学科分类
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435 个结果
  • 简介:Thenonlinearbehaviorofacantileveredfluidconveyingpipesubjectedtoprincipalparametricandinternalresonancesisinvestigatedinthispaper.Theflowvelocityisdividedintoconstantandsinusoidaiparts.Thevelocityvalueoftheconstantpartissoadjustedsuchthatthesystemexhibits3:1internalresonancesforthefirsttwomodes.Themethodofmultiplescalesisemployedtoobtaintheresponseofthesystemandasetoffourfirst-ordernonlinearordinary-differentialequationsforgoverningtheamplitudeoftheresponse.TheeigenvaluesoftheJacobianmatrixareusedtoassessthestabilityoftheequilibriumsolutionswithvaryingparameters.Thecodimension2derivedfromthedouble-zeroeigenvaiuesisanalyzedindetail.Theresultsshowthattheresponseamplitudemayundergosaddle-node,pitchfork,Hopf,homoclinicloopandperiod-doublingbifurcationsdependingonthefrequencyandamplitudeofthesinusoidalflow.Whenthefrequencyofthesinusoidalflowequalsexactlyhalfofthefirst-modefrequency,thesystemhasaroutetochaosbyperiod-doublingbifurcationandthenreturnstoaperiodicmotionastheamplitudeofthesinusoidalflowincreases.

  • 标签: 非线性动力学 分歧 稳定性 液-固相互作用 内谐振 混沌
  • 简介:Ameshlessapproachbasedonthemovingleastsquaremethodisdevelopedforelasto-plasticityanalysis,inwhichtheincrementalformulationisused.Inthisapproach,thedisplacementshapefunctionsareconstructedbyusingthemovingleastsquareapproximation,andthediscretegoverningequationsforelasto-plasticmaterialareconstructedwiththedirectcollocationmethod.Theboundaryconditionsarealsoimposedbycollocation.Themethodestablishedisatrulymeshlessone,asitdoesnotneedanymesh,eitherforthepurposeofinterpolationofthesolutionvariables,orforthepurposeofconstructionofthediscreteequations.Itissimplyformulatedandveryefficient,andnopost-processingprocedureisrequiredtocomputethederivativesoftheunknownvariables,sincethesolutionfromthismethodbasedonthemovingleastsquareapproximationisalreadysmoothenough.Numericalexamplesaregiventoverifytheaccuracyofthemeshlessmethodproposedforelasto-rdasticityanalysis.

  • 标签: 网格方法 弹塑性 配置法 移动最小二乘方 增量公式
  • 简介:TheDonnelltheoryofshellisappliedtodescribeshellmotionandlayermotionisdescribedbymeansofthree-dimensionalNavierequations.Usingdeformationharmoniousconditionsoftheinterface,theeffectsofstiffenersandlayeraretreatedasreverseforcesandmomentsactingonthecylindricalshell.Instudyingtheacousticfieldproducedbyvibrationofthesubmergedring-stiffenedcylindricalcoatedshell,thestructuredynamicequation,Helmholtzequationinthefluidfieldandthecontinuousconditionsofthefluid-structureinterfacecomposethecou-plingvibrationequationofthesound-fluid-structure.Theextractofsoundpressurecomesdowntotheextractofcouplingvibrationequation.Byuseofthesolutionoftheequation,theinfluencesofhydrostaticpressure,physicalcharactersandgeometricparametersofthelayeronsoundradiationarediscussed.

  • 标签: 黏弹性层 环压硬度圆柱涂层 耦合振动方程 声辐射 液体介质
  • 简介:Thefiniteelementformulationforanalyzingstaticdamagenearaconductingcrackinathinpiezoelectricplateisestablishedfromthevirtualworkprincipleofpiezoelectricity.Thedamagefieldsundervariousmechanicalandelectricalloadsarecalculatedcarefullybyusinganeffectiveiterativeprocedure.Thenumericalresultsshowthatallthedamagefieldsaroundacracktiparefan-shapedandtheelectricfieldappliedhasgreatinfluenceonthemechanicaldamage,whichisrelatedtothepiezoelectricproperties.

  • 标签: 压电陶瓷 非线性有限元方法 机械损伤 电损伤 导电裂缝
  • 简介:Anintervaloptimizationmethodforthedynamicresponseofstructureswithintervalparametersispresented.Thematricesofstructureswithintervalparametersaregiven.Combiningtheintervalextensionwiththeperturbation,themethodforintervaldynamicresponseanalysisisderived.Theintervaloptimizationproblemistransformedintoacorrespondingdeterministicone.Becausethemeanvaluesandtheuncertaintiesoftheintervalparameterscanbeelecteddesignvariables,moreinformationoftheoptimizationresultscanbeobtainedbythepresentmethodthanthatobtainedbythedeterministicone.Thepresentmethodisimplementedforatrussstructure.Thenumericalresultsshowthatthemethodiseffective.

  • 标签: 无定常结构 区间优化 动力学分析 函数区间扩展 区间参量结构 区间分析方法
  • 简介:Contributions:TheJournal,ActaMechanicaSolidaSinica,ispleasedtoreceivepapersfromengineersandscientistsworkinginvariousaspectsofsolidmechanics.Allcontributionsaresubjecttocriticalreviewpriortoacceptanceandpublication.Manuscriptrequirements:ManuscriptsofallcontributionsshouldbeinEnglish,andsubmittedonlinethroughhttp://amss.hust.edu.cn.ThisjournalacceptseitherLaTeXorMS-WORDdocuments.

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  • 简介:Astudyiscarriedoutonthestructuraldesignofwood-plasticcompositefloors.Thegeometricparametersofthecavities,thestructure,andthemeanstooptimizetheperformanceoftheselightboardsareinvestigated.Variousstructuralparametersoftheboards,suchassize,shape,andthepatternofcavitiesarealsostudied.Theoptimalstructurecanbedeterminedbycalculationandanalysisofthestrength,stiffness,weightandcostofthematerial.Afiniteelementmodelforthemechanicalanalysisofwood-plasticcompositefloorsisestablished;andtheresultsareusedtoverifythestrengthcriteriaunderbendingdeformation,whichisthemostcommonloadingconditionofflooringboard.

  • 标签: 木头塑料合成 flooring 董事会 最佳的结构 有限元素模型
  • 简介:Phononicmaterialswithspecificband-gapcharacteristicsatdesiredfrequencyrangesareingreatdemandforvibrationandnoiseisolation,elasticwavefilters,andacousticdevices.Theattenuationcoefficientcurvedepictsboththefrequencyrangeofbandgapandtheattenuationofelasticwave,wherethefrequencyrangescorrespondingtothenone-zeroattenuationcoefficientsarebandgaps.Therefore,theband-gapcharacteristicscanbeachievedthroughmaximizingtheattenuationcoefficientatthecorrespondingfrequencyorwithinthecorrespondingfrequencyrange.Becausetheattenuationcoefficientcurveisnotsmoothinthefrequencydomain,thegradient-basedoptimizationmethodscannotbedirectlyusedinthedesignoptimizationofphononicband-gapmaterialstoachievethemaximumattenuationwithinthedesiredfrequencyrange.Toovercomethisdifficulty,theobjectiveofmaximizingtheattenuationcoefficientistransformedintomaximizingitsCosine,andinthisway,theobjectivefunctionissmoothedandbecomesdifferentiable.Basedonthisobjectivefunction,anovelgradient-basedoptimizationapproachisproposedtoopenthebandgapataprescribedfrequencyrangeandtofurthermaximizetheattenuationefficiencyoftheelasticwaveataspecificfrequencyorwithinaprescribedfrequencyrange.Numericalresultsdemonstratetheeffectivenessoftheproposedgradient-basedoptimizationmethodforenhancingthewaveattenuationproperties.

  • 标签: 优化 乐队差距 基于坡度的优化 二拍子的圆舞优化途径
  • 简介:StraightandBentnano-cantileverspecimensarerespectivelyproposedtoinvestigatethesingle-modeandmixed-modecrackinitiationattheCu/Siinterfaceedgeinnanoscalecomponents.Withaminuteloadingapparatus,allnanoscalesamplesareinsituloadedandobserved.Numericalanalysisisemployedtoacquirethecriticalinterfacialstressdistributionsduringcrackinitiation.ThestressconcentrationregionsneartheedgeofCu/Siinterfaceinallspecimensarewithinthescaleof100nm,andthecriticalnormalandshearstresseshaveacircularrelationinnanoscalecomponents,whichrepresentsthefracturecriterionoftheinterfaceinnanoscalecomponents.

  • 标签: NANOSCALE 伸臂 接口 裂缝开始 混合模式 薄电影
  • 简介:Toconsidertheanisotropicdamageinfatigue,animprovedboom-panelmodelispresentedtosimulatearepresentativevolumeelement(RVE)intheframeworkofcontinuumdamagemechanics.TheanisotropicdamagestateoftheRVEisdescribedbythecontinuityextentsofboomsandpanels,whosedamageevolutionsareassumedtobeisotropic.Thenumericalimplementationisproposedonthebasisofdamagemechanicsandthefiniteelementmethod.Finally,theapproachisappliedtothefatiguelifepredictionof2A12-T4aluminiumalloyspecimenundercyclicloadingoftension-torsion.Theresultsindicateagoodagreementwiththeexperimentaldata.

  • 标签: 吊杆面板模型 各向异性的损坏 疲劳 紧张扭转 生活预言
  • 简介:BasedonthecontinuityofthederivativesoftheNon-UniformRationalB-Splines(NURBS)curveandtheJaumannstrainmeasure,thepresentpaperadoptedthepositioncoordinatesofthecontrolpointsasthedegreesoffreedomanddevelopedaplanarrotation-freeEuler-Bernoullibeamelementforisogeometricanalysis,wherethederivativesofthefieldvariableswithrespecttothearc-lengthwereexpressedasthesumoftheweightedsumofthepositioncoordinatesofthecontrolpoints,andtheNURBSbasisfunctionswereusedastheweightfunctions.Furthermore,theconceptofbendingstripwasusedtoinvolvetherigidconnectionbetweenmultiplepatches.Severaltypicalexampleswithgeometricnonlinearitieswereusedtodemonstratetheaccuracyandeffectivenessoftheproposedalgorithm.Thepresentedformulationfullyaccountsforthegeometricnonlinearitiesandcanbeusedtostudythesnap-throughandsnap-backphenomenaofflexiblebeams.

  • 标签: isogeometric 分析 NURBS 没有旋转的横梁 弯曲长带方法 突然将球踢回
  • 简介:Inthisstudy,theresidualstrainofathinconductivemetalwireonapolymersubstrateafterelectricalfailureismeasuredwithSEMmoir′e.Focusedionbeam(FIB)millingisappliedtofabricatemicronmoir′egratingsonthesurfacesofconstantanwiresandtherandomphaseshiftingtechniqueisusedtoprocessmoir′efringes.Thevirtualstrainmethodisbrieflyintroducedandusedtocalculatetherealstrainofspecimens.Inordertostudytheinfluenceofadefectontheelectricalfailureoftheconstantanwire,experimentswereconductedontwospecimens,onewithacrack,whiletheotheronewithoutanycrack.Bycomparingtheresults,wefoundthatthedefectmakesthecriticalbeamcurrentofelectricalfailuredecrease.Inaddition,thespecimensweresubjectedtocompressionafterelectricalfailure,inagreementwiththeobservedcrackclosureofthespecimen.Thesuccessfulresultsdemonstratethatthemoir′emethodiseffectivetocharacterizethefull-fielddeformationofconstantanwiresonthepolymermembrane,andhasagoodpotentialforfurtherapplicationtothedeformationmeasurementofthinfilms.

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  • 简介:ThepreviouspaperreportedanewderivativeintheEuleriandescriptioninflatspace—thegeneralizedcovariantderivativeofgeneralizedEuleriancomponentwithrespecttotime.ThispaperextendsthethoughtfromtheEuleriandescriptiontotheLagrangiandescription:onthebasisofthepostulateofcovariantforminvariabilityintimefield,wedefineanewderivativeintheLagrangiandescriptioninflatspace—thegeneralizedcovariantderivativeofgeneralizedLagrangiancomponentwithrespecttotime.Besides,thecovariantdifferentialtransformationgroupissetup.ThecovariantforminvariabilityofLagrangianspace-timeisascertained.

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  • 简介:ThispaperreportsanewderivativeintheEuleriandescriptioninflatspace-thegeneralizedcovariantderivativewithrespecttotime.Thefollowingcontentsareincluded:(a)therestrictedcovariantderivativewithrespecttotimeforEuleriancomponentisdefined;(b)thepostulateofthecovariantforminvariabilityintimefieldissetup;(c)thegeneralizedcovariantderivativewithrespecttotimeforgeneralizedEuleriancomponentisdefined;(d)thealgebraicstructureofthegeneralizedcovariantderivativewithrespecttotimeismadeclear;(e)thecovariantdifferentialtransformationgroupintimefiledisderived.TheseprogressesrevealthecovariantforminvariabilityofEulerianspaceandtime.

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  • 简介:Thisstudypresentsageneralapproachtoderivetheacousticnonlinearityparametersinducedbyvarioustypesofdislocationconfigurationsincludingdislocationstrings(monopoles),dislocationdipoles,dislocationpileupsandextendeddislocations.Itisfoundthatexpressionsoftheacousticnonlinearityparameterinducedbysuchavarietyofdislocationcon-figurationsshareacommonmathematicalform.Theyareallscaledwith(Lch/b)n,whereLchisacharacteristiclengthofthedislocationconfiguration,bisthemagnitudeoftheBurgersvector,andniseither3or4.Semiquantitativeanalysisispresentedtocomparethemagnitudesoftheacousticnonlinearityparametersamongdifferenttypesofdislocationconfigurations.

  • 标签: Nonlinear ULTRASOUND NONDESTRUCTIVE evaluation Acoustic NONLINEARITY