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A Nonlinear Elastic Model for Shear Thickening of

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ANonlinearElasticModelforShearThickeningofSuspensionsFlocculatedbyReversibleBridgingYasufumiOtsuboDepartmentofUrbanEnvironmentSystems,FacultyofEngineering,ChibaUniversity,Yayoi-cho1-33,Inage-ku,Chiba-shi263-8522,JapanReceivedAugust31,1998.InFinalForm:December22,1998TheflowofsuspensionsflocculatedbyreversiblebridgingofpolymerwithweakaffinityfortheparticlesurfaceisNewtonianinthelimitofzeroshearrate,shear-thickeningatmoderateshearrates,andplasticwithaconstantstressindependentofshearrateinhighshearfields.TheNewtonianflowimpliesthatthepolymerbridgesareconstantlyformingandbreakinginaquiescentstate.Thestressaftercessationofsteadyshearexponentiallyrelaxesatlongtimes.Therelaxationtimeisnotaffectedbytheshearrate.Thestrain-dependentcurveofstoragemodulusataconstantfrequencyshowsarapidincreasewhenthestrainisincreasedaboveacriticallevel.Thecriticalstrainisindependentoffrequency.Therefore,theshearthickeningmaybeprimarilyattributedtotheelasticeffectofextendedbridges.Sincethepolymercoilsareforcedtodesorbatsomedegreeofextension,thesuspensionsbecomenearlyplasticathighshearrates.Theintrinsicmechanismofshear-thickeningflowforsuspensionsflocculatedbyreversiblepolymerbridgingisthenonlinearelasticityduetoentropyeffectofextendedbridgesandforceddesorptionduetohydrodynamiceffect.Bycombinationofthenonlinearelasticityandsinglerelaxationtime,arheologicalmodelisderivedtoquantitativelyexpresstheshear-thickeningflow.Themodelpredictionandexperimentalresultsareingoodagreement.IntroductionThemostimportantfeatureofpolymeradsorptionisthatnotallthesegmentsofachainareincontactwiththesurface.Theconformationofadsorbedpolymerchainisexplainedintermsoftrainsofsegmentswhichattachtothesurface,loopsofsegmentswhichextendintosolutionbetweentrains,andtailswhicharethedanglingendsofchains.1-3Thetrainandloopsegmentsreversiblyinter-change.However,thepolymerchainattachestothesurfaceatmanypoints.Themobilityofapolymerchainismarkedlyreducedbyadsorption,andthemovementofthewholepolymerisveryslow.Inpractice,polymeradsorptionisessentiallyirreversibleinmanycasesbecausethepolymermaynotbeabletodesorbsimulta-neouslyfromallsites.Whenthepolymerchainsdonothaveverystrongaffinityforthesurface,thefractionofloopsincreasesattheexpenseoftrains.Thechainhasalowerfractionofadsorbedsegmentsandmoreconforma-tionalfreedom.Theirreversibilityofstrongadsorptionarisesfrommultipointattachmenttothesolidsurface.Therefore,thedecreaseinthefractionoftrainsduetoweakadsorptioncausestheadsorption-desorptionproc-esstooccurreversiblybyBrownianmotion.Incolloidalsuspensions,thesegmentsextendingfromoneparticlecanadsorbontoanotherparticleandbindthemtogether.Theeffectisreferredtoaspolymerbridging.4,5Flocculationofcolloidalsuspensionsbythebridgingmechanismtakesplaceunderconditionswherethepolymerchainislongenoughandthesurfacecoveragebyadsorbedpolymerislow.Whenthereversibleadsorp-tionispresentduetopolymerchainswithweakaffinityfortheparticlesurface,thepolymerbridgesareconstantlyforming,breaking,andre-forminginzeroshearfields.Incontrasttoordinaryflocculatedsuspensionswhoseflowprofileisplasticatverylowshearratesorshearthinningoverawiderangeofshearrates,thesuspensionsfloc-culatedbyreversiblebridgingareNewtonianinthelimitofzeroshearrate.Atshearrateswherethetimescaleofcoilextensionismuchlongerthanthatofdesorption,thepolymercoilshaveanequilibriumconformationun-changedfromzeroshearstate.Thestrikingcontractionofchainonthesolidsurfaceisnotobservedinthecaseofweakadsorption.Sincetwoparticlescanbebridgedbyaflexiblepolymercoil,elasticanddeformableflocsarebuiltupinsuspensionsflocculatedbyreversiblebridging.Inshearfields,thebridgesaresubjectedtorapidextension.Theextendedbridgescanleadtohighresistancetoflowduetotherestoringforces.Asaresult,theflowbecomesshearthickeningatintermediateshearrates.6-8Therestoringforcesproducedbyrapidextensionofflexiblebridgesareresponsiblefortheshearthickening.Thestrainenergystoredinextendedbridgesisreleasedbytraindesorptioninshearfiled.Hence,theonsetofshearthickeningcanbeanalyzedinconnectionwiththisrelaxationprocessofpolymerchains.Thedominantvariablesaffectingtheshearthickeningarethelifetimeandextensibilityofbridgeswhicharecontrolledbychangingtheadsorptionaffinityofpolymers.Inthepresentpaper,shear-thickeningbehaviorisstudiedforsuspensionsflocculatedbyreversiblebridgingofpolymercoilswhosesizeiscomparabletotheparticlediameter.Toquantitativelydescribetheresults,arheo-logicalmodelisdeveloped.Thecomparisonofexperimentalresultsandmodelpredictionwillbediscussedinrelationtothenonlinearelasticityofbridges.MaterialsandMethodsMaterials.Thesuspensionswerecomposedofstyrene-methylacrylatecopolymerparticles,poly(acrylicacid)(PAA),surfactant,andwater.ThepHvaluewasadjustedwithhydrochloricacidto(1)Scheutjens,J.M.H.M.;Fleer,G.J.J.Phys.Chem.1979,83,1619.(2)Scheutjens,J.M.H.M.;Fleer,G.J.J.Phys.Chem.1980,84,179.(3)Ploehn,H.J.;Russel,W.B.Adv.Chem.Eng.1990,15,137.(4)Iler,R.K.J.ColloidInterfaceSci.1971,37,364.(5)Fleer,G.J.;Lyklema,J.J.ColloidInterfaceSci.1974,46,1.(6)Otsubo,Y.Langmuir1992,8,2336.(7)Otsubo,Y.J.Rheol.1993,37,799.(8)Otsubo,Y.J.ColloidInterfaceSci.1994,163,507.1960Langmuir1999,15,1960-1965

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框架结构外文文献

框架结构外文文献

SeismicCollapseSafetyofReinforcedConcreteBuildings.II:ComparativeAssessmentofNonductileandDuctileMomentFramesAbbieB.Liel,M.ASCE1;CurtB.Haselton,M.ASCE2;andGregoryG.Deierlein,F.ASCE3Abstract:Thisstudyisthesecondoftwocompanionpaperstoexaminetheseismiccollapsesafetyofreinforcedconcreteframebuildings,andexaminesnonductilemomentframesthatarerepresentativeofthosebuiltbeforethemid-1970sinCalifornia.Theprobabilisticassessmentreliesonnonlineardynamicsimulationofstructuralresponsetocalculatethecollapserisk,accountingforuncertaintiesinground-motioncharacteristicsandstructuralmodeling.TheevaluationconsidersasetofarchetypicalnonductileRCframestructuresofvaryingheightthataredesignedaccordingtotheseismicprovisionsofthe1967UniformBuildingCode.TheresultsindicatethatnonductileRCframestructureshaveameanannualfrequencyofcollapserangingfrom5to14×10À3atatypicalhigh-seismicCaliforniasite,whichisapproximately40timeshigherthancorrespondingresultsformoderncode-conformingspecialRCmomentframes.Thesemetricsdemonstratetheeffectivenessofductiledetailingandcapacitydesignrequirements,whichhavebeenintroducedoverthepast30yearstoimprovethesafetyofRCbuildings.DataoncomparativesafetybetweennonductileandductileframesmayalsoinformthedevelopmentofpoliciesforappraisingandmitigatingseismiccollapseriskofexistingRCframebuildings.DOI:10.1061/(ASCE)ST.1943-541X.0000275.©2011AmericanSocietyofCivilEngineers.CEDatabasesubjectheadings:Structuralfailures;Earthquakeengineering;Structuralreliability;Reinforcedconcrete;Concretestructures;Seismiceffects;Frames.Authorkeywords:Collapse;Earthquakeengineering;Structuralreliability;Reinforcedconcretestructures;Buildings;Commercial;Seismiceffects.IntroductionReinforcedconcrete(RC)framestructuresconstructedinCalifor-niabeforethemid-1970slackimportantfeaturesofgoodseismicdesign,suchasstrongcolumnsandductiledetailingofreinforce-ment,makingthempotentiallyvulnerabletoearthquake-inducedcollapse.ThesenonductileRCframestructureshaveincurredsignificantearthquakedamageinthe1971SanFernando,1979ImperialValley,1987WhittierNarrows,and1994NorthridgeearthquakesinCalifornia,andmanyotherearthquakesworldwide.ThesefactorsraiseconcernsthatsomeofCalifornia’sapproxi-mately40,000nonductileRCstructuresmaypresentasignificanthazardtolifeandsafetyinfutureearthquakes.However,dataarelackingtogaugethesignificanceofthisrisk,inrelationtoeitherthebuildingpopulationatlargeortospecificbuildings.Thecollapseriskofanindividualbuildingdependsnotonlyonthebuildingcodeprovisionsemployedinitsoriginaldesign,butalsostructuralconfiguration,constructionquality,buildinglocation,andsite-spe-cificseismichazardinformation.Apartfromthechallengesofac-curatelyevaluatingthecollapseriskisthequestionofrisktoleranceandtheminimumlevelofsafetythatisappropriateforbuildings.Inthisregard,comparativeassessmentofbuildingsdesignedaccord-ingtooldversusmodernbuildingcodesprovidesameansofevalu-atingthelevelofacceptableriskimpliedbycurrentdesignpractice.Buildingcoderequirementsforseismicdesignanddetailingofreinforcedconcretehavechangedsignificantlysincethemid-1970s,inresponsetoobservedearthquakedamageandanin-creasedunderstandingoftheimportanceofductiledetailingofreinforcement.IncontrasttooldernonductileRCframes,moderncode-conformingspecialmomentframesforhigh-seismicregionsemployavarietyofcapacitydesignprovisionsthatpreventordelayunfavorablefailuremodessuchascolumnshearfailure,beam-columnjointfailure,andsoft-storymechanisms.Althoughthereisgeneralagreementthatthesechangestobuildingcoderequire-mentsareappropriate,thereislittledatatoquantifytheassociatedimprovementsinseismicsafety.Performance-basedearthquakeengineeringmethodsareappliedinthisstudytoassessthelikelihoodofearthquake-inducedcollapseinarchetypicalnonductileRCframestructures.Performance-basedearthquakeengineeringprovidesaprobabilisticframeworkforre-latingground-motionintensitytostructuralresponseandbuildingperformancethroughnonlineartime-historysimulation(Deierlein2004).TheevaluationofnonductileRCframestructuresisbasedonasetofarchetypicalstructuresdesignedaccordingtothepro-visionsofthe1967UniformBuildingCode(UBC)(ICBO1967).Thesearchetypestructuresarerepresentativeofregularwell-designedRCframestructuresconstructedinCaliforniabetweenapproximately1950and1975.Collapseispredictedthrough1AssistantProfessor,Dept.ofCivil,EnvironmentalandArchitecturalEngineering,Univ.ofColorado,Boulder,CO80309.E-mail:abbie.liel@2AssistantProfessor,Dept.ofCivilEngineering,CaliforniaStateUniv.,Chico,CA95929(correspondingauthor).E-mail:chaselton@3Professor,Dept.ofCivilandEnvironmentalEngineering,StanfordUniv.,Stanford,CA94305.Note.ThismanuscriptwassubmittedonJuly14,2009;approvedonJune30,2010;publishedonlineonJuly15,2010.DiscussionperiodopenuntilSeptember1,2011;separatediscussionsmustbesubmittedforindividualpapers.ThispaperispartoftheJournalofStructuralEngineer-ing,Vol.137,No.4,April1,2011.©ASCE,ISSN0733-9445/2011/4-492–502/$25.00.492/JOURNALOFSTRUCTURALENGINEERING©ASCE/APRIL2011J. Struct. Eng. 2011.137:492-502.Downloaded from by Sultan Qaboos University on 06/21/14. Copyright ASCE. For personal use only; all rights reserved.

非牛顿流体剪切变稀

非牛顿流体剪切变稀

非牛顿流体是指在剪切力作用下流动性质发生变化的流体。在非牛顿流体中，剪切应力与剪切速率之间的关系不符合牛顿流体的线性关系。非牛顿流体的剪切变稀是指在剪切力作用下流体流变性质发生从粘稠(高黏度)到稀薄(低黏度)的转变。这种流体的流动特性不仅在工程和科学领域中具有重要应用，还有许多生物、化学和地质体系中也存在。

下面是关于非牛顿流体剪切变稀的一些相关参考内容。

1. 剪切变稀现象的定义和描述：

Papanastasiou, T. C., “Yieldable Shear-Thinning Fluids: Rheology and

Extrudate Swell,” Journal of Rheology (1987): 这篇文章描述了剪切变稀现象的定义和描述，提出了一种描述剪切变稀流体流变性质的模型，并通过实验验证了该模型的有效性。

2. 剪切变稀机制的研究：

Hu, Y., et al., “Mechanism of Shear Thinning and Shear Thickening in

Non-Brownian Suspensions,” Physical Review E (2008): 这篇文章通过数值模拟和实验证明了非牛顿流体剪切变稀的机制与颗粒聚集和分散有关。文章详细解释了剪切变稀现象的微观机制，并提出了一种描述该现象的模型。

3. 剪切变稀流体的工业应用：

Boger, D. V., “Application of Non-Newtonian Flow to the Extrusion of

Polymeric Materials,” AIChE Journal (1985): 这篇文章介绍了剪切变稀流体在聚合物材料挤出过程中的工业应用。文章详细描述了剪切变稀流体的流变特性和挤出加工过程，并讨论了挤出过程中的流变力学行为和加工参数的影响。

4. 剪切变稀的生物学意义：

midas gts理论分析_1

midas gts理论分析_1

第一篇 MIDAS/GTS的分析功能

1 第一篇 MIDAS/GTS的分析功能

岩土分析(geotechnical analysis)与一般的结构分析(structural analysis)有较大差异。一般的结构分析注重荷载的不确定性，所以在分析时会加载各种荷载，然后对分析结果进行各种组合，最后取各组合中最不利的结果进行设计。岩土分析注重的是施工阶段和材料的不确定性，所以决定岩土的物理状态显得格外重要。在岩土分析中应尽量使用实体单元真实模拟围岩的状态、尽量接近地模拟岩土的非线性特点以及地基应力状态(自应力和构造应力)、并且尽量真实地模拟施工阶段开挖过程，这样才会得到比较真实的结果。

优秀的岩土分析程序应能真实地模拟现场条件和施工过程，并应为用户提供更多的材料模型和边界条件，让用户在做岩土分析时有更多的选择。

MIDAS/GTS不仅具有岩土分析所需的基本分析功能，并为用户提供了包含最新分析理论的强大的分析功能，是岩土和隧道分析与设计的最佳的解决方案之一。

MIDAS/GTS中提供的的分析功能如下：

A. 静力分析 (static analysis)

线弹性分析 (linear elastic analysis)

非线性弹性分析 (nonlinear elastic analysis)

弹性分析 (elastoplastic analysis)

B. 施工阶段分析 (construction staged analysis)

C. 渗流分析 (seepage analysis)

稳定流分析 (steady state seepage analysis)

非稳定流分析 (transient state seepage analysis)

D. 渗流-应力耦合分析 (seepage stress analysis)

第一篇 MIDAS/GTS的分析功能

2 E. 固结分析 (consolidation analysis)

非牛顿流体综述

非牛顿流体综述

1 非牛顿流体综述

非牛顿流体是指在受力作用下其流动性质不符合牛顿流体力学的一类流体。在非牛顿流体中，剪切速率和剪切应力之间的关系不是线性的，而是可以表现出更为复杂的行为。以下是非牛顿流体的一些常见类型和性质：

剪切稀释流体（Shear-Thinning Fluids）： 这是最常见的非牛顿流体类型。在剪切力作用下，粘度随剪切速率的增加而减小。常见的例子包括聚合物溶液、墨水和一些生物体液，如血液。

剪切增稠流体（Shear-Thickening Fluids）： 在这种情况下，粘度随剪切速率的增加而增加。这种非牛顿流体的典型例子是玉米淀粉和水的混合物，也被称为"奇异流体"，因为其行为相对罕见。

黏弹性流体（Viscoelastic Fluids）： 这种流体同时表现出粘性和弹性的特性。在受力后，它们可以恢复形状，但也具有一定的黏性。聚合物溶液和凝胶是黏弹性流体的例子。

粘塑性流体（Viscoplastic Fluids）： 这类流体在受到一定剪切力之前表现得像固体，而一旦超过某个剪切阈值，它们就开始流动。土壤、牙膏和墙漆都属于粘塑性流体。

液固两相流体（Fluid-Solid Transition）： 这是一种能够在液体和固体之间切换的流体，具有流变性质。它在无剪切力作用下表现为固体，在受到剪切力时表现为流体。

泡沫、乳液和胶体： 由于其中包含气体、液滴或颗粒，这些复杂的体系也常常表现出非牛顿性质。

非牛顿流体的研究和应用涉及到许多领域，包括食品工业、药物制造、油漆和涂料、生物医学、化学工程等。了解这些流体的行为对于设计和优化相应的工艺和产品具有重要意义。 2