【正文】 為了在傳遞扭矩時(shí)不發(fā)生過載，軸應(yīng)具。軸最常見的形狀是圓形，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）。諸如彎曲和拉伸這類金屬加工過程需要采用延性材料。延展性材料能夠承受較大的超載荷這個特性，是設(shè)計(jì)中的一個附加的安全岡素。因?yàn)檫@并不足對實(shí)際應(yīng)變量的測量，所以有時(shí)也采用另一種測量延展性的方法，這個方法在試件斷裂后，測量其斷裂處的截面的面積。概括地說，設(shè)計(jì)人員所遇到的基本問題是，不論對于哪一種應(yīng)力狀態(tài)或者載荷情況，都能利用通過簡單拉伸試驗(yàn)所獲得的數(shù)據(jù)并將其與零件的強(qiáng)度聯(lián)系起來。這就說，設(shè)計(jì)人員通常只能利用那些公開發(fā)表的屈服強(qiáng)度，極限強(qiáng)度和延伸率等數(shù)據(jù)資料．人們期望工程師在利用那些公開發(fā)表的資料的基礎(chǔ)上，對靜載荷和動載荷，二維應(yīng)力狀態(tài)與三維應(yīng)力狀態(tài)，高溫與低溫以及大零件和小零件進(jìn)行設(shè)計(jì)！而設(shè)計(jì)中所能利用的數(shù)據(jù)通常是從簡單的拉伸試驗(yàn)中得到，其載荷是漸漸加上去的，有充分的時(shí)間產(chǎn)生應(yīng)變。這時(shí)候需要采用分析的方法來弄清楚不能令人滿意的原因和應(yīng)該如何進(jìn)行改進(jìn)?；蛘咭蠛芸斓赝瓿稍O(shè)計(jì)，以至于沒有足夠的時(shí)間進(jìn)行試驗(yàn)。設(shè)計(jì)任何機(jī)械零件的理想情況為，工程師可以利用大量的他所選的這種材料的強(qiáng)度試驗(yàn)數(shù)據(jù)．這些試驗(yàn)應(yīng)該采用與所設(shè)計(jì)是零件有著相同是熱處理，表面粗糙度和尺寸大小的試件進(jìn)行，而且試驗(yàn)應(yīng)該在與零件使用過程中承受的載荷完全相同的情況下進(jìn)行．這表明，如果零件將要承受彎曲載荷，那么就應(yīng)該進(jìn)行彎曲載荷的試驗(yàn)．如果零什將要受彎曲和扭轉(zhuǎn)的復(fù)合載荷，那么就應(yīng)該進(jìn)行彎曲和扭轉(zhuǎn)復(fù)合載荷的試驗(yàn)，這些種類的試驗(yàn)可以提供非常有效和精準(zhǔn)的數(shù)據(jù)．它們可以告訴工程師應(yīng)該使用的安全系數(shù)和對于給定的壽命時(shí)的可靠性．在設(shè)計(jì)過程中，只要能夠獲得這種數(shù)據(jù)，工程師就可以盡可能好地進(jìn)行工設(shè)計(jì)工作如果零件的失效可能危害人的牛命安全，或者零件有足夠大的產(chǎn)量，則在設(shè)計(jì)前收集這樣廣泛的數(shù)據(jù)所花費(fèi)的費(fèi)用是很值得的，例如，汽車和冰箱的零件產(chǎn)量非常的人，可以在生產(chǎn)之前對它們進(jìn)行大量的試驗(yàn)，使其具有較高的可靠性，如果把進(jìn)行這些試驗(yàn)的費(fèi)用分?jǐn)偟剿a(chǎn)的零件上的話，則攤到所生產(chǎn)每個零件的費(fèi)用是非常低的。然后計(jì)算每個零件的體積，再去乘以所選材料的質(zhì)量密度，去取得零件最初的合理質(zhì)量。術(shù)語低副是用來描繪接頭間的面接觸，如針和孔的結(jié)合面，高副是用來描繪接頭間的點(diǎn)和線接觸，但是如果存針和孔之問有間隙存在（當(dāng)它們之間用于有相對運(yùn)動時(shí)）當(dāng)針和孔只有一面接觸時(shí)，在針間的面聯(lián)接實(shí)際上已經(jīng)變成了線接觸。接下來將要介紹相關(guān)的術(shù)語：純轉(zhuǎn)動物體同繞著在相對于一個靜止的座標(biāo)系靜止的一點(diǎn)（同轉(zhuǎn)中心）轉(zhuǎn)動，其他所有物體上的點(diǎn)都可以用相對中心的弧來描述．在物體上的參考線通過中心，只有在角度與方向上有變化。在通常情況下，剛體在相關(guān)平面內(nèi)能實(shí)現(xiàn)復(fù)雜的自由運(yùn)動，這個運(yùn)動同時(shí)包括轉(zhuǎn)動和平移。在機(jī)械設(shè)計(jì)中，零件受到的最人力是取決于材料本身的動態(tài)性能．這些動態(tài)力引起了零什的加速度，加速度又要回到運(yùn)動學(xué)中去計(jì)算，這是機(jī)械設(shè)計(jì)的基礎(chǔ)．運(yùn)動分析是最基本的也是最早出現(xiàn)在設(shè)計(jì)的過程中的，它對于一個零件的成功設(shè)計(jì)夠起著至關(guān)重要的作用，在設(shè)計(jì)過程中很差的運(yùn)動學(xué)分析會帶米麻煩和錯誤。hence,tha shaft must be rigid enough to prevent overloading of the supporting bearings ,in general, the bending deflection of a shaft should not exceed in per ft of length between bearing supports. In addition .the shaft must be able to sustain a bination of bending and torsional loads. Thus an equivalent load must be considered which takes into account both torsion and bending . also the allowable stress must contain a factor of safety which includes fatigue, since torsional and bending stress reversals occur. Many shafts are supported by three or more bearings, which means that the problem is Stacically indeterminate text on strench of matenals give methods of solving such probIems. The design effort should be in keeping with the economics of a given situation , for example , if one line shaft supported by three or more bearings id needed , it probably would be cheaper to make conservative assumptions to moments and design it as though it were determinate . the extra cost of an oversize shaft may be less than the extra cost of an claboratc design analysis There are several types of shaft couplings, their charactcristics depend on the purposc for which they are used. If an exceptionally long shaft is required in a manufacturing plant or apropeller shaft on a ship , it is made in sections that are coupled together with rigid couplings.A mon type of rigid coupling consists of two mating radial flanges that are attached by key driven hubs to the ends of adjacent shaft sections and bolted together through the flanges to form a rigid connection. Alignment of the connected shafts in usually effected by means of a rabbet joint on the face of the flanges.In connecting shafts belonging to separate device such as an electric motor and a gearbox),precise aligning of the shafts is difficult and a fkexible coupling is used . this coupling connects the shafts in such a way as to minimize the harmful effects of shafts misalignment of loads and to move freely float in the axial direction without interfering with one another ,flexiable couplings can also serve to reduce the intensity of shock loads and vibrations transrrutted from one shaft to another .機(jī)械運(yùn)動和動力學(xué)運(yùn)動學(xué)的基本目是去設(shè)計(jì)一個機(jī)械零件的理想運(yùn)動，然后再用數(shù)學(xué)的方法去描繪該零件的位置，速度和加速度，再運(yùn)用這些參數(shù)來設(shè)計(jì)零件。consequently, an elaborate testingprogram is justified during design . (2)the part is made in large enough quantities so that a moderate serues of tests is feasible. (3)The part is made in such small quantities that testing is not justified at all 。非常感謝百忙中抽空指導(dǎo)評審本設(shè)計(jì)的評閱老師和答辯委員會的老師英語翻譯Kinematics and dynamics of machineryOne principle aim of kinematics is to creat the designed motions of the subject mechanical parts and then mathematically pute the positions, velocitics ,and accelerations .which those motions will creat on the parts. Since .for most earthbound mechanical systems , the massremain sessentially constant with time, defining the accelerations as a function of time then also defines the dynamic forces: as a finction of time. In turn will be a function of both applied and incrials forces . Since engineering design is charged with creating systems which will not fail during their expected scrvice life, the goal is to keep stresses within acceptable limits for the materials chosen and the environmental conditions encountered. This obvisely requies that all systcm forces bc defined and kept within desired limits. In mechinery , the largest forces encountered are often those due to the dynamies of the machine itself. These dynamic forces are proportional to acceletation, which brings us back to kinematics ,the foundation of mechanical design Very basic and early decisions in the design process involving kinematics willprove troublesome and perform badly.Any mechanical system can be classified according to the number of degree of freedom which it possesses, the systems DOF is equal to the number of independent parameters which are needed to uniquely define its posion in space at any instant of time.Complex motion a simulaneous bination of rotion and translationm . any reference line drawn on the body will change both its linear pisition and its angular orientation. Points on the body will travel nonparallel paths ,and there will be . at every instant , a center of rotation ,which will continuously change location.A link is an (assumed)rigid body which possesses at least two or more links(at their nodes),which connection allows some motion, or potential motion, between the connected links.One of the primary considerations in designing any machine or strucre is that the strength must be sufficiently greater than the