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Riveting is the commonest method of assembling aircraft. A medium bomber requires 160. 000 rivets and a heavy bomber requires 400, 000 rivets. Some of the forms of rivets are solid rivets with chamfered shanks, tubular or hollow rivets, semitubular rivets, swaged rivets, split rivets, and blind rivets. Solid rivets are used where great strength is required. Tubular rivets are used in the fastening of leather braces. Split rivets are used frequently in the making of suitcases. The materials used in making rivets are aluminum alloys, Monet metal, brass, and steel. Aluminum rivets make possible the maximum saving in weight, and are also quite resistant to corrosion. Anodic coating of aluminum improves the resistance of the rivets to corrosion and also provides a better surface for painting. Steel rivets are stronger than aluminum rivets and offer certain advantages in ease of driving from the standpoint of equipment required; however, their use is limited to those applications in which the structure can be protected adequately against corrosion by painting. Some of the types of rivet heads are button, mushroom, brazier, universal, flat, cinners, and oval. Brazier and mushroom heads are used for interior work. The flat head is used for streamlined pieces.

Keys, Splines, and Pins

When power is being transmitted from a machine member such as a coupling, a clutch, a gear, a flywheel, or a pulley to the shaft on which it is mounted; means must be provided for preventing relative motion between the shaft and the member. On helical and bevel gears, relative movement along the shaft caused by the thrust (axial) loads is prevented by a step in the shaft or by having the gear contact the bearing directly or through a tubular spacer. When axial loads are incidental and of small magnitude, the members are kept from sliding along the shaft by means of a set screw. The primary purpose of keys, splines, and pins is to prevent relative rotary movement.

A commonly used type of key has a square cross section and is sunk half in the shaft and half in the hub of the other member. If the key is made of steel of the same strength as the shaft and has a width and depth equal to one fourth of the shaft diameter then it will have the same torque capacity as the solid shaft if its length is 1.57 times that of the shaft diameter. Another common type of key has a rectangular cross section with a depth to width ratio of 0. 75. Both of these keys may either be straight or tapered in depth. The straight keys fit snugly on the sides of the keyways only, the tapered keys on all sides. Gib-head keys are tapered keys with a projection on one end to facilitate removal.

Woodruff keys are widely used on machine tools and motor vehicles. The key is a segment of a disk and fits in a keyway in the shaft that is cut with a special milling cutter. Though the extra depth of these keys weakens the shaft considerably, it prevents any tendency of the key to rotate or move axially. Woodruff keys are particularly suitable for tapering shaft ends.

Because they weaken the shaft less, keys with straight or tapered circular cross sections are sometimes used in place of square and rectangular keys, but the keyways, half in the shaft and half in the hub, must be cut with a drill after assembly, and interchangeability of parts is practically impossible. When a large gear blank is made by shrinking a high-strength rim on a cheaper cast centre, circular keys, snugly fitted, are frequently used to ensure a permanent connection.

Splines are permanent keys integral with the shaft, fitting in keyways cut in the hub. The dimensions of splined fittings are standardized for both permanent (press) fits and sliding fits. The teeth have either straight or involutes profiles; the latter are stronger, more easily measured, and have a self-centering action when twisted.

Tapered circular pins can be used to restrain shaft-mounted members from both axial and rotary movement. The pin fits snugly in a reamed tapered hole that is perpendicular to the shaft axis and either radial or tangential to the shaft surface. A number of straight pins that grip by deforming elastically or plastically when driven into straight holes are commercially available.

All the keys and pins that have been described are standard driving devices. In some cases they are inadequate, and unorthodox means must be employed.

最新回答 (1条回答)

2009-12-15 回答
铆接装配是飞机最常见的方法。一辆中型轰炸机需要160。 000铆钉和重型轰炸机需要400,000铆钉。对一些表格铆钉与倒角柄,管状或空心铆钉,semitubular铆钉,锤造铆钉,铆钉分裂坚实铆钉和铆钉。实心铆钉的使用,伟大的力量是必需的。管状铆钉用于皮革括号紧固。斯普利特铆钉,频繁使用的行李箱决策。使铆钉,铝合金,莫奈金属,铜和钢铁所用的材料。铝铆钉成为可能的重量最大的节约使用,也非常耐腐蚀。铝阳极涂层提高了铆钉耐腐蚀,也提供了一个更好的表面涂装。不锈钢铆钉,强于铝铆钉,可以提供从设备所需的立场驾驶缓和某些优势,但是,它们的使用限制在其中的人的结构可以有防腐蚀保护充分绘画应用。铆钉头的一些类型的按钮,蘑菇,火盆,普遍的,扁平,cinners和椭圆形。火盆和蘑菇头用于室内工作。在平头用于简化件。 



阿主要有方形截面,是沉没在井下以及在其他成员枢纽一半常用的类型。如果密钥是由作为轴相同的强度钢,具有广度和深度等于一轴的直径第四那么它将作为实心轴相同的扭矩的能力,如果其长度为1.57倍,轴直径。另一个主要有,以宽度为0比矩形截面深入常见的类型。 75。这些项都既可以直接或深入的锥形。直键贴身地适合对键槽的双方只是,在各方的锥形键。培养液头键的一端圆锥投影键,方便清除。