【正文】 gn of the key and the corresponding keyway in the shaft must be properly evaluated. For example, stress concentrations occur in shafts due to keyways, and the material removed to from the keyway further weakens the shaft.齒輪和皮帶輪等零件通過(guò)鍵連接在軸上。 A shaft must have adequate torisonal strength to transmit torque and not be over stressed it must also be torsional stiff enough so that one mounted ponent does not deviate excessively from its original angular position relative to a second ponent mounted on the same shaft. 為了在傳遞扭矩時(shí)不發(fā)生過(guò)載，軸應(yīng)該有適當(dāng)?shù)目古?qiáng)度。軸的最常見(jiàn)的形狀是圓形，其截面可以是實(shí)心的，也可以是空心的（空心軸可以減輕重量）。2 、If this workpiece is held between the centers of the lathe, the centers exert a pressive force against the work. 如果這個(gè)工件在放在車床中心之間,中心車床對(duì)工作產(chǎn)生壓力。Lesson2（此課后面沒(méi)翻譯，翻譯的不太準(zhǔn)確諒解）1 、The turning of a part in a lathe is another example of several forces in action.（as shown in figure1） 車床車削是一些力在起作用的另一個(gè)例子。另一方面，矢量既有大小又有大小又有方向。標(biāo)量是那些只有大小的量。力偶臂是這兩個(gè)條作用線之間的垂直距離，力偶面是包含著兩條作用線的平面。靜力學(xué)對(duì)靜止系統(tǒng)進(jìn)行分析，即在其中不考慮時(shí)間這個(gè)引述，動(dòng)力學(xué)對(duì)事件而變化的系統(tǒng)進(jìn)行分析。Lesson1 the branch of scientific analysis, which deals with motions, time, and forces, is called mechanics and is made up of two parts, statics and dynamics. Statics deals with the analysis of stationary systems, ., those in which time is not a factor, and dynamics deals with systems, which change with time. 對(duì)運(yùn)動(dòng)時(shí)間和作用力作出科學(xué)分析的分支成為力學(xué)。他由靜力學(xué)和動(dòng)力學(xué)兩部分組成。Any two such forces acting on a body constitute a couple. The arm of the couple is the perpendicular distance between their lines of action, and the plane of the couple is the plane containing the two lines of action.作用在一個(gè)剛體上的兩個(gè)這樣的的里構(gòu)成一個(gè)力偶。Mechanics deal with two kinds of quantities: scalars and vectors. Scalar quantities are those with which a magnitude alone is associated. Examples of scalar quantities in mechanics are time, volume, density, speed, energy, and mass. Vector quantities, on the other hand, possess direction as well as magnitude. Examples of vectors are displacement, velocity, acceleration, force, moment, and momentum.力學(xué)涉及兩種類型的量，標(biāo)量 和矢量。在力學(xué)中標(biāo)量的例子有時(shí)間、體積、密度、速率、能量和質(zhì)量。矢量的例子有位移、速度、加速度、力、力矩、動(dòng)量。figure1(如圖)。 Rotary motion is required to drill holes, turn parts in a lathe, mill surfaces, or drive a generator or fan belt. 扶輪運(yùn)動(dòng)需要去鉆孔，在車床上轉(zhuǎn)換兩件,表面,或驅(qū)動(dòng)發(fā)電機(jī)或風(fēng)扇皮帶4 、Harmonic and Intermittent Motion（諧和運(yùn)動(dòng)和間歇運(yùn)動(dòng)）: Any simple vibration, such as the regular back, and forth movement of the end of a pendulum, is simple harmonic motion.Lesson41 、Virtually all machines contain shafts. The most mon shape for shafts is circular and the cross section can be either solid or hollow. 實(shí)際上，幾乎所有的機(jī)器中都裝有軸。有時(shí)也采用矩形軸，例如。軸還應(yīng)該具有足夠的抗扭強(qiáng)度，以使在同一軸上的兩個(gè)傳動(dòng)零件之間的相對(duì)轉(zhuǎn)角不會(huì)過(guò)大。在鍵及軸上與之相對(duì)應(yīng)的鍵槽的設(shè)計(jì)中，必須進(jìn)行認(rèn)真的計(jì)算。Another important aspect of shaft design is the method of directly connecting one shaft to another. Devices such as rigid and flexible couplings acplish this.軸的設(shè)計(jì)工作中的另一個(gè)重要方面是一根軸與另一根軸之間的直接連接方法。Lesson5The term shaft usually refers to a relatively long member of round cross section that rotates and transmits power. One or more members such as gears ,sprockers,pullys,and cams are usually attached to the shaft by means of pins, keys,splines,snap rings,and other devices . These latter members are among the associated parts consedered in this text,as ate couplings and universal joints , which serve to connect the shaft to the source of power or load.It is apparent that shafts can be subjected to various binations of axial,bending,and torsional loads,and that these loads may be static or fluctuating.Torsional defection can affect the accuracy of a cam or gear driven mechanism .Furthermore,the greater the flexibility either lateral or torsionalthe lower the corresponding critical speed.A gear can be gripped axially between a shoulder on the s