外文翻譯--軸

1 附錄： 外文資料與中文翻譯 外文資料： Shaft Solid shafts. As a machine component a shaft is commonly a cylindrical bar that supports and rotates with devices for receiving and delivering rotary motion and torque .The crankshaft of a reciprocating engine receive its rotary motion from each of the cranks, via the pistons and connecting roads (the slider-crank mechanisms), and delivers it by means of couplings, gears, chains or belts to the transmission, camshaft, pumps, and other devices. The camshafts, driven by a gear or chain from the crankshaft, has only one receiver or input, but each cam on the shaft delivers rotary motion to the valve-actuating mechanisms. An axle is usually defined as a stationary cylindrical member on which wheels and pulleys can rotate, but the rotating shafts that drive the rear wheels of an automobile are also called axles, no doubt a carryover from horse-and-buggy days. It is common practice to speak short shafts on machines as spindles, especially tool-carrying or work-carrying shafts on machine tools. In the days when all machines in a shop were driven by one large electric motor or prime mover, it was necessary to have long line shafts running length of the shop and supplying power, by belt, to shorter couter shafts, jack shafts, or head shafts. These line shafts were assembled form separate lengths of shafting clampled together by rigid couplings. Although it is usually more convenient to drive each machine with a separate electric motor, and the present-day trend is in this direction, there are still some oil engine receives its rotary motion from each of the cranks, via the pistons and connecting roads (the slider-crank mechanisms) , and delivers it by means of couplings, gears, chains or belts to the transmission, camshaft, pumps, and other devices. The camshafts, driven by a gear or chain from the crankshaft, has only one 2 receiver or input, but each cam on the shaft delivers rotary motion to the valve-actuating mechanisms. An axle is usually defined as a stationary cylindrical member on which wheels and pulleys can rotate, but the rotating shafts that drive the rear wheels of an automobile are also called axles, no doubt a carryover from horse-and-buggy days. It is common practice to speak short shafts on machines as spindles, especially tool-carrying or work-carrying shafts on machine tools. In the days when all machines in a shop were driven by one large electric motor or prime mover, it was necessary to have long line shafts running length of the shop and supplying power, by belt, to shorter coutershafts, jackshafts, or headshafts. These line shafts were assembled form separate lengths of shafting clampled together by rigid couplings. Although it is usually more convenient to drive each machine with a separate electric motor, and the present-day trend is in this direction, there are still some situation in which a group drive is more economical. A single-throw crankshaft that could be used in a single-cylinder reciprocating engine or pump is shown in Figure 21. The journals A and B rotate in the main bearings, C is the crankpin that fits in a bearing on the end of the connecting rod and moves on a circle of radius R about the main bearings, while D and E are the cheeks or webs. The throw R is one half the stroks of the piston, which is connected, by the wrist pin, to the other end of the connecting rod and guided so as to move on a straight path passing throw the axis XX. On a multiple-cylinder engine the crankshaft has multiple throws-eight for a straight eight and for a V-8-arranged in a suitable angular relationship. Stress and strains. In operation, shafts are subjected to a shearing stress, whose magnitude depends on the torque and the dimensions of the cross section. This stress is a measure of resistance that the shaft material offers to the applied torque. All shafts that transmit a torque are subjected to torsional shearing stresses. In addition to the shearing stresses, twisted shafts are also subjected to shearing distortions. The distorted state is usually defined by the angle of twist per unit length； i.e., the retation of one cross section of a shaft relative to another 3 cross section at a unit distance from it. Shafts that carry gears and pulleys are bent as well as twisted, and the magniude of the bending stresses, which are tensile on the convex side of the bend and compressive on the concave side, will depend on the load, the distance between the bearings of the shaft cross section. The combination of bending and twisting produces a state of stress in the shaft that is more complex than the state of pure shears produced by torsion alone or the state of tension-compression produced by bending alone. To the designer of shaft it is important to know if the shaft is likely to fail because of an excessive normal stress. If a piece of chalk is twisted, it will invariably rupture on a plane at about 45 degrees to the axis. This is because the maximum tensile stresses act on this plane, and chalk is weak in tension. Steel shafting is usually designed so that the maximum shearing stress produced by bending and torsion is less than a specified maximum. Shafts with circular cross sections are easier to produce in the steel mill, easier to machine, and easier to support in bearings than shafts with other cross section； there is seldom any need for using noncircular shapes. In addition, the strength and stiffness, both in bending and torsion, are more easily calculated for circular shafts. Lastly, for a given amount of materials the circular shafts has the smallest maximum shearing stress for a given torque, and the highest torsional rigidity. The shearing in a circular shaft is highest at the surface and drops off to zero at the axis. This means that most of the torque is carried by the material on and near the surface. Critical speeds. In the same way that a violin string vibrates when stroked with a bow, a cylindrical shaft suspended between two bearings has a natural frequency of lateral vibration. If the speed of revolution of the shaft coincides with the natural frequency, the shaft experience a whirling critical speed and become noisy. These speeds are more likely to occur with long, flexible shafts than with short, stiff ones. The natural frequency of a shaft can be raised by increasing its stiffness. 4 If a slender rod is fixed to the ceiling ta one end and supports a heavy disk at the other end, the disk will oscillate back and forth around the rod axis like a torsion pendulum if given an initial twist and let go. The frequency of the oscillations will depend on the torsional stiffness of the rod and the weight of the disk； the stiffer the rod and the lighter the disk the higher the frequency. Similar torsional oscillations can occur in the crankshafts of reciprocating engines, particularly those with many crank throws and a heavy flywheel. Each crank throw and part of the associated connecting rod acts like a small flywheel, and for the crankshaft as a whole, there are a number of ways or modes in which there small flywheels can oscillate back and forth around the shaft axis in opposition to one another and to the main flywheel. For each of these modes there corresponds a natural frequency of oscillation. When the engine is operating the torques delivered to the crankshaft by the connecting rods fluctuate, and if the crankshaft speed is such that these fluctuating impulses are delivered at a speed corresponding to one of the natural torsional frequencies of the shaft, torsional oscillations will be superimposed on the rotary motion of the shafts. Such speed are known as torsional critical speeds, and they can cause shaft failures. A number of devices to control the oscillations of crankshafts have been invented. Flexible shafts. A flexible shaft consists of a number of superimposed tightly wound right-and left-hand layers of helically wound wires wrapped about a single center wire or mandrel. The shaft is connected to source of power and the driven member by special fittings attached to the end of the shaft. Flexible easings of metallic or nonmetallic materials, which guide and protect the shaft and retain the lubricant, are also available. Compared with solid shafts, flexible shafts can be bent to much smaller radii without being overstressed. For transmitting power around corners and for considerable distances flexible shafts are usually cheaper and more convenient than belts, chains, or gears. Most speedometers on automobiles are driven by flexible shafts running from the transmission to the dashboard. When a valve, a switch, or other control devices is in 5 a hard-to-reach location, it can be operated by a flexible shaft from a more convenient position. For portable tools such as sanders, grinders, and drilling machines, flexible shafts are practically indispensable. 出處： 輸送機械相關英語 /forum.php?mod=viewthread&tid=212652 6 中文翻譯： 軸 實心軸 軸作為機械零件通常是一根圓柱形桿，用來支撐部件并隨部件一起轉(zhuǎn)動以接受和傳遞轉(zhuǎn)動和扭矩。往復式發(fā)動機的曲軸接受每一根曲軸通過活塞和連桿（滑塊 -曲柄機構）傳來的轉(zhuǎn)動，并通過聯(lián)軸器、齒輪、鏈條或皮帶把轉(zhuǎn)動傳遞到變速箱、凸輪軸、泵和其它裝置。由曲軸通過齒輪或鏈條驅(qū)動的凸輪軸只有一根受力軸即輸入軸，但軸上的每一個凸輪都能把 轉(zhuǎn)動傳遞給氣門的傳動機構溝。 輪軸通常的定義是車輪和皮帶輪能在其上旋轉(zhuǎn)的一根固定的圓柱形構件，但驅(qū)動汽車后輪的旋轉(zhuǎn)軸也叫輪軸，這可能是從過去馬車時代傳下來的。通常習慣上把機器上的短軸叫做主軸（或心軸），特別是指機床上安裝刀具和工件的軸。 在以前一個車間里所有的機器都由一個大電動機或原動機的，這樣就必須有一根同車間一樣長的主傳動軸（即天軸）通過皮帶把動力供給較短的副軸、中間軸或頂軸。這種主傳動軸是用一節(jié)節(jié)的軸裝配起來的，用剛性聯(lián)軸器固定在一起。盡管一般說來用單獨的電動機來驅(qū)動每一臺機器更為方便，并且現(xiàn)代的趨勢 也是按照這個方向發(fā)展的，但現(xiàn)在仍有某些場合采用分組傳動更為經(jīng)濟。 應力和變力 軸在轉(zhuǎn)動時承受剪應力，其大小取決于扭矩和斷面的尺寸。這個剪應力是軸的材料對作用扭矩所產(chǎn)生的抗力的一種量度。所有傳遞扭矩的軸都承受扭轉(zhuǎn)剪應力。 除剪應力之外，傳遞扭矩的軸還會產(chǎn)生剪切變形。扭轉(zhuǎn)的狀態(tài)通常用每單位長度的扭轉(zhuǎn)角來表示，即用軸的某一截面所轉(zhuǎn)過的角度來表示。 安裝齒輪和皮帶輪的軸不但會產(chǎn)生扭矩，而且還會產(chǎn)生彎矩，彎曲應力（在凸面是拉應力，在凹面是壓應力）的大小取決于兩軸承間的距離及軸的截面尺寸， 彎曲和扭轉(zhuǎn)綜合起來使軸內(nèi)所 產(chǎn)生的受力狀態(tài)比單純扭轉(zhuǎn)所產(chǎn)生的純剪切狀態(tài)或單純彎曲所產(chǎn)生的拉伸壓縮狀態(tài)更為復雜。 對軸的設計工作者來說，重要的是要知道軸是否可能產(chǎn)生過大的發(fā)向應力或過大的剪應力以致?lián)p壞。如果扭轉(zhuǎn)一支粉筆，它必定