模具專業(yè)畢業(yè)設計外文翻譯翻譯-- 材料選擇

1、<p>　　本科畢業(yè)設計（論文）</p><p><b>　　外文資料翻譯</b></p><p>　　Material Selection</p><p>　　During recant years the selection of engineering materials has assumed great importance

2、. 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 and w

3、orker 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 com</p><p>　　The

4、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 designer is con

5、cerned primarily with the functions the product is to fulfill Usually several concepts are visualized and considered, and a decision is made either that the idea is not practical or that the idea is sound and one or more

6、 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, and materials ar

7、e selected and specified for the various components. Often a prototype or working modal is made that can be tested to permit evaluation of the product as to function, reliability, appearance, serviceability, and so on. A

8、lthough it is expected that such testing might show that some changes may have to be made in materials before the product is advanced to th</p><p>　　At the production design stage, the primary concern relati

9、ve 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.</p>&

10、lt;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 can be made. In

11、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 most of this type of

12、 change. The more common type of change that occurs after manufacturin</p><p>　　Their characteristics are well established. One should always remember that it is indeed rare that as much is known about the p

13、roperties and reliability of a new material as about those of an existing one. A large proportion of product failure and product liability! Cases have resulted from new materials being substituted before their long-term

14、properties were really known.</p><p>　　Product liability actions have made it imperative that designers and companies employ the very best procedures in selecting materials. The five most common faults in ma

15、terial selection have been: (a) failure to know and use the latest and best information available about the materials utilized; (b) fail are to fore, and take into account the reasonable uses for the product( where poss

16、ible, the designer is further advised to foresee and account for misuse of the product, as there have been many </p><p>　　The Computer in Design and Graphics</p><p>　　Computers are widely used i

17、n engineering and related fields and their use is expected to grow even more rapidly than in the past Engineering and technology students must became computer literate, to understand the applications of computer and thei

18、r advantages. Not to do so well place students at a serious disadvantage in pursuing their careers.</p><p>　　Computer-aided design (CAD) involves solving design problems with the help of</p><p>

19、　　Computer: to make graphic images on paper with a plotter or printer, analyze design data, and store design information for easy retrieval. Many CAD systems perform these functions in all integrated manner, greatly incr

20、easing the designer's productivity.</p><p>　　Computer-aided design drafting (CADD), an offshoot of CAD, is the process of Generating engineering drawings and other technical documents by computer and is

21、more directly related to drafting than is CAD. The CADD user inputs data by keyboard and/or mouse to produce illustrations on the monitor screen that can be reproduced as paper copies with a plotter or printer.</p>

22、<p>　　Engineers generally agree that the computer does not change the nature of the design process but is a significant tool that improves efficiency and productivity. The designer and the CAD system may be descri

23、bed as a design team: the designer provides knowledge, creativity, and control; the computer generates accurate, easily modifiable graphics, performs complex design analysis at great speed, and stores and recalls design

24、information. Occasionally, the computer may augment or replace many of th</p><p>　　Depending on the nature of the problem and the sophistication of the computer system, computers offer the designer or drafte

25、r some or all of the following advantages.</p><p>　　1. Easier creation and correction of drawings. Working drawings may be created more quickly than by hand and making changes and modifications is more effic

26、ient than correcting drawings made by hand.</p><p>　　2. Better visualization of drawings. Many systems allow different views of the same object to be displayed and 3D pictorials to be rotated on the CRT scre

27、en.</p><p>　　3. Database of drawing aids. Creation and maintenance of design databases (libraries of designs) permits storing designs and symbols for easy recall and application to the solution of new proble

28、ms. </p><p>　　4. Quick and convenient design analysis the designer can evaluate alternative design thereby considering more p

29、ossibility while speeding up the process at the same time.</p><p>　　5. Simulation and testing of designs. Some computer systems make possible the simulation of a product's operation, testing the design u

30、nder a variety of conditions and stresses; computer testing may improve on or replace construction of models and prototypes.</p><p>　　6. Increased accuracy. The computer is capable of producing drawings wit

31、h more accuracy than is possible by hand; Many CAD systems are even capable of detecting errors and informing the user of them.</p><p>　　7. Improved filing. Drawings can be more conveniently filed, retrieved

32、, and transmitted on disks and tapes.</p><p>　　Computer graphics has an almost limitless number of applications in engineering and other technical fields. Most graphical solutions that are possible with a pe

33、ncil can done on a computer and usually more productively. Applications vary from 3D modeling and finite element analysisi4] to 2D drawings and mathematical calculations.</p><p>　　Once the domain of large co

34、mputer systems advanced applications can now be done on microcomputer. An important extension of CAD is its application to manufacturing. Computer-aided design/computer-aided manufacturing (CAD/CAM) systems may be used t

35、o design a part or product, devise the essential production steps, and electronically communicate this information to and control the operation of manufacturing equipment, including robots. These systems offer

36、 many advantages over traditional</p><p><b>　　材料選擇</b></p><p>　　近些年來，工程材料的選擇已經顯得非常重要。此外，選擇過程應該足一個對材料的連續(xù)不斷的重新評價過程。新材料不斷出現，而一些原有的材料的可以被利用的數量可能會減少。環(huán)境污染、材料的吸收利用、工人的健康及安全等方面經常會對材料選擇附加新的限制

37、條件。為減輕重量或者和約能源，可能要求使用不同的材料、來自國內和國際的競爭、對產品維修保養(yǎng)方便性要求的提高和顧客的反饋等方面的壓力，都會促使人們對材料進行重新評價。由于材料選用不當造成的產品責任訴訟，已經產生深刻的影響．此外，材料與材料加工之間的相互依賴關系已經被人們認識得更清楚。新的加工方法的出現，通常會促使人們對被加工材料進行重新評價。因此，為了能在合理的成本和確保質量的前提下，獲得滿意的結果，設計工程師和制造工程師都必須認真仔細地

38、選擇、確定和使用材料。</p><p>　　制造任何產品的第一步工作都是設汁。設計通常可以分為幾個明確的階段：(a)概念設計;(b)功能設計；(c)生產設計。在概念設計階段，設計者著重考慮產品應該具有的功能。通常要設想和考慮幾個方案，然后決定這種想法是否可行；如果可行，則應該對其中一個或幾個方案做進一步的改進。在此階段，關于材料選擇惟一需要考慮的問題是：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

39、把握在成本和時間都允許的限度內研制出一種新材料。</p><p>　　在功能設計或工程設計階段，要做出一個切實可行的設計。在這個階段需要繪制相當完整的圖紙，選擇并確定各種零件的材料。通常要制造出樣機或者實物模型，并對其進行試驗，評價產品的功能、可靠性、外觀和維修保養(yǎng)性等。雖然這種試驗可能表明，在產品進入生產階段之前，應該更換某些材料，但是，絕對不能將這一點作為不認真選擇材料的借口。應該結合產品的功能，認真仔細地考

40、慮產品的外觀、成本和可靠性。一個很有成就的公司在制造所自樣機時，所選用的材料應該和其在生產使用的材料相同．并盡可能使用同樣的制造技術。這樣做，對公司是很有好處的。功能完備的樣機如果不能根據預期的銷售量經濟地制造出來，或者樣機與正式生產的裝置在質量和可靠性方面有很大不同，則這種樣機就沒有多大的價值。設計工程師最好能在這一階段全部完成材料的分析、選擇和確定工作，而不是將其留到生產設計階段去做。因為，在生產設計階段材料的更換是由其他人進行的，

41、這些人對產品的所有功能的了解可能不如設計工程師．</p><p>　　在生產設計階段中，與材料有關的主要問題是應該把材料完全確定下來，使它們與現有的設備相適應，能夠利用現有設備經濟地進行加工，而且材料的數量能夠比較容易地保證供應。在制造過程中，不可避免地會出現使用中的材料做一些更改的情況。經驗表明，可以采用某些便宜材料作為替代品。然而，在大多數情況下，在進行生產以后改換材料比在開始生產前改換材料所花費的代價要高。

42、在生產設計階段做好材料選擇工作，可以避免大多數的這種材料更換情況，在生產制造開始后出現了可供使用的新材料是更換材料的最常見的原因。當然，這些新材料可能降低成本、改進產品性能。但是，必須對新材料進行認真的評價，以確保其所有性能都被人們所了解。應當時刻牢記，新材料的性能和可靠性很少能像現有的材料那樣為人們所了解。大部分的產品失效和產品責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期使用性能而引起的。</p>

43、<p>　　產品的責任訴訟迫使設計人員和公司在選擇材料時，采用最好的程序。在材料選擇過程中，五個最常見的問題為：(a)不了解或者未能利用關于材料應用的最新和最好的信息資料；(b)未能預見和考慮產品可能的合理用途(若有可能，設計人員還應進一步預測和考慮由于產品使用方法不當造成的后果。在近年來的許多產品責任訴訟案件中，由于錯誤地使用產品而受到傷害的原告控告生產廠家，并且贏得判決)；(c)所使用的材料的數據不全或者有些數據不確定

44、，尤其當其長期性能數據是如此的時候；(d)質量控制方法不適當和未經驗證；(e)由一些完全不稱職的人員選擇材料。</p><p>　　通過對上述五個問題的分析，可以得出這些問題是沒有充分理由存在的結論對這些問題的分析和研究可以給避免這些問題的出現指明方向。盡管采用最好的材料選擇辦法也不能避免發(fā)生產品責任訴訟，設計人員和工業(yè)界按照適當的程序進行材料選擇，可以大大減少訴訟的數量。</p><p>

45、;　　從上面的討論可以看出，選擇材料的人們應該對材料的性質、特點和加工方法有一個全面而基本的了解。</p><p>　　計算機在設計和制圖中的應用</p><p>　　計算機在工程和相關領域內得到廣泛的應用．而這種應用預計會得到越來越快的發(fā)展。工程技術專業(yè)的學生們應該通曉計算機．了解計算機的用途干和它們的優(yōu)點。不這樣做，就會使學生們在將來的職業(yè)生涯中處于非常不利的地位。</p>

46、<p>　　計算機輔助設計(CAD)是應用計算機來幫助解決設計問題：這包括在視頻顯示器上生成圖像，通過繪圖儀或扣印機將這圖像打印在紙上，分析試驗數據，以便用檢索的方式存儲設計信息。許多CAD系統(tǒng)以集成的方式完成這些功能，極大地提高了設計人員的工作效率。</p><p>　　計算機輔助設計制圖(CAD)是CAD的一個分支，它是通過計算機生成丁程圖樣和其他技術文件的過程。它與制圖之間的關系要比CAD更多

47、一些。CAD用戶采用鍵盤和(或)鼠標輸入數據．以便在顯示器屏幕上生成圖像。這些圖像可以通過繪圖儀或打印機輸出到紙上。</p><p>　　工程師們通常認為計算機不會改變設計過程的性質 。 它只是一個能夠顯著提高工作效率和生產效率的工具，工作人員和CAD系統(tǒng)可以被視為是一個集體。設計人員提供知識、創(chuàng)造力和控制；計算生成準確并易于修改的圖形，以很高的速度進行復雜的設計分析工作，以發(fā)存儲和檢索設汁信息。有時，計算機可對

48、工程師所使用的許多其他工具起增強或替代作用，但是它不能取代由設計控制的設計過程。</p><p>　　根據設計問題的本質和所使用計算機系統(tǒng)的先進程度的不同．對設計人員或制圖人員來說，計算機可以有下列中的一些或全部優(yōu)點。</p><p>　　1、易于繪制和修改圖樣。采用計算機可比用手工更快地繪制工作圖。在圖紙進行變更和修改時，也比用手工完成效率更高。</p><p>

49、　　2、對圖樣有更形象化的理解。許多系統(tǒng)可以顯不同物體的不同視圖，而且二維圖像可以在陰極射線管(CRT)屏幕上旋轉。</p><p>　　3、輔助制圖數據庫。建立和維護設計數據庫(設計方案庫可以存儲設計方案和符號，以便于檢索和用來解決新的難題。</p><p>　　4、快速和方便地進行設計分析。由于計算機可使分析變得容易，設計人員可對很多可供選擇的設計方案進行評價。因此，在加快設計過程的同

50、時，可以考慮更多的可能性．</p><p>　　5、對設計進行仿真和檢驗。一些計算機系統(tǒng)可對產品的工作情況進行仿真，對在各種狀況和應力作用下的設計方案進行檢查。用計算機進行檢驗可以改進或者替代模型構造或樣機。</p><p>　　6、提高精度。計算機能夠繪制出比手工繪制更為精確的圖紙。許多CAD系統(tǒng)都能檢測錯誤，且能將它通知用戶。</p><p>　　7、改善檔案管

51、理工作。圖紙可以更為方便地存檔，檢索和采用磁瓶或磁帶傳送。</p><p>　　計算機圖形學在工程技術領域的應用幾乎沒有任何限制，大部分可以鉛筆完成的圖解方法都可以用計算機完成。且通常效率更高。其應用從建立三維模型和有限元分析，直到繪制平面圖和進行數字計算。</p><p>　　許多曾經只能在大型計算機上運行的先進的應用軟件，也可以在微型計算機上運行。CAD的一個重要的應用領域是制造業(yè)。計