【正文】 tener could result in a simple nuisance such as a door rattle or in a serious situation such as a wheel ing off.Such possibilities must be taken into account in the selection of the type of fatener for the specific application.通過任何一個復(fù)雜的產(chǎn)品，都可以認(rèn)識到緊固件在其中的重要性。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 shaft and a spacer ,with torque being transmitted through a keyways.Lesson7Fasteners are devices which permit one part to be joined to a second part and ,hence,they are involved in almost all designs . The acceptability of any product depends not only on the selected ponents , but also on the means by which they are fastened together. The principal purposes of fasteners are to provide the following design features。在鍵及軸上與之相對應(yīng)的鍵槽的設(shè)計(jì)中，必須進(jìn)行認(rèn)真的計(jì)算。有時也采用矩形軸，例如。figure1(如圖)。在力學(xué)中標(biāo)量的例子有時間、體積、密度、速率、能量和質(zhì)量。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.作用在一個剛體上的兩個這樣的的里構(gòu)成一個力偶。 專業(yè)資料分享 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. 對運(yùn)動時間和作用力作出科學(xué)分析的分支成為力學(xué)。力偶臂是這兩個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。另一方面，矢量既有大小又有大小又有方向。2 、If this workpiece is held between the centers of the lathe, the centers exert a pressive force against the work. 如果這個工件在放在車床中心之間,中心車床對工作產(chǎn)生壓力。 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. 為了在傳遞扭矩時不發(fā)生過載，軸應(yīng)該有適當(dāng)?shù)目古?qiáng)度。例如，軸上的鍵槽會引起應(yīng)力集中，由于鍵槽的存在會使軸的橫截面積減小，會進(jìn)一步減弱軸的強(qiáng)度。緊固件是將一個零件與另一個零件進(jìn)行連接的零件。以汽車為例，它是由數(shù)千個零件連接在一起而成為一輛車。The deflection of less magnitude than that of the shafts or other ponents associated with the bearing .當(dāng)載荷較大時，軸承零件的變形，盡管它通常小于軸和其它與軸承一起工作的零部件的變形，將會變得重要起來。The inner race is frequently located axially by abutting against a shoulder .Aradius at this point is essential for the avoidance of stress concentration and ball races rae providede with a radius or chamfer to allow space for this .內(nèi)圈通常是通過緊靠在軸肩上進(jìn)行軸向定位的。Lesson13One of the primary considerations in designing any machine or structure is that the strength must be sufficiently greater that the stress to assure both safety and reliability. To assure that mechanical parts do not fail in service, it is necessary to learn why they sometimes do fail. Then we shall be able to relate the stresses with the strengths to achieve safety.在設(shè)計(jì)任何機(jī)器或者結(jié)構(gòu)時，所考慮的主要事項(xiàng)之一是其強(qiáng)度應(yīng)該比它所承受的應(yīng)力要大得多，以確保安全與可靠性。Most hardnesstesting syst