機器機械設備外文文獻翻譯、中英文翻譯、外文翻譯

機器機械設備外文文獻翻譯、中英文翻譯、外文翻譯,機器,機械設備,外文,文獻,翻譯,中英文 翻譯資料名稱(外文) Machine 翻譯資料名稱(中文) 機器 機 器 人們給機器這個詞下了各種各樣的定義，但對本文來說，機器是具有某種獨特用途的設備，用來簡少或代替人力或畜力，以完成各種體力工作。工具可以是看作最簡單的機器。機器的作用可以包括把化學能、熱能、電能或核能轉換成機械能，或者反過來把機械能轉換成其它幾種能，或者其作用僅僅是用來改變和傳遞力和運動。所有的機器都有一個輸入端，一個輸出端，一個轉換或變換裝置和傳遞裝置。 從天然能源（例如氣流、水流、煤、石油或鈾）獲得其輸入能量并將其轉換成機械能的機器稱作原動機。風車、水輪、汽輪機、蒸汽機和內燃機都是原動機。這些機器的輸入端是各不相同的，而輸出端則通常都是一根旋轉軸，它能用作其它機器（例如發(fā)電機、液壓泵、或空氣壓縮機）的輸入端，所有這后三種裝置都歸類為發(fā)動機，它們產生的電能、液能或氣能能夠分別用作電動機、液動機或氣動機的輸入端。這些發(fā)電機能夠用來驅動帶有各種輸出端的機器，諸如材料加工機、包裝機或輸送機。所有既不是原動機、發(fā)電機也不是電動機的機器都歸類為工作機。這類機器也包括各種手動機具，例如計算機和打字機。 如果工作機是一臺由電動機驅動的泵，來自發(fā)電站的原動機的能經(jīng)過發(fā)電機和電動機傳到工作機，其情況如圖1所示。工作機也能直接由一個小型的直接連接的原動機（例如汽油發(fā)電機）驅動，如圖1虛線所示；然而，對于大多數(shù)由動力傳動的工作機來說，來自原動機的能是沿圖中實線所示的順序傳輸?shù)摹? 在某些情況下，上述各種機器都組裝成一個機組。例如在柴油發(fā)電機車中，柴油機是原動機，它驅動發(fā)電機，發(fā)電機再把電供給電動機以驅動車輪。 下面舉汽車中的幾個例子。 在汽車中，基本問題是利用汽油的爆發(fā)力來提供動力使后輪轉動。幾個汽缸里汽油的爆發(fā)推動活塞向下，這種平移運動（線性運動）的傳遞和轉換成曲軸的旋轉運動是靠連桿來實現(xiàn)的，連桿把每一個活塞同曲軸（圖21）連接起來，曲柄是曲軸的一部分?；钊?、汽缸、曲柄和連桿組合稱作滑塊曲柄機構（也叫曲柄連桿機構）；這是將平移轉換成旋轉（例如發(fā)電機）或將旋轉轉換成平移（例如泵）通常采用的方法。 閥門作用在于允許汽油空氣混合物進入圓筒中并且耗盡燃燒的氣體；這些閥門由凸輪的楔入作用打開和關閉突出部分，通過齒輪或者鏈傳動由曲軸驅動旋轉的凸輪軸。 在八汽缸四沖程發(fā)電機中，曲軸每轉1/4圈在沿其長度方向某一點就獲得一個推力。為了消除這種斷續(xù)的推力對曲軸轉速的影響以使轉速平穩(wěn)，采用了一個飛輪。飛輪是一個連在曲軸上的重型輪子，它借助其慣性來抵消和減輕轉速的任何波動。 由于內燃機所傳遞的扭轉（旋轉力）取決于它的轉速，所以內燃機不能在有負載的情況下起動。為了使汽車發(fā)電機能夠在無負載狀態(tài)下起動然后再連到車輪上而又不致使發(fā)電機減速、停車或滅火，必須有離合器和變速箱。離合器用來使曲軸和變速箱接合或分離，而變速箱則分幾級改變輸入軸和輸出軸之間的速比和變速箱的扭矩。在低速檔，輸出轉速很低，而輸出軸扭矩較發(fā)電機的扭矩要大，所以汽車能夠起動；在高速檔，汽車正在高速前進，因此輸入和輸出的扭矩和轉速是相等的。 安裝車輪的軸都裝在固定在后彈簧上的后橋殼里，并且由變速箱借助主動軸來起動，當汽車行駛時，彈簧隨公路上的凸凹不平而上下彎曲，使橋殼同變速箱產生相對運動；要允許運動而不干涉扭矩傳輸，主動軸的每個末端都有一個萬向節(jié)。 主動軸是垂直于對后橋。直角連接通常用錐齒輪來實現(xiàn)，其傳動比使輪軸的轉速為主動軸轉速的1/3-1/4。后橋殼里還裝有差動齒輪，差動齒輪使兩個后輪既能由同一根主動軸來驅動，又能在轉彎時具有不同的轉速。 像所有的運動機械裝置一樣，汽車也不能避免摩擦力的作用。在發(fā)電機、變速箱、后橋殼和所有的軸承里，摩擦作用都是有害的，因為摩擦增加了對發(fā)電機要求的功率，潤滑可以減少但不能消除這種摩擦作用。另一方面，由于輪胎同路面之間以及同制動器之間的摩擦作用，才能實現(xiàn)牽引和制動。驅動風扇、發(fā)電機和其它輔助設備的皮帶，是一種依靠摩擦作用的裝置。摩擦對離合器的工作也是很有用的。上述的某些裝置以及下面要談到的其它一些裝置在以各種方式裝配起來的用來完成各種體力工作的各種機器里都能找到。由于各種工作機的功能不同，并缺乏共同的特性，所以本文不論述專用的工作機。本文既不討論原動機的工作性能，也不論述液壓裝置、氣動裝置或電器裝置的作用。本文只研究作為機器的各組成部分的基本機械裝置的作用和結構。大多數(shù)這些裝置的功能是用來傳遞和轉換力和運動。而另一些裝置，例如彈簧、飛輪、軸和緊固件，則是用來完成各種輔助功能。 從這篇文章的目的來說機器可以進一步被定義為：機器是由兩個或兩個以上耐用的、相對約束的部件組成的裝置，這些部件可以傳遞和轉換力和運動以便于做功。機械零件應該經(jīng)久耐用這一要求意味著它們應能承受外加負載而不致?lián)p壞和失靈。盡管大多數(shù)機械零件是具有適當尺寸的固態(tài)金屬零件，但也采用非金屬材料、彈簧、液壓元件以及像皮帶這樣的拉力零件。 機器最顯著的特性在于其零件都是相互連接或導向，從而它們彼此的相對運動都是受約束的。例如，相對于汽缸體來說，往復式發(fā)電機的活塞受汽缸的約束從而做直線運動；曲軸上的各點受主承軸的約束作圓周運動；要作其它形式的相對運動是不可能的。 在某些機器中，有些零件只部分受約束。如果零件用彈簧或摩擦件相互連接，零件彼此之間的相對行程可以是固定不變的，但零件的運動可能會受到彈簧的剛度、摩擦力和零件的質量的影響。 如果機器的所有零件都是剛度比較大的元件，在負載作用下?lián)隙瓤梢院雎圆挥?，那就可以看成完全約束并且零件的相對運動可以不必考慮引起相對運動的力。例如，對一臺往復式發(fā)動機的曲軸的某一規(guī)定的轉速來說，連桿和活塞上各點相應的速度是能夠計算出來的。對于規(guī)定的輸入運動來說，機器各零件的位移、速度和加速度的確定是機械運動學討論的主題。進行這樣的計算時不必考慮各種有關的力，因為運動都是受約的。 根據(jù)這一定義，力和運動都在機器中被傳遞和轉換。機器各零件相互連接和導向以便從一定的輸入運動產生所需的輸出運動的方式稱作機器的結構。往復式發(fā)電機的活塞、連桿和曲軸組成一個機構以便把活塞的直線運動變成曲軸的旋轉運動。 雖然機器在工作中既包括力又包括運動，但是機器的主要作用是為了省力或轉換運動。而變速箱常作為減速器，杠桿本質上是增力裝置。然而，在機器中運動和力是分不開的，并且總是反比。杠桿輸出的力大于輸入的力，但是輸出地運動小于輸入的運動。同樣，齒輪減速器的輸出轉速小于輸入轉速，但是輸出扭矩大于輸入扭矩。在第一種情況下，力的增加伴隨著運動損失，而在第二種情況下，運動的損失伴隨著扭矩的增大。 盡管某些機器的主要作用能夠辨認出來，還是難以把所有的機器都歸類為力的改變裝置或者運動的轉換裝置；某些機器應同時歸入這兩類裝置。然而，所有機器都必須能夠起到改變運動的作用，因為如果一個機械裝置的零件不會運動，則該機械裝置只是一個結構，而不是機器。在研究零件的運動時，機械設計者習慣于討論機器的機構。 雖然所有的機器都有機構，因此都能起到改變運動的作用，而某些機器在設計時并沒有改變力的要求；所產生的各個力是由運動部件的摩擦作用和慣性作用所引起的，并不表現(xiàn)為有用的輸出作用力。這一類通常包括量測儀表和時鐘。 在定義中提到的“功”要按照它的科學含義來解釋。在機械學中，功是力沿著力的作用方向做出的結果，它等于平均力和運動距離的乘積。如果一個人扛著一個重物沿水平路線運動，根據(jù)這個定義他沒有做功，因為力和運動相互垂直，即力是垂直的，而運動是水平的。如果他扛著重物登上一段樓梯或者梯子，他就做了功，因為他是沿著他作用力的同一方向運動的。從數(shù)學上來講，如果用F表示力（單位為磅或者公斤），S表示距離（單位為英尺或者米），則功等于作用力F乘以力所運動的距離S；即功=F*S。 如果一個力使一個物體繞一固定軸或樞軸旋轉，則所做的功等于扭矩（T）乘以旋轉的角度（以弧度表示的角度）。 在用力和運動來給機器的機械功的作用下定義時，上述有關功的概念是一些基本概念，這些概念表明機器中力和運動的不可分性。由于摩擦的關系，從機器中輸出的功永遠小于輸入的功，而效率，即輸出的功和輸入的功，兩者的比值永遠小于100%。 輸出的力和輸入的力之比稱作機械利益（MA），它表示改變力的功能，而輸入的運動和輸出的運動之比稱作速度比（VR），它表示改變運動的功能。如果效率很高，這兩個比值幾乎相等；如果輸出的力是輸入的力的十倍，則輸入的運動必須是輸入運動的十倍；即力之所得等于運動之所失。摩擦只影響機械利益而不影響速比。 為了從輸出功和輸入功的比值計算效率，就必須知道輸出的力和輸入的力通過規(guī)定的距離所作的功。由于這需要確定通過這一距離的平均力，所以它是很不方便的。比較方便的方法是從負載的瞬時值和負載的運動速率來測定機械的效率。為此，功率公式是非常有用的。 功率是做功的速率的單位在說英語的國家力是馬力（hp）——馬力等于每分鐘33，000英尺磅，因此每分鐘240英尺磅等于240/33,000=0.00727 hp。 在討論諸如杠桿和輪與軸這一類簡單的機械時，最方便是把輸入的力叫做“作用力”，而把輸出的力叫做“負載”。因此機械利益是負載和作用力之比，速比是作用力的運動（位移或速度）除以負載的相應運動。 MACHINE The word machine has been given a wide variety of definitions, but for the purpose of this article it is a device, having a unique purpose, that augments or replaces human effort for the accomplishments of physical tasks. Tools may be regarded as the simplest class of machines. The operation of a machine may involve the transformation of chemical, thermal, electrical, or nuclear energy into mechanical energy, or vice versa, or its function may simply be to modify and transmit forces and motions. All machines have an input, an output, and a transforming or modifying and transmitting device. Machines that receive their input energy form a natural source, such as air currents, moving water, coal, petroleum, or uranium, and transform it into mechanical energy are known as prime movers. Windmills, waterwheels, turbines, steam engines, and internal-combustion engines are prime movers. In these machines the inputs vary; the outputs are usually rotating shafts capable of being used as inputs to other machines, such as electric generators, hydraulic pumps, or air compressor. All three of the latter devices may be classified as generators; their outputs of electrical, hydraulic, and pneumatic energy can be used as input to electric, hydraulic, or air motors. These motors can be used to drive machines with a variety of outputs, such as materials processing, packaging, or conveying machinery. All machines that are neither prime movers, generators, nor motors may be classified as operators. This category also includes manually operated instruments of all kinds, such as calculating machines and typewriters. If the operator is a pump driven by an electric motor, the flow of energy from the prime mover at the power plant through the generator and motor to the operator is as shown in Figure 1. The operator can also be driven directly by a small, direct-connected prime mover, such as a gasoline engine, as shown by the dotted line Figure 1; for most power-driven operators, however, the flow of energy form the prime mover follows the solid lines. In some cases, machines in all categories are combined in one unit. In a diesel-electric locomotive, for example, the diesel engine is the prime mover, which drives the electric generator, which, in turn, supplies electric current to the motors that drive the wheels. The following are some examples supplied by an automobile. In an automobile, the basic problem is harnessing the explosive effect of gasoline to provide power to rotate the rear wheels. The explosion of the gasoline in the cylinders pushes the pistons down, and the transmission and modification of the crankshaft is effected by the connecting rods that join each piston to the cranks (Figure 21) that are part of the crankshaft. The piston, cylinder, crank, and connecting rod combination is known as a slider-crank mechanism; it is a commonly used method of converting translation to rotation (as in an engine) or rotation to translation (as in a pump). To admit the gasoline-air mixture to the cylinders and exhaust the burned gases, valves are used; these are opened and closed by wedging action of cams (projections) on a rotating camshaft that is driven from the crankshaft by gears or a chain. In a four-stroke-cycle engine with eight cylinders, the crankshaft receives an impulse at some point along its length every quarter revolution. To smooth out the effect of these intermittent impulses on the speed of the crank-shaft, a flywheel is used. This is a heavy wheel, attached to the crankshaft, that by its inertia opposes and moderates any speed fluctuations. Since the torque (turning force) that it delivers depends on its speed, an internal-combustion engine cannot be started under load. To enable an automobile engine to be started in an unloaded state and then connected to the wheels without stalling, a clutch and a transmission are necessary. The former makes and breaks the connection between the crankshaft and the transmission, while the latter changes, in finite steps, the ratio between the input and output speeds and torques of the transmission. In low gear, the output speed is low and the output torque higher than the engine torque, so that the car can be started moving; the car is moving at a substantial speed and the torques and speeds are equal. The axles to which the wheels are attached ate contained in the rear axle housing, which is clamped to je rear springs, and are driven from the transmission by the drive shaft, as the car moves and the springs flex in response to bumps in the road, the housing moves relative to the transmission; to permit this movement without interfering with the transmission of torque, a universal join is attached o each end of the drive shaft. The drive shaft is perpendicular to the rear axles. The right-angled connection is usually made with bevel gears having a ratio such that the axles rotate at from one-third to one-fourth the speed of the drive shaft. The rear axle housing also holds the differential gears that permit both rear wheels to be driven from the same source and to rotate at different speeds when turning a corner. Like all moving mechanical devices, automobiles cannot escape from the effects of friction. In the engine, transmission, rear axle housing, and all bearings, friction is undesirable, since it increases the power required from the engine; lubrication reduces bit does not eliminate this friction. On the other hand, friction between the tires and the road and in the brake shoes makes traction and braking possible. The belts that drive the fan, generator, and other accessories are friction-dependent devices. Friction is also useful in the operation of the clutch. Some of the devices cited above, and others that are described below, are found in machines of all kinds of physical tasks. Because of this diversity of function and the lack of common characteristics, this article will not be concerned with specific operators. Neither will it deal with the overall performance of prime movers, nor with the operation of hydraulic, pneumatic, or electrical devices. It will consider only the operation and structure of the basic mechanical devices that are the constituent part of machines. The function of most of these devices is to transmit and modify force and motion. Other devices, such as spring, flywheels, shafts, and fasteners, perform supplementary functions. For the purpose of this article a machine may be further defined as a device consisting of two or more resistant, relatively constrained parts that may serve to transmit and modify force and motion in order to do work. The requirement that the part of a machine be resistant implies that they be capable of carrying imposed loads without failure or loss of function. Although most machine part are solid materials bodies of suitable proportions, nonmetallic materials, springs, fluid pressure organs, and tension organs such as belts are also employed. The most distinctive characteristic of a machine is that the parts are interconnected and guided in such as way that their motions relative to one another are constrained. Relative to the block, for example, the piston of a reciprocating engine is constrained by the cylinder to move on a straight path; points on the crankshaft are constrained by the main bearings to move on circular paths; no other forms of relative motion are possible. On some machines the parts are only partially constrained. If the parts are interconnected by springs or friction members, the paths of the parts relative to one an other may be the stiffness of the parts may be affected by the stiffness of the springs, friction, and the masses of the parts. If all the parts of a machine are comparatively rigid member whose deflections under load are negligible, then the containment may be considered complete and the relative motions of the parts can be studied without considering the forces that produce them. For a specified rotational speed of the crankshaft of a reciprocating engine, for example, the corresponding speeds of points on the connecting rod and the piston can be calculated. The determination of the displacements, velocities, and accelerations of the parts of a machine for a prescribed input motion is the subject matter of kinematics of machines. Such calculations can be made without considering the forces involved, because the motions are constrained. According to the definition, both forces and motions are transmitted and modified in a machine. The way in which the parts of a machine are interconnected and guided to produce a required output motion from a given input motion is known as the mechanism of the machine. The piston, connecting rod, and crankshaft in a reciprocating engine constitute a mechanism for changing the rectilinear motion of the piston into the rotary motion of the crankshaft. Although both forces and motions are involved in the operation of machines, the primary function of a machine may be either the amplification of force or the modification of motion. A lever is essentially a force increase, while a gearbox is most often used as a speed reducer. The motions and forces in a machine are inseparable, however, and are always in an inverse ratio. The output force on a lever is greater than the input force, but the output motion is less than the input motion. Similarly, the output speed of a gear reducer is less than the input torque. In the first case a gain in force is accompanied by a loss in motion, while in the second case a loss in motion is accompanied by a gain in torque. Although the primary function of some machines can be indentified, it would be difficult to classify all machines as either force or motion modifiers; some machines belong in both categories. All machines, however, must perform a motion-modifying function, since if the parts of a mechanical device do not move, it is a structure, not a machine. It is customary for machinery designers, when studying the motions of the parts, to speak of the mechanism of a machine. While all machines have a mechanism, and consequently perform a motion-modifying function, some machines do not have a planned force-modifying purpose; the forces that exist are caused by friction and inertia of the moving masses and do not appear as a useful output effort. This group would include measuring instruments and clocks. The “word” referred to in the definition will be interpreted in its scientific sense. In the science of mechanics, word is something that forces do when they move in the direction in which they are acting, and it is equal to the product of the average force and the distance moved. If a man carries a weight along a horizontal path, he does no work according to this definition, since the force and the motion are at right angles to one another; that is, the force is vertical and the motion horizontal. If he carries the weight up a flight of stairs or a ladder, he does work, since he is moving in the same direction in which he is applying a force. Mathematically, if F equals force (in pounds or kilograms), and S equals distance (in feet or meters), work is then equal to the applied force F multiplied by the distance this force moves S; or WORK=F*S. When a force causes a body to rotate about a fixed axis, or pivot, the work done is obtained by multiplying the torque (T)by the angle of rotation. These concepts of work are fundamental in defining the mechanical work function of machines in terms of force and motions, and they bring out the inseparability of force and motions in machines. Because of friction, the work output from a machine is always less than the work input, and the efficiency, which is the ratio of the two, is always less than 100 percent. The ratio of the output to input forces is the mechanical advantage (MA), and it defines the force-modifying function, while the ratio of the input to output motions is the velocity ratio (VR), and it defines the motion-modifying function. When the efficiency is high, these ratios are approximately equal; if the output force is ten times the input force, the input motion must be ten times the output motion, i.e., what is gained in force is lost in motion. Friction affects the mechanical advantage but not the velocity ratio. To calculate the efficiency from the ratio of output to input work, it would be necessary to know the work done by the output and input forces over a specified distance. Since this would entail the determination of average forces over the interval, it would be inconvenient. The efficiency of a machine is more easily determined from instantaneous values of load and the rate at which the load is moving. For this purpose, power formulas are most useful. Power is the rate at which work is don. If a man carries a ten-pound weight a vertical height of 12 feet (i.e,up a ladder or stairs) in half a minute, his power expenditure is 10*12 or 120 foot-pounds in half a minute; his rate of doing word is then 240 foot-pounds per minute. The unit of power or rate of doing word in English speaking countries is the horsepower (hp), which is equal to 33,000 foot-pounds per minute, so that 240 foot-pounds per minute equal 240/33,000=0.00727 hp. In dealing with simple force-amplifying machines such as the lever and the wheel and axle, it is convenient to call the input force the “effort” and the output force the “l(fā)oad.” The mechanical advantage is then the ratio of the load to the effort, and the velocity ratio is the motion (displacement or velocity) of the effort divided by the corresponding motion of the load.