机械工程专业英语-L03课件

EnglishforMechanicalEngineering机械工程专业英语1课件机械工程专业英语预备知识Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)Thefiniteelementmethod(FEM)(sometimesreferredtoasfiniteelementanalysis)isanumericaltechniqueforfindingapproximatesolutionsofpartialdifferentialequations(PDE)aswellasofintegralequations.2课件机械工程专业英语预备知识Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)Thesolutionapproachisbasedeitheroneliminatingthedifferentialequationcompletely(steadystateproblems),orrenderingthePDEintoanapproximatingsystemofordinarydifferentialequations,whicharethennumericallyintegratedusingstandardtechniquessuchasEuler'smethod,Runge-Kutta,etc.3课件机械工程专业英语预备知识Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)Forinstance,inafrontalcrashsimulationitispossibletoincreasepredictionaccuracyin"important"areaslikethefrontofthecarandreduceitinitsrear(thusreducingcostofthesimulation);AnotherexamplewouldbethesimulationoftheweatherpatternonEarth,whereitismoreimportanttohaveaccuratepredictionsoverlandthanoverthewide-opensea.5课件机械工程专业英语预备知识Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)Thefinite-elementmethodoriginatedfromtheneedforsolvingcomplexelasticityandstructuralanalysisproblemsincivilandaeronauticalengineering.ItsdevelopmentcanbetracedbacktotheworkbyAlexanderHrennikoff(1941)andRichardCourant(1942).Whiletheapproachesusedbythesepioneersaredramaticallydifferent,theyshareoneessentialcharacteristic:meshdiscretizationofacontinuousdomainintoasetofdiscretesub-domains,usuallycalledelements.

6课件机械工程专业英语预备知识Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)Developmentofthefiniteelementmethodbeganinearnestinthemiddletolate1950sforairframeandstructuralanalysisandgatheredmomentumattheUniversityofStuttgartthroughtheworkofJohnArgyrisandatBerkeleythroughtheworkofRayW.Cloughinthe1960sforuseincivilengineering.Bylate1950s,thekeyconceptsofstiffnessmatrixandelementassemblyexistedessentiallyintheformusedtoday.NASAissuedrequestforproposalsforthedevelopmentofthefiniteelementsoftwareNASTRANin1965.7课件机械工程专业英语预备知识Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)FEMallowsdetailedvisualizationofwherestructuresbendortwist,andindicatesthedistributionofstressesanddisplacements.FEMsoftwareprovidesawiderangeofsimulationoptionsforcontrollingthecomplexityofbothmodelingandanalysisofasystem.Similarly,thedesiredlevelofaccuracyrequiredandassociatedcomputationaltimerequirementscanbemanagedsimultaneouslytoaddressmostengineeringapplications.FEMallowsentiredesignstobeconstructed,refined,andoptimizedbeforethedesignismanufactured.9课件机械工程专业英语预备知识Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)Thispowerfuldesigntoolhassignificantlyimprovedboththestandardofengineeringdesignsandthemethodologyofthedesignprocessinmanyindustrialapplications.TheintroductionofFEMhassubstantiallydecreasedthetimetotakeproductsfromconcepttotheproductionline.ItisprimarilythroughimprovedinitialprototypedesignsusingFEMthattestinganddevelopmenthavebeenaccelerated.Insummary,benefitsofFEMincludeincreasedaccuracy,enhanceddesignandbetterinsightintocriticaldesignparameters,virtualprototyping,fewerhardwareprototypes,afasterandlessexpensivedesigncycle,increasedproductivity,andincreasedrevenue.10课件机械工程专业英语预备知识Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationFiniteElementMethod(有限元法)GeneralformofthefiniteelementmethodChooseagrid.Intheprecedingtreatment,thegridconsistedoftriangles,butonecanalsousesquaresorcurvilinearpolygons.Then,onechoosesbasisfunctions.Weusedpiecewiselinearbasisfunctions,butitisalsocommontousepiecewisepolynomialbasisfunctions.11课件预备知识

一、预备知识有限元法起源于50年代航空工程中的机构分析矩阵法。为了解决航空结构设计问题，Turner、Clough等人首次采用三角形和矩形单元，成功地将结构力学中的位移用于平面应力问题的求解，1960年，首次提出了“有限元法”。

有限元法的基本步骤：1）结构离散---网格划分，关系到有限元计算的速度和精度2）单元分析：建立各节点位移和节点力之间的关系，从而求出单元刚度矩阵3）等效节点载荷计算4）整体分析，建立整体刚度方程5）约束条件引入和方程求解Lesson3OptimizationforFiniteElementApplications机械工程专业英语13课件机械工程专业英语预备知识Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationDesignOptimization(优化设计)Typicalengineeringsystemsaredescribedbyverylargenumbersofvariables,anditisthedesigner'stasktospecifyappropriatevaluesforthesevariables.Skilleddesignersutilizetheirknowledge,experience,andjudgmenttospecifythesevariablesanddesigneffectiveengineeringsystems.Becauseofthesizeandcomplexityofthetypicaldesigntask,however,eventhemostskilleddesignersareunabletotakeintoaccountallofthevariablessimultaneously.14课件机械工程专业英语预备知识Lesson3OptimizationforFiniteElementApplications一、BackgroundInformationDesignOptimization(优化设计)Inmathematics,optimization,ormathematicalprogramming,referstochoosingthebestelementfromsomesetofavailablealternatives.Optimizationmethodologiescanbeappliedduringtheproductdevelopmentstagetoensurethatthefinisheddesignwillhavethehighperformance,highreliability,lowweight,and/orlowcost.Alternatively,optimizationmethodscanbeappliedtoexistingproductstoidentifypotentialdesignimprovements.15课件optimization[7Cptimai5zeiFen]n.优化，优选（法）finiteelementanalysis[5fainait][5elimEnt][E5nAlEsis]

n.有限元分析iterative[5itErEtiv]

adj.反复的迭代的alternative

[C:l5tE:nEtiv]

n.二中择一,可供选择的办法,事物

adj.交替的可供选择的manual[5mAnjuEl]

adj.手工的，人工的trial-and-error反复试验试凑法bias[5baiEs]

n.偏向（重、差）vt.使存偏见adesktopplatform桌面平台词汇二、词汇Lesson3OptimizationforFiniteElementApplications机械工程专业英语17课件二、词汇Lesson3OptimizationforFiniteElementApplications机械工程专业英语constrain(t)[kEn5strein]n.vt.强制约束response[ris5pCns]n.反应灵敏度parameter[pE5rAmitE]n.参数，参量parametric[7pArE5metrik]adj.mesh[meF]n.网格vt.以网捕捉，啮合，编织，vi.落网，相啮合capability[7keipE5biliti]n.能力，性能，容量loop[lu:p]n.循环closedloop闭环openloop开环pose[pEuz]vt.摆出….姿态，提出model[5mCdl]

n.模型，样品词汇18课件displacement[dis5pleismEnt]

n.位移，排量，替换buckling[5bQkliN]

n.弯曲，翘曲，挠度factor[5fAktE]n.因素gradient[5greidiEnt]

n.梯度，倾斜度，坡度，倾斜的flux

[flQks]

n.

通量，流量，vi.溶化，流出vt.使溶融，用焊剂处理multidisciplinary[7mQlti5disiplinEri]adj.多学科的deflection[di5flekFEn]n.偏转，挠曲objectivefunction目标函数preprocess[pri:5prEuses]预处理词汇二、词汇Lesson3OptimizationforFiniteElementApplications机械工程专业英语19课件Asengineersworkwithincreasinglycomplexstructures,theyneedrational,reliable,fast,andeconomicaldesigntools.课文分析当工程师们需要求解越来越复杂的结构问题时，他们需要合理的、可靠的、快速而经济的设计工具。Overthepasttwodecades,finiteelementanalysishasproventobethemostfrequentlyusedmethodofidentifyingandsolvingtheproblemsassociatedwiththesecomplicateddesigns.

过去二十年里，有限元分析已经成为确定和解决涉及这些复杂设计问题时的最常用方法。Lesson3OptimizationforFiniteElementApplications机械工程专业英语21课件Becausemostofthedesigntasksinengineeringarequantifiable,computershaverevolutionizedthehighlyiterativedesignprocess,particularlytheproceduresforquicklyfindingalternativedesigns.Butevennow,manyengineersstillfollowamanualtrialanderrorapproach,Suchallapproachmakesdesigningevenforseeminglysimpletasksmoredifficultbecauseitusuallytakeslonger,requiresextensivehumanmachineinteraction,andtendstobebiasedbythedesigngroup'sexperience.课文分析Lesson3OptimizationforFiniteElementApplications机械工程专业英语22课件Becausemostofthedesigntasksinengineeringarequantifiable,computershaverevolutionizedthehighlyiterativedesignprocess,particularlytheproceduresforquicklyfindingalternativedesigns.课文分析因为工程实践中的大多数设计任务都是可量化的，计算机彻底改变了繁琐的重复设计过程，特别是有了快速找到比较设计方案的程序。Lesson3OptimizationforFiniteElementApplicationsadj.可以计量的，可计量的[’itərətiv]adj.重复的,迭代的机械工程专业英语23课件Designoptimization,whichisbasedonarationalmathematicalapproachtomodifyingdesignstoocomplexfortheengineertomodify,automatesthedesigncycle.课文分析优化设计是以合理的数学推倒方法为基础，改进那些对于工程师来说过于复杂无法改进的设计，使设计过程自动化。Ifautomatedoptimizationcanbedoneonadesktopplatform,itcansavealotoftimeandmoney.如果在—台计算机就能实现自动优化设计，那就可以节省大量的时间和金钱．Lesson3OptimizationforFiniteElementApplications机械工程专业英语25课件Thegoalofoptimizationistominimizeormaximizeanobjective,suchasweightorfundamentalfrequencythatissubjecttoconstraintsonresponseanddesignparameters.课文分析优化设计的目的就是要将设计目标最大化或最小化，例如，重量或基频这些受到频响和设计参数方向的约束的对象。Thesizeand/orshapeofthedesigndeterminetheoptimizationapproach.尺寸和(或)结构形状决定着优化设计的方法。Lesson3OptimizationforFiniteElementApplications机械工程专业英语26课件Inthesecondstep,theoptimizationobjectiveandresponseconstraintsaredefined.课文分析第二步，定义优化目标和响应约束。Andinthelaststep,therepetitivetaskofdesignadjustmentisautomated.

而最后—步，自动化的重复设计过程。Lesson3OptimizationforFiniteElementApplications机械工程专业英语29课件

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

课文分析Lesson3OptimizationforFiniteElementApplications机械工程专业英语30课件Optimizationprogramsshouldallowengineerstomonitortheprogressofthedesign,stopitifnecessary,changethedesignconditions,andrestart.课文分析优化设计程序将允许工程师们监督该设计过程，如果必要时可停止设计，改变设计条件并重新开始。Thepowerofanoptimizationprogramdependsontheavailablepreprocessingandanalysiscapabilities.一个优化设计程序的功能取决于其有效的预处理和分析能力。Lesson3OptimizationforFiniteElementApplications机械工程专业英语31课件Applicationsfor2Dand3Dneedbothautomaticandparametricmeshingcapabilities.课文分析二维和三维设计的应用既需要自动进行也需要设计参数的相互匹配性能。Errorestimateandadaptivecontrolmustbeincludedbecausetheproblem'sgeometryandmeshmightchangeduringtheoptimizationloops.

因为在优化循环过程中，问题的几何条件和网格会改变，所以优化程序必须包含误差估计和自适应控制。Lesson3OptimizationforFiniteElementApplications机械工程专业英语32课件Revising,remeshing,andreevaluatingmodelstoachievespecificdesigngoalsstartwithpreliminarydesigndatainput.Nextcomesthespecificationofacceptabletolerancesandposedconstraintstoachieveanoptimum,oratleastimprove,solution.Tooptimizeproductsrangingfromsimpleskeletalstructurestocomplicatedthreedimensionalsolidmodels,designersneedaccesstoawidevarietyofdesignobjectivesandbehaviorconstraints.Additionalcapabilitieswillalsobeneededforeasydefinitionanduseofthefollowing:weights,volumes,displacements,stresses,strains,frequencies,bucklingsafelyfactors,temperatures,temperaturegradients,andheatfluxesasconstraintsandobjectivefunctions。课文分析Lesson3OptimizationforFiniteElementApplications机械工程专业英语33课件Revising,remeshing,andreevaluatingmodelstoachievespecificdesigngoalsstartwithpreliminarydesigndatainput.课文分析修改、重配置和重新估算模型以期获得确定的设计目标是以输入预先设定的设计数据开始的。Nextcomesthespecificationofacceptabletolerancesandposedconstraintstoachieveanoptimum,oratleastimprove,solution.接着，是规定许用公差并提出约束条件等技术要求以获得最优结果，或至少能改进设计，解决问题。Lesson3OptimizationforFiniteElementApplications机械工程专业英语34课件Tooptimizeproductsrangingfromsimpleskeletalstructurestocomplicatedthreedimensionalsolidmodels,designersneedaccesstoawidevarietyofdesignobjectivesandbehaviorconstraints.课文分析为使从简单轮廓图形到复杂三维实体模型的产品得到优化，设计者必须利用各种各样的设计目标和特性约束条件。Lesson3OptimizationforFiniteElementApplications机械工程专业英语35课件Additionalcapabilitieswillalsobeneededforeasydefinitionanduseofthefollowing:weights,volumes,displacements,stresses,strains,frequencies,bucklingsafelyfactors,temperatures,temperaturegradients,andheatfluxesasconstraintsandobjectivefunctions。课文分析为了易于定义而利用下列辅助参数作为约束和目标函数也将是必要的：重量、体积、位移、应力，应变，频率，抗弯安全系数、温度、温度梯度和临界热负荷。Lesson3OptimizationforFiniteElementApplications机械工程专业英语36课件Moreover,engineersshouldbeabletocombineconstraintsfromdifferenttypesofanalysesinmultidisciplinaryoptimization.Forexample,designerscanperform