简介:AnewmechanicsmodelbasedonPeierlsconceptispresentedinthispaper,whichcanclearlycharacterizetheintrinsicfeaturesnearatipofaninterfacialcrack.Thestressanddisplacementfieldsarecalculatedundergeneralcombinedten-sileandshearloadings.Theneartipstressfieldsshowsomeoscillatorybehaviorsbutwithoutanysingularityandthecrackfacesopencompletelywithoutanyoverlappingwhenremotetensileloadingiscomparablewithremoteshearloading.Afracturecriterionforpredictinginterfacetoughnesshasbeenalsoproposed,whichtakesintoaccountfortheshieldingeffectsofemitteddislocations.Thetheoreticaltoughnesscurvegivesexcellentprediction,ascomparedwiththeexistingexperimentdata.
简介:SomeofthemainprogressontheinvestigationofthemechanismofthewaveformationinexplosiveweldingattheInstituteofMechanicsissummarizedandotters’previousworksarere-viewed.OursystematicexperimentsandanalysisdonotsubstantiatethetheoryofwaveformationbasedonKarmanvortex-streetanalogyorHelmholtzinstability.Onthecontrary,theyshowthatmateri-alstrengthinsensitivetostrainrateplaysanimportantrole.Asimplehydro-plasticmodelispresentedtoexplainthemainfeaturesregardingtheinterracialwaveformationandtoestimatethemagnitudeofwavelength.Theresultisinbroadagreementwithexperiment.
简介:Wheninterfaciallayersareviewedasaseparatephase,theinterfacethicknessplaysanessentialroleinassessingphysico-mechanicalpropertiesofparticulatematerials.However,theinterfacethicknessfromsectionalanalysisisoftenoverestimated,duetotheirregularityofsurfacetexturesofgrainsinopaquematerialsthatgivesrisetothenormalofacross-sectionalplanenon-perpendiculartothesurfaceofgrains.Hence,thedeterminationoftheoverestimationdegreeisverycriticaltopreciselyobtaintheinterfacethickness.Thisarticledevelopsanumericalmodelfortheoverestimationdegreeoftheinterfacethicknessaroundanellipsoidalgrainwithanarbitraryaspectratio,byapplyinganaccuratesectionalanalysisalgorithm,andquantitativestereologyandgeometricalprobabilitytheories.Furthermore,onthebasisofthedevelopednumericalmodel,theinfluenceofellipsoidalparticleshapeontheoverestimationdegreeisquantitativelycharacterized.
简介:Interfacedislocationsmaydramaticallychangetheelectricproperties,suchaspolarization,ofthepiezoelectriccrystals.Inthispaper,westudythelinearinteractionsoftwointerfacedislocationloopswitharbitraryshapeingenerallyanisotropicpiezoelectricbi-crystals.Asimpleformulaforcalculatingtheinteractionenergyoftheinterfacedislocationloopsisderivedandgivenbyadoublelineintegralalongtwocloseddislocationcurves.Particularly,interactionsbetweentwostraightsegmentsoftheinterfacedislocationsaresolvedanalytically,whichcanbeappliedtoapproximateanycurvedloopsothatananalyticalsolutioncanbealsoachieved.Numericalresultsshowtheinfluenceofthebi-crystalinterfaceaswellasthematerialorientationontheinteractionofinterfacedislocationloops.
简介:Thermalcontactresistanceplaysaveryimportantroleinheattransferefficiencyandthermomechanicalcouplingresponsebetweentwomaterials,andacommonmethodtoreducethethermalcontactresistanceistofillasoftinterfacematerialbetweenthesetwomaterials.AtestingsystemofhightemperaturethermalcontactresistancebasedonINSTRON8874isestablishedinthepresentpaper,whichcanachieve600Cattheinterface.Basedonthissystem,thethermalcontactresistancebetweensuperalloyGH600ma...
简介:Theturbulencestructuresnearashearedair-waterinterfacewereexperimentallyinvestigatedwiththehydrogenbubblevisualizationtechnique.Sur-faceshearwasimposedbyanairflowoverthewaterflowwhichwaskeptfreefromsurfacewaves.Resultsshowthatthewindshearhasthemaininfluenceoncoher-entstructuresunderair-waterinterfaces.Low-andhigh-speedstreaksformintheregionclosetotheinterfaceasaresultoftheimposedshearstress.Whenacertainairflowvelocityisreached,'turbulentspots'appearrandomlyatlow-speedstreakswithsomecharacteristicsofhairpinvortices.Atevenhighershearrates,theflowneartheinterfaceisdominatedprimarilybyintermittentburstingevents.Thecoher-entstructuresobservednearshearedair-waterinterfacesshowqualitativesimilaritieswiththoseoccurringinnear-wallturbulence.However,afewdistinctivephenomenawerealsoobserved,includingthefluctuatingthicknessoftheinstantaneousboundarylayerandverticalvorticesinburstingprocesses,whichappeartobeassociatedwiththecharacteristicsofair-waterinterfaces.
简介:界面的脱臼可以有相应于的一个传播核心一弱砍接口的抵抗。在这份报纸,一个圆锥形的模型被建议在各向异性的bimaterials模仿界面的脱臼的传播核心。由Stroh形式主义和草地功能,有弹性的地的分析表达式为如此的脱臼被推出。作为一个例子拿Cu/Nbbimaterial,方法的精确性和效率被接口条件很好验证,这被表明,一个传播核心能极大地与紧缩的核心相比在界面的脱臼附近减少压力紧张,并且传播核心区域附近的有弹性的地与压缩核心显著地不同,当他们对是的一个地点不太敏感时,1.5预定核心宽度离开传播核心的中心。
简介:Shapememoryalloy(SMA)reinforcedsmartstructurecanbeusedtomakestructuralshapeandstrengthselfadaptedandstructuraldamageself-restrained.AlthoughSMAsmartstructureswithoutdamageswereextensivelystudied,researchesonSMAsmartstructureswithdamageshaverarelybeenreportedthusfar.Inthispaper,thermo-mechanicalbehaviorsofSMAfiberreinforcedsmartstructureswithdamagesareanalyzedthroughashearlagmodelandthevariationalprinciple.Mathematicalexpressionsofthemeso-displacementfieldandthestress-strainfieldofatypicalelementwithdamagesareobtained,andafailurecriterionforinterfacefailurebetweenSMAfibersandmatrixisestablished,whichisappliedtoanexample.ResultspresentedhereinmayprovideatheoreticalfoundationforfurtherstudiesonintegrityofSMAsmartstructures.
简介:Regardlessofallkindsofdifferentformulaeusedforthetraction-separationrelationshipincohesivezonemodeling,thepeaktractionσ_mandtheseparation-to-failureδ_0(orequivalentlythework-to-separationΓ)aretheprimaryparameterswhichcontroltheinterfacialfracturebehaviors.Experimentally,itishardtodeterminethosequantities,especiallyforδ_0,whichoccursinaverylocalizedregionwithpossiblycomplicatedgeometriesbymaterialfailure.BasedontheDugdalemodel,weshowthatthesepa...
简介:TheRichtmyer–Meshkovinstabilityofa‘V'shapedair/heliumgaseousinterfacesubjectedtoaweakshockwaveisexperimentallystudied.Asoapfilmtechniqueisadoptedtocreatea‘V'shapedinterfacewithaccurateinitialconditions.Fivekindsof‘V'shapedinterfaceswithdifferentvertexanglesareformedtohighlighttheeffectsofinitialconditionsontheflowcharacteristics.Theresultsshowthataspikeisgeneratedaftertheshockimpact,andgrowsconstantlywithtime.Asthevertexangleincreases,vorticesgeneratedontheinterfacebecomelessnoticeable,andthespikedevelopslesspronouncedly.Thelineargrowthrateofinterfacewidthaftercompressionphaseisestimatedbyalinearmodelandarevisedlinearmodel,andthelatterisproventobemoreeffectivefortheinterfacewithhighinitialamplitudes.Thelineargrowthrateofinterfacewidthis,forthefirsttimeinaheavy/lightinterfaceconfiguration,foundtobeanon-monotonousfunctionoftheinitialperturbationamplitude–wavelengthratio.
简介:Inthispaper,wecombinethedirect-forcingfictitiousdomain(DF/FD)methodandthesharpinterfacemethodtoresolvetheproblemofparticledielectrophoresisintwodimensions.TheflowfieldandthemotionofparticlesaresolvedwiththeDF/FDmethod,theelectricfieldissolvedwiththesharpinterfacemethod,andtheelectrostaticforceontheparticlesiscomputedusingtheMaxwellstresstensormethod.Theproposedmethodisvalidatedviathreeproblems:effectiveconductivityofparticlecompositebetweentwoplanarplates,celltrappinginachannel,andmotionofparticlesduetobothconventionalandtravelingwavedielectrophoreticforces.
简介:Thispaperstudiestheinterfacecuringstressesbetweenpolymethylmethacrylate(PMMA)andcompositebymeansofdigitalspecklecorrelationmethod(DSCM).AnewmethodbycombiningDSCMwiththemarkerpointsisdevelopedtomeasuretheinterfacecuringstresses,andthemeasurementprincipleisintroduced.TheinterfacecuringstressesbetweenPMMAandcompositewithdifferentcuringbondingconditionsaremeasuredandanalyzed,thisindicatesthattheresidualstressforfurnaceheatingandfurnacecooling...
简介:Foracompression-shearmixedmodeinterfacecrack,itisdifficulttosolvethestressandstrainfieldsconsideringthematerialviscosity,thecrack-tipsingularity,thefrictionaleffect,andthemixedloadinglevel.Inthispaper,amechanicalmodelofthedynamicpropagationinterfacecrackforthecompression-shearmixedmodeisproposedusinganelastic-viscoplasticconstitutivemodel.Thegoverningequationsofpropagationcrackinterfaceatthecrack-tiparegiven.Thenumericalanalysisisperformedfortheinterfacecrackofthecompression-shearmixedmodebyintroducingadisplacementfunctionandsomeboundaryconditions.Thedistributedregularitiesofstressfieldoftheinterfacecrack-tiparediscussedwithseveralspecialparameters.Thefinalresultsshowthattheviscosityeffectandthefrictionalcontacteffectonthecracksurfaceandthemixed-loadparameterareimportantfactorsinstudyingthemixedmodeinterfacecracktipfields.Thesefieldsarecontrolledbytheviscositycoefficient,theMachnumber,andthesingularityexponent.
简介:Acompositebeamissymmetricifboththematerialpropertyandsupportaresymmetricwithrespecttothemiddlepoint.Inordertostudythefreevibrationperformanceofthesymmetriccompositebeamswithdifferentcomplexnonsmooth/discontinuousinterfaces,wedevelopanR(x)-orthonormaltheory,whereR(x)isanintegrableflexuralrigidityfunction.TheR(x)-orthonormalbasesinthelinearspaceofboundaryfunctionsareconstructed,ofwhichthesecond-orderderivativesoftheboundaryfunctionsareaskedtobeorthonormalwithrespecttotheweightfunctionR(x).WhenthevibrationmodesofthesymmetriccompositebeamareexpressedintermsoftheR(x)-orthonormalbaseswecanderiveaneigenvalueproblemendowedwithaspecialstructureofthecoefficientmatrixA:=[aij],aij=0ifi+jisodd.Basedonthespecialstructurewecanprovetwonewtheorems,whichindicatethatthecharacteristicequationofAcanbedecomposedintotheproductofthecharacteristicequationsoftwosub-matriceswithdimensionshalflower.Hence,wecansequentiallysolvethenaturalfrequenciesinclosed-formowingtothespecialtyofA.Weusethispowerfulnewtheorytoanalyzethefreevibrationperformanceandthevibrationmodesofsymmetriccompositebeamswiththreedifferentinterfaces.