机械工程专业英语课件--L03.ppt

EnglishforMechanicalEngineering 机械工程专业英语 常州工学院机电工程学院徐红丽 机械工程专业英语 预备知识 Lesson3OptimizationforFiniteElementApplications 一 BackgroundInformation FiniteElementMethod 有限元法 Thefiniteelementmethod FEM sometimesreferredtoasfiniteelementanalysis isanumericaltechniqueforfindingapproximatesolutionsofpartialdifferentialequations PDE aswellasofintegralequations 机械工程专业英语 预备知识 Lesson3OptimizationforFiniteElementApplications 一 BackgroundInformation FiniteElementMethod 有限元法 Thesolutionapproachisbasedeitheroneliminatingthedifferentialequationcompletely steadystateproblems orrenderingthePDEintoanapproximatingsystemofordinarydifferentialequations whicharethennumericallyintegratedusingstandardtechniquessuchasEuler smethod Runge Kutta etc 机械工程专业英语 预备知识 Lesson3OptimizationforFiniteElementApplications 一 BackgroundInformation FiniteElementMethod 有限元法 Insolvingpartialdifferentialequations theprimarychallengeistocreateanequationthatapproximatestheequationtobestudied butisnumericallystable meaningthaterrorsintheinputdataandintermediatecalculationsdonotaccumulateandcausetheresultingoutputtobemeaningless Therearemanywaysofdoingthis allwithadvantagesanddisadvantages TheFiniteElementMethodisagoodchoiceforsolvingpartialdifferentialequationsovercomplexdomains likecarsandoilpipelines whenthedomainchanges asduringasolidstatereactionwithamovingboundary whenthedesiredprecisionvariesovertheentiredomain orwhenthesolutionlackssmoothness 机械工程专业英语 预备知识 Lesson3OptimizationforFiniteElementApplications 一 BackgroundInformation FiniteElementMethod 有限元法 Forinstance inafrontalcrashsimulationitispossibletoincreasepredictionaccuracyin important areaslikethefrontofthecarandreduceitinitsrear thusreducingcostofthesimulation AnotherexamplewouldbethesimulationoftheweatherpatternonEarth whereitismoreimportanttohaveaccuratepredictionsoverlandthanoverthewide opensea 机械工程专业英语 预备知识 Lesson3OptimizationforFiniteElementApplications 一 BackgroundInformation FiniteElementMethod 有限元法 Thefinite elementmethodoriginatedfromtheneedforsolvingcomplexelasticityandstructuralanalysisproblemsincivilandaeronauticalengineering ItsdevelopmentcanbetracedbacktotheworkbyAlexanderHrennikoff 1941 andRichardCourant 1942 Whiletheapproachesusedbythesepioneersaredramaticallydifferent theyshareoneessentialcharacteristic meshdiscretizationofacontinuousdomainintoasetofdiscretesub domains usuallycalledelements 机械工程专业英语 预备知识 Lesson3OptimizationforFiniteElementApplications 一 BackgroundInformation FiniteElementMethod 有限元法 Developmentofthefiniteelementmethodbeganinearnestinthemiddletolate1950sforairframeandstructuralanalysisandgatheredmomentumattheUniversityofStuttgartthroughtheworkofJohnArgyrisandatBerkeleythroughtheworkofRayW Cloughinthe1960sforuseincivilengineering Bylate1950s thekeyconceptsofstiffnessmatrixandelementassemblyexistedessentiallyintheformusedtoday NASAissuedrequestforproposalsforthedevelopmentofthefiniteelementsoftwareNASTRANin1965 机械工程专业英语 预备知识 Lesson3OptimizationforFiniteElementApplications 一 BackgroundInformation FiniteElementMethod 有限元法 Avarietyofspecializationsundertheumbrellaofthemechanicalengineeringdiscipline suchasaeronautical biomechanical andautomotiveindustries commonlyuseintegratedFEMindesignanddevelopmentoftheirproducts SeveralmodernFEMpackagesincludespecificcomponentssuchasthermal electromagnetic fluid andstructuralworkingenvironments Inastructuralsimulation FEMhelpstremendouslyinproducingstiffnessandstrengthvisualizationsandalsoinminimizingweight materials andcosts 机械工程专业英语 预备知识 Lesson3OptimizationforFiniteElementApplications 一 BackgroundInformation FiniteElementMethod 有限元法 FEMallowsdetailedvisualizationofwherestructuresbendortwist andindicatesthedistributionofstressesanddisplacements FEMsoftwareprovidesawiderangeofsimulationoptionsforcontrollingthecomplexityofbothmodelingandanalysisofasystem Similarly thedesiredlevelofaccuracyrequiredandassociatedcomputationaltimerequirementscanbemanagedsimultaneouslytoaddressmostengineeringapplications FEMallowsentiredesignstobeconstructed refined andoptimizedbeforethedesignismanufactured 机械工程专业英语 预备知识 Lesson3OptimizationforFiniteElementApplications 一 BackgroundInformation FiniteElementMethod 有限元法 Thispowerfuldesigntoolhassignificantlyimprovedboththestandardofengineeringdesignsandthemethodologyofthedesignprocessinmanyindustrialapplications TheintroductionofFEMhassubstantiallydecreasedthetimetotakeproductsfromconcepttotheproductionline ItisprimarilythroughimprovedinitialprototypedesignsusingFEMthattestinganddevelopmenthavebeenaccelerated Insummary benefitsofFEMincludeincreasedaccuracy enhanceddesignandbetterinsightintocriticaldesignparameters virtualprototyping fewerhardwareprototypes afasterandlessexpensivedesigncycle increasedproductivity andincreasedrevenue 机械工程专业英语 预备知识 Lesson3OptimizationforFiniteElementApplications 一 BackgroundInformation FiniteElementMethod 有限元法 Generalformofthefiniteelementmethod Chooseagrid Intheprecedingtreatment thegridconsistedoftriangles butonecanalsousesquaresorcurvilinearpolygons Then onechoosesbasisfunctions Weusedpiecewiselinearbasisfunctions butitisalsocommontousepiecewisepolynomialbasisfunctions 机械工程专业英语 预备知识 Lesson3OptimizationforFiniteElementApplications 一 BackgroundInformation FiniteElementMethod 有限元法 Generalformofthefiniteelementmethod Byanalyzingtheresponseofeachfiniteelementoftheobjecttothestress strain heat orotherforceactingonit thecomputercanpredictthereactionofthewholeobject Thereisatrade offbetweenaccuracyandcomputationtime 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 机械工程专业英语 预备知识 Lesson3OptimizationforFiniteElementApplications 一 BackgroundInformation DesignOptimization 优化设计 Typicalengineeringsystemsaredescribedbyverylargenumbersofvariables anditisthedesigner stasktospecifyappropriatevaluesforthesevariables Skilleddesignersutilizetheirknowledge experience andjudgmenttospecifythesevariablesanddesigneffectiveengineeringsystems Becauseofthesizeandcomplexityofthetypicaldesigntask however eventhemostskilleddesignersareunabletotakeintoaccountallofthevariablessimultaneously 机械工程专业英语 预备知识 Lesson3OptimizationforFiniteElementApplications 一 BackgroundInformation DesignOptimization 优化设计 Inmathematics optimization ormathematicalprogramming referstochoosingthebestelementfromsomesetofavailablealternatives Optimizationmethodologiescanbeappliedduringtheproductdevelopmentstagetoensurethatthefinisheddesignwillhavethehighperformance highreliability lowweight and orlowcost Alternatively optimizationmethodscanbeappliedtoexistingproductstoidentifypotentialdesignimprovements 机械工程专业英语 预备知识 一 预备知识 Lesson3OptimizationforFiniteElementApplications 最优化问题 希望在可能的条件下用最少的付出得最满意的效果 最优化设计 借助最优化数值计算方法和计算机技术 求取工程问题的最优设计方案 用数学方法解决设计问题的设计方法 最优化设计的数学模型 由设计变量 目标函数和约束条件组成 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 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 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 Asengineersworkwithincreasinglycomplexstructures theyneedrational reliable fast andeconomicaldesigntools Overthepasttwodecades finiteelementanalysishasproventobethemostfrequentlyusedmethodofidentifyingandsolvingtheproblemsassociatedwiththesecomplicateddesigns 课文分析 Lesson3OptimizationforFiniteElementApplications 机械工程专业英语 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 Becausemostofthedesigntasksinengineeringarequantifiable computershaverevolutionizedthehighlyiterativedesignprocess particularlytheproceduresforquicklyfindingalternativedesigns Butevennow manyengineersstillfollowamanualtrialanderrorapproach Suchallapproachmakesdesigningevenforseeminglysimpletasksmoredifficultbecauseitusuallytakeslonger requiresextensivehumanmachineinteraction andtendstobebiasedbythedesigngroup sexperience 课文分析 Lesson3OptimizationforFiniteElementApplications 机械工程专业英语 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 Lesson3OptimizationforFiniteElementApplications adj 可以计量的 可计量的 it r tiv adj 重复的 迭代的 机械工程专业英语 Butevennow manyengineersstillfollowamanualtrial and errorapproach Suchallapproachmakesdesigningevenforseeminglysimpletasksmoredifficultbecauseitusuallytakeslonger requiresextensivehumanmachineinteraction andtendstobebiasedbythedesigngroup sexperience 课文分析 但是 即使是现在 许多工程师仍然使用人工试凑法 这种方法使得设计过程 即使是很简单的设计任务也变得困难 因为通常它要花更长的时间 需要广泛的人 机交流 且设计质量取决于设计人员的经验 Lesson3OptimizationforFiniteElementApplications 试凑法 取决于 机械工程专业英语 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 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 Lookingatoptimizationaspartofthedesignprocessmakesiteasiertounderstand Thefirststepincludespreprocessing analysis andpostprocessing justasii1customaryfiniteelementanalysis REA andcomputeraideddesign CAD programapplications thedifferenceinCADliesinbuildingtheproblem sgeometryintermsofthedesignparameters Inthesecondstep theoptimizationobjectiveandresponseconstraintsaredefined Andinthelaststep therepetitivetaskofdesignadjustmentisautomated 课文分析 Lesson3OptimizationforFiniteElementApplications 机械工程专业英语 Lookingatoptimizationaspartofthedesignprocessmakesiteasiertounderstand 课文分析 优化过程看作设计过程的一部分 使它变得更容易理解 Thefirststepincludespreprocessing analysis andpostprocessing justasincustomaryfiniteelementanalysis FEA andcomputeraideddesign CAD programapplications thedifferenceinCADliesinbuildingtheproblem sgeometryintermsofthedesignparameters 第一步 包括前处理 分析和后处理 正像通常使用的有限元分析 FEA 和计算机辅助设计 CAD 程序应用 CAD的特点在于根据设计参数建立了问题的几何图形 Lesson3OptimizationforFiniteElementApplications 机械工程专业英语 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 Optimizationprogramsshouldallowengineerstomonitortheprogressofthedesign stopitifnecessary changethedesignconditions andrestart Thepowerofanoptimizationprogramdependsontheavailablepreprocessingandanalysiscapabilities Applicationsfor2Dand3Dneedbothautomaticandparametricmeshingcapabilities Errorestimateandadaptivecontrolmustbeincludedbecausetheproblem sgeometryandmeshmightchangeduringtheoptimizationloops 课文分析 Lesson3OptimizationforFiniteElementApplications 机械工程专业英语 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 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 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 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 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 Additionalcapabilitieswillalsobeneededforeasydefinitionanduseofthefollowing weights volumes displacements stresses strains frequencies bucklingsafelyfactors temperatures temperaturegradients