简介:Thenonlinearbehaviorofacantileveredfluidconveyingpipesubjectedtoprincipalparametricandinternalresonancesisinvestigatedinthispaper.Theflowvelocityisdividedintoconstantandsinusoidaiparts.Thevelocityvalueoftheconstantpartissoadjustedsuchthatthesystemexhibits3:1internalresonancesforthefirsttwomodes.Themethodofmultiplescalesisemployedtoobtaintheresponseofthesystemandasetoffourfirst-ordernonlinearordinary-differentialequationsforgoverningtheamplitudeoftheresponse.TheeigenvaluesoftheJacobianmatrixareusedtoassessthestabilityoftheequilibriumsolutionswithvaryingparameters.Thecodimension2derivedfromthedouble-zeroeigenvaiuesisanalyzedindetail.Theresultsshowthattheresponseamplitudemayundergosaddle-node,pitchfork,Hopf,homoclinicloopandperiod-doublingbifurcationsdependingonthefrequencyandamplitudeofthesinusoidalflow.Whenthefrequencyofthesinusoidalflowequalsexactlyhalfofthefirst-modefrequency,thesystemhasaroutetochaosbyperiod-doublingbifurcationandthenreturnstoaperiodicmotionastheamplitudeofthesinusoidalflowincreases.
简介:Ameshlessapproachbasedonthemovingleastsquaremethodisdevelopedforelasto-plasticityanalysis,inwhichtheincrementalformulationisused.Inthisapproach,thedisplacementshapefunctionsareconstructedbyusingthemovingleastsquareapproximation,andthediscretegoverningequationsforelasto-plasticmaterialareconstructedwiththedirectcollocationmethod.Theboundaryconditionsarealsoimposedbycollocation.Themethodestablishedisatrulymeshlessone,asitdoesnotneedanymesh,eitherforthepurposeofinterpolationofthesolutionvariables,orforthepurposeofconstructionofthediscreteequations.Itissimplyformulatedandveryefficient,andnopost-processingprocedureisrequiredtocomputethederivativesoftheunknownvariables,sincethesolutionfromthismethodbasedonthemovingleastsquareapproximationisalreadysmoothenough.Numericalexamplesaregiventoverifytheaccuracyofthemeshlessmethodproposedforelasto-rdasticityanalysis.
简介:TheDonnelltheoryofshellisappliedtodescribeshellmotionandlayermotionisdescribedbymeansofthree-dimensionalNavierequations.Usingdeformationharmoniousconditionsoftheinterface,theeffectsofstiffenersandlayeraretreatedasreverseforcesandmomentsactingonthecylindricalshell.Instudyingtheacousticfieldproducedbyvibrationofthesubmergedring-stiffenedcylindricalcoatedshell,thestructuredynamicequation,Helmholtzequationinthefluidfieldandthecontinuousconditionsofthefluid-structureinterfacecomposethecou-plingvibrationequationofthesound-fluid-structure.Theextractofsoundpressurecomesdowntotheextractofcouplingvibrationequation.Byuseofthesolutionoftheequation,theinfluencesofhydrostaticpressure,physicalcharactersandgeometricparametersofthelayeronsoundradiationarediscussed.
简介:Thefiniteelementformulationforanalyzingstaticdamagenearaconductingcrackinathinpiezoelectricplateisestablishedfromthevirtualworkprincipleofpiezoelectricity.Thedamagefieldsundervariousmechanicalandelectricalloadsarecalculatedcarefullybyusinganeffectiveiterativeprocedure.Thenumericalresultsshowthatallthedamagefieldsaroundacracktiparefan-shapedandtheelectricfieldappliedhasgreatinfluenceonthemechanicaldamage,whichisrelatedtothepiezoelectricproperties.
简介:Anintervaloptimizationmethodforthedynamicresponseofstructureswithintervalparametersispresented.Thematricesofstructureswithintervalparametersaregiven.Combiningtheintervalextensionwiththeperturbation,themethodforintervaldynamicresponseanalysisisderived.Theintervaloptimizationproblemistransformedintoacorrespondingdeterministicone.Becausethemeanvaluesandtheuncertaintiesoftheintervalparameterscanbeelecteddesignvariables,moreinformationoftheoptimizationresultscanbeobtainedbythepresentmethodthanthatobtainedbythedeterministicone.Thepresentmethodisimplementedforatrussstructure.Thenumericalresultsshowthatthemethodiseffective.
简介:Contributions:TheJournal,ActaMechanicaSolidaSinica,ispleasedtoreceivepapersfromengineersandscientistsworkinginvariousaspectsofsolidmechanics.Allcontributionsaresubjecttocriticalreviewpriortoacceptanceandpublication.Manuscriptrequirements:ManuscriptsofallcontributionsshouldbeinEnglish,andsubmittedonlinethroughhttp://amss.hust.edu.cn.ThisjournalacceptseitherLaTeXorMS-WORDdocuments.
简介:Astudyiscarriedoutonthestructuraldesignofwood-plasticcompositefloors.Thegeometricparametersofthecavities,thestructure,andthemeanstooptimizetheperformanceoftheselightboardsareinvestigated.Variousstructuralparametersoftheboards,suchassize,shape,andthepatternofcavitiesarealsostudied.Theoptimalstructurecanbedeterminedbycalculationandanalysisofthestrength,stiffness,weightandcostofthematerial.Afiniteelementmodelforthemechanicalanalysisofwood-plasticcompositefloorsisestablished;andtheresultsareusedtoverifythestrengthcriteriaunderbendingdeformation,whichisthemostcommonloadingconditionofflooringboard.
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.
简介:StraightandBentnano-cantileverspecimensarerespectivelyproposedtoinvestigatethesingle-modeandmixed-modecrackinitiationattheCu/Siinterfaceedgeinnanoscalecomponents.Withaminuteloadingapparatus,allnanoscalesamplesareinsituloadedandobserved.Numericalanalysisisemployedtoacquirethecriticalinterfacialstressdistributionsduringcrackinitiation.ThestressconcentrationregionsneartheedgeofCu/Siinterfaceinallspecimensarewithinthescaleof100nm,andthecriticalnormalandshearstresseshaveacircularrelationinnanoscalecomponents,whichrepresentsthefracturecriterionoftheinterfaceinnanoscalecomponents.
简介:Formulationintermsofhypersingularintegralequationsfortheinteractionbetweenstraightandcurvedcracksinplaneelasticityisobtainedusingthecomplexvariablefunctionsmethod.Thecurvedlengthcoordinatemethodandasuitablenumericalschemeareusedtosolvesuchintegralsnumericallyfortheunknownfunction,whicharelaterusedtofindthestressintensityfactor,SIF.
简介:Toconsidertheanisotropicdamageinfatigue,animprovedboom-panelmodelispresentedtosimulatearepresentativevolumeelement(RVE)intheframeworkofcontinuumdamagemechanics.TheanisotropicdamagestateoftheRVEisdescribedbythecontinuityextentsofboomsandpanels,whosedamageevolutionsareassumedtobeisotropic.Thenumericalimplementationisproposedonthebasisofdamagemechanicsandthefiniteelementmethod.Finally,theapproachisappliedtothefatiguelifepredictionof2A12-T4aluminiumalloyspecimenundercyclicloadingoftension-torsion.Theresultsindicateagoodagreementwiththeexperimentaldata.
简介:BasedonthecontinuityofthederivativesoftheNon-UniformRationalB-Splines(NURBS)curveandtheJaumannstrainmeasure,thepresentpaperadoptedthepositioncoordinatesofthecontrolpointsasthedegreesoffreedomanddevelopedaplanarrotation-freeEuler-Bernoullibeamelementforisogeometricanalysis,wherethederivativesofthefieldvariableswithrespecttothearc-lengthwereexpressedasthesumoftheweightedsumofthepositioncoordinatesofthecontrolpoints,andtheNURBSbasisfunctionswereusedastheweightfunctions.Furthermore,theconceptofbendingstripwasusedtoinvolvetherigidconnectionbetweenmultiplepatches.Severaltypicalexampleswithgeometricnonlinearitieswereusedtodemonstratetheaccuracyandeffectivenessoftheproposedalgorithm.Thepresentedformulationfullyaccountsforthegeometricnonlinearitiesandcanbeusedtostudythesnap-throughandsnap-backphenomenaofflexiblebeams.
简介:Inthisstudy,theresidualstrainofathinconductivemetalwireonapolymersubstrateafterelectricalfailureismeasuredwithSEMmoir′e.Focusedionbeam(FIB)millingisappliedtofabricatemicronmoir′egratingsonthesurfacesofconstantanwiresandtherandomphaseshiftingtechniqueisusedtoprocessmoir′efringes.Thevirtualstrainmethodisbrieflyintroducedandusedtocalculatetherealstrainofspecimens.Inordertostudytheinfluenceofadefectontheelectricalfailureoftheconstantanwire,experimentswereconductedontwospecimens,onewithacrack,whiletheotheronewithoutanycrack.Bycomparingtheresults,wefoundthatthedefectmakesthecriticalbeamcurrentofelectricalfailuredecrease.Inaddition,thespecimensweresubjectedtocompressionafterelectricalfailure,inagreementwiththeobservedcrackclosureofthespecimen.Thesuccessfulresultsdemonstratethatthemoir′emethodiseffectivetocharacterizethefull-fielddeformationofconstantanwiresonthepolymermembrane,andhasagoodpotentialforfurtherapplicationtothedeformationmeasurementofthinfilms.
简介:ThepreviouspaperreportedanewderivativeintheEuleriandescriptioninflatspace—thegeneralizedcovariantderivativeofgeneralizedEuleriancomponentwithrespecttotime.ThispaperextendsthethoughtfromtheEuleriandescriptiontotheLagrangiandescription:onthebasisofthepostulateofcovariantforminvariabilityintimefield,wedefineanewderivativeintheLagrangiandescriptioninflatspace—thegeneralizedcovariantderivativeofgeneralizedLagrangiancomponentwithrespecttotime.Besides,thecovariantdifferentialtransformationgroupissetup.ThecovariantforminvariabilityofLagrangianspace-timeisascertained.
简介:ThispaperreportsanewderivativeintheEuleriandescriptioninflatspace-thegeneralizedcovariantderivativewithrespecttotime.Thefollowingcontentsareincluded:(a)therestrictedcovariantderivativewithrespecttotimeforEuleriancomponentisdefined;(b)thepostulateofthecovariantforminvariabilityintimefieldissetup;(c)thegeneralizedcovariantderivativewithrespecttotimeforgeneralizedEuleriancomponentisdefined;(d)thealgebraicstructureofthegeneralizedcovariantderivativewithrespecttotimeismadeclear;(e)thecovariantdifferentialtransformationgroupintimefiledisderived.TheseprogressesrevealthecovariantforminvariabilityofEulerianspaceandtime.
简介:Thisstudypresentsageneralapproachtoderivetheacousticnonlinearityparametersinducedbyvarioustypesofdislocationconfigurationsincludingdislocationstrings(monopoles),dislocationdipoles,dislocationpileupsandextendeddislocations.Itisfoundthatexpressionsoftheacousticnonlinearityparameterinducedbysuchavarietyofdislocationcon-figurationsshareacommonmathematicalform.Theyareallscaledwith(Lch/b)n,whereLchisacharacteristiclengthofthedislocationconfiguration,bisthemagnitudeoftheBurgersvector,andniseither3or4.Semiquantitativeanalysisispresentedtocomparethemagnitudesoftheacousticnonlinearityparametersamongdifferenttypesofdislocationconfigurations.