【正文】 彈性聯(lián)軸器也可以用來(lái)減輕從一根軸傳到另一根軸上的沖擊載荷和振動(dòng)的強(qiáng)度。這種聯(lián)軸器聯(lián)接軸的方式可以把由于被連結(jié)的軸之間的軸線的不重合所造成的有害影響減少到最低程度。但在緊急情況一下，或者在需要更換已磨損的零件時(shí)，可以先把聯(lián)軸器拆開，然后在聯(lián)接上。聯(lián)軸器是用來(lái)把相鄰的兩根軸聯(lián)接起來(lái)的裝置。軸的設(shè)計(jì)工作中的另外一個(gè)重要的方面是一根軸和另一根軸之間的聯(lián)接方法。知道這些臨界速度的大小是很重要的，岡為這樣可以避開它。例如，軸上的鍵槽會(huì)引起應(yīng)力集中，由于鍵槽的存在會(huì)使軸的橫截面減小，會(huì)進(jìn)一步減弱軸的強(qiáng)度。齒輪和皮帶輪等零件通過(guò)鍵聯(lián)接在軸上。輕載時(shí)，廣泛采用塑料軸。因此，要考慮扭矩與彎矩的當(dāng)量載荷矩和彎矩會(huì)產(chǎn)生交變應(yīng)力，在許用應(yīng)力中也應(yīng)該有一個(gè)考慮疲勞現(xiàn)象的安全系數(shù)?？偠灾?，在兩個(gè)軸承之問(wèn)。通過(guò)這些零件傳來(lái)的力可能會(huì)使軸產(chǎn)生彎曲變形。一般來(lái)說(shuō)，在長(zhǎng)度等于軸的直徑的20倍時(shí)，軸的扭轉(zhuǎn)角不應(yīng)該超過(guò)l度。為了在傳遞扭矩時(shí)不發(fā)生過(guò)載，軸應(yīng)具有適當(dāng)?shù)目古?qiáng)度。軸最常見(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）。諸如彎曲和拉伸這類金屬加工過(guò)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(gè)特性，是設(shè)計(jì)中的一個(gè)附加的安全岡素。因?yàn)檫@并不足對(duì)實(shí)際應(yīng)變量的測(cè)量，所以有時(shí)也采用另一種測(cè)量延展性的方法，這個(gè)方法在試件斷裂后，測(cè)量其斷裂處的截面的面積。概括地說(shuō)，設(shè)計(jì)人員所遇到的基本問(wèn)題是，不論對(duì)于哪一種應(yīng)力狀態(tài)或者載荷情況，都能利用通過(guò)簡(jiǎn)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(lái)。這就說(shuō)，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(duì)靜載荷和動(dòng)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(jiǎn)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(lái)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(méi)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(guò)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(duì)于給定的壽命時(shí)的可靠性．在設(shè)計(jì)過(guò)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(duì)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(gè)零件的費(fèi)用是非常低的。然后計(jì)算每個(gè)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(yǔ)低副是用來(lái)描繪接頭間的面接觸，如針和孔的結(jié)合面，高副是用來(lái)描繪接頭間的點(diǎn)和線接觸，但是如果存針和孔之問(wèn)有間隙存在（當(dāng)它們之間用于有相對(duì)運(yùn)動(dòng)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(lái)將要介紹相關(guān)的術(shù)語(yǔ)：純轉(zhuǎn)動(dòng)物體同繞著在相對(duì)于一個(gè)靜止的座標(biāo)系靜止的一點(diǎn)（同轉(zhuǎn)中心）轉(zhuǎn)動(dòng)，其他所有物體上的點(diǎn)都可以用相對(duì)中心的弧來(lái)描述．在物體上的參考線通過(guò)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(dòng)，這個(gè)運(yùn)動(dòng)同時(shí)包括轉(zhuǎn)動(dòng)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(dòng)態(tài)性能．這些動(dòng)態(tài)力引起了零什的加速度，加速度又要回到運(yùn)動(dòng)學(xué)中去計(jì)算，這是機(jī)械設(shè)計(jì)的基礎(chǔ)．運(yùn)動(dòng)分析是最基本的也是最早出現(xiàn)在設(shè)計(jì)的過(guò)程中的，它對(duì)于一個(gè)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(guò)程中很差的運(yùn)動(dòng)學(xué)分析會(huì)帶米麻煩和錯(cuò)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(dòng)和動(dòng)力學(xué)運(yùn)動(dòng)學(xué)的基本目是去設(shè)計(jì)一個(gè)機(jī)械零件的理想運(yùn)動(dòng)，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(lái)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(píng)審本設(shè)計(jì)的評(píng)閱老師和答辯委員會(huì)的老師英語(yǔ)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