典型屈服应力流体的非线性流变行为以与局部流动行为的分析

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1、上海交通大学硕士学位论文然后着重考察了两种屈服应力流体在控应力模式的大振幅振荡剪切(Largeamplitudeoscillatoryshear,LAOS)流场下的非线性流变行为的差异。比较了这两种流体表观的动态模量和傅里叶变换(Fouriertransform)后高次倍频的参数的差异，发现表观的动态模量不足以描述两种屈服应力流体在LAOS下屈服转变的历程和机理的区别，而傅里叶变换流变学的方法得到的高次倍频的参数可以很清晰地界定两种样品在LAOS下的非线性行为和屈服转变行为的差异。此外提出了利用应变分解法(Straindecomposition)处理LAOS下得到的应变响应数据，定义了非线性模

2、量和非线性粘度参数来描述流体的特性。发现应变分解发得到的参数更能反映屈服应力流体的内部结构和流动状态信息，可以界定振荡流场下两种屈服应力流体不同的老化(Aging)和剪切回复(ShearRejuvenation)的机理。为了考察震荡剪切流场下，触变性的屈服应力流体和简单屈服应力流体的局部流动行为宏观的非线性流变行为的影响，本文还利用粒子示踪测速（PTV）的方法来对两种流体的局部流动行为进行了初步的研究。关键词：大振幅振荡剪切傅里叶变换流变学屈服应力触变性应变分解ii万方数据上海交通大学硕士学位论文NonlinearRheologyandLocalFlowBehaviorofTypicalYie

3、ldStressFluidsABSTRACTYieldstressfluids(YSF)areverycommonineverydaylife.Theyarebroadlydefinedasmaterialsthatbehavelikesolidsbelowacriticalappliedstressandflowlikesimpleliquidsbeyondacriticalstress.Forhandlingandusingthesefluids,itiscrucialtoknowthesolid-liquidtransition,thixotropyandsomeothercomplex

4、rheologicalbehaviorofthesefluids.Inthiswork,therheologicalbehaviorofathixotropicyieldstressfluid(3.0wt%Laponitegel)andasimpleyieldstressfluid(0.25wt%Carbopolgel)wasinvestigatedandcompared.Thenonlinearbehaviorofmanykindsofsimpleandthixotropicyieldstressfluidindifferentrheologicaltestmodehavebeenwidel

5、ystudied,butpreviousresearchisnotsystematicenough.Inthiswork,theirdifferentresponsesinthixotropiclooptest,shearrateramp,shearstressramp,ceeptestandstart-upsheartestweresystematicallycompared,whichcanreflecttheirdifferentagingandshearrejuvenationmechanisms.Thenthenonlinearrheologicalbehavioroftheseto

6、wfluidsunderlargeamplitudeoscillatoryshear(Largeamplitudeoscillatoryshear,LAOS)wasinvestigated.Itwasfoundthattheapparentdynamicmodulusiii万方数据上海交通大学硕士学位论文isinsufficienttodescribethedifferenceofthetransformationprocessandthemechanismofsolid-liquidtransition,whiletherelativeintensityandrelativephaseang

7、leofhigherharmonicsobtainedbytheFouriertransformcanclearlydefinethedifferencesintransitionbehaviorofthesetwofluidsunderLAOS.Inaddition,anewframeworkcalledStrainDecompositionissuggestedinthisworktoacco