畢業(yè)論文中英文翻譯---計(jì)算機(jī)輔助設(shè)計(jì)（cad）

1、<p>　　附錄：英文資料及翻譯</p><p>　　Computer-Aided Design (CAD)</p><p>　　A CAD system is basically a design tool in which the computer is used to analyze various aspects of a designed product. The CA

2、D system supports the design process at all levels—conceptual, preliminary, and final design. The design can then test the product in various environmental conditions, such as temperature changes, or under different mech

3、anical stress.</p><p>　　Although CAD systems do not necessarily involve computer graphics, the display of the designed object on a screen is one of the most valuable features of CAD systems. The picture of t

4、he object is usually displayed on the surface of cathode-ray tube (CRT).Computer graphics enables the designer to study the object by rotating it on the computer screen, separating it into segments, enlarging a specific

5、portion of the object in order to observe it in detail, and studying the motion of mechanisms wit</p><p>　　Most CAD systems are using interactive graphics system. Interactive graphics allows the user to inte

6、ract directly with the computer in order to generate manipulate, and modify graphic displays. Interactive graphics has become a valuable tool, if not a necessary prerequisite, of CAD system.</p><p>　　The end

7、 products of many CAD systems are drawing generated on a plotter interfaced with the computer. One of the most difficult problems in CAD drawing is the elimination of hidden lines. The computer produces the drawing as wi

8、re frame diagram. Since the computer defines the object without regard to one’s perspective, it will display all the object’s surfaces, regardless of whether they are located on the side facing the viewer or on the back,

9、 which normally the eye cannot see.</p><p>　　Various methods are used to generate the drawing of the part on the computer screen. One method is to use a geometric modeling approach, in which fundamental shap

10、es and basic elements are used to build the drawing. The lengths and radii of the elements can be modified. For example, a cylinder is a basic element, the subtraction of a cylinder with a specific radius and length will

11、 create hole in the displayed part. Each variation, however, maintains the overall geometry of the part.</p><p>　　Other CAD systems use group technology in the design of parts. Group technology is a method o

12、f coding and grouping parts on the basis of similarities in function or structure or in the ways they are produced. Application of group technology can enable a company to reduce the number of parts in use and to make th

13、e production of parts and their movement in the plant efficient.</p><p>　　Recently CAD systems are using the finite-element method (FEM) of stress analysis. By this approach the object to be analyzed is repr

14、esented by a model consisting of small elements, each of which has stress and deflection characteristics. The analysis requires the simultaneous solution of many equations; a task which is performed by the computer, the

15、deflections of the object can be displayed on the computer screen by generating animation of the model.</p><p>　　With any of these methods, or other which are used, the CAD system generates at the design sta

16、ge a single geometric data base which can be used in all phases of the design and later in the manufacturing, assemble, and inspection processes.</p><p>　　CAD/CAM Systems</p><p>　　Computer-aided

17、 design (CAD) means the use of a computer to assist in the design of an individual part or a system, such as an aircraft. The design process usually involves computer graphics.</p><p>　　Computer-aided manufa

18、cturing (CAM) means the use of a computer to assist in the manufacture of a part. CAM can be divided into two main classes: (1) On-line applications, namely, the use of the computer to control manufacturing systems in re

19、al time, such as CNC and AC systems of machine tools. (2) Off-line applications, namely the use of the computer in production planning and non-real-time assistance in the manufacturing of parts.</p><p>　　CAD

20、/CAM is a unified software system, in which the CAD portion is interfaced inside the computer with the CAM system. The end result of current CAD/CAM systems is usually a part program in the form of a list or punched tape

21、. In advanced CAD/CAM systems part programs can be directly fed into the control computers of CNC machines and inspection stations.</p><p>　　The main concept of CAD/CAM systems is the generating of a common

22、database which is used for all the design and manufacturing activities. These include specifications of the product, conceptual design, final design, drafting, manufacturing, and inspection. At each stage of this process

23、, data can be added, modified, used, and distributed over networks of terminals and computers. The single database provides a substantial reduction in human errors and a significant shortening of the time required </p

24、><p>　　The size and capability of the required computer system depend on the complexity of the product. In the aerospace and aeronautics industry, where a complete aircraft can be designed with a CAD/CAM proces

25、sor, the system must accommodate new data and changes in data arriving from a variety of users. Therefore these systems must have a strong data management capability. By contrast, if a company designed simple products, t

26、he required CAD/CAM system would need only one computer terminal. Today the m</p><p>　　Advanced CAD/CAM systems include solid geometry modeling capability, in addition to the wire frame mode diagrams. The so

27、lid description is important when NC verification programs are included in the CAM system, and the changing status of the work piece during machining simulation should be observed.</p><p>　　In recent years C

28、AD/CAM technology has improved industry productivity. It is a significant step toward the design of the factory of the future.</p><p>　　Optimization for Finite Element Applications</p><p>　　As e

29、ngineers work with increasing complex structures, they need rational, reliable, fast, and economical design tools. Over the past two decades, finite element analysis has proven to be the most frequently used method of id

30、entifying and solving the problems associated with these complicated designs.</p><p>　　Because most of the design tasks in engineering are quantifiable, computers have revolutionized the highly iterative des

31、ign process, particularly the procedures for quickly finding alternative designs. But even now, many engineers still follow a manual trial-and-error approach. Such </p><p>　　An approach makes designing-even

32、 for seemingly simple tasks more difficult because it usually takes longer, requires extensive human-machine interaction, and tends to be biased by the design group’s experience.</p><p>　　Design optimization

33、, which is based on a rational mathematical approach to modifying designs too complex for the engineer to modify, automates the design cycle. If automated optimization can be done on a desktop platform, it can be save a

34、lot time and money.</p><p>　　The goal of optimization is to minimize or maximize an objective, such as weight or fundamental frequency that is subject to constraints on response and design parameters. The si

35、ze and/or shape of the design determine the optimization approach.</p><p>　　Looking at optimization as part of the design process makes it easier to understand. The first step includes preprocessing, analysi

36、s, and post processing , just as in customary finite element analysis (FEA) and computer-aided design (CAD) program applications (the difference in CAD lied in building the problem’s geometry in terms of the design param

37、eters ). In the step, the optimization objective and response constraints are defined. And in the last step, The repetitive task of design adjustment</p><p>　　Revising, and reevaluating models to achieve spe

38、cific design goals start with preliminary design data input. Next comes the specification of acceptable tolerances and posed constraints to achieve an optimum, or at least improve solution. To optimize products ranging f

39、rom simple skeletal structures to complicated three-dimensional solid models, designers need access to a wide variety of design objectives and behavior constraints. Additional capabilities will also be needed for easy de

40、finition and</p><p>　　Moreover, engineers should be able to combine constraints from different types of analyses in multidisciplinary optimization. For example, designers can perform thermal analysis and t

41、ransfer temperatures as thermal loads for stress analysis, put constraints over maximum temperature, maximum stress, and deflection, and then specify a range for the desired fundamental frequency. The objective funct

42、ion can represent the whole model or only parts of it. Even more important, it should reflect t</p><p>　　TWO-Dimensional Drawings</p><p>　　CAD makes possible 2D drawings, with an endless possibi

43、lity of views in a range of scales from microns to meters. It gives the mechanical designer the ability to magnify even the smallest of components to ascertain if the assembled components fit properly and even to design

44、programs to identify automatically potential problems in CAD assembly. Parts with different characteristics, such as movable or stationary, can be assigned different colors on the display. Parts can be dimensioned with a

45、utoma</p><p>　　Three-Dimensional Drawings</p><p>　　Designers have even more freedom with the advent of 3D modeling. They can create 3D parts and manipulate them in endless variations to achieve

46、the desired results. Through finite element analysis (FEA), stresses can be applied to a computer model and the results graphically displayed, giving the designer quick feedback on any inherent problems in a design befor

47、e the creation of a physical prototype.</p><p>　　3D models can be created in wire-frame, in surfaces or in solid form. In wire-frame, lines and arcs form edges that generate the model (Fig.8-la). The result

48、is a 3D form that can be viewed from any location but is still only a skeletal form. Creating a surface stretches a skin over the skeleton (Fig.8-lb). Once this is done, the model can be rendered so that appears more tan

49、gible. Surface models are commonly used in the creation of sheet metal developments that can be unfolded for manufacture.</p><p>　　Solid models are the most complex level of modeling and while the programs t

50、o create them have been available for some time on large mainframe computers, it is only recently that microcomputer have reached a level of power that allows the running of the sophisticated algorithms needed to create

51、solid model (Fid.8-2).The computer “thinks” the solid model is a solid mass so it can be “drilled,” machined, “welded” as if it were an actual physical part. It can be made out of any material and can tak</p><

52、p>　　CAD’s Benefits</p><p>　　The benefits of computer use in drafting and design tasks are impressed speed, greater accuracy, reduction of hardcopy storage space as well as better recall, enhanced communic

53、ation capabilities, improved quality and easier modification.</p><p><b>　　Speed</b></p><p>　　A personal computer used in industry can perform a task at an average rate of 33 million

54、operations per second; newer computer are even faster. This is an important feat when using it to calculate the amount of deflection of a component, when theoretical physical forces are applied to it, through finite elem

55、ent analysis (FEA) or when displaying an entire city plan on a monitor, both of which are time-consuming and calculation-intensive tasks. AutoCAD software can duplicate any geometry as many t</p><p><b>

56、;　　Accuracy</b></p><p>　　The AutoCAD program has an accuracy of 14 significant digits of precision for each point, depending on the operating system and computer platform. This extremely important when

57、 the program must round off numbers during mathematical calculation such as segmenting a circle.</p><p><b>　　Storage</b></p><p>　　The computer can store thousands of drawings in the

58、physical space that it would take to store hundreds of manual drawings. Also, the computer can search and find a drawing with ease, as long as the operator possesses the correct file name.</p><p>　　Communica

59、tion </p><p>　　Because the computer’s data is stored in an electronic form, it can be sent to a variety of locations. The first obvious location is the monitor. The computer can display the data on the scree

60、n in different forms such as graphics, easily converting the data into readable drawings. The data can also be sent to a plotter to produce the familiar paper drawing, via a direct link to a computer-aided manufacturing

61、(CAM) machine or via telephone to anywhere around the globe. You no longer have to mail </p><p><b>　　Quality</b></p><p>　　The computer always retains the data in the form in which it

62、 was first created. It can repeat the same output of data continuously without regard to fatigue. Lines will always be crisp and clear, with uniform line weight, and text will always be legible. The computer doesn’t alte

63、r its output quality because of a wild weekend or a late night watching the game.</p><p>　　Modification</p><p>　　The computer data is stored in a format that allows easy modification to any face

64、t of a drawing and gives instant feedback to the user. When something is drawn once, it never has to be drawn again because the object in question can be duplicated, stretched, sized, and changed in many ways without hav

65、ing to be redrawn.</p><p>　　Except for the initial cost to purchase a CAD workstation, CAD’s only disadvantage is a small one because it can be so easily overcome. Because the drawing is stored in an electro

66、nic format and not a paper format, it is possible to erase a drawing file easily. That’s why it is essential to train yourself in good CAD practices to avoid an accidental erasure. And, although an ounce of prevention tr

67、uly is worth a pound of cure, there are even ways of files that are usually successful if you follow </p><p>　　計(jì)算機(jī)輔助設(shè)計(jì)（CAD）</p><p>　　計(jì)算機(jī)輔助設(shè)計(jì)系統(tǒng)基本上是一種設(shè)計(jì)工具，計(jì)算機(jī)是用來(lái)分析所設(shè)計(jì)的產(chǎn)品的各個(gè)方面。CAD系統(tǒng)支持各種階段的設(shè)計(jì)過(guò)程—設(shè)計(jì)構(gòu)想

68、、初步設(shè)計(jì)及最終設(shè)計(jì)。設(shè)計(jì)者然后可在各種環(huán)境條件，比如溫度的變化或不同機(jī)械壓力下檢驗(yàn)產(chǎn)品的狀況。</p><p>　　盡管CAD系統(tǒng)并非一定要包含計(jì)算機(jī)繪圖，但能將設(shè)計(jì)的產(chǎn)品顯示在屏幕上是CAD系統(tǒng)的最有價(jià)值的特征之一。物體的圖形通常顯示在陰極線(xiàn)管屏幕上（CRT）。計(jì)算機(jī)圖形功能使設(shè)計(jì)者可用多種辦法研究物體：將物體在計(jì)算機(jī)屏幕上旋轉(zhuǎn)、將其分成幾段、將物體局部放大以仔細(xì)研究以及在運(yùn)動(dòng)程序的幫助下研究機(jī)構(gòu)的運(yùn)動(dòng)。&l

69、t;/p><p>　　大多數(shù)CAD系統(tǒng)使用互動(dòng)式圖形系統(tǒng)?；ソ皇綀D形系統(tǒng)使用戶(hù)可直接和計(jì)算機(jī)通過(guò)交互作用以對(duì)圖形進(jìn)行調(diào)整及修改。對(duì)CAD系統(tǒng)來(lái)說(shuō)，交互式圖形系統(tǒng)就算不是必要的，也已經(jīng)是很有價(jià)值的工具。</p><p>　　許多CAD系統(tǒng)的最終產(chǎn)品是在與計(jì)算機(jī)連接的繪圖儀中產(chǎn)生的圖形。在CAD圖形中，最難解決的問(wèn)題之一是消去那些被擋住的線(xiàn)。計(jì)算機(jī)生成的圖形是線(xiàn)框圖線(xiàn)。由于計(jì)算機(jī)定義物體時(shí)沒(méi)有考慮

70、圖的透視效果，它顯示出物體的所有面，而不考慮這些面是在朝向觀測(cè)者的一面還是位于通常人眼無(wú)法看到的背面。</p><p>　　可使用多種不同辦法在計(jì)算機(jī)屏幕上生成圖形。一種辦法是采用幾何模板形式，這種辦法是用基本形狀和基本的元素創(chuàng)建圖形，元素的長(zhǎng)度及半徑可以修改。例如，圓柱是一個(gè)基本元素，在已顯示的零件上去掉一個(gè)規(guī)定半徑和長(zhǎng)度的圓柱就可以生成一個(gè)孔。但是每次變化都保留零件所有的幾何特征。</p>&l

71、t;p>　　另外，CAD系統(tǒng)使用成組技術(shù)設(shè)計(jì)零件。成組技術(shù)是在功能、結(jié)構(gòu)相同或加工方法相似的工件基礎(chǔ)上采用分組編碼的一種加工方法。采用成組技術(shù)可使工廠(chǎng)減少所用零件得數(shù)量，并使零件在工廠(chǎng)中的制造、運(yùn)輸效率更高。</p><p>　　最近的CAD系統(tǒng)使用了壓力有限元分析法。在用這種方法時(shí)，待分析物體用很多有壓力及彎曲特征的小元素組成的模型表示。這種分析辦法要求同時(shí)分解許多方程，用計(jì)算機(jī)執(zhí)行一項(xiàng)任務(wù)，物體的彎曲可

72、以通過(guò)生成動(dòng)畫(huà)的方式顯示在計(jì)算機(jī)屏幕上。</p><p>　　采用這些辦法中的任一種或其它常用辦法，CAD系統(tǒng)在設(shè)計(jì)段生成了單個(gè)的幾何數(shù)據(jù)庫(kù)，它可用于設(shè)計(jì)的各個(gè)階段及其后的制造、裝配和檢驗(yàn)過(guò)程。</p><p><b>　　二維繪圖</b></p><p>　　CAD使多視圖的二維繪圖成為可能，視圖空間可以從微米到米的比例范圍內(nèi)無(wú)限變化。它提供

73、給機(jī)械設(shè)計(jì)師放大的功能，即使在恰當(dāng)配合的裝配零件中最小的元件也能看清楚，設(shè)計(jì)程序甚至能自動(dòng)辨認(rèn)CAD裝配圖中的潛在問(wèn)題。針對(duì)具有不同特征的零件，如運(yùn)動(dòng)的或靜止的，在顯示時(shí)可以被指定成不同的顏色。為了有利于工程設(shè)計(jì)的變化，可使用帶有自動(dòng)尺寸變化的系統(tǒng)對(duì)零件進(jìn)行尺寸標(biāo)注。</p><p><b>　　三維繪圖</b></p><p>　　隨著三維建模的出現(xiàn)，設(shè)計(jì)者具有了更

74、多的自由度。他們可以生成三維零件圖并且可以無(wú)限制地修改以獲得所需的結(jié)果。通過(guò)有限元分析，應(yīng)力加到計(jì)算機(jī)模型上，并且以圖形化的方式顯示其結(jié)果，在產(chǎn)品物理模型真正生產(chǎn)之前，對(duì)設(shè)計(jì)中的任何內(nèi)在問(wèn)題給設(shè)計(jì)者一個(gè)快速的反饋。</p><p>　　三維模型可用線(xiàn)框、曲線(xiàn)或?qū)嶓w方式生成。在線(xiàn)框模型中，直線(xiàn)和圓弧構(gòu)成了模型邊界。結(jié)果是一個(gè)可以從任何位置觀察的三維模型，但仍只是一個(gè)框架形式。創(chuàng)建曲面猶如在骨架上包上皮。一旦這樣生成

75、后，模型就可以被渲染，使得圖形看上去更逼真。曲面模型普遍用于構(gòu)建板金的展開(kāi)和重疊以用于制造。</p><p>　　實(shí)體模型是最復(fù)雜的建模層次，并且用于建立實(shí)體模型的程序在一段時(shí)期內(nèi)只用在大型計(jì)算機(jī)上。只有近年來(lái)微型計(jì)算機(jī)才達(dá)到這個(gè)能力水平，也可運(yùn)行復(fù)雜的算法，生成實(shí)體模型。計(jì)算機(jī)“認(rèn)為”實(shí)體模型是一種具有實(shí)體質(zhì)量的模型，所以它可被“鉆孔“加工”“焊接”，好象它是一個(gè)實(shí)際的零件。它能夠由任何材料構(gòu)成并呈現(xiàn)其材料特性

76、，因此，能夠進(jìn)行質(zhì)量計(jì)算。</p><p>　　計(jì)算機(jī)輔助設(shè)計(jì)/制造系統(tǒng)</p><p>　　計(jì)算機(jī)輔助設(shè)計(jì)（CAD）意思是用計(jì)算機(jī)幫助設(shè)計(jì)單個(gè)零件或設(shè)計(jì)系統(tǒng)，如航空器。設(shè)計(jì)過(guò)程經(jīng)常包括計(jì)算機(jī)繪圖。</p><p>　　計(jì)算機(jī)輔助制造（CAM）意思是用計(jì)算機(jī)來(lái)幫助制造零件。CAM可分為兩種主要類(lèi)型：（1）在線(xiàn)應(yīng)用，即用計(jì)算機(jī)實(shí)時(shí)控制加工系統(tǒng)，比如計(jì)算機(jī)數(shù)字控制（CN

77、C）以及機(jī)床的自適應(yīng)（AC）；（2）離線(xiàn)應(yīng)用，即在產(chǎn)品的規(guī)劃以及非實(shí)時(shí)輔助零件加工時(shí)使用計(jì)算機(jī)。</p><p>　　CAD/CAM是一個(gè)統(tǒng)一的軟件系統(tǒng)，其中CAD部分是在計(jì)算機(jī)內(nèi)與CAM連接在一起的。當(dāng)今CAD/CAM系統(tǒng)的最終結(jié)果通常是程序列或穿孔帶形式的零件程序。先進(jìn)的CAD/CAM系統(tǒng)中，零件程序可直接輸入到控制數(shù)控機(jī)床的計(jì)算機(jī)及檢驗(yàn)站中。</p><p>　　CAD/CAM系統(tǒng)中

78、的主要構(gòu)想是生成可用于所有設(shè)計(jì)及加工動(dòng)作的通用數(shù)據(jù)庫(kù)。這其中包括：產(chǎn)品的規(guī)格化、設(shè)計(jì)構(gòu)想、最終設(shè)計(jì)、繪圖、加工及檢驗(yàn)。在次過(guò)程中的每一個(gè)階段，數(shù)據(jù)都可以添加、修改、使用以及分配給工作站的終端和計(jì)算機(jī)中。單個(gè)數(shù)據(jù)庫(kù)從實(shí)質(zhì)上減少了認(rèn)為誤差，極大的縮短了從產(chǎn)品設(shè)計(jì)構(gòu)想到制造出最終產(chǎn)品所需的時(shí)間。</p><p>　　所需計(jì)算機(jī)系統(tǒng)的大小及容量取決于產(chǎn)品的復(fù)雜程度。在航空航天工業(yè)中，要用CAD/CAM處理器完成航天器設(shè)計(jì)

79、，系統(tǒng)必須能夠容納從不同用戶(hù)處得到的新的數(shù)據(jù)以及對(duì)數(shù)據(jù)的修改。因此，它們所用的系統(tǒng)必須有強(qiáng)大的數(shù)據(jù)處理能力。與之相對(duì)，如果公司設(shè)計(jì)的產(chǎn)品簡(jiǎn)單，所需的CAD/CAM只需一個(gè)計(jì)算機(jī)終端即可。如今CAD/CAM系統(tǒng)的主要用戶(hù)是航天工業(yè)及汽車(chē)工業(yè)。但是隨著CAD/CAM系統(tǒng)價(jià)格的降低，也增加了其他方面用戶(hù)的數(shù)量。</p><p>　　先進(jìn)的CAD/CAM系統(tǒng)除了有線(xiàn)框方式圖形外還包括固體幾何模塊功能。當(dāng)CAM系統(tǒng)中涉及數(shù)

80、控檢驗(yàn)程序以及加工時(shí)要求同時(shí)觀測(cè)零件的變化狀況時(shí)，固體幾何模塊描述就很重要。最近幾年CAD/CAM技術(shù)已經(jīng)提高了工業(yè)生產(chǎn)率。CAD/CAM技術(shù)是朝向未來(lái)工廠(chǎng)設(shè)計(jì)方向邁出的重要一步。</p><p><b>　　有限元優(yōu)化的應(yīng)用</b></p><p>　　在結(jié)構(gòu)日益復(fù)雜的情況下，當(dāng)工程師們工作時(shí)，他們需要合理的、可靠的、快速而經(jīng)濟(jì)的設(shè)計(jì)工具。過(guò)去二十多年里，有限元分析

81、法已經(jīng)成為判別和解決涉及這些復(fù)雜設(shè)計(jì)課題時(shí)的最常用方法。</p><p>　　因?yàn)楣こ讨械拇蠖鄶?shù)設(shè)計(jì)任務(wù)都是可定量的，所以實(shí)踐上，為了快速找到一些可供選擇的設(shè)計(jì)方案。計(jì)算機(jī)令繁瑣的重復(fù)設(shè)計(jì)過(guò)程發(fā)生了深刻的變革。但是，即使是現(xiàn)在，許多工程師仍然使用人工的試湊法。這樣一種方法使得即使是很簡(jiǎn)單的設(shè)計(jì)任務(wù)也變的困難，因?yàn)橥ǔＫǜL(zhǎng)的時(shí)間，需要廣泛的人一機(jī)交互配合，且偏于用設(shè)計(jì)組的經(jīng)驗(yàn)來(lái)設(shè)計(jì)。優(yōu)化設(shè)計(jì)是以理論數(shù)學(xué)的方法

82、為基礎(chǔ)，改進(jìn)那些對(duì)于工程師來(lái)說(shuō)過(guò)于復(fù)雜的設(shè)計(jì)，使其設(shè)計(jì)過(guò)程自動(dòng)化。如果在一部臺(tái)式計(jì)算機(jī)平臺(tái)上能實(shí)現(xiàn)自動(dòng)優(yōu)化設(shè)計(jì)，那就可以節(jié)省大量的時(shí)間和金錢(qián)。優(yōu)化設(shè)計(jì)的目的就是要將對(duì)象極大化或極小化，例如，重量或基頻，主要受到頻響和設(shè)計(jì)參數(shù)方向的約束。尺寸和結(jié)構(gòu)形狀決定著優(yōu)化設(shè)計(jì)的方法。觀察一下作為零件優(yōu)化設(shè)計(jì)過(guò)程，使它變的更容易理解。第一步，包括預(yù)處理分析和后處理分析，正像慣常使用的有限元分析（FEA）和計(jì)算機(jī)輔助設(shè)計(jì)（CAD）程序應(yīng)用。（CAD的特

83、點(diǎn)在于根據(jù)設(shè)計(jì)參數(shù)建立了課題的幾何圖形）。</p><p>　　第二步，定義優(yōu)化目標(biāo)和響應(yīng)約束。而最后一步，反復(fù)自動(dòng)調(diào)節(jié)設(shè)計(jì)作業(yè)。優(yōu)化設(shè)計(jì)程序?qū)⒃试S工程師們監(jiān)督該設(shè)計(jì)步驟和進(jìn)度，必要時(shí)停止設(shè)計(jì)，改變?cè)O(shè)計(jì)條件和重新開(kāi)始。一項(xiàng)優(yōu)化設(shè)計(jì)程序的功力取決于有效的預(yù)處理和分析能力。二維和三維設(shè)計(jì)的應(yīng)用既需要自動(dòng)進(jìn)行也需要設(shè)計(jì)參數(shù)的結(jié)網(wǎng)性能。因?yàn)樵趦?yōu)化循環(huán)過(guò)程中，課題的幾何條件和網(wǎng)格會(huì)改變，所以?xún)?yōu)化程序必須包含誤差估計(jì)和自適應(yīng)

84、控制。</p><p>　　修改、重配網(wǎng)格和重新估算模式以期獲得特定目標(biāo)的實(shí)現(xiàn)是以輸入初始設(shè)計(jì)數(shù)據(jù)開(kāi)始的。接著，是規(guī)定合格的公差并形成約束條件以獲得最優(yōu)結(jié)果，或最后改進(jìn)設(shè)計(jì)，解決問(wèn)題。為了使產(chǎn)品從簡(jiǎn)單輪廓圖形到三維實(shí)體模型系統(tǒng)化、系列化，設(shè)計(jì)者必須廣泛接觸設(shè)計(jì)目標(biāo)和特性約束條件。為了易于確定而利用下列參數(shù)作為約束和 目標(biāo)函數(shù)的附加特性條件，也將是需要的：重量、體積、位移、應(yīng)力、應(yīng)變、頻率、翹曲安全系數(shù)、溫度、溫度

85、梯度和熱通量。</p><p>　　此外，工程師們應(yīng)該能夠通過(guò)多學(xué)科的不同類(lèi)型的優(yōu)化分析使多種約束條件結(jié)合起來(lái)。例如設(shè)計(jì)者為了應(yīng)力分析，可以進(jìn)行熱力分析和加熱以變更溫度，也可將多種約束條件，諸如最高溫度、最大應(yīng)力和變形聯(lián)系在一起進(jìn)行研究，然后規(guī)定一個(gè)所希望的基本頻率范圍。目標(biāo)函數(shù)代表著整體模式或部分模式。甚至更重要的是通過(guò)說(shuō)明重量或者成本應(yīng)因素，就應(yīng)該能反映該模式的各個(gè)部分的重要性。</p><

86、;p>　　計(jì)算機(jī)輔助繪圖的好處</p><p>　　用計(jì)算機(jī)完成繪圖及設(shè)計(jì)任務(wù)的好處是令人難忘的：提高速度、提高準(zhǔn)確性、減少硬拷貝存儲(chǔ)空間及易于恢復(fù)信息、加強(qiáng)信息傳遞能力、改善傳輸質(zhì)量和便于修改。</p><p><b>　　速度</b></p><p>　　工業(yè)用計(jì)算機(jī)能以平均每秒3300萬(wàn)次完成一項(xiàng)任務(wù)；更新的計(jì)算機(jī)起速度更快。用計(jì)算

87、機(jī)計(jì)算零件的變形量是一個(gè)重要功績(jī)。當(dāng)理論上的載荷力加到零件上時(shí)、通過(guò)計(jì)算機(jī)進(jìn)行有限元分析或者在監(jiān)視器上顯示一個(gè)城市的整體規(guī)劃時(shí)，這兩者都是既費(fèi)時(shí)又計(jì)算最大的任務(wù)。AutoCAD軟件可根據(jù)需要多次復(fù)制所需模型的形狀和幾何尺寸，快速自動(dòng)地進(jìn)行剖面填充及尺寸標(biāo)注。</p><p><b>　　準(zhǔn)確</b></p><p>　　AutoCAD程序依靠操作系統(tǒng)及計(jì)算機(jī)平臺(tái)每點(diǎn)具

88、有14位的精度。這在用數(shù)字計(jì)算諸如一個(gè)圓的線(xiàn)段數(shù)、程序必須圓整線(xiàn)段數(shù)時(shí)是十分重要的。</p><p><b>　　存儲(chǔ)</b></p><p>　　計(jì)算機(jī)能夠在物理中存儲(chǔ)上千幅圖，這空間能夠存儲(chǔ)上百幅手工圖。而且計(jì)算機(jī)能夠很容易地搜索和找到一幅圖，只要操作者擁有正確的文件名。</p><p><b>　　傳輸</b><

89、;/p><p>　　由于計(jì)算機(jī)的數(shù)據(jù)是以電子形式存儲(chǔ)，它能被送到各個(gè)位置。最明顯的位置是監(jiān)視器。計(jì)算機(jī)可以在屏幕上以不同方式顯示數(shù)據(jù)，如圖形，并能方便地將數(shù)據(jù)轉(zhuǎn)換成可讀圖形。這些數(shù)據(jù)也可被傳送給繪圖機(jī)，打印出常見(jiàn)的圖紙，通過(guò)直接連接到計(jì)算機(jī)輔助制造機(jī)床或電話(huà)線(xiàn)傳到地球的任何地方。你可以不再冒損壞或丟失的危險(xiǎn)去郵寄圖紙，現(xiàn)在圖紙可以通過(guò)電信網(wǎng)立即發(fā)送到目的地。</p><p><b>

90、　　質(zhì)量</b></p><p>　　計(jì)算機(jī)總是從最初生成的數(shù)據(jù)形式保存數(shù)據(jù)。它可以不顧疲勞的不斷地重復(fù)同一個(gè)數(shù)據(jù)輸出。線(xiàn)型將總是鮮明和清晰的，具有一致的線(xiàn)寬，而文本也總是清晰明了的。計(jì)算機(jī)不會(huì)改變輸出質(zhì)量，因?yàn)橛?jì)算機(jī)不會(huì)像人那樣因周末的郊游或深夜觀看娛樂(lè)節(jié)目而疲勞。</p><p><b>　　修改</b></p><p>　　計(jì)

91、算機(jī)以某種便于修改的形式存儲(chǔ)數(shù)據(jù)并且不斷地提供反饋給用戶(hù)。某些圖形一旦畫(huà)成，它就不必再畫(huà)，因?yàn)槲矬w可以被復(fù)制、延伸、改變尺寸并且在不重畫(huà)的情況下，可以多種形式加以修改。</p><p>　　除了最初購(gòu)買(mǎi)CAD工作站的花費(fèi)，CAD的唯一缺點(diǎn)是它是一個(gè)小軟件，而它能容易被克服。由于圖形是以電子格式存儲(chǔ)而不是圖紙格式，所以有可能會(huì)容易地刪除繪圖文件。這就是為什么強(qiáng)調(diào)要培養(yǎng)自己一個(gè)好的繪圖習(xí)慣以避免意外地刪除繪圖文件。一