機(jī)構(gòu)設(shè)計(jì)外文翻譯

1、<p><b>　　附錄：</b></p><p><b>　　1 外文資料譯文</b></p><p><b>　　機(jī)構(gòu)</b></p><p>　　機(jī)構(gòu)被定義為：“是由剛體或者有承載能力的物體聯(lián)接而形成的組合體，它們?cè)谶\(yùn)動(dòng)時(shí)彼此之間應(yīng)該具有確定的相對(duì)運(yùn)動(dòng)。”</p><

2、;p>　　機(jī)構(gòu)是構(gòu)成許多機(jī)械設(shè)備的基本幾何單元，這些機(jī)械設(shè)備包括自動(dòng)包裝機(jī)、打字機(jī)、機(jī)械式玩具、紡織機(jī)等等。機(jī)構(gòu)設(shè)計(jì)的目的通常是使一個(gè)剛體相對(duì)某一參考構(gòu)件產(chǎn)生所需要的相對(duì)運(yùn)動(dòng)。機(jī)構(gòu)的運(yùn)動(dòng)設(shè)計(jì)通常是設(shè)計(jì)一臺(tái)完整的機(jī)器的第一步。在考慮力的作用時(shí)，應(yīng)該考慮動(dòng)力學(xué)、軸承載荷、應(yīng)力、潤(rùn)滑等一系列問題。在所考慮的問題的范圍擴(kuò)大之后，機(jī)構(gòu)設(shè)計(jì)就變成了機(jī)器設(shè)計(jì)。</p><p>　　作為機(jī)器的一個(gè)組成部分，機(jī)構(gòu)的作用是在剛

3、體之間傳遞或轉(zhuǎn)換運(yùn)動(dòng)。常用的基本機(jī)構(gòu)有以下三種：</p><p>　　齒輪機(jī)構(gòu) 在這種機(jī)構(gòu)中，各轉(zhuǎn)軸之間的運(yùn)動(dòng)由相互嚙合的齒輪來傳遞。齒輪通常用來傳遞角速度比為常值的運(yùn)動(dòng)，但是非圓齒輪可以用來傳遞角速度比為變數(shù)的運(yùn)動(dòng)。</p><p>　　凸輪機(jī)構(gòu) 在這種機(jī)構(gòu)中，輸入件的等速連續(xù)運(yùn)動(dòng)被轉(zhuǎn)換成輸出件的不等速運(yùn)動(dòng)。輸出的運(yùn)動(dòng)可以是軸的轉(zhuǎn)動(dòng)、滑塊的移動(dòng)、或者其他從動(dòng)件的運(yùn)動(dòng)。這些運(yùn)動(dòng)都是使從

4、動(dòng)件與作為輸入件的凸輪的輪廓的直接接觸而產(chǎn)生的。凸輪的運(yùn)動(dòng)設(shè)計(jì)就是采用解析法或者圖解法來確定凸輪的輪廓形狀，使其能夠帶動(dòng)從動(dòng)件實(shí)現(xiàn)輸出運(yùn)動(dòng)時(shí)輸入運(yùn)動(dòng)的指定函數(shù)這一功能。</p><p>　　平面和空間連桿機(jī)構(gòu) 這類機(jī)構(gòu)也是用來使機(jī)構(gòu)上某一點(diǎn)或者剛體實(shí)現(xiàn)機(jī)械運(yùn)動(dòng)的。連桿的基本作用有三種：</p><p>　　(1)剛體導(dǎo)向。剛體導(dǎo)向機(jī)構(gòu)用來引導(dǎo)一個(gè)剛體，使其通過空間一系列預(yù)定的位置。<

5、;/p><p>　　(2)導(dǎo)軌。實(shí)現(xiàn)導(dǎo)軌機(jī)構(gòu)將引導(dǎo)剛體上的一個(gè)點(diǎn)，使其通過指定的空間軌跡上的一系列點(diǎn)。</p><p>　　(3)實(shí)現(xiàn)函數(shù)。這類機(jī)構(gòu)所產(chǎn)生的輸出運(yùn)動(dòng)是輸入運(yùn)動(dòng)的指定函數(shù)。 </p><p>　　為了強(qiáng)調(diào)各種機(jī)構(gòu)之間的相同之處與不同之處，可以把它們按照幾種不同的方式進(jìn)行分類。一種分類方式是將機(jī)構(gòu)分為平面、球面和空間三類。這三類機(jī)構(gòu)有共同之處，然而，可以

6、根據(jù)其構(gòu)件的運(yùn)動(dòng)特點(diǎn)來確定分類準(zhǔn)則。</p><p>　　在平面機(jī)構(gòu)中，所有質(zhì)點(diǎn)走過的軌跡都是平面曲線，所有這些平面曲線都位于相互平行的平面上，即所有點(diǎn)的軌跡都是平行于一個(gè)共同平面的平面曲線。這一特點(diǎn)使得平面機(jī)構(gòu)上任意選定的一個(gè)點(diǎn)都可以按其真實(shí)尺寸和形狀在一個(gè)視圖上表示出運(yùn)動(dòng)軌跡。平面四連桿機(jī)構(gòu)、平板凸輪和它的從動(dòng)件、曲柄滑塊機(jī)構(gòu)是大家所熟悉的平面機(jī)構(gòu)的例子?，F(xiàn)在使用中的大多數(shù)機(jī)構(gòu)是平面機(jī)構(gòu)。</p>

7、<p>　　在球面機(jī)構(gòu)中，當(dāng)機(jī)構(gòu)運(yùn)動(dòng)時(shí)，每一個(gè)構(gòu)件上都有一個(gè)點(diǎn)是靜止的，所有構(gòu)件上的靜止點(diǎn)都處于同一個(gè)位置，也就是每一個(gè)構(gòu)件上都有一個(gè)點(diǎn)是靜止的，所有構(gòu)件上的靜止點(diǎn)都處于同一個(gè)位置，也就是每個(gè)點(diǎn)的軌跡都是球面曲線。所有各點(diǎn)運(yùn)動(dòng)時(shí)所在的球面是同心的。因而，所有質(zhì)點(diǎn)的運(yùn)動(dòng)都能用它們?cè)谝赃m當(dāng)選取的點(diǎn)為中心的球面上的徑向投影來完整地進(jìn)行描述?；⒖巳f向聯(lián)軸器可能會(huì)是人們最熟悉的一個(gè)球面機(jī)構(gòu)的例子。</p><p&

8、gt;　　從另一方面來說，在空間機(jī)構(gòu)中質(zhì)點(diǎn)的相對(duì)運(yùn)動(dòng)不受約束。運(yùn)動(dòng)的變換既不要求共面，也不要求同心?？臻g機(jī)構(gòu)上許多質(zhì)點(diǎn)的運(yùn)動(dòng)軌跡可能具有雙重曲率。</p><p>　　例如，任何含有螺旋副的連桿機(jī)構(gòu)，由于其相對(duì)運(yùn)動(dòng)是螺旋線形的，因此是空間機(jī)構(gòu)。</p><p><b>　　材料選擇</b></p><p>　　近些年來，工程材料的選擇已經(jīng)顯得非

9、常重要。此外，選擇過程應(yīng)該是一對(duì)材料的連續(xù)不斷的重新評(píng)價(jià)過程。新材料不斷出現(xiàn)，而一些原有的材料的可以被利用的數(shù)量可能會(huì)減少。環(huán)境污染、材料的回收利用、工人的健康及安全等方面經(jīng)常會(huì)對(duì)材料選擇附加新的限制條件。為了減輕重量或者節(jié)約能源，可能會(huì)要求使用不同的材料。來自國(guó)內(nèi)和國(guó)際的競(jìng)爭(zhēng)、對(duì)產(chǎn)品維修保養(yǎng)方便性要求的提高和顧客的反饋等反面的壓力，都會(huì)促使人們對(duì)材料進(jìn)行重新評(píng)價(jià)。由于材料選用不當(dāng)造成的產(chǎn)品責(zé)任訴訟，已經(jīng)產(chǎn)生了深刻的影響。此外，材料與材

10、料加工之間的相互依賴關(guān)系已經(jīng)被人們認(rèn)識(shí)得更清楚。新的加工方法的出現(xiàn)，通常會(huì)促使人們對(duì)被加工材料進(jìn)行重新評(píng)價(jià)。因此，為了能在合理的成本和確保質(zhì)量的前提下獲得滿意的結(jié)果，設(shè)計(jì)工程師和制造工程師都必須認(rèn)真仔細(xì)地選擇、確定和使用材料。</p><p>　　制造任何產(chǎn)品的第一步工作都是設(shè)計(jì)。設(shè)計(jì)通?？梢苑譃閹讉€(gè)明確的階段：（a）概念設(shè)計(jì)；（b）功能設(shè)計(jì)；（c）生產(chǎn)設(shè)計(jì)。在概念設(shè)計(jì)階段，設(shè)計(jì)者著重考慮產(chǎn)品應(yīng)該具有的功能。通常

11、要設(shè)想和考慮幾個(gè)方案，然后決定著中想法是否可行；如果可行，則應(yīng)該對(duì)其中一個(gè)或幾個(gè)方案作進(jìn)一步的改進(jìn)。在此階段，關(guān)于材料選擇唯一要考慮的問題是：是否有性能符合要求的材料可供選用；如果沒有的話，是否有較大的把握在成本和時(shí)間都允許的限度內(nèi)研制出一種新材料。</p><p>　　在功能設(shè)計(jì)或工程實(shí)際階段，要做出一個(gè)切實(shí)可行的設(shè)計(jì)。在這個(gè)階段要繪制出相當(dāng)完整的圖紙，選擇并確定各種零件的材料。通常要制造出樣機(jī)或者食物模型，并

12、對(duì)其進(jìn)行試驗(yàn)，評(píng)價(jià)產(chǎn)品的功能、可靠性、外觀、和維修保養(yǎng)性等。雖然這種實(shí)驗(yàn)可能會(huì)表明，在產(chǎn)品進(jìn)入到生產(chǎn)階段之前，應(yīng)該更換某些材料，但是，絕對(duì)不能將這一點(diǎn)作為不認(rèn)真選擇材料的借口。應(yīng)該結(jié)合產(chǎn)品的功能，認(rèn)真仔細(xì)地考慮產(chǎn)品的外觀、成本、可靠性。一個(gè)很有成就的公司在制造所有樣機(jī)時(shí)，所選用的材料應(yīng)該和其在生產(chǎn)中使用的材料相同，并盡可能使用同樣的制造技術(shù)。這樣做對(duì)公司是很有好處的。功能完備的樣機(jī)如果不能根據(jù)預(yù)期的銷售量經(jīng)濟(jì)地制造出來，或者是樣機(jī)與正式

13、生產(chǎn)的裝置在質(zhì)量和可靠性方面有很大的不同，則這種樣機(jī)就沒有多大的價(jià)值。設(shè)計(jì)工程師最好能在這一階段全部完成材料分析、選擇和確定工作，而不是將其留到生產(chǎn)設(shè)計(jì)階段去做。因?yàn)?，在生產(chǎn)設(shè)計(jì)階段材料的更換時(shí)由其他人進(jìn)行的，這些人對(duì)產(chǎn)品的所有功能的了解可能不如設(shè)計(jì)工程師。</p><p>　　在生產(chǎn)設(shè)計(jì)階段中，與材料有關(guān)的主要問題是應(yīng)該把材料完全確定下來，使它們與現(xiàn)有的設(shè)備相適應(yīng)，能夠利用現(xiàn)有設(shè)備經(jīng)濟(jì)地進(jìn)行加工，而且材料的數(shù)量

14、能夠比較容易地保證供應(yīng)。</p><p>　　在制造過程中，不可避免地會(huì)出現(xiàn)對(duì)使用材料作一些更改的情況。經(jīng)驗(yàn)表明，可以采用某些便宜材料作為替代品。然而，在大多數(shù)情況下，在進(jìn)行生產(chǎn)以后改換材料要比開始生產(chǎn)前改換材料所花費(fèi)的代價(jià)要高。在生產(chǎn)設(shè)計(jì)階段做好材料選擇工作，可以避免大多數(shù)的這種材料更換情況。在生產(chǎn)開始后出現(xiàn)了可供使用的新材料是更換材料的最常見的原因。當(dāng)然，這些新材料可能降低成本、改進(jìn)產(chǎn)品性能。但是，必須對(duì)新材

15、料進(jìn)行認(rèn)真評(píng)價(jià)，以確保其所有性能都被人們所了解。應(yīng)當(dāng)時(shí)刻牢記，新材料的性能和可靠性很少能像現(xiàn)有材料那樣為人們所了解。大部分的產(chǎn)品失效和產(chǎn)品責(zé)任事故案件是由于在選用新材料作為替代材料之前，沒有真正了解它們的長(zhǎng)期使用性能而引起的。</p><p><b>　　1 外文資料原文</b></p><p><b>　　Mechanism</b></p

16、><p>　　A mechanism has been defined as“a combination of rigid or resistant bodies so formed and connected that they move upon each other with definite relative motion.”</p><p>　　Mechanisms form the

17、 basic geometrical element of many mechanical devices including automatic packaging machinery, typewriters, mechanical, toys, textile machinery, and others. A mechanism typically is designed to create a desired motion of

18、 a rigid body relative to a reference member. Kinematic design of mechanisms is often the first step in the design of a complete machine. When force are considered, the additional problem of dynamics, bearing loads, stre

19、sses, lubrication ,and the like are intro</p><p>　　The function of a mechanism is to transmit or transform motion from one rigid body to another as part of the action of a machine. There are three types of c

20、ommon mechanical devices that can be used as basic elements of a mechanism.</p><p>　　Gear Systems Ger systems, in which toothed members in contact transmit motion between rotating shafts. Gear normally are u

21、sed for the transmission of motion with a constant angular velocity ratio, although noncircular gears can be used for nonuniform transmission of motion.</p><p>　　Cam Systems Cam systems, where a uniform mot

22、ion of an input member is converted into a nonuniform motion of the output member. The output motion may be either shaft rotation, slider translation, or other follow </p><p>　　motions created by direct cont

23、act between the input cam shape and the follower. The kinematic design of cams involves the analytical or graphical specification of the cam surface shape required to drive the follower with a motion that is a prescribed

24、 function of the input motion.</p><p>　　Plane and Spatial Linkage they are also useful in creating mechanical motions for a point or rigid body. Linkages can be used for three basic tasks.</p><p&g

25、t;　　(1)Rigid body guidance. A rigid body guidance mechanism is used to guide a rigid body through a series of prescribed positions in space.</p><p>　　(2)Path generation. A path generation mechanism will guid

26、e a point on a rigid body through a series of points on a specified path in space.</p><p>　　(3)Function generation. A mechanism that creates an output motion that is a specified function of the input motion.

27、</p><p>　　Mechanisms may be categorized in several different ways to emphasize their similarities and differences, One such grouping divides mechanisms into planar, spherical, and spatial categories. All thr

28、ee groups have many things in common; the criterion which distinguishes the groups, however, is to be found in the characteristics of the motion of the links.</p><p>　　A planar mechanism is one in which all

29、particles describe plane curves in space and all those curves lie in parallel planes; i.e., the loci of all points re plane curves parallel to a single common plane. This characteristic makes it possible to present the l

30、ocus of any chosen point of a planar mechanism in its true size and shape on a single drawing or figure. The plane four-bar linkage, the plate cam and follower, and the slider-crank mechanism are familiar examples of pla

31、nar mechanism. The va</p><p>　　A spherical mechanism is one in which each link has some point which remains stationary as the linkage moves and in which the stationary point of all links lie at a common loca

32、tion; i.e. ,the locus of each point is a curve contained in a spherical surface ,and the spherical surfaces defined by several arbitrarily chosen points are all concentric . The motions of all particles can therefore be

33、completely described by their radial projections, or“shadows,” on the surface of a sphere with properly </p><p>　　Spatial mechanisms, on the other hand, include no restrictions on the relative motions of the

34、 particles. The motion transformation is not necessarily coplanar, nor must it be concentric. A spatial mechanism may have particles with loci of double curvature. Any linkage which contains a screw pair, for example, is

35、 a spatial mechanism, since the relative motion within a screw pair is helical.</p><p>　　Materials selection</p><p>　　During recent years the selection of engineering materials has assumed great

36、 importance. Moreover the process should be one of continual reevaluation. New materials often become available and there may be a decreasing availability of others. Concerns regarding environmental pollution, recycling

37、and worker health and safety often impose new constraints. The desire for weight reduction or energy savings may dictate the use of different materials. Pressures from domestic and foreign competition, in</p><

38、p>　　The first step in the manufacture of any product is design, which usually takes place in several distinct stages :(a) conceptual; (b) functional; (c) production design. During the conceptual-design stage, the desi

39、gner is concerned primarily with the functions the product is so fulfill. Usually several concept are visualized and considered, and a decision is made either that the idea is not practical or that the idea is sound and

40、 one or more of the conceptual designs should be developed further.</p><p>　　At the functional- or engineering-design stage, a practical, workable design is developed. Fairly complete drawings are made, an

41、d materials are selected and specified for the various components. Often a prototype or working model is made that can be tested to permit evaluation of the product as to function, reliability, appearance, serviceabilit

42、y, and so on. Although it is expected that such testing might show that some changes may have to be made in materials before the product is advanced </p><p>　　At the production-design stage ,the primary con

43、cern relative to materials should be that they are specified fully ,that they are compatible with , and can be processed economically by , existing equipment, and that they are readily available in the needed quantities

44、.</p><p>　　As manufacturing progresses , it is inevitable that situations will arise that may require modifications of the materials being used. Experience may reveal that substitution of cheaper materials

45、can be made .In most cases, however, changes are much more costly to make after manufacturing is in progress than before it starts. Good selection during the production-design phase will eliminate the necessity for thi

46、s type of change . The more common type of change that occurs after manufacturing st</p><p>　　Product liability actions have made it imperative that designers and companies employ the very best procedures in

47、 selecting materials. The five most common faults in material selection have been (a) failure to know and use the latest and best information available about the materials utilized; (b) failure to foresee, and take int

48、o account the reasonable uses for the product (where possible ,the designer is further advised to foresee and account for misuse of the product, as there have been ma</p><p>　　An examination of the faults a

49、bove will lead one to conclude that there is no good reason why they should exist .Consideration of them provides guidance as to how they can be eliminated. While following the very best methods in material selection ma

50、y not eliminated all product-liability claims, the use of proper procedures by designers and industries can greatly reduce their numbers.</p><p>　　From the previous discussion, it is apparent that those who