機(jī)械模具類(lèi)外文翻譯----現(xiàn)在設(shè)計(jì)優(yōu)化方法基礎(chǔ)

1、<p><b>　　外文原文</b></p><p>　　A Discussion on Modern Design Optimization</p><p>　　The integration of optimization techniques with Finite Element Analysis(FEA) and CAD is having pro

2、nounced effects on the product design process.This integration has the power to reduce design costs by shifting the burden from the engineer to the computer.Furthermore,the mathematical rigor of a properly implemented op

3、timization tool can add confidence to the design process.Generally,an optimization method controls a series of applications,including CAD software as well as FEA automatic solid mesh</p><p>　　Modern optimiza

4、tion methods perform shape optimizations on components generated within a choice of CAD packages.Ideally,there is seamless data exchange via direct memory transfer between the CAD and FEA applications without the need fo

5、r file translation.Furthermore,if associativity between the CAD and FEA software exists,any changes made in the CAD geometry are immediately reflected in the FEA model.In the approach taken by ALGOR,the design optimizati

6、on process begins before the FEA model is gen</p><p>　　Introduction</p><p>　　The typical design process involves iterations during which the geometry of the part(s) is altered.In general,each it

7、eration also involves some from of analysis in order to obtain viable engineering results.Optimal designs may require a large number of such iterations,each of which is costly,especially if one considers the value of an

8、engineer’s time.The principle behind design optimization applications is to relieve the engineer of the laborious task by automatically conducting these iterations</p><p>　　Fig.7.1 Procedure of shape Optimiz

9、ation</p><p>　　This is certainly not the case because any design optimization application cannot infer what should be optimized,and what are the design variables,the quantities or parameters that can be chan

10、ged in order to achieve an optimum design.Thus,design optimization applications are simply another tool available to the engineer.The usefulness of this tool is gauged by its ability to efficiently identify the optimum.&

11、lt;/p><p>　　Design optimization applications tend to be numerically because they must still perform the geometrical and analysis iterations.Fortunately,most design optimization problems can be cast as a mathema

12、tical optimization problem for which there exist many efficient solution methods.The drawback to having many methods is that there usually exists an optimum mathematical optimization method for a given problem.This compl

13、exity should be remedied by the design optimization application by giving the engi</p><p>　　In this paper,we focus on the design optimization of mechanical parts or assemblies.In this case,a typical optimize

14、d quantity is the maximum stress experienced.Typical design variables include geometric quantities,such as the thickness of a particular part.The design of the part or assembly is initiated within a CAD software applicat

15、ion.If the component warrants an engineering analysis,the engineer will generally opt to apply finite element analysis(FEA) in order to model or simulate its mechani</p><p>　　Background and Theoy</p>

16、<p>　　In this section,wo focus on the theory underlying some of the machematical methods employed by design optimization procedures.But,first we describe how the optimization problem arises.Consider a three-step pro

17、cess:</p><p>　　（1）Generation of geometry of part or assembly in CAD;</p><p>　?。?）Creation of FEA model of part or assembly;</p><p>　?。?）Evaluation of results of FEA models.</p>

18、;<p>　　For now,we limit ourselves to the case of linear static FEA.Therefore,the results are comprised of deflections and stresses at one instance.The manual design process involves all three steps,with the result

19、s being used to evaluate whether the design is appropriate.If the design is found inadequate,changes are made to steps (1) or (2) or both.It is clear from this description that the output of the FEA results is what shoul

20、d be optimized,and that any input to the CAD or FEA models can be viewed a</p><p>　　Most optimization problems are made up of three basic components.</p><p>　?。?）An objective function which we w

21、ant to minimize(or maximize).For instance,in designing an automobile panel,we might want to minimize the stress in a particular region.</p><p>　　（2）A set of design variables that affect the value of the obje

22、ctive funtion.In the automobile panel design problem,the variables used define the geometry and material of the panel.</p><p>　?。?）A set of constrains that allow the design variables to have certain values b

23、ut exclude others.In the automobile panel design problem,we would probably want to limit its weight.</p><p>　　It is possible to develop an optimization problem without constraints.Some may argue that almost

24、all problems have some form of constraints.For instance,the thickness of the automotive panel cannot be negative.Although in practice,answers that make good sense in terms of the underlying physics,such as a positive thi

25、ckness,can often be obtained without enforcing constraints on the design variables.</p><p>　　Benefits and Drawbanks</p><p>　　The elimination or reduction of repetitive manual tasks has been the

26、impetus behind many software applications.Automatic design optimization is one of the latest applications used to reduce man-hours at the expense of possibly increasing the computational effort.It is even possible that a

27、n automatic design optimization scheme may actually require less computational effort than a manual approach.This is because the mathematical rigor on which these schemes are based may be more efficient than a h</p>

28、;<p>　　Mould Design and Manufacturing</p><p>　　CAD and CAM are widely applied in mould design and mould making.CAD allows you to draw a model on screen,then view it from every angel using 3-D animatio

29、n and,finally,to test it by introducing various parameters into the digital simulation models(pressure,temperature,impact,etc.).CAM,on the other hand ,allows you to control the manufacturing quality.The advantages of the

30、se computer technologies are legion:shorter design times(modifications can be made at the speed of the computer),lower cost,fas</p><p>　?。ㄍ馕膩?lái)源：朱林，楊春杰．機(jī)電工程專(zhuān)業(yè)英語(yǔ)（第2版）．北京大學(xué)出版社，2010）</p><p><b>

31、　　外文翻譯</b></p><p>　　現(xiàn)在設(shè)計(jì)優(yōu)化方法基礎(chǔ)</p><p>　　如今，綜合運(yùn)用機(jī)械設(shè)計(jì)方法、有限元分析方法和計(jì)算機(jī)輔助設(shè)計(jì)技術(shù)進(jìn)行產(chǎn)品設(shè)計(jì)過(guò)程產(chǎn)生了深遠(yuǎn)的影響。這種綜合運(yùn)用的手段將工程師身上的設(shè)計(jì)重?fù)?dān)交由計(jì)算機(jī)完成，因而降低了產(chǎn)品的設(shè)計(jì)成本。此外，正確運(yùn)用優(yōu)化設(shè)計(jì)中嚴(yán)謹(jǐn)?shù)臄?shù)學(xué)推理也可以提高產(chǎn)品的設(shè)計(jì)的可靠性。優(yōu)化方法決定了產(chǎn)品設(shè)計(jì)過(guò)程中的精度問(wèn)題，包括CAD

32、軟件建模的準(zhǔn)確度，有限元分析中網(wǎng)格劃分的正確度以及分析處理器的計(jì)算精度等，這種方法能夠在考慮機(jī)械，熱等許多實(shí)際情況的影響下，對(duì)CAD系統(tǒng)構(gòu)建的零部件、裝配體的結(jié)構(gòu)進(jìn)行優(yōu)化。</p><p>　　現(xiàn)代優(yōu)化設(shè)計(jì)技術(shù)能夠?qū)AD軟件構(gòu)建的零件結(jié)構(gòu)進(jìn)行優(yōu)化。從優(yōu)化設(shè)計(jì)理論的角度上說(shuō)，CAD格式的文件和FEA格式的文件之間不需要任何的格式轉(zhuǎn)換，就可以實(shí)現(xiàn)數(shù)據(jù)的無(wú)縫交換。這時(shí)這兩個(gè)文件之間存在關(guān)聯(lián)性，對(duì)CAD文件所做的任何修

33、改在相應(yīng)的FEA文件中都能反映出來(lái)。例如，在使用有限元分析軟件ALGOR對(duì)某零部件或裝配體計(jì)算時(shí)，根本不需要建立其有限元模型就可以進(jìn)行優(yōu)化設(shè)計(jì)。用戶(hù)只要挑選出零部件或裝配體CAD模型中需要優(yōu)化的幾何尺寸，確定相應(yīng)的設(shè)計(jì)準(zhǔn)則（如最大應(yīng)力、最高溫度和最大頻率），然后運(yùn)行相應(yīng)的分析計(jì)算過(guò)程，該軟件通過(guò)計(jì)算、比較，就可以完成CAD模型的結(jié)構(gòu)優(yōu)化，并且整個(gè)過(guò)程通常不需要使用者參與。需要注意的是，CAD與FEA格式文件之間的關(guān)聯(lián)性使得FEA模型更新

34、了，但約束和施加的載荷保持不變，因此需要對(duì)更新過(guò)后的有限元模型進(jìn)行計(jì)算，對(duì)整個(gè)過(guò)程不斷重復(fù)迭代，直到最終的計(jì)算結(jié)果滿(mǎn)足設(shè)計(jì)要求為止。圖7.1所示的是零部件形狀優(yōu)化流程圖。</p><p><b>　　引言</b></p><p>　　零部件結(jié)構(gòu)的優(yōu)化過(guò)程往往需要近視迭代計(jì)算，在整個(gè)計(jì)算過(guò)程中，零部件的幾何外形不斷變化，優(yōu)化。在每一步迭代計(jì)算中要進(jìn)行一定的分析，以便得到

35、與工程實(shí)際較為相符的設(shè)計(jì)結(jié)果。優(yōu)化設(shè)計(jì)一般需要很多部這樣的迭代計(jì)算，每一步計(jì)算都較為費(fèi)時(shí)。所以，在進(jìn)行機(jī)械結(jié)構(gòu)優(yōu)化設(shè)計(jì)過(guò)程中使用優(yōu)化設(shè)計(jì)軟件的主要目的是自動(dòng)運(yùn)行上述的迭代計(jì)算，減少工程師的工作負(fù)擔(dān)。咋看上去，優(yōu)化設(shè)計(jì)技術(shù)是一種能夠替代工程師進(jìn)</p><p>　　行工程設(shè)計(jì)的工具，但事實(shí)上不是這樣，因?yàn)槿魏蝺?yōu)化設(shè)計(jì)軟件都不能確定應(yīng)該優(yōu)化什么對(duì)象，哪些是設(shè)計(jì)變量，需要改變哪些量或參數(shù)，所以，優(yōu)化設(shè)計(jì)軟件只是工程師進(jìn)

36、行設(shè)計(jì)的一種工具，其用途由其優(yōu)化計(jì)算的能力來(lái)決定。</p><p>　　優(yōu)化設(shè)計(jì)軟件常常要進(jìn)行零部件幾何外形的優(yōu)化計(jì)算，一般具有較強(qiáng)的數(shù)值計(jì)算能</p><p>　　圖7.1 零部件形狀優(yōu)化設(shè)計(jì)過(guò)程示意</p><p>　　力。慶幸的是，大多數(shù)零部件結(jié)構(gòu)優(yōu)化設(shè)計(jì)的問(wèn)題都可以看成是數(shù)學(xué)中的極值問(wèn)題。求極值的有效方法很多，但方法太多也不好，因?yàn)閷?duì)于一個(gè)待定的問(wèn)題，其最佳

37、的解法只有一種。利用優(yōu)化設(shè)計(jì)軟件可以很好地解決這個(gè)問(wèn)題，因?yàn)閮?yōu)化設(shè)計(jì)軟件不僅可以幫助工程師選擇解決問(wèn)題的方法，而且還能夠幫助工程師找到最佳解決方法。</p><p>　　本文重點(diǎn)闡述機(jī)械零部件或裝配體結(jié)構(gòu)的優(yōu)化設(shè)計(jì)。我們經(jīng)常需要優(yōu)化零部件或裝配體在實(shí)際工作過(guò)程中承受的最大應(yīng)力，所涉及的設(shè)計(jì)變量一般是零部件或裝配體的幾何尺寸，比如一個(gè)指定零件的厚度。我們一般先用CAD軟件構(gòu)建零部件或裝配體的幾何外形，如果設(shè)計(jì)結(jié)構(gòu)正

38、確，那么工程師會(huì)選擇相應(yīng)的有限元分析軟件，對(duì)上述結(jié)構(gòu)的機(jī)械性能進(jìn)行數(shù)值模擬；然后根據(jù)計(jì)算結(jié)果，比如最大應(yīng)力的分布狀況，來(lái)判斷設(shè)計(jì)是否有效。在設(shè)計(jì)過(guò)程中，工程師可能需要改變CAD或FEA模型的一些參數(shù)或特征屬性，如零部件或裝配體的幾何尺寸、材料參數(shù)以及約束和加載狀況。CAD和FEA軟件之間的關(guān)聯(lián)性使得工程師只需要修改其中任何一個(gè)模型即可，例如，在CAD軟件中改變了某個(gè)零件的厚度或增加了一個(gè)孔，它的有限元模型會(huì)也自動(dòng)做相應(yīng)修改。大多數(shù)情況下

39、，工程師采用線性靜力學(xué)的方法來(lái)分析應(yīng)力狀況，這種方法的優(yōu)點(diǎn)在于能用較少的耗時(shí)，較多的有限元分析單元得到需要的有限元分析結(jié)果。但該方法也存在缺點(diǎn)，例如，在估算處于運(yùn)動(dòng)狀態(tài)的零部件或裝配體的載荷大小或方向時(shí)，往往需要較豐富的專(zhuān)業(yè)知識(shí)（這種方法無(wú)法滿(mǎn)足要求）。</p><p><b>　　基礎(chǔ)知識(shí)和理論</b></p><p>　　本部分著重討論優(yōu)化設(shè)計(jì)的一些數(shù)學(xué)理論方法，

40、首先介紹利用有限元方法進(jìn)行優(yōu)化設(shè)計(jì)的過(guò)程，該過(guò)程一般有3個(gè)步驟：</p><p>　?。?）在CAD軟件中構(gòu)造出某一零部件或裝配體的幾何模型；</p><p>　?。?）建立相應(yīng)的有限元分析模型；</p><p>　?。?）對(duì)有限元分析的計(jì)算結(jié)果進(jìn)行分析和判斷。</p><p>　　現(xiàn)在只討論線性靜力學(xué)有限元分析方法，需要計(jì)算的是零部件/裝配

41、體在外載荷作用下的應(yīng)變和應(yīng)力分布狀況。一般人工優(yōu)化設(shè)計(jì)過(guò)程都要涉及上述3個(gè)步驟，也需要根據(jù)計(jì)算結(jié)果來(lái)判斷設(shè)計(jì)的合理性；如果設(shè)計(jì)結(jié)果不合理，就要對(duì)步驟（1）和（2）做修改，也可能（1）、（2）都要改。可以清楚的看出，有限元分析的結(jié)果就是優(yōu)化的結(jié)果，由于每個(gè)輸入到CAD或FEA模型中的參數(shù)或特征屬性都可以看成是設(shè)計(jì)變量。優(yōu)化設(shè)計(jì)算法對(duì)許多有限元分析都要指導(dǎo)作用，它的每一種算法對(duì)不同的設(shè)計(jì)變量會(huì)產(chǎn)生不同的數(shù)據(jù)組，所以，CAD軟件和FEA軟件之

42、間必須具有關(guān)聯(lián)性，才能將人工設(shè)計(jì)方法轉(zhuǎn)化為優(yōu)化設(shè)計(jì)算法?？梢酝ㄟ^(guò)例子來(lái)說(shuō)明上述問(wèn)題，例如，在剛開(kāi)始對(duì)某一零部件或裝配體進(jìn)行有限元分析時(shí)，工程師一般要對(duì)其有限元分析模型上的某一平面施加約束。假定這個(gè)平面就是零部件或裝配體CAD模型上的平面?，F(xiàn)在需要優(yōu)化這個(gè)平面的結(jié)構(gòu)，由于CAD軟件和FEA軟件之間的關(guān)聯(lián)性，其FEA模型上的平面會(huì)隨著CAD模型的變化而變化，這樣，上述約束就會(huì)施加在改變了的平面模型上。為了實(shí)現(xiàn)CAD模型與FEA模型之間的自動(dòng)

43、數(shù)據(jù)交換，CAD軟件和FEA軟件之間必須具備這種關(guān)聯(lián)性。下面</p><p>　　大多數(shù)優(yōu)化設(shè)計(jì)都要涉及以下3個(gè)基本問(wèn)題：</p><p>　　（1）目標(biāo)函數(shù)的最小值（或最大值）：例如，在設(shè)計(jì)汽車(chē)的儀表板時(shí)，往往需要它在某一指定區(qū)域上受到應(yīng)力最小。</p><p>　?。?）影響目標(biāo)函數(shù)值的設(shè)定變量組：例如，在汽車(chē)儀表板設(shè)計(jì)中用來(lái)確定儀表板幾何外形和材料的變量。&l

44、t;/p><p>　?。?）約束條件：這些約束條件使得優(yōu)化設(shè)計(jì)中的變量只能在某一范圍內(nèi)取值。例如，在設(shè)計(jì)汽車(chē)的儀表板時(shí)，常常需要限制它的質(zhì)量。</p><p>　　實(shí)際上，建立一個(gè)無(wú)約束的優(yōu)化問(wèn)題也是非?？赡艿?。也許有人會(huì)認(rèn)為幾乎所有的問(wèn)題都應(yīng)具有一定的約束條件。例如，汽車(chē)儀表板的厚度不能為負(fù)值，不過(guò)實(shí)際上無(wú)須對(duì)一些設(shè)計(jì)變量施加約束條件，常常也可以獲得與基本常識(shí)相符的結(jié)果，如上述的儀表板厚度為

45、正值的問(wèn)題即是如此。</p><p>　　優(yōu)化設(shè)計(jì)的優(yōu)點(diǎn)和缺點(diǎn)</p><p>　　目前許多應(yīng)用軟件都以解除或減少人的重復(fù)工作為目的?；谟?jì)算機(jī)的優(yōu)化設(shè)計(jì)技術(shù)屬于一種最新的應(yīng)用設(shè)計(jì)技術(shù)，其目的計(jì)算增加計(jì)算機(jī)的計(jì)算量，減少人的工作時(shí)間。實(shí)際上在進(jìn)行優(yōu)化設(shè)計(jì)計(jì)算時(shí)，使用計(jì)算機(jī)需要的計(jì)算甚至比人工設(shè)計(jì)方法還要少，這是因?yàn)閮?yōu)化設(shè)計(jì)技術(shù)采用了嚴(yán)謹(jǐn)?shù)臄?shù)學(xué)計(jì)算方法，所以它的設(shè)計(jì)效率要比人工設(shè)計(jì)方法高。當(dāng)

46、然基于計(jì)算機(jī)的優(yōu)化設(shè)計(jì)技術(shù)取代不了人的思維，因?yàn)槿说乃枷胗袝r(shí)可以大大縮短設(shè)計(jì)過(guò)程?；谟?jì)算機(jī)的優(yōu)化設(shè)計(jì)方法與人工設(shè)計(jì)方法相比，其明顯的優(yōu)點(diǎn)是，如果優(yōu)化設(shè)計(jì)軟件使用正確，它能夠考慮到所有的設(shè)計(jì)方案，也就是說(shuō)，會(huì)考慮到各種可行的設(shè)計(jì)參數(shù)，因此利用優(yōu)化設(shè)計(jì)軟件進(jìn)行計(jì)算的結(jié)果應(yīng)該是最精確的。</p><p><b>　　模具設(shè)計(jì)與制造</b></p><p>　　目前CAD和

47、CAM技術(shù)已經(jīng)廣泛地應(yīng)用早模具的設(shè)計(jì)和制造中。例如，首先利用CAD軟件在計(jì)算機(jī)上構(gòu)建出模具的模型，然后采用三維動(dòng)畫(huà)的方法從各個(gè)角度察看模具的結(jié)構(gòu)，最后將模具的各種參數(shù)（壓力、溫度、沖力等）導(dǎo)入到數(shù)字模型中進(jìn)行模擬試驗(yàn)與分析。另外，CAM能夠控制模具的制造質(zhì)量。采用上述計(jì)算機(jī)技術(shù)對(duì)模具進(jìn)行設(shè)計(jì)和制造有很多優(yōu)點(diǎn)：如較短的設(shè)計(jì)時(shí)間（該時(shí)間可隨著計(jì)算機(jī)的運(yùn)行速度而變化）、較低的制造成本和較高的制造效率等。這種新的設(shè)計(jì)、制造方法可以進(jìn)行小批量的模