EnglishforMechanicalEngineering機械工程專業(yè)英語1課件機械工程專業(yè)英語預備知識Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)Thefiniteelementmethod(FEM)(sometimesreferredtoasfiniteelementanalysis)isanumericaltechniqueforfindingapproximatesolutionsofpartialdifferentialequations(PDE)aswellasofintegralequations.2課件機械工程專業(yè)英語預備知識Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)Thesolutionapproachisbasedeitheroneliminatingthedifferentialequationcompletely(steadystateproblems),orrenderingthePDEintoanapproximatingsystemofordinarydifferentialequations,whicharethennumericallyintegratedusingstandardtechniquessuchasEuler'smethod,Runge-Kutta,etc.3課件機械工程專業(yè)英語預備知識Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)Forinstance,inafrontalcrashsimulationitispossibletoincreasepredictionaccuracyin"important"areaslikethefrontofthecarandreduceitinitsrear(thusreducingcostofthesimulation);AnotherexamplewouldbethesimulationoftheweatherpatternonEarth,whereitismoreimportanttohaveaccuratepredictionsoverlandthanoverthewide-opensea.5課件機械工程專業(yè)英語預備知識Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)Thefinite-elementmethodoriginatedfromtheneedforsolvingcomplexelasticityandstructuralanalysisproblemsincivilandaeronauticalengineering.ItsdevelopmentcanbetracedbacktotheworkbyAlexanderHrennikoff(1941)andRichardCourant(1942).Whiletheapproachesusedbythesepioneersaredramaticallydifferent,theyshareoneessentialcharacteristic:meshdiscretizationofacontinuousdomainintoasetofdiscretesub-domains,usuallycalledelements.

6課件機械工程專業(yè)英語預備知識Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)Developmentofthefiniteelementmethodbeganinearnestinthemiddletolate1950sforairframeandstructuralanalysisandgatheredmomentumattheUniversityofStuttgartthroughtheworkofJohnArgyrisandatBerkeleythroughtheworkofRayW.Cloughinthe1960sforuseincivilengineering.Bylate1950s,thekeyconceptsofstiffnessmatrixandelementassemblyexistedessentiallyintheformusedtoday.NASAissuedrequestforproposalsforthedevelopmentofthefiniteelementsoftwareNASTRANin1965.7課件機械工程專業(yè)英語預備知識Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)FEMallowsdetailedvisualizationofwherestructuresbendortwist,andindicatesthedistributionofstressesanddisplacements.FEMsoftwareprovidesawiderangeofsimulationoptionsforcontrollingthecomplexityofbothmodelingandanalysisofasystem.Similarly,thedesiredlevelofaccuracyrequiredandassociatedcomputationaltimerequirementscanbemanagedsimultaneouslytoaddressmostengineeringapplications.FEMallowsentiredesignstobeconstructed,refined,andoptimizedbeforethedesignismanufactured.9課件機械工程專業(yè)英語預備知識Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)Thispowerfuldesigntoolhassignificantlyimprovedboththestandardofengineeringdesignsandthemethodologyofthedesignprocessinmanyindustrialapplications.TheintroductionofFEMhassubstantiallydecreasedthetimetotakeproductsfromconcepttotheproductionline.ItisprimarilythroughimprovedinitialprototypedesignsusingFEMthattestinganddevelopmenthavebeenaccelerated.Insummary,benefitsofFEMincludeincreasedaccuracy,enhanceddesignandbetterinsightintocriticaldesignparameters,virtualprototyping,fewerhardwareprototypes,afasterandlessexpensivedesigncycle,increasedproductivity,andincreasedrevenue.10課件機械工程專業(yè)英語預備知識Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)GeneralformofthefiniteelementmethodChooseagrid.Intheprecedingtreatment,thegridconsistedoftriangles,butonecanalsousesquaresorcurvilinearpolygons.Then,onechoosesbasisfunctions.Weusedpiecewiselinearbasisfunctions,butitisalsocommontousepiecewisepolynomialbasisfunctions.11課件預備知識

一、預備知識有限元法起源于50年代航空工程中的機構分析矩陣法。為了解決航空結構設計問題，Turner、Clough等人首次采用三角形和矩形單元，成功地將結構力學中的位移用于平面應力問題的求解，1960年，首次提出了“有限元法”。

有限元法的基本步驟：1）結構離散---網格劃分，關系到有限元計算的速度和精度2）單元分析：建立各節(jié)點位移和節(jié)點力之間的關系，從而求出單元剛度矩陣3）等效節(jié)點載荷計算4）整體分析，建立整體剛度方程5）約束條件引入和方程求解Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語13課件機械工程專業(yè)英語預備知識Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationDesignOptimization(優(yōu)化設計)Typicalengineeringsystemsaredescribedbyverylargenumbersofvariables,anditisthedesigner'stasktospecifyappropriatevaluesforthesevariables.Skilleddesignersutilizetheirknowledge,experience,andjudgmenttospecifythesevariablesanddesigneffectiveengineeringsystems.Becauseofthesizeandcomplexityofthetypicaldesigntask,however,eventhemostskilleddesignersareunabletotakeintoaccountallofthevariablessimultaneously.14課件機械工程專業(yè)英語預備知識Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationDesignOptimization(優(yōu)化設計)Inmathematics,optimization,ormathematicalprogramming,referstochoosingthebestelementfromsomesetofavailablealternatives.Optimizationmethodologiescanbeappliedduringtheproductdevelopmentstagetoensurethatthefinisheddesignwillhavethehighperformance,highreliability,lowweight,and/orlowcost.Alternatively,optimizationmethodscanbeappliedtoexistingproductstoidentifypotentialdesignimprovements.15課件optimization[7Cptimai5zeiFen]n.優(yōu)化，優(yōu)選（法）finiteelementanalysis[5fainait][5elimEnt][E5nAlEsis]

n.有限元分析iterative[5itErEtiv]

adj.反復的迭代的alternative

[C:l5tE:nEtiv]

n.二中擇一,可供選擇的辦法,事物

adj.交替的可供選擇的manual[5mAnjuEl]

adj.手工的，人工的trial-and-error反復試驗試湊法bias[5baiEs]

n.偏向（重、差）vt.使存偏見adesktopplatform桌面平臺詞匯二、詞匯Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語17課件二、詞匯Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語constrain(t)[kEn5strein]n.vt.強制約束response[ris5pCns]n.反應靈敏度parameter[pE5rAmitE]n.參數(shù)，參量parametric[7pArE5metrik]adj.mesh[meF]n.網格vt.以網捕捉，嚙合，編織，vi.落網，相嚙合capability[7keipE5biliti]n.能力，性能，容量loop[lu:p]n.循環(huán)closedloop閉環(huán)openloop開環(huán)pose[pEuz]vt.擺出….姿態(tài)，提出model[5mCdl]

n.模型，樣品詞匯18課件displacement[dis5pleismEnt]

n.位移，排量，替換buckling[5bQkliN]

n.彎曲，翹曲，撓度factor[5fAktE]n.因素gradient[5greidiEnt]

n.梯度，傾斜度，坡度，傾斜的flux

[flQks]

n.

通量，流量，vi.溶化，流出vt.使溶融，用焊劑處理multidisciplinary[7mQlti5disiplinEri]adj.多學科的deflection[di5flekFEn]n.偏轉，撓曲objectivefunction目標函數(shù)preprocess[pri:5prEuses]預處理詞匯二、詞匯Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語19課件Asengineersworkwithincreasinglycomplexstructures,theyneedrational,reliable,fast,andeconomicaldesigntools.課文分析當工程師們需要求解越來越復雜的結構問題時，他們需要合理的、可靠的、快速而經濟的設計工具。Overthepasttwodecades,finiteelementanalysishasproventobethemostfrequentlyusedmethodofidentifyingandsolvingtheproblemsassociatedwiththesecomplicateddesigns.

過去二十年里，有限元分析已經成為確定和解決涉及這些復雜設計問題時的最常用方法。Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語21課件Becausemostofthedesigntasksinengineeringarequantifiable,computershaverevolutionizedthehighlyiterativedesignprocess,particularlytheproceduresforquicklyfindingalternativedesigns.Butevennow,manyengineersstillfollowamanualtrialanderrorapproach,Suchallapproachmakesdesigningevenforseeminglysimpletasksmoredifficultbecauseitusuallytakeslonger,requiresextensivehumanmachineinteraction,andtendstobebiasedbythedesigngroup'sexperience.課文分析Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語22課件Becausemostofthedesigntasksinengineeringarequantifiable,computershaverevolutionizedthehighlyiterativedesignprocess,particularlytheproceduresforquicklyfindingalternativedesigns.課文分析因為工程實踐中的大多數(shù)設計任務都是可量化的，計算機徹底改變了繁瑣的重復設計過程，特別是有了快速找到比較設計方案的程序。Lesson3OptimizationforFiniteElementApplicationsadj.可以計量的，可計量的[’it?r?tiv]adj.重復的,迭代的機械工程專業(yè)英語23課件Designoptimization,whichisbasedonarationalmathematicalapproachtomodifyingdesignstoocomplexfortheengineertomodify,automatesthedesigncycle.課文分析優(yōu)化設計是以合理的數(shù)學推倒方法為基礎，改進那些對于工程師來說過于復雜無法改進的設計，使設計過程自動化。Ifautomatedoptimizationcanbedoneonadesktopplatform,itcansavealotoftimeandmoney.如果在—臺計算機就能實現(xiàn)自動優(yōu)化設計，那就可以節(jié)省大量的時間和金錢．Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語25課件Thegoalofoptimizationistominimizeormaximizeanobjective,suchasweightorfundamentalfrequencythatissubjecttoconstraintsonresponseanddesignparameters.課文分析優(yōu)化設計的目的就是要將設計目標最大化或最小化，例如，重量或基頻這些受到頻響和設計參數(shù)方向的約束的對象。Thesizeand/orshapeofthedesigndeterminetheoptimizationapproach.尺寸和(或)結構形狀決定著優(yōu)化設計的方法。Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語26課件Inthesecondstep,theoptimizationobjectiveandresponseconstraintsaredefined.課文分析第二步，定義優(yōu)化目標和響應約束。Andinthelaststep,therepetitivetaskofdesignadjustmentisautomated.

而最后—步，自動化的重復設計過程。Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語29課件

Optimizationprogramsshouldallowengineerstomonitortheprogressofthedesign,stopitifnecessary,changethedesignconditions,andrestart.Thepowerofanoptimizationprogramdependsontheavailablepreprocessingandanalysiscapabilities.Applicationsfor2Dand3Dneedbothautomaticandparametricmeshingcapabilities.Errorestimateandadaptivecontrolmustbeincludedbecausetheproblem'sgeometryandmeshmightchangeduringtheoptimizationloops.

課文分析Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語30課件Optimizationprogramsshouldallowengineerstomonitortheprogressofthedesign,stopitifnecessary,changethedesignconditions,andrestart.課文分析優(yōu)化設計程序將允許工程師們監(jiān)督該設計過程，如果必要時可停止設計，改變設計條件并重新開始。Thepowerofanoptimizationprogramdependsontheavailablepreprocessingandanalysiscapabilities.一個優(yōu)化設計程序的功能取決于其有效的預處理和分析能力。Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語31課件Applicationsfor2Dand3Dneedbothautomaticandparametricmeshingcapabilities.課文分析二維和三維設計的應用既需要自動進行也需要設計參數(shù)的相互匹配性能。Errorestimateandadaptivecontrolmustbeincludedbecausetheproblem'sgeometryandmeshmightchangeduringtheoptimizationloops.

因為在優(yōu)化循環(huán)過程中，問題的幾何條件和網格會改變，所以優(yōu)化程序必須包含誤差估計和自適應控制。Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語32課件Revising,remeshing,andreevaluatingmodelstoachievespecificdesigngoalsstartwithpreliminarydesigndatainput.Nextcomesthespecificationofacceptabletolerancesandposedconstraintstoachieveanoptimum,oratleastimprove,solution.Tooptimizeproductsrangingfromsimpleskeletalstructurestocomplicatedthreedimensionalsolidmodels,designersneedaccesstoawidevarietyofdesignobjectivesandbehaviorconstraints.Additionalcapabilitieswillalsobeneededforeasydefinitionanduseofthefollowing:weights,volumes,displacements,stresses,strains,frequencies,bucklingsafelyfactors,temperatures,temperaturegradients,andheatfluxesasconstraintsandobjectivefunctions。課文分析Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語33課件Revising,remeshing,andreevaluatingmodelstoachievespecificdesigngoalsstartwithpreliminarydesigndatainput.課文分析修改、重配置和重新估算模型以期獲得確定的設計目標是以輸入預先設定的設計數(shù)據(jù)開始的。Nextcomesthespecificationofacceptabletolerancesandposedconstraintstoachieveanoptimum,oratleastimprove,solution.接著，是規(guī)定許用公差并提出約束條件等技術要求以獲得最優(yōu)結果，或至少能改進設計，解決問題。Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語34課件Tooptimizeproductsrangingfromsimpleskeletalstructurestocomplicatedthreedimensionalsolidmodels,designersneedaccesstoawidevarietyofdesignobjectivesandbehaviorconstraints.課文分析為使從簡單輪廓圖形到復雜三維實體模型的產品得到優(yōu)化，設計者必須利用各種各樣的設計目標和特性約束條件。Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語35課件Additionalcapabilitieswillalsobeneededforeasydefinitionanduseofthefollowing:weights,volumes,displacements,stresses,strains,frequencies,bucklingsafelyfactors,temperatures,temperaturegradients,andheatfluxesasconstraintsandobjectivefunctions。課文分析為了易于定義而利用下列輔助參數(shù)作為約束和目標函數(shù)也將是必要的：重量、體積、位移、應力，應變，頻率，抗彎安全系數(shù)、溫度、溫度梯度和臨界熱負荷。Lesson3OptimizationforFiniteElementApplications機械工程專業(yè)英語36課件Moreover,engineersshouldbeabletocombineconstraintsfromdifferenttypesofanalysesinmultidisciplinaryoptimization.Forexample,designerscanperform