机械论问翻译
机械制造及自动化毕业设计---外语文献翻译
攀枝花学院本科毕业设计（论文）外文译文院（系）：机电工程学院专业：机械设计制造及其自动化姓名：**************学号：ZJD02043外语文献翻译摘自: 《制造工程与技术（机加工）》（英文版）《Manufacturing Engineering and Technology—Machining》机械工业出版社2004年3月第1版页P560—564美s. 卡尔帕基安(Serope kalpakjian)s.r 施密德(Steven R.Schmid) 著原文：20.9 MACHINABILITYThe machinability of a material usually defined in terms of four factors:1、Surface finish and integrity of the machined part;2、Tool life obtained;3、Force and power requirements;4、Chip control.Thus, good machinability good surface finish and integrity, long tool life, and low force And power requirements. As for chip control, long and thin (stringy) cured chips, if not broken up, can severely interfere with the cutting operation by becoming entangled in the cutting zone.Because of the complex nature of cutting operations, it is difficult to establish relationships that quantitatively define the machinability of a material. In manufacturing plants, tool life and surface roughness are generally considered to be the most important factors in machinability. Although not used much any more, approximate machinability ratings are available in the example below.20.9.1 Machinability Of SteelsBecause steels are among the most important engineering materials (as noted in Chapter 5), their machinability has been studied extensively. The machinability of steels has been mainly improved by adding lead and sulfur to obtain so-calledfree-machining steels.Resulfurized and Rephosphorized steels. Sulfur in steels forms manganese sulfide inclusions (second-phase particles), which act as stress raisers in the primaryshear zone. As a result, the chips produced break up easily and are small; this improves machinability. The size, shape, distribution, and concentration of these inclusions significantly influence machinability. Elements such as tellurium and selenium, which are both chemically similar to sulfur, act as inclusion modifiers in resulfurized steels.Phosphorus in steels has two major effects. It strengthens the ferrite, causing increased hardness. Harder steels result in better chip formation and surface finish. Note that soft steels can be difficult to machine, with built-up edge formation and poor surface finish. The second effect is that increased hardness causes the formation of short chips instead of continuous stringy ones, thereby improving machinability.Leaded Steels. A high percentage of lead in steels solidifies at the tip of manganese sulfide inclusions. In non-resulfurized grades of steel, lead takes the form of dispersed fine particles. Lead is insoluble in iron, copper, and aluminum and their alloys. Because of its low shear strength, therefore, lead acts as a solid lubricant (Section 32.11) and is smeared over the tool-chip interface during cutting. This behavior has been verified by the presence of high concentrations of lead on thetool-side face of chips when machining leaded steels.When the temperature is sufficiently high-for instance, at high cutting speeds and feeds (Section 20.6)—the lead melts directly in front of the tool, acting as a liquid lubricant. In addition to this effect, lead lowers the shear stress in the primary shear zone, reducing cutting forces and power consumption. Lead can be used in every grade of steel, such as 10xx, 11xx, 12xx, 41xx, etc. Leaded steels are identified by the letter L between the second and third numerals (for example, 10L45). (Note that in stainless steels, similar use of the letter L means “low carbon,” a condition that improves their corrosion resistance.)However, because lead is a well-known toxin and a pollutant, there are serious environmental concerns about its use in steels (estimated at 4500 tons of lead consumption every year in the production of steels). Consequently, there is a continuing trend toward eliminating the use of lead in steels (lead-free steels). Bismuth and tin are now being investigated as possible substitutes for lead in steels.Calcium-Deoxidized Steels. An important development is calcium-deoxidized steels, in which oxide flakes of calcium silicates (CaSo) are formed. These flakes, in turn, reduce the strength of the secondary shear zone, decreasing tool-chip interfaceand wear. Temperature is correspondingly reduced. Consequently, these steels produce less crater wear, especially at high cutting speeds.Stainless Steels. Austenitic (300 series) steels are generally difficult to machine. Chatter can be s problem, necessitating machine tools with high stiffness. However, ferritic stainless steels (also 300 series) have good machinability. Martensitic (400 series) steels are abrasive, tend to form a built-up edge, and require tool materials with high hot hardness and crater-wear resistance. Precipitation-hardening stainless steels are strong and abrasive, requiring hard and abrasion-resistant tool materials.The Effects of Other Elements in Steels on Machinability. The presence of aluminum and silicon in steels is always harmful because these elements combine with oxygen to form aluminum oxide and silicates, which are hard and abrasive. These compounds increase tool wear and reduce machinability. It is essential to produce and use clean steels.Carbon and manganese have various effects on the machinability of steels, depending on their composition. Plain low-carbon steels (less than 0.15% C) can produce poor surface finish by forming a built-up edge. Cast steels are more abrasive, although their machinability is similar to that of wrought steels. Tool and die steels are very difficult to machine and usually require annealing prior to machining. Machinability of most steels is improved by cold working, which hardens the material and reduces the tendency for built-up edge formation.Other alloying elements, such as nickel, chromium, molybdenum, and vanadium, which improve the properties of steels, generally reduce machinability. The effect of boron is negligible. Gaseous elements such as hydrogen and nitrogen can have particularly detrimental effects on the properties of steel. Oxygen has been shown to have a strong effect on the aspect ratio of the manganese sulfide inclusions; the higher the oxygen content, the lower the aspect ratio and the higher the machinability.In selecting various elements to improve machinability, we should consider the possible detrimental effects of these elements on the properties and strength of the machined part in service. At elevated temperatures, for example, lead causes embrittlement of steels (liquid-metal embrittlement, hot shortness; see Section 1.4.3), although at room temperature it has no effect on mechanical properties.Sulfur can severely reduce the hot workability of steels, because of the formation of iron sulfide, unless sufficient manganese is present to prevent such formation. Atroom temperature, the mechanical properties of resulfurized steels depend on the orientation of the deformed manganese sulfide inclusions (anisotropy). Rephosphorized steels are significantly less ductile, and are produced solely to improve machinability.20.9.2 Machinability of Various Other MetalsAluminum is generally very easy to machine, although the softer grades tend to form a built-up edge, resulting in poor surface finish. High cutting speeds, high rake angles, and high relief angles are recommended. Wrought aluminum alloys with high silicon content and cast aluminum alloys may be abrasive; they require harder tool materials. Dimensional tolerance control may be a problem in machining aluminum, since it has a high thermal coefficient of expansion and a relatively low elastic modulus.Beryllium is similar to cast irons. Because it is more abrasive and toxic, though, it requires machining in a controlled environment.Cast gray irons are generally machinable but are. Free carbides in castings reduce their machinability and cause tool chipping or fracture, necessitating tools with high toughness. Nodular and malleable irons are machinable with hard tool materials.Cobalt-based alloys are abrasive and highly work-hardening. They require sharp, abrasion-resistant tool materials and low feeds and speeds.Wrought copper can be difficult to machine because of built-up edge formation, although cast copper alloys are easy to machine. Brasses are easy to machine, especially with the addition pf lead (leaded free-machining brass). Bronzes are more difficult to machine than brass.Magnesium is very easy to machine, with good surface finish and prolonged tool life. However care should be exercised because of its high rate of oxidation and the danger of fire (the element is pyrophoric).Molybdenum is ductile and work-hardening, so it can produce poor surface finish. Sharp tools are necessary.Nickel-based alloys are work-hardening, abrasive, and strong at high temperatures. Their machinability is similar to that of stainless steels.Tantalum is very work-hardening, ductile, and soft. It produces a poor surfacefinish; tool wear is high.Titanium and its alloys have poor thermal conductivity (indeed, the lowest of all metals), causing significant temperature rise and built-up edge; they can be difficult to machine.Tungsten is brittle, strong, and very abrasive, so its machinability is low,although it greatly improves at elevated temperatures.Zirconium has good machinability. It requires a coolant-type cutting fluid,however, because of the explosion and fire.20.9.3 Machinability of Various MaterialsGraphite is abrasive; it requires hard, abrasion-resistant, sharp tools.Thermoplastics generally have low thermal conductivity, low elastic modulus, and low softening temperature. Consequently, machining them requires tools with positive rake angles (to reduce cutting forces), large relief angles, small depths of cut and feed, relatively high speeds, andproper support of the workpiece. Tools should be sharp.External cooling of the cutting zone may be necessary to keep the chips from becoming “gummy” and sticking to the tools. Cooling can usually be achieved w ith a jet of air, vapor mist, or water-soluble oils. Residual stresses may develop during machining. To relieve these stresses, machined parts can be annealed for a period of time at temperatures ranging from C ︒80 to C ︒160 (F ︒175to F ︒315), and then cooled slowly and uniformly to room temperature.Thermosetting plastics are brittle and sensitive to thermal gradients duringcutting. Their machinability is generally similar to that of thermoplastics.Because of the fibers present, reinforced plastics are very abrasive and aredifficult to machine. Fiber tearing, pulling, and edge delamination are significant problems; they can lead to severe reduction in the load-carrying capacity of the component. Furthermore, machining of these materials requires careful removal of machining debris to avoid contact with and inhaling of the fibers.The machinability of ceramics has improved steadily with the development of nanoceramics (Section 8.2.5) and with the selection of appropriate processing parameters, such as ductile-regime cutting (Section 22.4.2).Metal-matrix and ceramic-matrix composites can be difficult to machine, depending on the properties of the individual components, i.e., reinforcing or whiskers, as well as the matrix material.20.9.4 Thermally Assisted MachiningMetals and alloys that are difficult to machine at room temperature can be machined more easily at elevated temperatures. In thermally assisted machining (hot machining), the source of heat—a torch, induction coil, high-energy beam (such as laser or electron beam), or plasma arc—is forces, (b) increased tool life, (c) use of inexpensive cutting-tool materials, (d) higher material-removal rates, and (e) reduced tendency for vibration and chatter.It may be difficult to heat and maintain a uniform temperature distribution within the workpiece. Also, the original microstructure of the workpiece may be adversely affected by elevated temperatures. Most applications of hot machining are in the turning of high-strength metals and alloys, although experiments are in progress to machine ceramics such as silicon nitride.SUMMARYMachinability is usually defined in terms of surface finish, tool life, force and power requirements, and chip control. Machinability of materials depends not only on their intrinsic properties and microstructure, but also on proper selection and controlof process variables.译文：20.9 可机加工性一种材料的可机加工性通常以四种因素的方式定义：1、分的表面光洁性和表面完整性。
毕业设计外文翻译模板
本科生毕业设计（论文）外文翻译毕业设计（论文）题目：组合钻床动力滑台液压系统及电控系统设计外文题目： Drilling machine译文题目：组合钻床学生姓名：马莉莉专业：机械设计制造及其自动化0701班指导教师姓名：王洁评阅日期：正文内容小四号字，宋体，行距1.5倍行距。
The drilling machine is a machine for making holes with removal of chips and it is used to create or enlarge holes. There are many different types of drilling machine for different jobs, but they can be basically broken down into two categories.The bench drill is used for drilling holes through raw materials such as wood, plastic and metal and gets its name because it is bolted to bench for stability so that larger pieces of work can be drilled safely. The pillar drill is a larger version that stands upright on the floor. It can do exactly the same work as the bench drill, but because of its size it can be used to drill larger pieces of materials and produce bigger holes. Most modern drilling machines are digitally automated using the latest computer numerical control (CNC) technology.Because they can be programmed to produce precise results, over and over again, CNC drilling machines are particularly useful for pattern hole drilling, small hole drilling and angled holes.If you need your drilling machine to work at high volume, a multi spindle drill head will allow you to drill many holes at the same time. These are also sometimes referred to as gang drills.Twist drills are suitable for wood, metal and plastics and can be used for both hand and machine drilling, with a drill set typically including sizes from 1mm to 14mm. A type of drill machine known as the turret stores tools in the turret and positions them in the order needed for work.Drilling machines, which can also be referred to as bench mounted drills or floor standing drills are fixed style of drills that may be mounted on a stand or bolted to the floor or workbench. A drilling machine consists of a base, column, table, spindle), and drill head, usually driven by an induction motor.The head typically has a set of three which radiate from a central hub that, when turned, move the spindle and chuck vertically, parallel to the axis of the column. The table can be adjusted vertically and is generally moved by a rack and pinion. Some older models do however rely on the operator to lift and re clamp the table in position. The table may also be offset from the spindles axis and in some cases rotated to a position perpendicular to the column.The size of a drill press is typically measured in terms of swing which can be is defined as twice the throat distance, which is the distance from the centre of the spindle to the closest edge of the pillar. Speed change on these drilling machines is achieved by manually moving a belt across a stepped pulley arrangement.Some drills add a third stepped pulley to increase the speed range. Moderndrilling machines can, however, use a variable-speed motor in conjunction with the stepped-pulley system. Some machine shop drilling machines are equipped with a continuously variable transmission, giving a wide speed range, as well as the ability to change speed while the machine is running.Machine drilling has a number of advantages over a hand-held drill. Firstly, it requires much less to apply the drill to the work piece. The movement of the chuck and spindle is by a lever working on a rack and pinion, which gives the operator considerable mechanical advantage.The use of a table also allows a vice or clamp to be used to position and restrain the work. This makes the operation much more secure. In addition to this, the angle of the spindle is fixed relative to the table, allowing holes to be drilled accurately and repetitively.Most modern drilling machines are digitally automated using the latest computer numerical control (CNC) technology. Because they can be programmed to produce precise results, over and over again, CNC drilling machines are particularly useful for pattern hole drilling, small hole drilling and angled holes.Drilling machines are often used for miscellaneous workshop tasks such as sanding, honing or polishing, by mounting sanding drums, honing wheels and various other rotating accessories in the chuck. To add your products click on the traders account link above.You can click on the links below to browse for new, used or to hire a drilling machine.Drilling machines are used for drilling, boring, countersinking, reaming, and tapping. Several types are used in metalworking: vertical drilling machines, horizontal drilling machines, center-drilling machines, gang drilling machines, multiple-spindle drilling machines, and special-purpose drilling machines.Vertical drilling machines are the most widely used in metalworking. They are used to make holes in relatively small work-pieces in individual and small-lot production; they are also used in maintenance shops. The tool, such as a drill, countersink, or reamer, is fastened on a vertical spindle, and the work-piece is secured on the table of the machine. The axes of the tool and the hole to be drilled are aligned by moving the workpiece. Programmed control is also used to orient the workpiece and to automate the operation. Bench-mounted machines, usually of the single-spindle type, are used to make holes up to 12 mm in diameter, for instance, in instrument-making.Heavy and large workpieces and workpieces with holes located along a curved edge are worked on radial drilling machines. Here the axes of the tool and the hole to be drilled are aligned by moving the spindle relative to the stationary work-piece.Horizontal drilling machines are usually used to make deep holes, for instance, in axles, shafts, and gun barrels for firearms and artillery pieces.Center-drilling machines are used to drill centers in the ends of blanks. They are sometimes equipped with supports that can cut off the blank before centering, and in such cases they are called center-drilling machines. Gang drilling machines with more than one drill head are used to produce several holes at one time. Multiple-spindle drilling machines feature automation of the work process. Such machines can be assembled from several standardized, self-contained heads with electric motors and reduction gears that rotate the spindle and feed the head. There are one-, two-, and three-sidedmultiple-spindle drilling machines with vertical, horizontal, and inclined spindles for drilling and tapping. Several dozen such spindles may be mounted on a single machine. Special-purpose drilling machines, on which a limited range of operations is performed, are equipped with various automated devices.Multiple operations on workpieces are performed by various combination machines. These include one- and two-sided jig boring machines,drilling-tapping machines (usually gang drilling machines with reversible thread-cutting spindles), milling-type drilling machines and drilling-mortising machines used mainly for woodworking, and automatic drilling machines.In woodworking much use is made of single- and multiple-spindle vertical drilling machines, one- and two-sided, horizontal drilling machines (usually with multiple spindles), and machines equipped with a swivel spindle that can be positioned vertically and horizontally. In addition to drilling holes, woodworking machines may be used to make grooves, recesses, and mortises and to remove knots.英文翻译指导教师评阅意见。
机械设计外文翻译--- 轴承的摩擦与润滑
毕业设计（论文）外文翻译毕业设计（论文）题目：外文题目：Friction , Lubrication of Bearing 译文题目：轴承的摩擦与润滑系别：机械工程系专业：机械工程制造及其自动化班级：学号：姓名：指导教师：2012年03 月03 日外文文献原文：Friction , Lubrication of BearingIn many of the problem thus far , the student has been asked to disregard or neglect friction . Actually , friction is present to some degree whenever two parts are in contact and move on each other. The term friction refers to the resistance of two or more parts to movement.Friction is harmful or valuable depending upon where it occurs. friction is necessary for fastening devices such as screws and rivets which depend upon friction to hold the fastener and the parts together. Belt drivers, brakes, and tires are additional applications where friction is necessary.The friction of moving parts in a machine is harmful because it reduces the mechanical advantage of the device. The heat produced by friction is lost energy because no work takes place. Also , greater power is required to overcome the increased friction. Heat is destructive in that it causes expansion. Expansion may cause a bearing or sliding surface to fit tighter. If a great enough pressure builds up because made from low temperature materials may melt.There are three types of friction which must be overcome in moving parts: (1)starting, (2)sliding,and(3)rolling. Starting friction is the friction between two solids that tend to resist movement. When two parts are at a state of rest, the surface irregularities of both parts tend to interlock and form a wedging action. To produce motion in these parts, the wedge-shaped peaks and valleys of the stationary surfaces must be made to slide out and over each other. The rougher the two surfaces, the greater is starting friction resulting from their movement .Since there is usually no fixed pattern between the peaks and valleys of two mating parts, the irregularities do not interlock once the parts are in motion but slide over each other. The friction of the two surfaces is known as sliding friction. As shown in figure ,starting friction is always greater than sliding friction .Rolling friction occurs when roller devces are subjected to tremendous stress which cause the parts to change shape or deform. Under these conditions, the material in front of a roller tends to pile up and forces the object to roll slightly uphill. This changing of shape , known as deformation, causes a movement of molecules. As a result ,heat is produced from the added energy required to keep the parts turning and overcome friction.The friction caused by the wedging action of surface irregularities can be overcome partly by the precision machining of the surfaces. However, even these smooth surfaces may require the use of a substance between them to reduce the friction still more. This substance is usually a lubricant which provides a fine, thin oil film. The film keeps the surfaces apart and prevents the cohesive forces of the surfaces from coming in close contact and producing heat .Another way to reduce friction is to use different materials for the bearing surfaces and rotating parts.This explains why bronze bearings, soft alloys, and copper and tin iolite bearings are used with both soft and hardened steel shaft. The iolite bearing is porous. Thus, when the bearing is dipped in oil, capillary action carries the oil through the spaces of the bearing. This type of bearing carries its own lubricant to the points where the pressures are the greatest.Moving parts are lubricated to reduce friction, wear, and heat. The most commonly used lubricants are oils, greases, and graphite compounds. Each lubricant serves a different purpose. The conditions under which two moving surfaces are to work determine the type of lubricant to be used and the system selected for distributing the lubricant.On slow moving parts with a minimum of pressure, an oil groove is usually sufficient to distribute the required quantity of lubricant to the surfaces moving on each other .A second common method of lubrication is the splash system in which parts moving in a reservoir of lubricant pick up sufficient oil which is then distributed to all moving parts during each cycle. This system is used in the crankcase of lawn-mower engines to lubricate the crankshaft, connecting rod ,and parts of the piston.A lubrication system commonly used in industrial plants is the pressure system. In this system, a pump on a machine carries the lubricant to all of the bearing surfaces at a constant rate and quantity.There are numerous other systems of lubrication and a considerable number of lubricants available for any given set of operating conditions. Modern industry pays greater attention to the use of the proper lubricants than at previous time because of the increased speeds, pressures, and operating demands placed on equipment and devices.Although one of the main purposes of lubrication is reduce friction, any substance-liquid , solid , or gaseous-capable of controlling friction and wear between sliding surfaces can be classed as a lubricant.V arieties of lubricationUnlubricated sliding. Metals that have been carefully treated to remove all foreign materials seize and weld to one another when slid together. In the absence of such a high degree of cleanliness, adsorbed gases, water vapor ,oxides, and contaminants reduce frictio9n and the tendency to seize but usually result in severe wear; this is called “unlubricated ”or dry sliding.Fluid-film lubrication. Interposing a fluid film that completely separates the sliding surfaces results in fluid-film lubrication. The fluid may be introduced intentionally as the oil in the main bearing of an automobile, or unintentionally, as in the case of water between a smooth tuber tire and a wet pavement. Although the fluid is usually a liquid such as oil, water, and a wide range of other materials, it may also be a gas. The gas most commonly employed is air.Boundary lubrication. A condition that lies between unlubricated sliding and fluid-film lubrication isreferred to as boundary lubrication, also defined as that condition of lubrication in which the friction between surfaces is determined by the properties of the surfaces and properties of the lubricant other than viscosity. Boundary lubrication encompasses a significant portion of lubrication phenomena and commonly occurs during the starting and stopping off machines.Solid lubrication. Solid such as graphite and molybdenum disulfide are widely used when normal lubricants do not possess sufficient resistance to load or temperature extremes. But lubricants need not take only such familiar forms as fats, powders, and gases; even some metals commonly serve as sliding surfaces in some sophisticated machines.Function of lubricantsAlthough a lubricant primarily controls friction and ordinarily does perform numerous other functions, which vary with the application and usually are interrelated .Friction control. The amount and character of the lubricant made available to sliding surfaces have a profound effect upon the friction that is encountered. For example, disregarding such related factors as heat and wear but considering friction alone between the same surfaces with on lubricant. Under fluid-film conditions, friction is encountered. In a great range of viscosities and thus can satisfy a broad spectrum of functional requirements. Under boundary lubrication conditions , the effect of viscosity on friction becomes less significant than the chemical nature of the lubricant.Wear control. wear occurs on lubricated surfaces by abrasion, corrosion ,and solid-to-solid contact wear by providing a film that increases the distance between the sliding surfaces ,thereby lessening the damage by abrasive contaminants and surface asperities.T emperature control. Lubricants assist in controlling corrosion of the surfaces themselves is twofold. When machinery is idle, the lubricant acts as a preservative. When machinery is in use, the lubricant controls corrosion by coating lubricated parts with a protective film that may contain additives to neutralize corrosive materials. The ability of a lubricant to control corrosion is directly relatly to the thickness of the lubricant film remaining on the metal surfaces and the chermical composition of the lubricant.Other functionsLubrication are frequently used for purposes other than the reduction of friction. Some of these applications are described below.Power transmission. Lubricants are widely employed as hydraulic fluids in fluid transmission devices.Insulation. In specialized applications such as transformers and switchgear , lubricants with highdielectric constants acts as electrical insulators. For maximum insulating properties, a lubricant must be kept free of contaminants and water.Shock dampening. Lubricants act as shock-dampening fluids in energy transferring devices such as shock absorbers and around machine parts such as gears that are subjected to high intermittent loads.Sealing. Lubricating grease frequently performs the special function of forming a seal to retain lubricants or to exclude contaminants.The object of lubrication is to reduce friction ,wear , and heating of machine pars which move relative to each other. A lubricant is any substance which, when inserted between the moving surfaces, accomplishes these purposes. Most lubricants are liquids(such as mineral oil, silicone fluids, and water),but they may be solid for use in dry bearings, greases for use in rolling element bearing, or gases(such as air) for use in gas bearings. The physical and chemical interaction between the lubricant and lubricating surfaces must be understood in order to provide the machine elements with satisfactory life.The understanding of boundary lubrication is normally attributed to hardy and doubleday , who found the extrememly thin films adhering to surfaces were often sufficient to assist relative sliding. They concluded that under such circumstances the chemical composition of fluid is important, and they introduced the term “boundary lubrication”. Boundary lubrication is at the opposite end of the spectrum from hydrodynamic lubrication.Five distinct of forms of lubrication that may be defined :(a) hydrodynamic;(b)hydrostatic;(c)elastohydrodynamic (d)boundary; (e)solid film.Hydrodynamic lubrication means that the load-carrying surfaces of the bearing are separated by a relatively thick film of lubricant, so as to prevent metal contact, and that the stability thus obtained can be explained by the laws of the lubricant under pressure ,though it may be; but it does require the existence of an adequate supply at all times. The film pressure is created by the moving surfaces itself pulling the lubricant under pressure, though it maybe. The film pressure is created by the moving surface to creat the pressure necessary to separate the surfaces against the load on the bearing . hydrodynamic lubrication is also called full film ,or fluid lubrication .Hydrostatic lubrication is obtained by introducing the lubricant ,which is sometime air or water ,into the load-bearing area at a pressure high enough to separate the surface with a relatively thick film of lubricant. So ,unlike hydrodynanmic lubrication, motion of one surface relative to another is not required .Elasohydrodynamic lubrication is the phenomenon that occurs when a lubricant is introduced between surfaces which are in rolling contact, such as mating gears or rolling bearings. The mathematical explanation requires the hertzian theory of contact stress and fluid mechanics.When bearing must be operated at exetreme temperatures, a solid film lubricant such as graphite or molybdenum disulfide must be use used because the ordinary mineral oils are not satisfactory. Must research is currently being carried out in an effort, too, to find composite bearing materials with low wear rates as well as small frictional coefficients.In a journal bearing, a shaft rotates or oscillates within the bearing , and the relative motion is sliding . in an antifriction bearing, the main relative motion is rolling . a follower may either roll or slide on the cam. Gear teeth mate with each other by a combination of rolling and sliding . pistions slide within their cylinders. All these applications require lubrication to reduce friction ,wear, and heating.The field of application for journal bearing s is immense. The crankshaft and connecting rod bearings of an automotive engine must poerate for thousands of miles at high temperatures and under varying load conditions . the journal bearings used in the steam turbines of power generating station is said to have reliabilities approaching 100 percent. At the other extreme there are thousands of applications in which the loads are light and the service relatively unimportant. a simple ,easily installed bearing is required ,suing little or no lubrication. In such cases an antifriction bearing might be a poor answer because because of the cost, the close ,the radial space required ,or the increased inertial effects. Recent metallurgy developments in bearing materials , combined with increased knowledge of the lubrication process, now make it possible to design journal bearings with satisfactory lives and very good reliabilities.参考文献：1. Chambers T. L., Parkinson A. R., 1998, “Knowledge Representation and Conversion ofHybridExpert Systems.” Transactions of the ASME, v 120,pp 468-4742. Koelsch, James R., 1999, “Software boosts mold design efficiency“ Molding Systems,v57, n 3,p16-23.3. Lee, Rong-Shean, Chen, Y uh-Min, Lee, Chang-Zou,1997 “Development of a concurrentmolddesign system: A knowledge-based approach”, Computer Integrated Manufacturing Systems, v 10,n 4, p 287-3074. Steadman Sally, Pell Kynric M, 1995, “ Expert systems in engineering design: An applicationforinjection molding of plastic parts“ Journal of Intelligent Manufacturing, v6, p 347-353.5. Fernandez A., Castany J., Serraller F., Javierre C., 1997, “CAD/CAE assistant for the designofmolds and prototypes for in jection of thermoplastics “Information Technological, v 8, p 117-124.6. Douglas M Bryce, 1997, “Plastic injection molding -Material selection and product design”, v 2,pp1-48.7. Douglas M Bryce, 1997, “Plastic injection molding-Mold design fundamentals”, v2, pp 1-120 中文译文：轴承的摩擦与润滑现在看来，有很多这种情况，许多学生在被问到关于摩擦的问题时，往往都没引起足够的重视，甚至是忽视它。
外文翻译-引擎机械概述
本科毕业设计（论文）中英文对照翻译院（系部）专业名称年级班级学生姓名指导老师2012年5月ENGINE MECHANICALOperation Main Components and Classification of the Engine The automotive engine is essentially a heat mobiles are internal combustion engines.Princiole of OperationThe spark-ignition engine is an internal-combustion engine with externally supplied in ignition .The gasoline engine is a kind of spark-ignition engines.The four-stroke-cycle gasoline engine cycle is spread over four pistion strokes.The first stroke in your engine is called the intake stroke. Instead of opening the intake valve after you have drawn the poston down . you will find it better to open the intake valve as the piston starts down . This allows the air to draw fuel in the entire time the piston is moving down.Remember , the intake stroke starts with the piston at the top of the cylinder(intake valve open and exhaust valve closed)and stops with the piston at the bottom of its travel . This requires one half turn of the crankshaft.As the crankshaft continues to move , the piston is forced up through the cylinder . If you keep both valves closed , the fuel mixture will be squeezed , or compressed , as the piston reaches the top .This is called the compression stroke . It , too , requires a half turn of the crankshaft .The compression stroke serves to break up the fule into even smaller particles . This happens due to the the sudden swelling and churning of the mixture as it is compressed .When the air fule mixture is subjected to a sudden sharp compression force . its temperature rises .This increase in temperature makes the mixture easier to ignite and causes it to explode with greater force , As the piston reaches the top of its travel on the compression sroke , it has returned to the pro[er position to be pushed back down by the explosion.Remember , the compression stroke starts with the piston at the bottom of the cylinder(both valves closed)and the stops with the piston at the top of the cylinder . This requires an additional half turn of crankshaft .As the piston reaches the top the compression stroke ,the mixture is broken into tiny particles and heated up . when ignited , it will explode with great force . This is the right time to explode the mixture . A spark plug provides a spark inside the combustion chamber ,The spark produced at the plug is formed by the ignition system.Just imagine that a hot spark has been provided in the fuel mixture .The mixture will explode and , in turn , force the piston down into the cylinder . This gives the crankshaft a quick and forceful push . This is the power stroke , Both valves must be kept closed during the power stroke or the pressure of the burning fuel will squirt out through the valve ports . Remenber , the power storke starts with the piston at the top of ylinder(both valves closed) and stops with the piston at the botton of the cylinder , T his requires another half turn of the crankshaft .When the piston reaches the bottom of the power stroke .the exhaust valve opens . The spinning crankshaft forces the piston up through the cylinder , pushing burned gases out . This is the exhaust stroke .Remenber , the exhaust stroke starts with the piston at the bottom of the cylinder (exhaust valve open and intake valve closed) . It stops with the piston at the top of the cylinder . This requires one more half turn of the crankshaft .If you count the number of half turns in the intake , compression , power , and exhaust storkes , You will find you have a total of four , This gives you two complete turns , or revolutions ,of the crankshaft . When the crankshaft is turning around twice ,it is receiving power only during one half turn , or one fourth of the time .As soon as the piston reaches the top of the exhaust stroke , it starts down on another intake , compression , power ,and exhaust cycle , this cycle is repeated over and over ,Each complete cycle consists of four strokes of the piston , hence the name four-storke cycle.Main Engine ComponenntsEngine BlockThe engine block serves as a rigid metal foundation for all parts of engine . It contains the cylinders and supports the crankshaft and camshaft . In older engines ,the valve seats , ports ,and guides are built into the block ,Accessry unis and the clutch housing are boled to it .Blocks are made of either cast iron or aluninum ,The lighter the block(providing it has sufficient strength), the better ,The modern thin-wall casting proces controls core size and placement much more accuratcely than the older casting process .This permits casting the block walls much thinner , reducing the weight of the block .Since the bolck wall thickness is more uniform , block distortion during service less severe .CylindersThe cylinder is a aroud hole formed in the block .It forms a guide guide for the piston and acts as a containner for taking in , compressing ,firing , and the exhausting the air-fuel chareg , Cylinder have been made of both steel and cast iron .Cast iron is by far the most popular.When steel cylinders are desired in an aluminum block, they are installed in the form of cylinder sleeves(round , pipe-like liners ), These sleeves may be eiher cast or pressed into the block ,Some engines use removable cylinder sleeves . When the cylinde becomes won The old sleeves can be pulled out and new sleeves can be pressed in . The sleeves are pressed into oversize cylinder holes ,Cylinder sleeves are widely used in heavy-duty truck and industrial engines ,Sleeves can also be used to be repair a won or cracked cylinder in a cast iron block .PistonsThe piston must move down through the cylinder to the cylinder to produce a vacuum to draw a fuel charge into the cylinder . It then travels up in the cylinder and compresses the mixture ,When the mixture is fired , the pressure of the expanding gas is transmitted to the top of piston . This drives the piston back down through the cylinder with great force , transmitting the expanding gas to the crankshaft ,The piston then then travels up through the cylinder and exhaust the burned fuel charge.Pistons are usually made of aluminum . Often ,aluminum piston are tin-plated to allow proper break-in when the engine is stared ,Aluminum pistons can be forged ,but they are more commonly cast .Cast iron is a good material for pistons used m a slow-speed engine .It has excellent wear characteristics and will provide good performance .Connecting RodsAs the name implies , connecting rods are used to connect protons to the crankshaft .The upper end of the rod oscillates(swings back and forth), while the lower ,or big end ,bearing rotates(turns).Because there is very little bearing movement in the upper end , the bearing area can be reasonably small . The lower end rotates very fast , and the crankshaft bearing journal turns inside the connecting rod . This rotational speed tends to produce heat and wear .To make the rod wear well, a larger bearing area is required.The upper end of the rod has a hole through it for the piston pin ,The botton of the large end of the connecting red must be removed SO the rod can be installed on the crankshaft journal .The section that is removed is called the connecting rod cap.Connecting rods are normally made of alloy steel .They are drop-forged shape and then machined .CrankshaftThe engine crankshaft provides a constant turning force to the wheels ,it has through to which connecting rods are attached ,and its function to change the reciprocating motion of the piston to a rotary motion to drivethe wheels . Crankshaft are made of alloy steel or cast iron.The crankshaft is held in position by a series of main bearings ,The maximum mumber of main bearings for a crankshaft is one more than the munber of cylinders. It may have fewer main bearings than cylinder .Most engines use pressman insert bearings that are constructed like the connecting rod bearings, But are somewhat larger .In addition to supporting the crankshaft , one of the main bearings must control the forward and backward movement.FlywheelA heavy flywheel is attached to the rear of the crankshaft with bolts ,The function of the flywheel is to smooth out engine speed and keep the crankshaft spinning between power strokes . in some engines , the flywheel also serves as a mounting ,surface for the clutch . The outer rim of the flywheel has a large ring attached with gear teeth cut into it , The teeth of the starter motor engine these teeth and spin the flywheel to crank the engine . When all automatic transmission is used ,the torque converter assembly works with the flywheel.CamshaftThe camshaft is used to open and close the valves . There is one cam on the camshaft for each valve in the engine ,Generally only one camshaft is used in most engines . Newer engines are increasingly equipped with two or more camshaft.ValvesEach engine cylinder ordinarily has two valves . However , modern engines often use four valves per cylinder(two intake and two exhaust), A few engines used in smaller vehicles have three intake valves per cylinder : two intake valves and one exhaust valves or three intake valves and two exhaust valves .Because the head of an exhaust valve operates at temperatures up to 1300C(704C) ,valves are made of heat-resistant metal . In order to prevent burning ,the valve must give off heat to the valve seat and to the valve guide . The valve must be make good contact with seat and must run with minimum clearance in the guide .Valve LiftersMechanical valve lifters are usually made of cast iron , The bottom Dart that contacts the camshaft is hardened .Some lifters are hollow to reduce weight .Most valve trains that contain mechanical lifters have some provision for adjusting clearance . Mechanical valve lifters were used in older engines .Hydraulic valve lifters perform the same job as mechanical lifters , However ,hydraulic lifters are self-adjusting , operate with no lifte-to –rockerarm clearance . and uses engine oil under pressure to operate ,Hydraulic lifters are quite in operration .Engine ClassificationCycle ClassificationEngines are often classified according to cycle . Most internal combustion piston engines use a two-or four –stroke cycle .All modern automobile engines use the four stroke cycle engine .The two-stroke cycle engine performs the intake , compression , firing , and exhaust sequence in one revolution of the crankshaft.Cylinder ClassificationThe inline engine has its cylinders arranged one after the other in a straight line , They are in a vertical , or near vertical position . Most modern inline engines are four cylinders .A V-type engine places two banks or rows of cylinders at an angle to each other-genre-ally at 60or 90 ,The V-type engine has several advantages: short length , extra block rigidity , a short , heavy crankshaft , and low profile that is conducive to low hood lines , The shorter block permits a reduction in vehicle length with riot sacrifice in passenger room .The horizontal opposed engine is like a V-type engine , except that both banks lie in a horizontal plane . The advantage here is all extrmely low overall height .Which makes this engine ideally suited installations where space is limited .Cooling ClassificationAs you have learned ,engines are either liquid-collde or air-colled . Most vehicles use liquid-colled engines .Air-colled engines are used in limited numbers modern vehicles .Fuel ClassificationAutomobile engines can use gasoline , diesel fule , gasohol(mixture of gasoline and alcohol), alcohol , LNG(liquefied natural gas) ,CNG(compressed natural gas) ,or LPG(liquefied propane gas ) .Gasoline powers the majority of vehicles , but diesel fule is used in some vehicles .Gosohol ,LNG ,CNG ,and LPG are beginning to see wider use .One of the principle differences in these engines is in method of fuel delivery and carburction .Gasoline ,LNG ,CNG ,and LPG utilize the same basic type of engine , but LNG ,CNG ,and LPG utilize a slightly different fule delivery setup .Diesel engines do not use a carburetor or all ignition system .Valve SystemOperation of Valve systemYou have seen that the intake valve stroke .Both valves must remain closed during the compression and power stroke ,and the eshaust valve opens during the exhaust stroke , The designer must design a device to open and close the valves at the proper times .The shaft will have an egg-shaped bump called a cam lobe .The cam lobe is machined as an integral part of the shaft .This shaft is called a camshaft .The distance the valve will be raised , how long it will stay open , and how fast it opens and closes can all be controlled by the height and shape of the hole .As you will see later , it is impractical to have the cam lobe contact the end of valve stem .When the camshaft is turn ,the lobes will not even touch the valve stem ,The lifter is installed between the cam lobe and the valve stem . The upper end rides on the lobe and the lower and almost touches the valve stem . The lifter slides up and down in a a hole bored in the head metal that separates the valve stem from the camshaft .You have developed a method of opening and closing the valves .The next problem is how and at what speed to turn the camshafts , Each valve must be open for one storke .The intake valve is open during the intake storke and remains closed during the compression ,power ,and exhaust stroke .This would indicate that the cam lobe must be turn fast enough to raise the valve erery fourth stroke .You can see that it takes one complete revolution of the cam lobe four strokes of the piston .Remember that four srokes of the piston require two revolutions of the crankshaft , the cam shaft must be once , If you are speaking of the speed of the camshaft ,you can say that the camshaft must turn at one-half crankshaft speed .If the crankshaft is turning and the camshaft must turn at one-half crankshaft speed , it seems logical to use the spinning crankshaft to turn the camshaft ,One very simple way to drive the camshaft would be by means of gears and a belt . One gear is fastened on the end of the crankshaft ,and the other is fastened on the end of the camshaft .The large camshaft gear drives the smaller crankshaft gear through the belt .If ,for instance ,the small gear Oil the crankshaft has 10 teeth and the large gear on the camshaft has 20 teeth ,the crankshaft will truth the camshaft at exactly one-half crankshaft speed .VVT-Toyota`s Continuously Variable Valve TimingThe most significant and satisfying changes to the Lexus GS line are inthe area power train . In the case of GS300 , Lexus breathes new life into last year`s 3.0Lin-line six by introducing VVT-continuously variable valve timing syestem .On the dyne ,VVT shows up as only five additional horsepower and 10 lb-ft of torque . But in the car it meansfuel economy improvements of 1.6 mpg .smoother idle ,California TLEV (transitional tow-emissions vehicle )certification and zero-to 60 mph a half second quicker .Toyota eliminates the compromise of conventional valve timig with the introduction of VVT , By continuously varying intake valve timing (up to 60 crank angle degrees) , Toyota optimizes low-to mid-speed torque , improves fule economy and lowers emissions without having a negative impact on idle .In essence ,the system controls valve overlap ,which means it can climinate it completyly for a glass smooth idle . or maximize it to boost volumetric efficiency ang reduce pumping losses this translates into power ,economy and cleaner running at all engine speeds.The heart of the system is the intake cam pulley , which consists of an inner and outer section ,The inner portion is fixed to the camshaft and nests inside the belt-driven outer pulley via helical spline gears . An electronically controlled hydraulic piston moves the pully halves relative to one another ,causing the cam portion to rotate within the outer pulley.This rotation davances or retarda intake valve timing .A spool valve reacting to signals from the ECU controls hydraulic pressure .VTEC-Honda Variable Valve Timing and Lift Electronic Control By desiging a higher valve lift ,wider valve-timing ,and large valve valve diameter ,it is possible to obtain a higher volumetric efficienvy to copy with higer output engine speeds ,The VTEC is used to improve volumetric effiency from low engine speed to high engine speed .With VTEC, the valve timing and lift can be dajusted at low engine rotation to increase troque and prevent air from being forced back through the intake .VTEC OperationFig.2-4 shows the VTEC mechanism while operating at low engine speeds . In the low-speed mode the 3 rocker arms are separated and use cams A&B only . At this time the mid rocker arm is in contact with the high speed cam due to the spring force in the lost motion mechanism .It is separated from the primary and secondary rocker arm and thus is not actuating the valve .Fig.2-5shows the VTEC mechanism while operating in the high speed mode . During high speed engine operation the 3 rocker arms are connected and move together due to the 2 hydraulic pistons which have moved over due to increased hydraulic presure.MIVEC-Mitsubishi Innovative Valve timing Elecctronnic Control systemThe MIVEC dual-intake valve canshaft enables changing betweeen low-speed and high-speed moders(Fig.2-6), resulting in easy operation from low to high rams ,improving the driving experience when staring from a stop light , merging on to the freeway ,or accelerating to overtake another car .In the pursuit of pure driving enjoyment,potentially incompatible goals like fuel economy ,environment-friendiness,and clean driving have all been achieved . Low-speed ModeThe difference in the dual-intake valve lift(low lift and medium lift)and enhanced in-cylinder streaming further stabilize combustion without compromising fuel econmy ,emissions ,and torque .High-speed ModeExtending the injection valve opening time and expanding the valve lift range in ,creases intake air mass and achieves output close to best in class .The Grandis is equipped with the 2.4L MIVEC and the Colt is equipped with the 1.3 and 1.5L MIVEC .Electronic Valve Control SystemAn electronic valve control (EVC) system replace the mechanical camshaft ,controling each valve with actuators for inpendent valve with actuators for independent valve timing .The EVC system control the opening and closing time and lift amout of each intake and exhaust valve with independent actuators on each valve .Changing from a mechanical camshaft driven valve into dependently controled actuator valves provide a huge amount of flexibility in engine control strategy .Vehicles utilizing EVC can realize several benefits including :1)increase engine power and fuel economy.2)Allows centralized and distributed EVC system to perform at their full potential.3)Adapts to engines of varied cylinder counts .With all of improved efficiencies and consumer benefits , auto manufacturers are eager to get their first EVC systems on the road ,The EVC system is targeted to operate in temperatures up to 125C ,while the actuator can be controlled in a centralized syetem with a high-speed multiplex bus (up to 10Mbps)or in a distributed system with a nominal speed bus .EVC systems must be compact in size ,specifically the actuators that must be small enough to fit in the engine space .A vchicle that use a 42V system is ideal for EVC because it requires high voltage to control the valveactuators , and EVC is targeted for V8 and V12 engines.Smart ValvesValco is actively developing technology for reducing fuel consumption and emissions with an engine cylinder-head design that uses its smart valve. Actuation(SV A)in place of conventional operation of engine valves by the cam belt ,camshaft,and hydraulic cam followers .SV A is the first of many innovations that Valco intends to actively develop and market to meet increasing demand for better fuel economy and reduced pollution following its acquisition of Johnson Control`s Engine Electronics Division .In a camless engine ,each engine valve is operated by an actuator mounted above the Valve guides.Each actuator is linked to an engine-mounted valve control units that ensures optimal of all valves and performs the power drive function .By controlling residual gases ,minimizing pumping losses ,and deactivating cylinders and valves ,this technology can reduce consumption and pollutant emissions by 20%. Consumers will benfit from enhanced performance from increases in low-end engine torque .The SV A development program is supposed by several car manufactures and is scheduled for volume production in 2009.Piston and Rod RepairThis repair procedure requires removal of the cylinder head and oil pan .It is much easier to perform this work with the engine removed from the vehicle and mounted on a stand .These procedures requires certain hand tools .A cylinder ridge reamer, a numbered punch set ,piston ring expander ,snapring tools and piston intallation tool ring compressor are all necessary for correct piston and rod repair .Cleaning&InspectionIf the piston is out of specification or otherwise unusable ,it must be replaced,If the cylinder is worm or damaged ,the engine block must be bored and oversize pistons installed.1.Remove the piston rings from the piston .The compression rings (top and middle rings) must be removed using a piston ring expander ,to prevent breakage and /or scratching the piston.2.If there is no obvious damage to the piston and the intent is to reuse the piston ,clean the ring grooves with a ring groove cleaner , being careful not to cut into the piston metal .Heavy carbon deposits can be cleaned from the top of the piston with a scraper or Wire brush .Do not ,however ,use a wire wheel on the ring grooves or lands .Clean the he oil drain holes in the ring grooves .Clean all remaining dirt ,carbon and varmish from the piston with a suitable solvate and abrush ,Do not use a caustic solution on alumnum parts .3.After cleaning ,inspect the piston for scuffing , scoring ,cracks ,pitting or excessive ring groove wear . Replace the piston if obviusly worm .4.If the piston appears servicable , measure the piston diameter usinga micrometer . Measure the Piston diameter in the thrust direction ,90 degrees to the piston pin axis ,1-1/4 inch below the top of the piston .5.Inspect the cylinder bores for taper and out-of-round .The cylinder bores must be measured at 3 levels top to bottom in directions of East-to-West and North-to-South .Measure the cylinder using a bore gauge, or with a telescope gauge and micrometer .The measurement shoud be made in the piston thrust direction at the top ,middle and bottom of the cylinder . Note: Piston diameter and cylinder measurements shoud be made with the parts at room temperature ,70F(21C).6.Subtract the piston diameter measurement from the cylinder measurement .This I the piston-to-cylinder wall claerance .If the clearance is excesive or if the cylinder wall is badly scored or scuffied ,the cylinder may have to be bored and an oversize piston installed .7.Verify that the cylinder has a proper cross-hatch pattern .These tiny marks are the result of the honing operation dating engine manufacture .They retain engine oil to keep the piston tings from scuffing during engine break-in after overhaul .If little or no cross ,hatch is evident ,the cyliunder may require re-honing if the cylinder is in otherwise good condition or reborn if the cylinder is worn or damaged .8.If the piston-to-cylinder wall clearance is within specifications ,check the ring groove clearance .Roll the piston ring around the ring groove in which it is to be installed and check the clearance with a feeker gauge .Compare the measurement with permeation .High points in the ring groove that may cause the ring to bind may be cleaned up carefully with a small flat file .Replace the piston if the ring groove clearance is not within specification.9.Check the connecting rod for damager or obvious wear .Check for signs of over heating(blue appearance)or fractures and check the bearing bore for out-of-round and taper ,A shiny surface on the pin boss side of the piston usually indicates that the connecting rod is bent or the wrist pin hole is not in proper relation to the piston skirt and ring grooves .Abnormal connecting rob beating wear can be caused by either abent connecting rob . An improperly machined journal or a tapered connecting rob bore .Twisted connecting robs will not create an easily identifiable wear pattern ,but badly twisted robs will disturb the action of the entire piston ,rings ,and connectingrob assembly and may be the cause of excessive oil consumption .10.If the piston must be removed from the connectong rob ,mark the side of the connecting rob that corrresponds with the side of the piston that faces the front of the engine ,so the new piston will be installed facing the same direction ,Most pistons have an zrrow or notch on the top of the piston ,indicating that this side should face the front of the engine .If the original piston is to be reinstalled , use paint or a marker to indicate the cylinder number on the piston , so it can reinstalled on the same connecting rob .11.The piston pin is a press fit in the connecting rob .If the piston and /or connecting rob must be replaced ,the pin must be pressed into the connecting rob using a fixture that will not damage or distort the piston and /or connecting rob .The piston must move freely on the pin after installation . Ridge Removal& HoningRidge RemovalThis particular procedure applies to all vehicles .Inspect the upper portions of cylinder (near the head )for a didge formed by ring wear .If there is ridge , it must be removed by forst shifting the piston down in the cylinder and then covering the piston top completely with a clean rag .Use a ridge reamer to remove metal at the lip until the cylinder , If this is not done , the rings will be damaged during removal of the piston .HoningBefore honing the cylindersa ,stuff plently of clean shop towels under the bores and over the crankshaft (if still in the engine (to keep the abrasive materials from entering the crankshaft area.1. The cylinder bore resizing hone equipped with 220 grit or equivalent is the best tool for this job .In addition to deglazing , it will reduce taper and out-of-round as well a removing light scuffing ,scoring or scratches .Usualy a few strokes will clean up a bore and maintain required limits .2.Deglazing of the cylinder walls may be done using a cylinder surfacing hone (or equivalent ) .Use a tool equipped with 280 grit stones if the cylinder is already straight and round .Usually 20-60strokes ,depending on the bore condition will be sufficient to provide a satisfactory surface .Inspect the cylinder walls each 20 strokes ,using a light hotdog on available from an automotive part store .3.Honing should be done by moving the hone up and down fast enough to get a cross-hatch pattern .When hone marks intersect at 50~60 , the cross-hatch angle is most satisfactory for proper seating of the rings /4. A controlled hone motor speed between 200~300rpm is neccssary to obtain the proper cross-hatch angle .The number of up and down strokes perminute can be regulated to get the desired 50-60angle .Faster up and down strokes increase the crosshatch angle .5.After honing , it will be neccssary to clean the block to remove all traces of abrasive .Rod Bearing ReplacementThe engine crankshaft and connecting rod bearing clearances can be determined by the use of plastigage or a similar product . The follwing is the recommended procedure for the use of of plastigage .1.Rotate the crankshaft until the connecting rod boss to be checked is at the bottom of its stroke /2.With the connecting rod and the connectong and the connecting rod bearing cap removed from the crankshaft ,remove the oil film from the surface to be checked .Plastigage is soluble in oil3.Place a piece of plastigage across the entire width of the bearing shell in the bearing cap approximately 1/4 inch (6.3ram) off center and away from the oil hole .In daaition ,suspect areas can be checked by placing plastigage in the suspect area .4.Before assembling the rod bearing cap with the plaetigage in place , the rankshaft must be rotated until the connecting rod being checked starts moving toward the top of the engine .Only then should the cap be assembled and tightened to specifications .Do not rotate the crankshaft while assembling the cap or the plastigage may be smeared ,giving inaccurate results .5.Remove the bearing cap and compare the width of the flattened plastigage with the metric scale provided on the packaged .Locate the band closest to the same width .This hand shows the amount of clearance in thousandths of a millimeter .Differnces in readings between the ends indicate the amount of taper present . Record all readings taken ,Plastigage generally is accompainied by to scales . Oneself is in inches , the other is a metric scale ,plasigage is available in a variety of clearance ranges .。
机械专业文献翻译--微型模具成型的热量和挤压控制
中文2245字毕业设计(论文)外文资料翻译系部：机械工程系专业：机械工程及自动化姓名：学号： 05010121外文出处：Shanghai University附件： 1.外文资料翻译译文；2.外文原文。
指导教师评语：该生的外文翻译基本正确，能达到本科毕业的水平。
基本上能准确地表达原文思想，语句较为通顺，条理清楚，基本符合中文习惯，整体翻译质量较好签名：年月日附件1：外文资料翻译译文微型模具成型的热量和挤压控制在这篇文章中,我们为了有效地复制出该微型模具产品的微小结构,将一个挤压机器和一个小核心传感器组合起来，构建一个注射模具的挤压系统。
在一些重要的部位，由一个压力装置，它作为原动力，驱动中心模具工作。
举例说吧，在注射以后，模腔中的压力会从二十兆帕上升到三十四兆帕。
那些小小的感应器形成感受到压力，那些周围的装置和热敏传感器，排列在洞腔的同围。
我们可以根据这些信号推测里面状况朝着有利的方向发展。
为了评估该注射系统，我们做了一个厚度为1lm角度为140℃三角凹朝槽来进行工作。
说明大部分的医疗信息设备都有一个基础工作部分，另外还有一些辅助部件来完成某种特定的功能。
模具成型技术在现实中广泛应用，而且在大批量生产中多有应用，这篇文章即是研究成型过程在传统的成型压力系统中,其为系统提供很大的压力差,这种特点为模具成型过程提供了很好的动力源.然而,传统的成型过程在注射成型的过程中,特别是在微型模具的成型过程中,有两个很明显的问题.首先,在用单模腔成型微小结构的模具时,不同的温度和硬度会引起不一致的成型压力.一般来说,模腔中心的温度越高,中心周围的温度也会越高.其次,即使通过冷却和控制压力的方法来展平那些不平的区域,但是通过检测发现,热流量和压力仍是高于成型微型模具工作时所规定的压力,而且腔内的这种情况很不好控制,这样以来就只好通来侦测热流面不是温度来控制型腔中各种成型条件.这篇文章的作者，也就是该机器的设计者，他通过在模具重要部位安放一个叫做模具核心挤压机的部件来及时了解并控制模腔内成型的具体情况。
机械类车床外文翻译
毕业设计（论文）——外文翻译（原文）Lathe来源：/wiki/LatheA lathe is a machine tool which spins a block of material to perform various operations such as cutting, sanding, knurling, drilling, or deformation with tools that are applied to the workpiece to create an object which has symmetry about an axis of rotation.Lathes are used in woodturning, metalworking, and glassworking. Lathes can be used to shape pottery, the best-known design being the potter's wheel. Most suitably equipped metalworking lathes can also be used to produce most solids of revolution, plane surfaces and screw threads or helices. Ornamental lathes can produce three-dimensional solids of incredible complexity. The material is held in place by either one or two centers, at least one of which can be moved horizontally to accommodate varying material lengths. Examples of objects that can be produced on a lathe include cue sticks, table legs, bowls, baseball bats, crankshafts and camshafts.HistoryThe lathe is an ancient tool, dating at least to the Egyptians ，and known and used in Greece, the Roman and Byzantine Empires.The origin of turning dates to around 1300BC when the Egyptians first developed a two-person lathe. One person would turn the wood workpiece with a rope while the other used a sharp tool to cut shapes in the wood. The Romans improved the Egyptian design with the addition of a turning bow. Early bow lathes were also developed and used in Germany, France and Britain. In the Middle Ages a pedal replaced hand-operated turning, freeing both the craftsman's hands to hold the woodturning tools. The pedal was usually connected to a pole, often a straight-grained sapling. The system today is called the "spring pole" lathe. Spring pole lathes were in common use into the early 20th Century. A two-person lathe, called a "great lathe", allowed a piece to turn continuously (like today's power lathes). A master would cut the wood while an apprentice turned the crank。
机械类专业英语阅读教程部分翻译
1. Metals and Their UseIt is known that metals are very important in our life. Metals have the greatest importance for industry. All machines and other en gineering constructions have metal parts; some of them consist only of metal parts.There are two large groups of metals:1) Simple metal- more or less pure chemical elements2) Alloys -materials consisting of a simple metal combined with some other elements. About two thirds of all elements found in the earth are metals, but not all metals may be used in industry. Those metals which are used in industry are called engineering metals. The most important engineering metal is iron , which in the form of alloys with carbon and other elements, finds greater use than any other metal. Metals consisting of iron combined with some other elements are known as ferrous metals; all the other metals are called nonferrous metals. The most important nonferrous metal are copper , aluminum ,lead ,zinc ,tin , but all these metals are used much less than ferrous metals, because the ferrous metals are much cheaper. Engineering metals are used in industry in the form of alloys because the properties of alloys are much better than the properties of pure metals. Only aluminum may be largely used in the form of simple metal. Metals have such a great importance because of their useful properties or their strength, hardness, and their plasticity .Different metals are produced in different ways, but almost all the metal are found in the forms of metal ore (iron ore, copper ore, etcet cetra.)The ore is a mineral consistence of a metal combined with some impurities . In order to produce a metal from some metal ore, we must separate these impurities from the metal that is done by metallurgy .2. Plastics and Other MaterialsPlastics have specific properties which may make them preferable to traditional materials for certain uses. In comparison with metals, for example, plastics have both advantages and disadvantages. Metals tend to be corroded by inorganic acids , such as sulphuric acid and hydrochloric acid. Plastics tend to be resistant to these acids, but can have dissolved or deformed by solvent , such as carbon tetrachloride , which have the same carbon base as the plastics. Color must be applied to the surface of metals, whereas it can be mixed in with plastics. Metals are more rigid than most plastics while plastics are very light, with a specific gravity normally between 0.9 and 1.8. Most plastics do not readily conduct heat or electricity . Plastics soften slowly and can easily be shaped when they are soft.塑料具有特殊的性能。
《机械外文翻译文献翻译液压传动》
英文原文Hydraulic SystemHydraulic presser drive and air pressure drive hydraulic fluid as the transmission is made according to the 17th century, Pascal's principle of hydrostatic pressure to drive the development of an emerging technology, the United Kingdo m in 1795 • Braman Joseph (Joseph Braman ,1749-1814), in London water as a medium to form hydraulic press used in industry, the birth of the world's first hydraulic press. Media work in 1905 will be replaced by oil-water and further improved.Hydraulic transmission There are many outstanding advantages, it is widely used, such as general industr- ial use of plastics processing machinery, the pressure of machinery, machine tools, etc.; operating machinery engineering machinery, construction machinery, agricultural machinery, automobiles, etc.; iron and steel indu- stry metallurgical machinery, lifting equipment, such as roller adjustment device; civil water projects with flo- od control and dam gate devices, bed lifts installations, bridges and other manipulation of institutions; speed turbine power plant installations, nuclear power plants, etc.; ship from the deck heavy machinery (winch), the bow doors, bulkhead valve, stern thruster, etc.; special antenna technology giant with control devices, measu- rement buoys, movements such as rotating stage; military-industrial control devices used in artillery, ship anti- rolling devices, aircraft simulation, aircraft retractable landing gear and rudder control devices and other devi- ces.A complete hydraulic system consists of five parts, namely, power components, the implementation of co- mponents, control components, auxiliary components and hydraulic oil.The role of dynamic components of the original motive fluid into mechanical energy to the pressure that the hydraulic system of pumps, it is to power the entire hydraulic system. The structure of the form of hydra- ulic pump gears are generally pump, vane pump and piston pump.Implementation of components (such as hydraulic cylinders and hydraulic motors) which is the pressure of the liquid can be converted to mechanical energy to drive the load for a straight line reciprocating movement or rotational movement.Control components (that is, the various hydraulic valves) in the hydraulic system to control and regulate the pressure of liquid, flow rate and direction. According to the different control functions, hydraulic pressure control valve can be divided into valves, flow control valves and directional control valve. Pressure control valves are divided into benefits flow valve (safety valve), pressure relief valve, sequence valve, pressure relays, etc.; flow control valves including throttle, adjusting the valves, flow diversion valve sets, etc.; directional control valve includes a one-way valve , one-way fluid control valve, shuttle valve, valve and so on. Under the control of different ways, can be divided into the hydraulic valve control switch valve, control valve and set the value of the ratio control valve.Auxiliary components, including fuel tanks, oil filters, tubing and pipe joints, seals, pressure gauge, oil level, such as oil dollars.Hydraulic oil in the hydraulic system is the work of the energy transfer medium, there are a variety of mineral oil, emulsion oil hydraulic molding Hop categories.The role of the hydraulic system is to help humanity work. Mainly by the implementation of components to rotate or pressure into a reciprocating motion.Hydraulic system and hydraulic power control signal is composed of two parts, the signal control of some parts of the hydraulic power used to drive the control valve movement.Part of the hydraulic power means that the circuit diagram used to show the different functions of the interrelationship between components. Containing the source of hydraulic pump, hydraulic motor and auxiliary components; hydraulic control part contains a variety of control valves, used to control the flow of oil, pressure and direction; operative or hydraulic cylinder with hydraulic motors, according to the actual requirements of their choice.In the analysis and design of the actual task, the general block diagram shows the actual operation of equi - pment. Hollow arrow indicates the signal flow, while the solid arrows that energy flow.Basic hydraulic circuit of the action sequence - Control components (two four-way valve) and the spring to reset for the implementation of components (double-acting hydraulic cylinder), as well as the extending and retracting the relief valve opened and closed . For the implementation of components and control components, presentations are based on the corresponding circuit diagram symbols, it also introduced ready made circuit diagram symbols.Working principle of the system, you can turn on all circuits to code. If the first implementation of components numbered 0, the control components associated with the identifier is 1. Out with the implementation of components corresponding to the identifier for the even components, then retracting and implementation of components corresponding to the identifier for the odd components. Hydraulic circuit carried out not only to deal with numbers, but also to deal with the actual device ID, in order to detect system failures.DIN ISO1219-2 standard definition of the number of component composition, which includes the following four parts: device ID, circuit ID, component ID and component ID. The entire system if only one device, device number may be omitted.Practice, another way is to code all of the hydraulic system components for numbers at this time, components and component code should be consistent with the list of numbers. This method is particularly applicable to complex hydraulic control system, each control loop are the corresponding number with the systemWith mechanical transmission, electrical transmission compared to the hydraulic drive has the following advantages:1, a variety of hydraulic components, can easily and flexibly to layout.2, light weight, small size, small inertia, fast response.3, to facilitate manipulation of control, enabling a wide range of stepless speed regulation (speed range of 2000:1).4, to achieve overload protection automatically.5, the general use of mineral oil as a working medium, the relative motion can be self-lubricating surface, long service life;6, it is easy to achieve linear motion /7, it is easy to achieve the automation of machines, when the joint control of the use of electro-hydraulic, not only can achieve a higher degree of process automation, and remote control can be achieved.The shortcomings of the hydraulic system:1, as a result of the resistance to fluid flow and leakage of the larger, so less efficient. If not handled properly, leakage is not only contaminated sites, but also may cause fire and explosion.2, vulnerable performance as a result of the impact of temperature change, it would be inappropriate in the high or low temperature conditions.3, the manufacture of precision hydraulic components require a higher, more expensive and hence the price. 4, due to the leakage of liquid medium and the compressibility and can not be strictly the transmission ratio. 5, hydraulic transmission is not easy to find out the reasons for failure; the use and maintenance requirements for a higher level of technology.In the hydraulic system and its system, the sealing device to prevent leakage of the work of media within and outside the dust and the intrusion of foreign bodies. Seals played the role of components, namely seals. Medium will result in leakage of waste, pollution and environmental machinery and even give rise to malfunctioning machinery and equipment for personal accident. Leakage within the hydraulic system will cause a sharp drop in volumetric efficiency, amounting to less than the required pressure, can not even work. Micro-invasive system of dust particles, can cause or exacerbate friction hydraulic component wear, and further lead to leakage.Therefore, seals and sealing device is an important hydraulic equipment components. The reliability of its机械专业中英文文献翻译work and life, is a measure of the hydraulic system an important indicator of good or bad. In addition to the closed space, are the use of seals, so that two adjacent coupling surface of the gap between the need to control the liquid can be sealed following the smallest gap. In the contact seal, pressed into self-seal-style and self-styled self-tight seal (ie, sealed lips) two.The three hydraulic system diseases1, as a result of heat transmission medium (hydraulic oil) in the flow velocity in various parts of the existence of different, resulting in the existence of a liquid within the internal friction of liquids and pipelines at the sam- e time there is friction between the inner wall, which are a result of hydraulic the reasons for the oil tempera- ture. Temperature will lead to increased internal and external leakage, reducing its mechanical efficiency. At the same time as a result of high temperature, hydraulic oil expansion will occur, resulting in increased com- pression, so that action can not be very good control of transmission. Solution: heat is the inherent characte -ristics of the hydraulic system, not only to minimize eradication. Use a good quality hydraulic oil, hydraulic piping arrangement should be avoided as far as possible the emergence of bend, the use of high-quality pipe and fittings, hydraulic valves, etc.2, the vibration of the vibration of the hydraulic system is also one of its malaise. As a result of hydraulic oil in the pipeline flow of high-speed impact and the control valve to open the closure of the impact of the process are the reasons for the vibration system. Strong vibration control action will cause the system to error, the system will also be some of the more sophisticated equipment error, resulting in system failures. Solutions: hydraulic pipe should be fixed to avoid sharp bends. To avoid frequent changes in flow direction, can not avoid damping measures should be doing a good job. The entire hydraulic system should have a good damping measures, while avoiding the external local oscillator on the system.3, the leakage of the hydraulic system leak into inside and outside the leakage leakage. Leakage refers to the process with the leak occurred in the system, such as hydraulic piston-cylinder on both sides of the leakage, the control valve spool and valve body, such as between the leakage. Although no internal leakage of hydra- ulic fluid loss, but due to leakage, the control of the established movements may be affected until the cause system failures. Outside means the occurrence of leakage in the system and the leakage between the external environment. Direct leakage of hydraulic oil into the environment, in addition to the system will affect the working environment, not enough pressure will cause the system to trigger a fault. Leakage into the enviro- nment of the hydraulic oil was also the danger of fire. Solution: the use of better quality seals to improve the machining accuracy of equipment.Another: the hydraulic system for the three diseases, it was summed up: "fever, with a father拉稀" (This is the summary of the northeast people). Hydraulic system for the lifts, excavators, pumping station, dynamic, crane, and so on large-scale industry, construction, factories, enterprises, as well as elevators, lifting platforms, Deng Axle industry and so on.Hydraulic components will be high-performance, high-quality, high reliability, the system sets the direction of development; to the low power, low noise, vibration, without leakage, as well as pollution control, water-based media applications to adapt to environmental requirements, such as the direction of development; the development of highly integrated high power density, intelligence, mechatronics and micro-light mini-hydraulic components; active use of new techniques, new materials and electronics, sensing and other high-tech.Hydraulic coupling to high-speed high-power and integrated development of hydraulic transmission equ- ipment, development of water hydraulic coupling medium speed and the field of automotive applications to develop hydraulic reducer, improve product reliability and working hours MTBF; hydraulic torque converter to the development of high-power products, parts and components to improve the manufacturing process tech -nology to improve reliability, promote computer-aided technology, the development of hydraulic torque con- verter and power shift transmission technology supporting the use of ; Clutch fluid viscosity should increase the quality of products, the formation of bulk to the high-power and high-speed direction.Pneumatic Industry:Products to small size, light weight, low power consumption, integrated portfolio of development, the implementation of the various types of components, compact structure, high positioning accuracy of the direction of development; pneumatic components and electronic technology, to the intelligent direction of development; component performance to high-speed, high-frequency, high-response, high-life, high temp- erature, high voltage direction, commonly used oil-free lubrication, application of new technology, new technology and new materials.(1)used high-pressure hydraulic components and the pressure of continuous work to reach 40Mpa, the maximum pressure to achieve instant 48Mpa;(2) diversification of regulation and control;(3) to further improve the regulation performance, increase the efficiency of the powertrain;(4) development and mechanical, hydraulic, power transmission of the composite portfolio adjustment gear;(5) development of energy saving, energy efficient system function;(6) to further reduce the noise;(7) Application of Hydraulic Cartridge V alves thread technology, compact structure, to reduce the oil spill Water-based hydraulic systemsWater-based hydraulic systems traditionally have been used in hot-metal areas of steel mills. The obvious advantage of water systems in these industries is their fire resistance. Water-based hydraulic systems also have obvious cost advantages over oil-based fluid. First, non-toxic, biodegradable synthetic additives for water cost $5 to $6 per gallon. One gallon of concentrate can make 20 gallons of a 5% solution, so the cost of water-based hydraulic fluid actually can be less than 30 cents per gallon.Considering the costs associated with preventing and cleaning up environmental contamination, water-based hydraulic systems hold the potential for tremendous cost savings at the plant level. Oil that has leaked already becomes a very important problem. It must be collected, properly contained. Water containing synthetic additives, however, can by dumped into plant effluent systems.Cost savings at the plant level don't stop at the lower cost of the fluid and its disposal. Because water-based hydraulic fluid consists of 10 parts water and one part synthetic additive, 5 gallons of additive mixes with water to make 100 gallons of water-based fluid. A 50gallon container is certainly easier to handle than two 55-gallon drums, so warehousing is simpler, cleaner, and less cluttered. Transportation costs also are lower.Other potential plant-wide savings include improved safety for workers because the water-based fluid is non-toxic as well as non-flammable. These attributes can reduce plant insurance rates. Spills cost less to clean up because granular absorbents or absorbent socks are unnecessary. Water is "hot" againThe oil embargo in the 1970s sparked interest in water-based fluids as a less-costly alternative to oils. Even the most expensive water additives became attractive when designers learned that one gallon of concentrate would make 20 gallons of fluid.As oil prices gradually dropped, so did interest in water-based hydraulics. In retrospect, interest in water-based fluids centered around their cost saving potential. Most designers lost interest when they discovered that they could not just change the fluid in their systems from oil to water without making other substantial changes. They then become reluctant to accept other "disadvantages" - read substantial changes - of switching over to water-based hydraulics.What were viewed as disadvantages were really different rules that apply to water-based hydraulic systems? Designers probably resisted learning more about water-based hydraulics because they were intimated by all the work required to lean about how to design a new system or retrofit an older system. By closing their minds to this different technology, they missed the many other advantages of water-based fluid beyond initial cost. Now that environmental concerns have added disposal costs to the price of hydraulic fluids, water-based hydraulics has again become a hot topic.Fighting freezeWater-based hydraulic systems do, of course, have limits to their applications. One limitation is the potential of freezing. This possibility is probably the most significant blockade to more widespread application of机械专业中英文文献翻译water-based systems, especially in the mobile equipment industry. Longwall mining is by far the largest sector of mobile equipment that has been able to take advantage of water-based systems. Temperatures underground do not approach the freezing point of water, and fire resistance is essential. Mobile and even marine equipment used in temperate climates could cash in one the advantages of water based systems, but there is no guarantee that such equipment always will be used in above-freezing temperatures.Nevertheless, adding an anti-freeze to a water-based fluid can depress its freezing temperature to well below 32°F. Ethylene glycol - used in automotive anti-freeze - is toxic and is not biodegradable, so its use for anti-freeze in water-based hydraulic fluid would defeat the environmental advantage water-based fluid has. There is an alternative. Propylene glycol is not toxic and is biodegradable. It costs more than ethylene glycol and is not quite as effective antifreeze, so it must be used in slightly higher concentrations. Two more techniques to reduce freezing potential are to keep fluid circulating continuously and use hose where practical. Sealing the systemTwo more perceived problems with water hydraulic systems are bacterial infestation and difficulty in maintain proper concentrations. Sealing the system from atmosphere can hold bacterial growth in check. Addition of an anti-bacterial agent to the fluid can have a lasting effect on preventing bacterial buildup if air is excluded from the system.A sealed reservoir eliminates another problem suffered by many hydraulic systems: water ingression. This addresses another misconception about water-based systems: water-based systems not sealed from the atmosphere must be closely monitored to ensure that the additive concentration stays within tolerance. That is because water evaporates from the reservoir more readily than the additive does. Consequently, water evaporation causes the additive concentration to increase. When new fluid is added to a system, samples of the existing fluid must be taken to determine the concentration of additive in solution. These results then reveal the ratio of additive to fluid that must be added so that fluid concentration is correct.With a system that seals fluid from the atmosphere, the evaporation problem is virtually eliminated. Fluid that escapes by leakage is a solution containing water and additive. Therefore, the quantity of fluid in the system changes, but concentration does not. System fluid is replen ished simply by adding a pre-mixed solution of water and additive to the reservoir.中文原文液压传动液压传动和气压传动称为流体传动，是根据17世纪帕斯卡提出的液体静压力传动原理而发展起来的一门新兴技术，1795年英国约瑟夫•布拉曼(Joseph Braman,1749-1814)，在伦敦用水作为工作介质，以水压机的形式将其应用于工业上，诞生了世界上第一台水压机。
【机械类文献翻译】采摘机器人机械手
毕业论文（设计）外文翻译题目：运动学和轨迹规划的黄瓜采摘机器人机械手系部名称：专业班级：学生姓名：学号：指导教师：教师职称：20**年03月10日运动学和轨迹规划的黄瓜采摘机器人机械手摘要：为了降低成本，提高黄瓜收获经济效益，黄瓜收获机器人得以发展。
黄瓜果蔬采摘机器人由一辆汽车,一个四自由度关节机械手,一个手端,一个上一个视觉系统与监控、四直流伺服驱动系统组成。
把黄瓜的运动学果蔬采摘机器人机械手使用D-H标系建立了框架模型。
而且它提供了一个逆运动学轨迹规划的基础已经解决了逆变换技术。
摆线针轮运动，它具有的性能的连续性和零速度和加速度的港口及有界区间，采用一种可行的方法在关节空间轨迹规划，研究了果蔬采摘机器人的机械臂的黄瓜。
此外，硬件和摘要软件基于上面的显示器之间的交流及关节的控制器的设计。
实验结果表明，上面的显示器与四关节控制器的沟通，有效地摘要错误的思想和综合四关节角不超过四度。
误差产生的可能因素分析及相应的解决方案，为提高测量精度的措施提出了建议。
关键词：黄瓜果蔬采摘机器人轨迹规划、关节机械臂、运动、摘要、摆线针轮分类号：10.3965/j.issn.1934-6344.2009.01.001-007。
引文：张利兵，杨庆华，宝冠君，高锋，薰易。
运动学和轨迹规划黄瓜收获机器人的机械手。
农业与生物学工程，2009；2（1）：1-7。
一．介绍水果和蔬菜的收获是一个劳力密集的工作，由人类劳动和收获的成本大约是33％〜总数的50％，生产成本[1]。
因此，机械化和自动化，迫切需要水果和蔬菜收获。
目前，许多国家正在研究。
收稿日期：08-11-20接受日期：009-03-28传记：张利兵，教授，博士，主要从事农业机器人，机电一体化和控制。
王雁，博士候选人浙江工业大学，主要从事，机器人，智能仪表。
杨庆华，教授，博士，主要从事机器人技术，机电一体化和控制。
宝冠君，讲师，博士，主要从事机器人技术，控制人数及机器视觉。
机械专业英文翻译
机械专业英文翻译Mechanical engineering is an essential field of engineering that deals with the design, manufacture, and operation of mechanical systems, ranging from simple machines to complex structures such as spacecraft. The field of mechanical engineering covers a wide range of topics such as mechanics, thermodynamics, manufacturing, robotics, and materials science. In this document, we will discuss the essential aspects of the mechanical engineering profession and the required skills for becoming a successful mechanical engineer.A Mechanical Engineer's ResponsibilitiesA mechanical engineer's primary responsibility is to design, develop, and test various mechanical products and systems. This could include anything from tiny mechanical components for electronic devices to massive industrial machinery. It is the mechanical engineer's responsibility to ensure that the products they design meet the required standards for performance and safety.Mechanical engineers must also work with other professionals in the creation of complex systems, such as designing an entire factory production line or a complete aircraft. This requires the ability to communicate effectively with other engineers and professionals to ensure the smooth running of themanufacturing process. Mechanical engineers must also be skilled in project management, as they may be responsible for overseeing large projects from start to finish.Required Skills for a Mechanical EngineerMechanical engineering is a challenging profession that requires a wide range of skills. Some of these skills include:1. Analytical skills: Mechanical engineers must have strong analytical skills to be able to examine complex systems and identify problems or inefficiencies.2. Creativity: Mechanical engineers must be creative to develop innovative solutions to complex engineering problems.3. Technical knowledge: A mechanical engineer must have a strong foundation in mathematics, physics, mechanics, and materials science to be able to create and analyze mechanical systems.4. Problem-solving skills: A mechanical engineer must have excellent problem-solving skills to identify and resolve problems in mechanical systems.5. Communication skills: Mechanical engineers must be able to communicate effectively with other professionals to ensure that the entire engineering team is on the same page.6. Project management skills: A mechanical engineer must be able to manage large engineering projects and collaborate with other team members.ConclusionIn conclusion, the mechanical engineering profession is a critical field of engineering that involves designing and creating mechanical structures, devices, and systems. Mechanical engineers are responsible for ensuring that the products they design meet the required standards for performance and safety. To be a successful mechanical engineer, you must have strong analytical skills, excellent problem-solving skills, technical knowledge, project management skills, and be an excellent communicator.。
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Automobile manufacturers welding application of new technologies with the overall development trend Welding is a modern mechanical manufacturing process a necessary way to get car manufacturers at a wide range of applications. Automobile engine, gearbox, axle, frame, body, inside the six can not be separated from the total Chengdu welding techniques. At the manufacture of automotive components, spot welding, projection welding, seam welding, roll welding, arc welding electrodes, CO2 gas shielded arc welding, argon arc welding, gas welding, brazing, friction welding, electron beam welding and laser welding, etc. types of welding methods, because of spot welding, gas shielded arc welding, brazing with the production volume is very large, a high degree of automation, high-speed, low power, welding deformation of small, easy-to-use features, so the coverage of auto body sheet metal parts is particularly suitable, so , in automobile production in the most widely used. Investment costs at about 75% in spot welding, other welding methods account for only 25%.With the development of the automobile industry, auto-body welding production line is also gradually develop in the direction to the fully automated, in order to catch up with international standards, improve productivity at the same time, requires efforts to improve the quality of automobile manufacturers. As we all know, implementation is a prerequisite for automated manufacture of parts and components to high precision, the smallest hope of welding distortion, welding sites want fresh appearance, and called for more and more high-welding technology. Facing our country's accession to WTO opportunities and challenges, welding area of the popularization and application of new technologies for the automotive industry to enhance the brand has an extremely important role.First, the auto industry used welding methods and the application of parts and components Automotive applications are welding industry noodle one of the most widely used method of welding a wide range of applications as follows:1. Resistance Welding(1) Spot welding used mainly for body assembly, flooring, doors, side Wai Wai after, the former bridge and small parts.(2) Multi-spot welding for body baseboard containing boxcar doors, engine cover and trunk cover.(3) Projection welding and roll welding for body parts, shock absorber stem, brake shoe, screws, nuts and small, such as stents.(4) Seam welding the body cap for rain canopies, shock absorber head, fuel tank, muffler and oil, such as disk.(5) For butt welding steel, was discharged into the air stem, cutting tools, etc..2. Electric arc welding(1) CO2 arc welding for the car, rear axle, frame, shock absorber stem, beam, shell and tube rear axle, drive shaft, hydraulic cylinders and jacks, such as welding.(2) Welding for the oil plate, aluminum alloy parts for welding and repair welding.(3) Electric arc welding electrode for thick parts such as stents, spare tire racks, trailers and so on.(4) Submerged for half-bridge casing, flange, and natural gas vehicles, such as pressure vessels.3. Special welding(1) Friction welding for automotive stem, rear axle, axle, steering rod and the attendant tools.(2) For electron beam welding gear, after the bridges.(3) Laser Welding for Body backplanes, gear, materials and spare parts under the edge and so on.4. Oxyacetylene weldingRepair welding for body assembly.5. BrazingFor radiators, copper and steel parts, hard alloy welding.Two, the automobile industry welding application of new technologies Nowadays, the automobile industry a lot of advanced welding technology, only to set out the relevant body welding and welding of new technologies.1. Resistance and control of energy-saving technology(1) Conjoined hanging spot welding in the automotive industry the most widely used are hanging spot welding machine, a workshop is often dozens or hundreds of units, mostly in its capacity above 100kVA, automotive sheet metal at the welding has been widely applications.(2) Of resistance welding machine current resistance welding machine communicate substantial use of the single-phase AC 50Hz power supply, large capacity, low power factor. The development of three-phase low-frequency resistance welding machine, three-phase secondary rectification welding contacts (in ordinary type spot welder, seam welder, welding machine application convex) and the IGBT inverter resistance welding machine, you can solve the imbalance and improve power grid power factor (up to 0 9 above) the problem. At the same time can be further save power, the realization of microcomputer control parameters can be better applied to welding of aluminum alloy, stainless steel and other difficult to weld metal welding. It could also further reduce the equipment weight.(3) The control of resistance against the Southwest Jiaotong University 1 Rim Factory Alloy Rim Butt Welding development of PLC (programmable controller) Intelligent controller, on the original machine had a transformation, to solve the aluminum alloy car lap welding quality problems, improve welding productivity. Factory has been developed after the same seam welding PLC controller to solve the general clean-up requirements parts of the seam welding problem. These two controllers through the development, proved more than single-chip microprocessor controller PLC anti-interference ability, high reliability; IPC controller than small size, low cost, use of a common single-phase AC power frequency resistance welding machine achieve a high degree of difficulty of the butt welding and seam welding job.2. Gas shielded welding technology(1) The surface tension of the transition waveform control method, the key is to usetwo current pulse achieve a droplet transition, the first current pulse to form a droplet and up until a short circuit droplet and the workpiece; No. 2 current pulse is a short-term narrow pulse and continuous detection of its di / dt, at the same time to control the value of current pulse to generate the appropriate electromagnetic contractile force, so that droplet contraction thin neck, and finally by the pool surface tension pull off, finish a droplet transfer without spatter.(2) Inverter power inverter power source waveform to control the use of dynamic characteristics of a good and flexible controllability, the use of waveform control, in the short-circuit current increased by inhibiting the early stages to reduce the electromagnetic force when the little bridge in the newly formed droplet transfer obstacles and blasting off to reduce the large particles flying, and in favor of droplet spread in the pool; when droplet spread out in the pool after making a rapid increase in current in order to speed up the formation of necking later slow rise to a lower peak so that when the little bridge blasting off to reduce spatter.(3) TIG welding of new technologies have a very non-melting (TIG) and MIG (MIG) two non-ferrous metals are used in the automotive industry and high-alloy steel welding. In order to improve the CO2 gas shielded arc welding spatter forming and reduce the use of add 80% or 20% Ar mixed gas shielded arc welding.3. High-energy beam welding and heat processing technologyHigh-energy beam source is the energy density has been greater than 5 × 108W/m2 of the heat source (electron beam, ion beam and laser), is used in automobile industry, is currently abroad, the development of new technologies have:(1) Laser and arc welding composite heating laser welding can be a narrow and deep weld seam, welding the electric arc welding can be wide and shallow weld; the former investment, the latter low-cost combination of both characteristics, will greatly enhance welding efficiency. Composite heating laser and arc welding torch de sign is particularly important, the two sources of heat to the angle as small as possible, the torch is also designed to power laser + double arc.This method has been at 4 ~ 8mm thick steel structures used, is intended to be used in thinner aluminum alloy automobile parts production and welding. In addition to laser welding and precision cutting application, but also the formation of friction surface reservoir fine patterns or remelting composite layer to enhance wear resistance applications.(2) The application of plasma argon plasma welding protection already cutting applications in different sectors, mainly for steel and non-ferrous metal processing. At present, air plasma cutting has generally been applied to general steel and non-ferrous metal cutting, domestic rail passenger car plant to introduce the underwater plasma cutting, so as to reduce distortion and improve accuracy. Engine valve body is already being used in plasma-filled lap welding. Over the last decade plasma powder surfacing there is great development, it can conduct small-fusion fine material than the thin-layer surfacing, surfacing to a variety of special alloy surface.Three, the automobile industry in the development of new welding materials trends With the development of increasingly compact cars smaller and lighter, the application of new materials to make car material composition of the apparentchanges happen, the future of car body material is still the main plate, in order for the plate thickness thinning will be widely used in high strength steel . At the same time in order to enhance the body's anti-corrosion, the world on a number of car manufacturers in car production in substantial use of galvanized steel sheet. In addition, the use of aluminum alloy, plastic and ceramic materials. According to the experts predict that the end of this century will not be at high-volume production cars appeared in aluminum or plastic body body.1. Galvanized steel plateAmerican Welding Society at chapter meetings to discuss the automobile industry on the application of metal plates welded problem, the relevant experts have pointed out that welding galvanized steel sheet most promising method is laser welding. However, because of the degree of automation of the process is now not e nough, we must improve the automobile industry widely used method of contact spot welding. The main disadvantage of this method are Weldment at electrode contacts with substantial transition of zinc electrode burn faster. It is suggested that the use of Al2O3 particle dispersion strengthened Cu-Zn and Cu-Cr alloy electrode can be at a minimum under the electric resistance welding, in order to guarantee access to the smallest size welded joints.2. High-strength steel plateIn order to realize lightweight cars, improve vehicle safety performance, high strength steel in the automotive application is increasing year by year, the current emergence of a new generation of high strength steel materials - ultra-fine grained steel. The steel major means to further enhance economic indicators, based on iron and steel materials, strength, toughness than the existing steel doubled. A new generation of ultra-fine grained steel at the organizational structure with ultra-fine grain, high purity and high uniformity of properties.Currently used to study a new generation of ultra-fine grained steel major has 400MPa and 800MPa grade two level.At a new generation of research on iron and steel, our country and the international level and there is no gap, almost simultaneously started, with Japan and South Korea between the two countries living side by side the world's leading position. However, due to appear shorter, so the unit participated in the study is not much, and is based on Iron & Steel Research Institute and the Department of Mechanical Engineering, Tsinghua University-based. In the ultra-fine grained steel welding technology for the study must have achieved a number of advanced results.3. Aluminum AlloyAluminum alloy with light weight, high strength and corrosion resistance, etc., are good building materials, automobile industry is gradually Materials in the use of aluminum alloy parts. Aluminum alloy welding has five main features:(1) Aluminum alloy surface has a layer of dense oxide film (melting point of about 2050 ℃), welding if the latter fails to clear, it will affect the quality of basic metals melting, forming a mixture of such quality issues.(2) Thermal conductivity of large (approximately 4 times that of steel), electrical conductivity, and welding and steel to achieve the same welding speed, the weldingheat input than when welding steel large 2 ~ 4 times.(3) Coefficient of linear expansion, and there is Weldment have a greater thermal stress, deformation and the tendency to crack.(4) Stomatal easily.(5) Aluminum alloy to reduce the strength of welded joints.Aluminum alloy welding of these characteristics, it is in the development of our welding equipment and welding technology should be taken seriously the problem, the only way to develop a suitable aluminum alloy welding equipment, materials and welding technology.Four, the automobile industry's general trend of development of welding1. The development of flexible automated production systemsTaking an overall view of the welding automotive industry status quo, it is not difficult to analyze the development trend of the automotive industry for welding: the development of flexible automated production systems. And industrial robots, automated production because of set production features and flexibility all in one, so large-scale car production in recent years, the rapid use of the robot. In welding, the main use is to spot welding robot and welding robot.Welding want highly automated production line, widely used in the 6-DOF robot and welding robot with forceps repository can be made under different welding parts welding product requirements or changes from the repository automatically grasping forceps for welding required. Transmission devices have been developed into a more flexible use of unmanned sensors and car-oriented.2. The development of lightweight modular intelligent automatic welding machine The level of the domestic automobile welding gap compared with foreign countries. In recent years, the domestic automobile factory attaches great importance to the automation of welding. Such as the introduction of the Jetta FAW body welding workshop 13 production line automation rate of more than 80%. Each line by computer (programmable logic controller PLC-3) control, auto-complete the transmission of the workpiece and welding. By R30-type welding robot in polar coordinates and G60 toggle-type robot 61, the robot driven by a microcomputer control, numbers and characters revealed that the tape recorder input and output procedures. Robot moves step-by-step sequence using point-to-point trajectory, with a high level of automation of welding, both to improve the working conditions, improve product quality and productivity and reducing material consumption.Similar high level of production line in Shanghai, Wuhan and other places have a joint venture and introducing, including Germany, the United States, France and Japan's advanced automotive manufacturing technology. But these are after all still far from our country can not adapt to the rapid development of the national auto industry needs, we must insist on technological innovation, and vigorously accelerate the development of welding energy efficient new materials and new technologies and new equipment, development of applications for robot technology, the development of portable intelligent devices smarter establish a highly efficient economy welding automation systems, we must use computers and information technology to transform traditional industries, improve grades.Believe that in the near future, through our joint efforts, the domestic auto industry's welding technology will be gradually shortened with advanced welding technology levels, the auto industry to meet WTO brings opportunities and challenges.。