学科分类
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15 个结果
  • 简介:AnewmechanicsmodelbasedonPeierlsconceptispresentedinthispaper,whichcanclearlycharacterizetheintrinsicfeaturesnearatipofaninterfacialcrack.Thestressanddisplacementfieldsarecalculatedundergeneralcombinedten-sileandshearloadings.Theneartipstressfieldsshowsomeoscillatorybehaviorsbutwithoutanysingularityandthecrackfacesopencompletelywithoutanyoverlappingwhenremotetensileloadingiscomparablewithremoteshearloading.Afracturecriterionforpredictinginterfacetoughnesshasbeenalsoproposed,whichtakesintoaccountfortheshieldingeffectsofemitteddislocations.Thetheoreticaltoughnesscurvegivesexcellentprediction,ascomparedwiththeexistingexperimentdata.

  • 标签: MICROMECHANICS INTERFACE CRACK TOUGHNESS
  • 简介:SomeofthemainprogressontheinvestigationofthemechanismofthewaveformationinexplosiveweldingattheInstituteofMechanicsissummarizedandotters’previousworksarere-viewed.OursystematicexperimentsandanalysisdonotsubstantiatethetheoryofwaveformationbasedonKarmanvortex-streetanalogyorHelmholtzinstability.Onthecontrary,theyshowthatmateri-alstrengthinsensitivetostrainrateplaysanimportantrole.Asimplehydro-plasticmodelispresentedtoexplainthemainfeaturesregardingtheinterracialwaveformationandtoestimatethemagnitudeofwavelength.Theresultisinbroadagreementwithexperiment.

  • 标签: INTERFACE WAVES INSTABILITY of INTERFACE EXPLOSIVE
  • 简介:Wheninterfaciallayersareviewedasaseparatephase,theinterfacethicknessplaysanessentialroleinassessingphysico-mechanicalpropertiesofparticulatematerials.However,theinterfacethicknessfromsectionalanalysisisoftenoverestimated,duetotheirregularityofsurfacetexturesofgrainsinopaquematerialsthatgivesrisetothenormalofacross-sectionalplanenon-perpendiculartothesurfaceofgrains.Hence,thedeterminationoftheoverestimationdegreeisverycriticaltopreciselyobtaintheinterfacethickness.Thisarticledevelopsanumericalmodelfortheoverestimationdegreeoftheinterfacethicknessaroundanellipsoidalgrainwithanarbitraryaspectratio,byapplyinganaccuratesectionalanalysisalgorithm,andquantitativestereologyandgeometricalprobabilitytheories.Furthermore,onthebasisofthedevelopednumericalmodel,theinfluenceofellipsoidalparticleshapeontheoverestimationdegreeisquantitativelycharacterized.

  • 标签: 界面厚度 数值评价 球形颗粒 接口 物理机械性能 数值计算模型
  • 简介:Interfacedislocationsmaydramaticallychangetheelectricproperties,suchaspolarization,ofthepiezoelectriccrystals.Inthispaper,westudythelinearinteractionsoftwointerfacedislocationloopswitharbitraryshapeingenerallyanisotropicpiezoelectricbi-crystals.Asimpleformulaforcalculatingtheinteractionenergyoftheinterfacedislocationloopsisderivedandgivenbyadoublelineintegralalongtwocloseddislocationcurves.Particularly,interactionsbetweentwostraightsegmentsoftheinterfacedislocationsaresolvedanalytically,whichcanbeappliedtoapproximateanycurvedloopsothatananalyticalsolutioncanbealsoachieved.Numericalresultsshowtheinfluenceofthebi-crystalinterfaceaswellasthematerialorientationontheinteractionofinterfacedislocationloops.

  • 标签: 相互作用能 晶体界面 压电晶体 位错环 界面位错 电学性质
  • 简介:Thermalcontactresistanceplaysaveryimportantroleinheattransferefficiencyandthermomechanicalcouplingresponsebetweentwomaterials,andacommonmethodtoreducethethermalcontactresistanceistofillasoftinterfacematerialbetweenthesetwomaterials.AtestingsystemofhightemperaturethermalcontactresistancebasedonINSTRON8874isestablishedinthepresentpaper,whichcanachieve600Cattheinterface.Basedonthissystem,thethermalcontactresistancebetweensuperalloyGH600ma...

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  • 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.

  • 标签: AIR-WATER interface surface SHEAR COHERENT structures
  • 简介:在组成的部件之间的有瑕疵的结合能极大地影响合成结构的性质。处于2Dfibrereinforced的问题产生的有瑕疵的接口的不同类型的asymptotic分析合成材料被建议。执行学习基于管理biharmonic问题的asymptotic减小进二个泛音问题。所有答案在一种关上的分析形式被获得。获得的结果能被用于撤退和pushout测试的计算,以及为合成材料的破裂的调查。

  • 标签: 复合材料界面 纤维增强 2D 复合材料结构 双调和问题 组成成分
  • 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。

  • 标签: 接口脱臼 核心传播 有弹性的地 各向异性的 bimaterial
  • 简介:Shapememoryalloy(SMA)reinforcedsmartstructurecanbeusedtomakestructuralshapeandstrengthselfadaptedandstructuraldamageself-restrained.AlthoughSMAsmartstructureswithoutdamageswereextensivelystudied,researchesonSMAsmartstructureswithdamageshaverarelybeenreportedthusfar.Inthispaper,thermo-mechanicalbehaviorsofSMAfiberreinforcedsmartstructureswithdamagesareanalyzedthroughashearlagmodelandthevariationalprinciple.Mathematicalexpressionsofthemeso-displacementfieldandthestress-strainfieldofatypicalelementwithdamagesareobtained,andafailurecriterionforinterfacefailurebetweenSMAfibersandmatrixisestablished,whichisappliedtoanexample.ResultspresentedhereinmayprovideatheoreticalfoundationforfurtherstudiesonintegrityofSMAsmartstructures.

  • 标签: 形状记忆合金 分界面缺陷 敏感结构 形状变化规则 机械性质
  • 简介:Regardlessofallkindsofdifferentformulaeusedforthetraction-separationrelationshipincohesivezonemodeling,thepeaktractionσ_mandtheseparation-to-failureδ_0(orequivalentlythework-to-separationΓ)aretheprimaryparameterswhichcontroltheinterfacialfracturebehaviors.Experimentally,itishardtodeterminethosequantities,especiallyforδ_0,whichoccursinaverylocalizedregionwithpossiblycomplicatedgeometriesbymaterialfailure.BasedontheDugdalemodel,weshowthatthesepa...

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  • 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.

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  • 简介:Inthispaper,wecombinethedirect-forcingfictitiousdomain(DF/FD)methodandthesharpinterfacemethodtoresolvetheproblemofparticledielectrophoresisintwodimensions.TheflowfieldandthemotionofparticlesaresolvedwiththeDF/FDmethod,theelectricfieldissolvedwiththesharpinterfacemethod,andtheelectrostaticforceontheparticlesiscomputedusingtheMaxwellstresstensormethod.Theproposedmethodisvalidatedviathreeproblems:effectiveconductivityofparticlecompositebetweentwoplanarplates,celltrappinginachannel,andmotionofparticlesduetobothconventionalandtravelingwavedielectrophoreticforces.

  • 标签: 接口方法 颗粒 夏普 虚拟 导电粒子 应力张量
  • 简介:Thispaperstudiestheinterfacecuringstressesbetweenpolymethylmethacrylate(PMMA)andcompositebymeansofdigitalspecklecorrelationmethod(DSCM).AnewmethodbycombiningDSCMwiththemarkerpointsisdevelopedtomeasuretheinterfacecuringstresses,andthemeasurementprincipleisintroduced.TheinterfacecuringstressesbetweenPMMAandcompositewithdifferentcuringbondingconditionsaremeasuredandanalyzed,thisindicatesthattheresidualstressforfurnaceheatingandfurnacecooling...

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  • 简介:Foracompression-shearmixedmodeinterfacecrack,itisdifficulttosolvethestressandstrainfieldsconsideringthematerialviscosity,thecrack-tipsingularity,thefrictionaleffect,andthemixedloadinglevel.Inthispaper,amechanicalmodelofthedynamicpropagationinterfacecrackforthecompression-shearmixedmodeisproposedusinganelastic-viscoplasticconstitutivemodel.Thegoverningequationsofpropagationcrackinterfaceatthecrack-tiparegiven.Thenumericalanalysisisperformedfortheinterfacecrackofthecompression-shearmixedmodebyintroducingadisplacementfunctionandsomeboundaryconditions.Thedistributedregularitiesofstressfieldoftheinterfacecrack-tiparediscussedwithseveralspecialparameters.Thefinalresultsshowthattheviscosityeffectandthefrictionalcontacteffectonthecracksurfaceandthemixed-loadparameterareimportantfactorsinstudyingthemixedmodeinterfacecracktipfields.Thesefieldsarecontrolledbytheviscositycoefficient,theMachnumber,andthesingularityexponent.

  • 标签: compression-shear MIXED mode INTERFACE crack dynamic
  • 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.

  • 标签: SYMMETRIC composite beams R(x)-orthogonality of second-order