搜索
RheologyandApplication⌕বᄺǃ⌕বҾঞ݊ᑨ⫼㕢TAҾ఼݀ৌᴼ㚰呄SimonYangⷨおᴤ᭭ⱘ⌕ࡼϢবᔶNonlinearFlowBehavior䴲㒓ᗻ⌕ࡼ㸠Ў•Pseudo-plasticElasticandviscousdeformationsᔍᗻ㉬ᗻবᔶ㾺ᯊ䯈ⷁ[1s]䭓㾺ᯊ䯈[1hour]•ᔍᗻ•㉬ᗻ•ᯊ䯈ձᄬᗻLinear&Non-linearBehavior㒓ᗻ䴲㒓ᗻ㸠Ў•Linearflowregime㒓ᗻ⌕ࡼ•Nonlinearbehavior䴲㒓ᗻ㸠Ў•StructurebreakingNonlinearFlowBehavior䴲㒓ᗻ⌕ࡼ㸠Ў•Flowinducedstructure⌕ࡼ䇅থ㒧ᵘ•Lowviscosityatrest䴭㕂ᯊԢ㉬ᑺFlowandviscometry⌕ࡼϢ㉬ᑺ䅵Flow–Viscometry⌕ࡼˉ㉬ᑺ䅵Singlepointmeasurementoftheviscosity㉬ᑺⱘऩ⚍⌟䆩㉬ᑺⱘऩ⚍⌟䆩K=V/J.ᮑࡴ䗳ᑺ⌟䞣ᑨTimestressrateVTypicalViscosityValues(Pas)ൟⱘ㉬ᑺؐ(Pas)•AsphaltBinder≹䴦⏋ড়᭭--•PolymerMelt㘮ড়⠽❨ԧ---•Molasses㊪⌚-----•LiquidHoney㳖㳰----------•Glycerol⫬⊍-----------•OliveOil‘⊍---------•Water∈-------------•Airぎ⇨------------100,0001,0001001010.010.0010.00001䳔㽕ᇍ᭄തᷛMulti-stepflow–Viscometryℹ⌕ࡼˉ㉬ᑺ⊩stressrateTimeV J .K J =V J /J...Multi-pointmeasurementoftheviscosity.V(J)=flowcurveK(J)=viscositycurve..TypesofFlowcurves⌕ࡼ᳆㒓ⱘߚ㉏ShearStress,VNewtonianxShearRate,JBinghamPlastic(shear-thinningw/yieldstress)ShearThickening(Dilatent)VyShearThinning(Pseudoplastic)Bingham(Newtonianw/yieldstress)Viscosityandflowcurvemodels㉬ᑺ⌕ࡼ᳆㒓ൟVKJVJVJVVKJVVKJVVJ !xxxxxxKKKnnypcynnn()()11120121212SummaryofViscosityModelsNewtonianPowerlaw(Pseudoplastic)Powerlaw(Dilatant)BinghamCassonHerschel-BulkleyThixotropicloop㾺ব⦃ShearrampupanddownorthixotropicloopThestressrepresentstheinstantaneousresponsetotheappliedrate.Ifthematerialistimedependent,theupanddownstressrateTimeV J .updownK J =V J /J...Thixotropicloop㾺ব⦃0100200300400500020406080100Thixotropicloopfor3Mayonnaiseemulsions.sampleAupsampleAdownsampleBupsampleBdownsampleCupsampleCdownStressV[Pa]RateJ[1/s]ThixotropicmaterialUpanddownrampsdonotsuperposeAreaunderthecurveisameasureofthixotropyStressrampinstresscontrolledmodeᑨᠿᦣStressrampThestressisincreasefromzerotoafinitevalueandthedeformationismeasuredasafunctionoftime.AninstantaneousviscositycanbecalculatedfromstressdeformationTimeJ t K V =V/J V .Yieldstressinastressrampሜ᳡ᑨ05010015020011010010000.00.51.01.52.02.53.03.54.0㪿[Pas]YieldstressofacosmeticlotionYieldstess(atmaximum)=5.4PaViscosityK[Pas]Stress[Pa]StrainStrain(x10-6)ThemaximumviscositymethodismorerepresentativeandreproduciblethenthestraintangentmethodRelaxationandoscillationᵒᓯࡼᗕᤃ㤵⌟䆩Siliconeputtytest㉬ᔍᗻᴤ᭭⌟䆩shortlongWhetherthesiliconeputtybehavesviscousorelasticdependsonthetimeRelaxationtimeᵒᓯᯊ䯈JKt=0timestressJ=Jsp+Jdpconstant!V(t)=Voexp{-t/W}withtherelaxationtime/GW=KG(t)=Goexp{-t/W}DynamicMechanicalAnalysisࡼᗕᄺߚᵤtimetPeriodTForceG(t)=Goexp{-t/W}G*(Z)=Go1+Z2W2Z=1/2ST=1/tZWPhaseangleⳌԡ㾦•ThemeasuredshiftbetweentheinputwaveandtheoutputwaveiscalledPhaseangleG•TheratiobetweenstressamplitudeandstrainamplitudeistheComplexmodulusG*Stimulus(stressorstrain)Response(strainorstress)-1.501.506.3Anglephaseangle,GViscoelasticParameters㉬ᔍᗻখ᭄G*=G’+iG”G”/G’=tanG•ThemodulusmeasuredinadynamicexperimentisreferredtoasthecomplexmodulusG*•Thecomplexmoduluscanbeseparatedintotwocomponents:oAnelasticcomponentinphasewiththestrain.G'=G*cosGG'isthedegreetowhichmaterialbehaveslikeanelasticsolidandstoresenergy.oAviscousmodulusinphasewiththestrainrate.G=G*sinGGisthedegreetowhichmaterialbehaveslikeanidealliquidanddissipatesenergy.DynamicMechanicalBehaviorࡼᗕᄺ㸠Ў10-310-210-110010110210-1100101102103104105106103104105G‘‘=ZK|K*|=KDe=0Liquid10-310-210-110010110210-1100101102103104105106103104105G‘=G|K*|=G/ZDe=fSolid10-310-210-110010110210-1100101102103104105106103104105G“G‘|K*|De1De=1De1¾IfthematerialtimeisshorterthantheobservationtimeDe1(fluidbehavior)tWtobs=De¾IfthematerialtimeislongerthantheobservationtimeDe1(solidbehavior)Nonlinearresponse䴲㒓ᗻડᑨNonlinearbehaviour䴲㒓ᗻ㸠ЎStructureproperties:Ifastructureisstrainedtoitslimitsitwilleventuallybreak.Beforebreakingthestructurewillbehaveverynon-linear.Duringthisphase,higherharmonicsbecomeimportantJJc10-110010110%210310-11001010.01.0Jc=TanGG‘G“RheologicalCharacterization⌕বᗻ㛑㸼ᕕRheologyRheologydynamicoscillationdynamicoscillationG‘undG‘‘=f()linearregimeJsteadyshearingsteadyshearingKundN1=f()Jnon-linearregime,time-independentelongationalflowelongationalflowlinearandnon-linearregimeH0=f()HFT-RheologyFT-Rheology¾FTnon-linearregime,time-dependent JZZfI3I11Summaryᇣ㒧•Flowandviscometry–Pseudoplastic;Thixotropic;Yield;Dilatant•Relaxationtimeandoscillation–Conceptoftherelaxationtime•Separationofenergystorageanddissipation•Mechanicalspectroscopy–MaterialtimeandObservationtime–Deborah•Non-linearbehaviorDefinitionofRheology•Rheologyisthescienceofflowanddeformationofmatter•Weuserheologytostudyfundamentalrelations,calledconstitutiverelations,betweenforcesanddeformationsinmaterialsFlowandDeformationParameters:ShearStress,ShearStrain,&ShearRateÂStress:Forceperunitarea.ËSymbol:VUnits:Pa(SI)ordyn/cm²(cgs)ÂShearStrain:Relativedeformationinshear.ËSymbol:JUnits:NoneÂShearRate:Changeofshearstrainperunittime.ËSymbol:JUnits:s-1ClassicalExtremes:ElasticityÂ1678:RobertHookedevelopshis“TrueTheoryofElasticity”Ë“Thepowerofanyspringisinthesameproportionwiththetensiontherof.”ËHooke’sLaw:V=GJor(stress=Gxstrain)whereGistheRIGIDIT