機(jī)械工程專業(yè)英語-L03課件

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

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

一、預(yù)備知識(shí)有限元法起源于50年代航空工程中的機(jī)構(gòu)分析矩陣法。為了解決航空結(jié)構(gòu)設(shè)計(jì)問題，Turner、Clough等人首次采用三角形和矩形單元，成功地將結(jié)構(gòu)力學(xué)中的位移用于平面應(yīng)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(jié)構(gòu)離散---網(wǎng)格劃分，關(guān)系到有限元計(jì)算的速度和精度2）單元分析：建立各節(jié)點(diǎn)位移和節(jié)點(diǎn)力之間的關(guān)系，從而求出單元?jiǎng)偠染仃?）等效節(jié)點(diǎn)載荷計(jì)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(jī)械工程專業(yè)英語13課件機(jī)械工程專業(yè)英語預(yù)備知識(shí)Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationDesignOptimization(優(yōu)化設(shè)計(jì))Typicalengineeringsystemsaredescribedbyverylargenumbersofvariables,anditisthedesigner'stasktospecifyappropriatevaluesforthesevariables.Skilleddesignersutilizetheirknowledge,experience,andjudgmenttospecifythesevariablesanddesigneffectiveengineeringsystems.Becauseofthesizeandcomplexityofthetypicaldesigntask,however,eventhemostskilleddesignersareunabletotakeintoaccountallofthevariablessimultaneously.14課件機(jī)械工程專業(yè)英語預(yù)備知識(shí)Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationDesignOptimization(優(yōu)化設(shè)計(jì))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(fù)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(fù)試驗(yàn)試湊法bias[5baiEs]

n.偏向（重、差）vt.使存偏見adesktopplatform桌面平臺(tái)詞匯二、詞匯Lesson3OptimizationforFiniteElementApplications機(jī)械工程專業(yè)英語17課件二、詞匯Lesson3OptimizationforFiniteElementApplications機(jī)械工程專業(yè)英語constrain(t)[kEn5strein]n.vt.強(qiáng)制約束response[ris5pCns]n.反應(yīng)靈敏度parameter[pE5rAmitE]n.參數(shù)，參量parametric[7pArE5metrik]adj.mesh[meF]n.網(wǎng)格vt.以網(wǎng)捕捉，嚙合，編織，vi.落網(wǎng)，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(xué)科的deflection[di5flekFEn]n.偏轉(zhuǎn)，撓曲objectivefunction目標(biāo)函數(shù)preprocess[pri:5prEuses]預(yù)處理詞匯二、詞匯Lesson3OptimizationforFiniteElementApplications機(jī)械工程專業(yè)英語19課件Asengineersworkwithincreasinglycomplexstructures,theyneedrational,reliable,fast,andeconomicaldesigntools.課文分析當(dāng)工程師們需要求解越來越復(fù)雜的結(jié)構(gòu)問題時(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。Overthepasttwodecades,finiteelementanalysishasproventobethemostfrequentlyusedmethodofidentifyingandsolvingtheproblemsassociatedwiththesecomplicateddesigns.

過去二十年里，有限元分析已經(jīng)成為確定和解決涉及這些復(fù)雜設(shè)計(jì)問題時(shí)的最常用方法。Lesson3OptimizationforFiniteElementApplications機(jī)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(jī)械工程專業(yè)英語22課件Becausemostofthedesigntasksinengineeringarequantifiable,computershaverevolutionizedthehighlyiterativedesignprocess,particularlytheproceduresforquicklyfindingalternativedesigns.課文分析因?yàn)楣こ虒?shí)踐中的大多數(shù)設(shè)計(jì)任務(wù)都是可量化的，計(jì)算機(jī)徹底改變了繁瑣的重復(fù)設(shè)計(jì)過程，特別是有了快速找到比較設(shè)計(jì)方案的程序。Lesson3OptimizationforFiniteElementApplicationsadj.可以計(jì)量的，可計(jì)量的[’it?r?tiv]adj.重復(fù)的,迭代的機(jī)械工程專業(yè)英語23課件Designoptimization,whichisbasedonarationalmathematicalapproachtomodifyingdesignstoocomplexfortheengineertomodify,automatesthedesigncycle.課文分析優(yōu)化設(shè)計(jì)是以合理的數(shù)學(xué)推倒方法為基礎(chǔ)，改進(jìn)那些對(duì)于工程師來說過于復(fù)雜無法改進(jìn)的設(shè)計(jì)，使設(shè)計(jì)過程自動(dòng)化。Ifautomatedoptimizationcanbedoneonadesktopplatform,itcansavealotoftimeandmoney.如果在—臺(tái)計(jì)算機(jī)就能實(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．Lesson3OptimizationforFiniteElementApplications機(jī)械工程專業(yè)英語25課件Thegoalofoptimizationistominimizeormaximizeanobjective,suchasweightorfundamentalfrequencythatissubjecttoconstraintsonresponseanddesignparameters.課文分析優(yōu)化設(shè)計(jì)的目的就是要將設(shè)計(jì)目標(biāo)最大化或最小化，例如，重量或基頻這些受到頻響和設(shè)計(jì)參數(shù)方向的約束的對(duì)象。Thesizeand/orshapeofthedesigndeterminetheoptimizationapproach.尺寸和(或)結(jié)構(gòu)形狀決定著優(yōu)化設(shè)計(jì)的方法。Lesson3OptimizationforFiniteElementApplications機(jī)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(biāo)和響應(yīng)約束。Andinthelaststep,therepetitivetaskofdesignadjustmentisautomated.

而最后—步，自動(dòng)化的重復(fù)設(shè)計(jì)過程。Lesson3OptimizationforFiniteElementApplications機(jī)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(jī)械工程專業(yè)英語30課件Optimizationprogramsshouldallowengineerstomonitortheprogressofthedesign,stopitifnecessary,changethedesignconditions,andrestart.課文分析優(yōu)化設(shè)計(jì)程序?qū)⒃试S工程師們監(jiān)督該設(shè)計(jì)過程，如果必要時(shí)可停止設(shè)計(jì)，改變?cè)O(shè)計(jì)條件并重新開始。Thepowerofanoptimizationprogramdependsontheavailablepreprocessingandanalysiscapabilities.一個(gè)優(yōu)化設(shè)計(jì)程序的功能取決于其有效的預(yù)處理和分析能力。Lesson3OptimizationforFiniteElementApplications機(jī)械工程專業(yè)英語31課件Applicationsfor2Dand3Dneedbothautomaticandparametricmeshingcapabilities.課文分析二維和三維設(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)的相互匹配性能。Errorestimateandadaptivecontrolmustbeincludedbecausetheproblem'sgeometryandmeshmightchangeduringtheoptimizationloops.

因?yàn)樵趦?yōu)化循環(huán)過程中，問題的幾何條件和網(wǎng)格會(huì)改變，所以優(yōu)化程序必須包含誤差估計(jì)和自適應(yīng)控制。Lesson3OptimizationforFiniteElementApplications機(jī)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(jī)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(shè)計(jì)目標(biāo)是以輸入預(yù)先設(shè)定的設(shè)計(jì)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(shù)要求以獲得最優(yōu)結(jié)果，或至少能改進(jìn)設(shè)計(jì)，解決問題。Lesson3OptimizationforFiniteElementApplications機(jī)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(fù)雜三維實(shí)體模型的產(chǎn)品得到優(yōu)化，設(shè)計(jì)者必須利用各種各樣的設(shè)計(jì)目標(biāo)和特性約束條件。Lesson3OptimizationforFiniteElementApplications機(jī)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(biāo)函數(shù)也將是必要的：重量、體積、位移、應(yīng)力，應(yīng)變，頻率，抗彎安全系數(shù)、溫度、溫度梯度和臨界熱負(fù)荷。Lesson3OptimizationforFiniteElementApplications機(jī)械工程專業(yè)英語36課件Moreover,engineersshouldbeabletocombineconstraintsfromdifferenttypesofanalysesinmultidisciplinaryoptimization.Forexample,designerscanperform