarbonate. The best machinable material is preferred, and the one used on the AxeBot‟s shell. Wh en using a plastic that can be injection molded, molds have been designed to check the prices of injection moulding.4. Shooting DeviceThis design consists of a vertical arm (the kick arm), that can swing around an axle which is fixed to the robot. This movement will be actuated by one of the two servos, the kicking servo, that is also fixed to the robot. The other servo, the directional servo, is attached to the bottom of the kick arm (the servosocket). A pendulum-like system is formed, so a large mass is concentrated in the lower part of a rotating arm. The kicking servo has a kicking plate attached to it which can rotate and thereby makes it possible to shoot in different directions. The kicking plate can be positioned very accurately since servos are designed for these kinds of tasks. The kicking plate is also connected to the servosocket. Therefore the collision force between the ball and the kicking plate will be guided to and divided by these two connection points. There will be less bending in the kicking platethen with one connection point and smaller reaction forces will act on the connection points.Figure 6: The AxeBot shooting device5. Shell and AxeBot AssemblyThe shell is the cover of the total robot. It will be made from fiberglass as well, for the same reasons as stated in the section about the chassis. In the figure below the design of the shell is shown. There are cutouts to make room for the wheels as well as for the shooting device. The diameter of the shell is 178 mm. Because the maximum allowable diameter is 180 mm, a margin of 2 mm is created.On top of the shell a vision system will be mounted. For the sake of compactness of the robot the height should be as small as possible, with all the parts fitting in. Thismould can be built with the simple milling machine that is available.To assemble the robot the most important demand is to obtain a total centre of gravity that has the lowest possible position in the robot. This will give the robot positive driving abilities. Another demand is of course that all the parts fit in the maximum height of 150 mm.To check this, all the parts of the robot have been modeled in Solid Edge. In figure 7 an exploded view of the total robot assembly is shown.The robot consists of an upper and lower chassis. Three motors with three omnidirectional wheels are attached to it. On the bottom of the robot, the two battery packs are placed, because these parts have the largest mass. The three motor processors are attached to two general processors. Also the overall processor with the data-transfer-unit is assembled. The latter parts are assembled in a way that is most compact. With this assembly it is possible for all parts to fit in a shell with height of 100 mm.A model for the shell of the robot is designed. Also a molt to produce these parts is modeled. It is possible to produce this model by using the milling machine that is available at the university. The assembly of all the parts, except the shooting device, shows that a shell height of 100 mm is possible.Figure 7: Exploded view of the total robot assemblyFigure 8: Total robot assembly6. ConclusionThe AxeBot mechanical design, a fully autonomous mobile robot, for the RoboCup Small Size League, was presented in this paper. This mechanical design brings up a new concept of chassis for three wheels omnidirectional mobile for RoboCup F-180 league, that can be built easily and cheap. Also a new effectuator mobile robot design for RoboCup F-180 league is presented here. This new effectuator allows the mobile robot to shoot the ball in different directions, instead of just shoot a head like the othershooting devices. Finally the mechanical project presented here encloses all part, sensor, actuators, effectuator, computer systems, wheels, chassis and cover shell into the AxeBot prototype. The AxeBot robot was concept for academical proposes, using the robot soccer as a laboratory to research in Autonomous Mobile Robots, Artificial Intelligence and related areas. Looking forward, in a few months, four more AxeBots are expected to be built like the two in figure 9. These robots will form the MecaTeam F-180, and height of 100 mm is possible.will support our research in to multi-robot systems, as it can be seen in figure 9 below.Figure 9: AxeBot photo7. References[1] Kitano, H. “Robocup: The robot world cup initiative”. In: Proc. of The First International Conference on Autonomous Agent (Agents-97)). Marina del Ray, The ACM Press. 1997.[2] Franco, A. C. “Geração e controle de tra jetória de robôs móveis omni-direcionais”, Master‟s thesis, Programa de Pós-Graduação Mecatrônica, UFBA. 2007.[3] PIRES, E. J. S.; MACHADO, J. A. T.; OLIVEIRA, P. B. de M. “Robot trajectory planning using multi-objective genetic algorithm optimization”. In: DEB, K. et al. (Ed.). GECCO (1). [S.l.]: Springer, 2004. (Lecture Notes in Computer Science, v. 3102), p.615-626. ISBN 3-540-22344-4.[4] Oliveira, L. R., Costa, A. L., Schnitman, L. and Souza, J. “An architecture of sensor fusion for spatial locat ion of objects in mobile robotics”, in B. H. Spring-Verlag (ed.), Encontro Português de Inteligência Artificial, EPIA‟2005, Covilhã, 2005. pp. 462–473.[5] Nascimento, T. P., Costa, A. L., Paim, C. C. “Uma abordagem multivariável para modelagem de robôs móveis omnidirecionais”, XVI CBA - Congresso Brasileiro de Automação. 2008.[6] ANGELES, J. “Fundamentals of Robotic Mechanical Systems: Theory, Methods, and Algorithms”. 2. ed. New York: Springer-Verlag New York, Inc., 2003. [7] B. Carter, M. Good, M. Dorohoff, J. Lew, R. L. W. II, and P. Gallina, “Mechanical design and modeling of an omni-directional robocup player,” in Proceedings RoboCup 2001 International Symposium, (Athens, Ohio), pp. 1–10, 2001.[8] Anderson, G., Chang, C., Chung, D., Evansic, L., Law, H., Richardson, S., Robers, J., Sterk, K. and Yim, J. 2003 cornell robocup, mechanical group final documentation, Technical report, /. 2003.翻译：AxeBot机器人：全方位自主移动机器人的机械设计摘要:这篇文章中介绍了一个用来参与机器人世界杯小尺寸等级比赛的完全自主移动AxeBot机器人的机械设计。

毕业设计(论文)外文资料翻译系部：专业：姓名：学号：外文出处：English For Electromechanical(用外文写)Engineering附件：1.外文资料翻译译文；2.外文原文。

附件1：外文资料翻译译文机床机床是用于切削金属的机器。

工业上使用的机床要数车床、钻床和铣床最为重要。

其它类型的金属切削机床在金属切削加工方面不及这三种机床应用广泛。

车床通常被称为所有类型机床的始祖。

为了进行车削，当工件旋转经过刀具时，车床用一把单刃刀具切除金属。

用车削可以加工各种圆柱型的工件，如：轴、齿轮坯、皮带轮和丝杠轴。

镗削加工可以用来扩大和精加工定位精度很高的孔。

钻削是由旋转的钻头完成的。

大多数金属的钻削由麻花钻来完成。

用来进行钻削加工的机床称为钻床。

铰孔和攻螺纹也归类为钻削过程。

铰孔是从已经钻好的孔上再切除少量的金属。

攻螺纹是在内孔上加工出螺纹，以使螺钉或螺栓旋进孔内。

铣削由旋转的、多切削刃的铣刀来完成。

铣刀有多种类型和尺寸。

有些铣刀只有两个切削刃，而有些则有多达三十或更多的切削刃。

铣刀根据使用的刀具不同能加工平面、斜面、沟槽、齿轮轮齿和其它外形轮廓。

牛头刨床和龙门刨床用单刃刀具来加工平面。

用牛头刨床进行加工时，刀具在机床上往复运动，而工件朝向刀具自动进给。

在用龙门刨床进行加工时，工件安装在工作台上，工作台往复经过刀具而切除金属。

工作台每完成一个行程刀具自动向工件进给一个小的进给量。

磨削利用磨粒来完成切削工作。

根据加工要求，磨削可分为精密磨削和非精密磨削。

精密磨削用于公差小和非常光洁的表面，非精密磨削用于在精度要求不高的地方切除多余的金属。

车床车床是用来从圆形工件表面切除金属的机床，工件安装在车床的两个顶尖之间，并绕顶尖轴线旋转。

车削工件时，车刀沿着工件的旋转轴线平行移动或与工件的旋转轴线成一斜角移动，将工件表面的金属切除。

车刀的这种位移称为进给。

车刀装夹在刀架上，刀架则固定在溜板上。

溜板是使刀具沿所需方向进行进给的机构。