简介:Byusingthefinite-partintegralconceptsandlimittechnique,thehypersingularinte-grodifferentialequationsofthree-dimensional(3D)planarinterfacecrackwereobtained;thenthedominant-partanalysisof2Dhypersingularintegralwasfurtherusedtoinvestigatethestressfieldsnearthecrackfronttheoretically,andtheaccurateformulaewereobtainedforthesingularstressfieldsandthecomplexstressintensityfactors.Afterthat,anumericalmethodisproposedtosolvethehyper-singularintegrodifferentialequationsof3Dplanarinterfacecrack,andtheproblemofellipticalplanarcrackisthenconsideredtoshowtheapplicationofthemethod.Thenumericalresultsobtainedaresat-isfactory.
简介:Thethermalstressofthequartzoscillatormodulepackagingisinvestigatedusingdistal-im-agecorrelationmethod(DICM),andtheexperimentalresultsaregiven.Underthequartzoscillatormodulepackaging,thequartzoscillatorandtheFe-Sn-Cualloyframearejoinedtogetherwiththeelectroconductiveadhesive(PI),andtheelectroconductiveadhesiveneedstobecuredtwiceat150℃and275℃respective-ly.AsthequartzoscillatorandtheFe-Sn-Cualloyframehaveadistinctdifferenceinboththermalexpansioncoefficientsandmechanicalpropertiesandinprocessofpackagingtemperaturerisesordrops,thethermalstressisyieldedeasily.Whiletemperaluredrops,thenormalstressatthequartzoscillatoredgeisatensilestress,whichcanmakethequartzoscillatorfracture.
简介:StresscalculationformulaeforaringhavebeenobtainedbyusingAirystressfunctionoftheplanestrainfieldwiththedecompositionofthesolutionsfornormalstressesofAirybiharmonicequationintotwopartswhenitisloadedundertwooppositeinsideforcesalongadiameter.Onepartshouldfulfillaconstraintconditionaboutnormalstressdistributionalongthecircumferenceatanenergyvalleytodotheminimumwork.Otherpartisastressresidueconstant.Inordertoverifytheseformulaeandthecomputedresults,thecomputedcontourlinesofequi-maximalshearstresseswereplottedandquitecomparedwiththatofphoto-elasticitytestresults.ThisconstraintconditionaboutnormalstressdistributionalongcircumferenceisconfirmedbyusingGreens’theorem.Anadditionalcompressionexistsalongthecircumferenceoftheloadedring,explainingthedivorcementanddisplacementofsingularitypointsatinnerandouterboundaries.
简介:TheSelf-SimilarCrackExpansion(SSCE)methodisproposedtoevaluatestressintensi-tyfactorsatcracktips,wherebystressintensityfactorsofacrackcanbedeterminedbythecrackopeningdisplacementoverthecrack,notjustbythelocaldisplacementaroundthecracktip.Thecrackexpansionrateisestimatedbytakingadvantageofthecrackself-similarity.Therefore,theaccuracyofthecalculationisimproved.Thesingularintegralsoncracktipelementsarealsoanalyzedandarepre-ciselyevaluatedintermsofaspecialintegralanalysis.Combinationofthesetwotechniquesgreatlyin-creasestheaccuracyinestimatingthestressdistributionaroundthecracktip.Avarietyoftwo-dimen-sionalcracks,suchassubsurfacecracks,edgecracks,andtheirinteractionsarecalculatedintermsoftheself-similarexpansionrate.Solutionsaresatisfiedwitherrorslessthan0.5%ascomparedwiththeanalyticalsolutions.Basedonthecalculationsofthecrackinteractions,atheoryforcrackinteractionsisproposedsuchthatforagroupofalignedcracksthesummationofthesquareofSIFsattherighttipsofcracksisalwaysequaltothatatthelefttipsofcracks.ThistheorywasprovedbythemehtodofSelf-SimilarCrackExpansioninthispaper.
简介:Aclosed-formsolutionforpredictingthetangentialstressofaninclusionlocatedinmixedmodeⅠandⅡcracktipfieldwasdevelopedbasedontheEshelbyequivalentinclusiontheory.Thenamixedmodefracturecriterion,includingthefracturedirectionandthecriticalload,wasestablishedbasedonthemaximumtangentialstressintheinclusionforbrittleinclusioninducedfracturematerials.Theproposedfracturecriterionisafunctionoftheinclusionfracturestress,itssizeandvolumefraction,aswellastheelasticconstantsoftheinclusionandthematrixmaterial.Thepresentcriterionwillreducetotheconventionaloneastheinclusionhavingthesameelasticbehaviorasthematrixmaterial.Theproposedsolutionsareingoodagreementwithdetailedfiniteelementanalysisandmeasurement.
简介:Thispaperisconcernedwiththenumericaltechniquebasedonthemethodofcharacter-isticsforthree-dimensionaldynamicthermoelasticproblems.Anumericalexampleforthethree-di-mensionalstresswavepropagationinathermoelasticbarofsquarecrosssectionsubjectedtobothanimpactloadingandathermalshockispresented.
简介:Stress-dependenceoftheintrinsictimeofviscoelasticmaterialsisinvestigated.Theinfluenceofstresslevelontheintrinsictimeisconsideredtobesimilartothatoflemperature,pressure,solventcon-centration,damageandphysicalaging.Thetime-lemperature-stressequivalenceprincipleisproposed,byemployingwhich,thecreepcurvesatdifferenttemperaturesandstresslevelscanbeshiftedintoamastercurveatreferencetemperatureandstresslevel.Thusthelong-termcreepbehaviorofviscoelasticmaterialsatalowertemperatureandstresscanbepredictedfromtheshort-termoneatahighertemperatureandstress.Asanexample,thenonlinearcreepbehaviorofhigh-densitypolyethylene(HDPE)atroomtemperatureisstudiedusingthetime-temperature-stressequivalenceprinciplepresented.
简介:Tsinghai-TibetPlateaubecomesanimportantresearchtopicofglobaltectonics,becauseofitsmarvelousthicknessandrapidupliftingsinceQuaternary.Byusingfiniteelementmethod,thenumericalsimulationiscarriedoutforthemovementofstructurallithosphere.Thedeformableelementsareemployedtosimulatestructuralzones,andthefrictionalmechanismisintroducedtoillustratethecharacteristicofazonewithacontactcracksurface.Theboundaryconditionsareprescribedbythedisplacementsaroundthepla-teau.Asaresult,thestressanddisplacementdistributionsareobtained,whichareconsistentwithPaxialorientationsoftheearthquakefocusmechanismandthemeasuredprincipalstressdirection.Analysisandes-timatearealsomadefortheevolutionofhistoricalprocessandpresentsituationoftheplateaulithosphere.
简介:Inthispaper,afiniteelementmethodisdevelopedtonumericallyevaluatetheshearcoefficientofTimoshenko'sbeamwithmultiplyconneetedcrosssection.Withfocusonanalyzingshearstressesdistributedattheneutralaxisofthebeam,animproveddefinitionoftheshearcoefficientispresented.Basedonthisdefinition,aGalerkin-typefiniteelementformulationisproposedtoanalyzetheshearstressesandsheardeflections.Numericalsolutionsoftheexamplesforsometypicalcross-sectionsarecomparedwiththetheoreticalresults.TheshearcoefficientoftowersectionsoftheTsingMaBridgeiscalculatedbyuseoftheproposedapproach,sothatthefiniteelementmodelingofthebridgecanbedevelopedwiththeaccuratevaluesofthesectionalproperties.
简介:Applyingtheparametricderivationmethod,PeierlsenergyandPeierlsstressarecalculatedwithanon-sinusoidalforcelawinthelatticetheory,whiletheresultsobtainedbythepower-seriesexpansionaccordingtosinusoidallawcanbededucedasalimitingcaseofnon-sinusoidallaw.ThesimplifiedexpressionsofPeierlsenergyandPeierlsstressareobtainedforthelimitofwideandnarrow.PeierlsenergyandPeierlsstressdecreasemonotonicallywiththefactorofmodificationofforcelaw.PresentresultscanbeusedexpedientlyforpredictionofthecorrectorderofmagnitudeofPeierlsstressformaterials.
简介:Formulationintermsofhypersingularintegralequationsfortheinteractionbetweenstraightandcurvedcracksinplaneelasticityisobtainedusingthecomplexvariablefunctionsmethod.Thecurvedlengthcoordinatemethodandasuitablenumericalschemeareusedtosolvesuchintegralsnumericallyfortheunknownfunction,whicharelaterusedtofindthestressintensityfactor,SIF.
简介:Thedynamicstressintensityfactorhistoryforahalfplanecrackinanotherwiseunboundedelasticbody,withthecrackfacessubjectedtoatractiondistributionconsistingoftwopairsofcombinedmodepointloadsthatmoveinadirectionperpendiculartothecrackedgeisconsidered.Theanalyticexpressionforthecombinedmodestressintensityfactorsasafunctionoftimeforanypointalongthecrackedgeisobtained.ThemethodofsolutionisbasedontheapplicationofintegraltransformtogetherwiththeWiener-HopftechniqueandtheCagniard-deHoopmethod.Somefeaturesofthesolutionarediscussedandgraphicalresultsforvariouspointloadspeedsarepresented.
简介:Thedistributionofstressandstrainfieldsinamicro-structuralareaofaparticlereinforcedcompositeisstudiedbyacombinationofexperimentalandnumericalmethod(hybridmethod).Withtheex-perimentalvaluesofdisplacementsinamicro-regionastheboundaryloadingcondition,strainandstressfieldsinsidethemicro-regionarecalculatedbythefiniteelementmethodtmdertwodifferentkindsofmodel-ing,namely,asplanestressandplanestraincondition.Thedifferencesbetweenthetwokindsofmodelingconditionsasappliedtomicro-structuralareasarediscussed.
简介:Inthispaper,thestresssingularityanalysisatthecracktiponelasticbi-materialinter-facesisconsidered.ThegoverningequationsofplaneelasticityinsectorialdomainarederivedtobeinHamiltonianformviavariablesubstitutionandvariationalprinciple.Themethodsofseparationofvariablesandconjugatesymplecticeigen-functionexpansionaredevelopedtosolvetheequationsinsectorialdomain.Thegeneralformulaeforthesolutionofstresssingularitiesatthecracktiponbi-ma-terialinterfacesareputforward,andanewsolutiontechniqueforfractureproblemsispresented.