企业培训_caesarii管道应力分析培训

2020 2 19 BasicStressTheory CAESARII管道应力分析培训 王大辉北京艾思弗软件公司 2020 2 19 BasicStressTheory 2020 2 19 BasicStressTheory 介绍 培训的目的在于让您了解和掌握应力分析的基础概念模型和边界条件的建立结果的分析和评判往复压缩机的分析专题日常遇到的问题和解决方法 2020 2 19 BasicStressTheory 介绍 3D梁单元的特征无限细的杆单元全部行为靠端点位移决定弯曲变形是主要的 2020 2 19 BasicStressTheory 介绍 3DBeamElementCharacteristics3D梁单元的特征仅说明整体行为无局部作用 表面没有碰撞 忽略二次影响 小转动 遵循胡克定律 2020 2 19 BasicStressTheory StressBasics应力基础 局部坐标系下管道应力分类 引发应力的载荷 轴向应力LongitudinalStress SL环向应力HoopStress SH径向应力RadialStress SR剪切应力ShearStress 2020 2 19 BasicStressTheory 轴向应力 沿管道轴向Alongaxisofpipe轴向力引起AxialForce轴向力 面积 F A 内压引起PressurePd 4torP di do2 di2 弯矩引起BendingMomentMc I最大应力环向的外表面某点处I radius Z 截面模量 useM Z 2020 2 19 BasicStressTheory 压力引起的环向应力 环向 垂直于半径 Pd 2t和壁厚紧密相关环向应力十分重要 但规范应力不考虑它 Hoopisveryimportant itsjustnotpartofthe codestress 环向应力用来确定壁厚 依据直径 许用应力 腐蚀裕量 加工偏差 压力确定管道壁厚 2020 2 19 BasicStressTheory 压力引发的径向应力 沿半径方向向内内壁的径向应力大小是 P外壁的径向应力大小为0最大弯曲应力发生在管道的外表面 故该项忽略 2020 2 19 BasicStressTheory 剪切应力ShearStresses 平面内垂直半径ShearForce剪力在外表面剪力很小 应力计算忽略支架设计有时需要考虑Torque扭矩最大应力在外表面MT 2Z 2020 2 19 BasicStressTheory 3 D应力评定 Aloaded 3 Dpipecontainsarepresentativeinfinitesimalstresscubeaddgraphic Fig1 13 Thisstresscubeisinequilibriumandcanberotatedinspaceaddgraphic rotatedcubewithloads Thiscubecanberotatedsothatshearstressesarezero ThisresultsinthePrincipalStresses 2020 2 19 BasicStressTheory Simplifyingtoa2 DStress ThisplanecanberotatedtoeithereliminateormaximizeshearstressbyusingMohr sCircle Sinceweusetheoutsidesurfacewhereradialstressiszero let smovetoaplaneelement 2020 2 19 BasicStressTheory UsingMohr sCircle Cutthesquareat tocalculateS1 Cutthesquareat 90tocalculateS2 Cutthesquareat 45tocalculate max 2020 2 19 BasicStressTheory UsingMohr sCircle Brittlematerial failurebyfracture maxprincipalstressDuctilematerial failurebygeneralyielding maxprincipalstressisusedtosetwallthicknessMaximumshearstressisagoodpredictionanderrsontheconservativesideseep84 85ofAdv Mech OfMat ls 2020 2 19 BasicStressTheory 基本应力 CodeStress规范应力 应力评定Evaluatinga3 DStressS F A Pd 4t M Z轴向力 轴向压力 轴向弯矩一起的分量加和规范不同 上面的算式也不同那些应力没有包含进来 2020 2 19 BasicStressTheory 基本应力 CodeStress规范应力 几个实效理论AFewFailureTheories变形能或八面体剪切应力 根据米赛斯理论和其它的理论 最大剪应力理论 Columb理论 大多数理论都根据这个理论 由于剪切影响而限制最大主应力 Rankine理论 CAESARII132列输出应力报告中显示了米赛斯或最大剪应力强度理论 应力报告由configuration设置来决定 2020 2 19 BasicStressTheory 基本应力 CodeStress规范应力 基于最大剪应力实效理论 ASME规范委员会颁布了规范应力方程Basedonthemaximumshearfailuretheory theCodeCommitteedevelopedthe codeequations 目的在于避免管道系统实效Purposewastoreducesystemfailures这种解决办法很实用 但仍然有问题存在Thisapproachworkedwell buttherewerestillproblems evenaslateaspostWorldWarII 研究表明直管道比较符合理论Studiesshowedsystemsofstraightpipematchedtheory研究表明元件失效比理论发生的早Studiesshowedsystemswithfittingsfailedearlierthantheorypredicted ASME规范委员会委托Markl来研究这个问题CodeCommitteecommissionedMarkltostudythis 2020 2 19 BasicStressTheory 基本应力 CodeStress规范应力 Markl s试验和结果将试验用的管道充满水 按某个方向和位移反复摇晃管道 Testconfigurationsfilledwithwaterandcycledthroughapredetermineddisplacement预测失效循环次数Theoryshouldbeabletopredict cyclestofailure 发现最先失效的管件及其原因Fittingscausedearlyfailure because 对管件引入应力集中Stressesconcentrationsareintroducedbyfittings分析试验数据 修正轴向应力弯曲项Testdataanalyzedandamodificationtothebendingtermofthecodestressequationwasintroduced Sbending iM z 2020 2 19 BasicStressTheory 基本应力 CodeStress规范应力 Markl s试验和结果应力增强系数i和元件的形式有关对于弯头 i 的计算需要如下 我们需要弯头的几何参数计算弯头柔性 h 计算应力增大系数StressIntensificationFactor i 石化规范对平面内 外的SIF取值不同 电力取相同的sif 2020 2 19 BasicStressTheory 基本应力 CodeStress规范应力 Markl s试验和结果Aload intheplane ofthefittingcauses in plane bending平面内Aload outoftheplane ofthefittingcauses out of plane bending平面外 2020 2 19 BasicStressTheory 基本应力 CodeStress规范应力 Markl s试验和结果规范上的附注十分重要PetroChemcodesmodifySIF andflexibilityfactor basedonpressurestiffeninginanote石化规范规定压力硬化影响 和柔性系数应力算式变化如下S F A Pd 4t iM z应力增大系数不能小于 2020 2 19 BasicStressTheory Basisfor CodeStressEquations Markl s试验和结果TheSIFisa fudge factorSIF是个近似的参数TheSIFattemptstoincreasethebendingstresscomputedatthenodepoint tomatchtheactualhigherstressduetothestressconcentrationcausedbythefitting 引入SIF在于改变特殊管件应力集中 让他们的应力根实际大小更接近 Marklonlytested4x4Stdfittings 但Markl仅测试了 AdditionalworkisstillbeingdonetodayinthefieldofSIFs Resultsarepublishedin PVP WRC JournalofPressureVesselTechnology 其余的工作人们仍然在继续进行 2020 2 19 BasicStressTheory 规范效验的工况 两种失效 Primaryfailure一次失效Secondaryfailure二次失效 AthirdfailuremodeaddressedisOccasional whichissimilartoPrimary 2020 2 19 BasicStressTheory 规范效验的工况 PrimaryFailureCase一次失效力的作用ForceDriven非自限性NotSelf Limiting重量 压力 集中力Weight Pressure ConcentratedForces 2020 2 19 BasicStressTheory 规范效验的工况 PrimaryFailureCase一次失效力的作用ForceDriven非自限性NotSelf Limiting重量 压力 集中力 Weight Pressure ConcentratedForces 2020 2 19 BasicStressTheory 规范效验的工况 SecondaryFailureCase二次失效位移作用DisplacementDriven自限性IsSelf Limiting温度 位移和其他变化载荷引起的Temperature Displacement plusothervaryingloads i e weight 2020 2 19 BasicStressTheory 规范效验的工况 1 W T1 P1 OPE 2 W P1 SUS 3 DS1 DS2 EXP Operatingcase usedfor 热态restraint equipmentloads推力和弯矩maximumdisplacements最大位移computationofEXPcase计算二次应力SustainedcaseforPRIMARYloadsandstresscompliance计算一次应力Expansioncasefor extremedisplacementstressrange 膨胀工况 计算二次应力displacementsforcase3aredisplacementsfromcase1minusdisplacementsfromcase2 2020 2 19 BasicStressTheory 规范效验的工况 膨胀工况的解释ExpansionCaseExplainedWhatdoes DS1 DS2 EXP mean Isaloadcasewith T1 EXP thesamething 2020 2 19 BasicStressTheory LoadCasesforCodeCompliance 膨胀工况的解释ExpansionCaseExplainedThecodestatesthattheexpansionstressesaretobecomputedfromthe extremedisplacementstressrange Theseareallveryimportantwords Considertheirmeaning EXTREME极端 Inthissenseitmeansthemost orthelargest RANGE范围 Typicallyadifference Whatdifference Thedifferencebetweentheextremes Whatextremes DISPLACEMENT位移 Thisdefineswhatextremestotakethedifferenceof STRESS应力 Whatweareeventuallyafter 2020 2 19 BasicStressTheory LoadCasesforCodeCompliance 膨胀工况的解释ExpansionCaseExplainedPuttingeverythingbacktogether wearetoldtocomputestressesfromtheextremedisplacementrange Howcanwedothis 计算最大位移范围的应力Considertheequationbeingsolved K x f Inthisequation weknow K and f andwearesolvingfor x thedisplacementvector InCAESARII whenwesetupanexpansioncase wedefineitas DS1 DS2 wherethe 1 and 2 refertothedisplacementvector x ofloadcases1and2respectively 2020 2 19 BasicStressTheory LoadCasesforCodeCompliance 膨胀工况的解释ExpansionCaseExplained Obviouslytheloadcasenumbersaresubjecttochangeonajobbyjobbasis Whatdoyougetwhenyoutake DS1 DS2 Well x1 x2 yields x apseudodisplacementvector x isnotarealsetofdisplacementsthatyoucangooutandmeasurewitharuler ratheritisthedifferencebetweentwopositionsofthepipe Oncewehave x wecanusethesameroutinesusedintheOPEorSUScasestocomputeelementforces andfinallyelementstresses 2020 2 19 BasicStressTheory LoadCasesforCodeCompliance 膨胀工况的解释ExpansionCaseExplainedHowever theseelementforcesarealsopseudoforces i ethedifferenceinforcesbetweentwopositionsofthepipe 力的大小是两个工况力的差值Similarly thestressescomputedarenotrealstresses butstressdifferences 应力不是真实应力 是应力的差值Thisisexactlywhatthecodewants thestressdifference whichwascomputedfromadisplacementrange 二次应力是位移变化量导致的Astowhetherornotthisstressdifferenceistheextreme wellthatdependsonthejob 2020 2 19 BasicStressTheory LoadCasesforCodeCompliance 膨胀工况的解释ExpansionCaseExplainedDS1 DS2和T1 一样吗 有可能 如果是线性系统 答案是一样的 如果是非线性系统 如你有 Ys orgaps orfriction 答案是不一样的 原因是两个工况应用 K x f Thereasonforthiscanbefoundbyexaminingtheequation K x f forthetwodifferentmethods 2020 2 19 BasicStressTheory LoadCasesforCodeCompliance ExpansionCaseExplainedForthisdiscussion rearrangetheequationto x f K whereweknowwedon treallydivideby K wemultiplybyitsinverse OPE xope fope Kope W T1 P1 Kope SUS xsus fsus Ksus W P1 Ksus EXP xexp xope xsus W T1 P1 Kope W P1 Ksus Canwesimplifytheaboveequationasfollows EXP xexp W T1 P1 K W P1 K 2020 2 19 BasicStressTheory LoadCasesforCodeCompliance 膨胀工况解释ExpansionCaseExplainedCanwesimplifytheaboveequationasfollows EXP xexp W T1 P1 K W P1 K Cancelingliketerms theonesinred yields xexp T1 K 问题在于 Kope 和 Ksus 是否相等 线性系统相等 非线性系统不相等 2020 2 19 BasicStressTheory LoadCasesforCodeCompliance 膨胀工况解释ExpansionCaseExplained如果一个系统有两个操作温度 Anotherproofthatthe DS1 DS2 methodisthecorrectwaytogoistoconsiderajobwithtwooperatingtemperatures oneaboveambientandonebelowambient 如T1 300 andT2 50 CAESARII软件自动建立如下工况 1 W T1 P1 OPE 2 W T2 P1 OPE 3 W P1 SUS 4 DS1 DS3 EXP 5 DS2 DS3 EXP 2020 2 19 BasicStressTheory LoadCasesforCodeCompliance 膨胀工况解释ExpansionCaseExplained上述工况正确 但没能说明规范要求的最大应力范围因为CII并不能判断荷载所代表的具体含义为满足规范的要求 用户必须自己定义 6 DS1 DS2 EXP 这个工况是最大位移膨胀应力 正是规范所要求的 您根本不能考虑使用T1来计算膨胀应力 2020 2 19 BasicStressTheory LoadCasesforCodeCompliance ExpansionCaseExplained膨胀工况的解释Tosummarize 概括如下Wetakethedifferencebetweentwoloadcasestodetermineadisplacementrange 两个工况确定位移范围Fromthisrangewecomputeaforcerangeandthenastressrange 由此我们确定力的范围和应力范围Thecoderequirestheextremedisplacementstressrange 规范要求极端的应力范围Theuseronlyhastoworryaboutwhetherornotthe extreme casehasbeenaddressed 用户仅考虑最大应力范围即可 2020 2 19 BasicStressTheory LinearvsNon Linear线性和非线性 Terminologyappliestoboundaryconditions 边界条件的类型Recalltheequationbeingsolved K x f Thisistheequationofaspring Thepipingsystemboundaryconditions i e therestraints arerepresentedasstiffnesses orsprings 管道边界条件代表刚度或弹簧Morecomplexboundaryconditionscanbedefined invalidatingthe linearspring assumption 2020 2 19 BasicStressTheory LinearvsNon Linear线性和非线性 线性约束boundaryconditionisadoubleactingrestraint suchasa Y support 一种是上下约束Anotherexampleofalinearboundaryconditionisaspringhanger 一种是弹簧Theforceversusdisplacementcurvefortheserestraintsisastraightline 力和位移是线性关系Thereforetheserestraintsarelinear 约束是线性的Theslopeofthelineisthestiffness 斜率是刚度 2020 2 19 BasicStressTheory LinearvsNon Linear线性和非线性 非线性约束A Y supportisanon linearsupport 支架Itsforcevsdisplacementcurveisnotastraightline 力和位移不是直线关系Stiffnessonlyexistsfornegativedisplacements 向下的位移是刚度是存在的Forpositivedisplacements thestiffnessiszero 向上的位移 刚度变为 2020 2 19 BasicStressTheory LinearvsNon Linear线性和非线性 A gap isalsoanon linearsupport 间隙的引进Theforcevsdisplacementcurveisnotastraightline 力和位移不是线性关系Thereisnostiffnessinthegap 间隙部分没有刚度 2020 2 19 BasicStressTheory LinearvsNon Linear线性和非线性 Frictionmakesarestraintnon linear摩擦让约束非线性Largerotationrodsarealsonon linearrestraints大的转动吊杆让约束非线性Non linearrestraintsinajobmeanthat Kope isnotequalto Ksus 非线性后 热态管道刚度和冷态刚度不一致 EXP and OCC loadcasesmustbeconstructedusingthedifferencebetweentwootherloadcasestoaccountfornon linearrestraints 2020 2 19 BasicStressTheory 偶然工况的建立 Occasionalloadsareconsidered primary sincetheyareforcedriven 偶然荷载是主要载荷 力引起的 Occasionalloadsoccurinfrequently 不经常发生Thecodesemployan allowableincrease factorbasedonthefrequencyofoccurrenceinthedeterminationoftheallowable i e k Sh 基于发生的频率 确定 值的大小Examplesofoccasionalloadsarewindandearthquake 偶然载荷是风载荷和地震载荷 2020 2 19 BasicStressTheory 偶然工况的建立 ThecodeequationfortheOCCasionalloadcaseis MA Z MB Z kShHere MAisthemomenttermfromtheSUStainedloads 冷态荷载引发力矩andMBisthemomentfromtheOCCasionalloads 偶然荷载引发力矩ThisequationstatesthattheOCCasionalcaseisthesumoftheSUStainedstressesandtheOCCasionalstresses 偶然工况是冷态和偶然的叠加Sowecan trunaloadcasewithjusta WIND loadandsatisfythiscoderequirement Whatabout W P1 WIND asaloadcase 2020 2 19 BasicStressTheory OccasionalLoadCaseSetup The W P1 WIND casewillworkfor linear systemsonly For non linear systems thisisnotsufficient forthesamereason T1 isnotsufficientfortheEXPansionloadcase ThebestwaytosetupOCCasionalloadcasesis 1 W P1 T1 OPE 2 W P1 T1 WIND OPE 3 W P1 SUS 4 DS1 DS3 EXP 5 DS2 DS1 OPE 6 ST5 ST3 OCC 2020 2 19 BasicStressTheory OccasionalLoadCaseSetup 1 W P1 T1 OPE 2 W P1 T1 WIND OPE 3 W P1 SUS 4 DS1 DS3 EXP 5 DS2 DS1 OPE 6 ST5 ST3 OCC ThisisthenormalOPEratingcaseThisisacombinedOPEratingcasewhichincludestheOCCloadsThisisthestandardSUStainedcaseThisisthestandardEXPansioncaseThisdifferenceyieldstheeffectsoftheOCCasionalloadonthesystem Thisisnotacodecase onlyaconstructioncase therefore OPE Thishandlesnon linearities ThisisourOCCasionalcodecompliancecase stressesfromPrimaryplusOccasionalloads 2020 2 19 BasicStressTheory 工况的定义和维护 CAESARIIwillrecommendloadcasesfor new jobs By new jobs wemeanjobsthatdonothavea J file For old jobs havinga J file CAESARIIreadsinthedefinedloadcasesandpresentsthemtotheuser Theloadcaseeditingscreenisshownattheright 2020 2 19 BasicStressTheory 工况的定义和维护 Onthisdialog availableloadtypesarelistedintheupperleftlistbox 载荷类型Availableloadcasetypesarelistedinthelowerleftlistbox 工况类型Loadcases recommendedorpreviouslydefined areshowninthegridattheright 推荐生成的工况Recommendedloadcasescanalwaysbeobtainedbyclickingonthe Recommend button Theanalysiscommencesbyclickingon therunningman 2020 2 19 BasicStressTheory LoadCaseGeneration Maintenance Sayfora new job theloadcasesattherightarerecommended Sayyouacceptandruntheseloadcases Uponreviewingtheoutputyoudiscoverthatpre defineddisplacementsatnode5wereomitted Youreturntoinput addthedisplacements andstarttheStaticAnalysisprocessoragain 2020 2 19 BasicStressTheory LoadCaseGeneration Maintenance CAESARIIreadstheseexistingloadcasesandpresentsthem Whatwillyourresultsbeifyouruntheseloadcases Exactlythesameasbefore becausetheseloadcasesdon tincludethepredefineddisplacements Youmustmanuallyadd D1 totheOPEloadcase oraskCAESARIItore recommendtheloadcases 2020 2 19 BasicStressTheory LoadCaseGeneration Maintenance Noticetheloadtypelistintheupperleftcontains D1 now Thecorrectedloadcasesareshownattheright 2020 2 19 BasicStressTheory LoadCaseGeneration Maintenance Noticetheloadtypelistintheupperleftcontains D1 now Thecorrectedloadcasesareshownattheright 2020 2 19 BasicStressTheory LoadCaseGeneration Maintenance Noticetheloadtypelistintheupperleftcontains D1 now Thecorrectedloadcasesareshownattheright Anytimeyouaddorremoveacompleteloadtype theloadcasesareinsufficient Ifyouaddeddisplacementstonode110 wouldtheloadcasesbesufficient 2020 2 19 BasicStressTheory 确保您分析对象的正确性 RememberCAESARIIisafiniteelementprogram 有限元RememberCAESARIIusesa3Dbeamelement 3D梁单元Rememberyoumusthaveequilibrium 保持平衡Resultantloadsshouldequalappliedloads作用力等于反作用力Gravity weightonly loadcaseshouldequaltheweightofthesystem重力等于整个系统的总重量OtherbasicchecksVerifynodal3Dcoordinates尺寸输入是否正确Checkforextremedisplacementsand orloads最大位移和推力 seehandout 2020 2 19 BasicStressTheory ProblemSolving问题的处理 Whatdoyoudowhenyoudon tliketheresults Recalltheequationbeingsolved K x f wherewesolvefor x thedisplacementsFromthesedisplacements wecomputeelementforces momentsFromtheseforces moments theCodeequationsareappliedandwecomputestresses 2020 2 19 BasicStressTheory ProblemSolving Whatdoyoudowhenyoudon tliketheresults Soifyouhaveastressproblem itcanonlybecausedbytwothings ACoderelatedissue SIFs codeequation etc Extremeforcesand ormomentsIfyouhaveaforce momentproblem theycanbecausedbyonlytwothings ImproperelementcharacteristicsExtremedisplacements 2020 2 19 BasicStressTheory ProblemSolving Whatdoyoudowhenyoudon tliketheresults Ifyouhaveadisplacementproblem itcanonlybecausedbytwothings Improperinput density elasticmodulus appliedloads ImproperboundaryconditionsDon tforgettocheckandrechecktheinput Rememberthatin3Dsystems aloadinonelocationcancausepivotingsomewhereelsedownstream resultinginexcessiveforcesandmoments Trytoisolatetheloadcausingtheproblem andtraceitsorigin 2020 2 19 BasicStressTheory ProblemSolving 设计和分析过程DesignbyAnalysis TheDesignCycle收集数据Gatherallthedata withassumptions建立分析模型和工况Generatethemodelandloadsets分析计算Performtheanalysis检查结果Checktheresultsandassumptions诊断问题Diagnoseanyproblems调整 改进和精细模