简介：Withthickplatesof2219high-strengthalloy,themicrostructuresofweldedjointswithtwinwireMIGweldingwereanalyzed.Experimentalresultsshowthatnohotcrackwasfoundintheweldduetodiscontinuousdistributionofcocrystallizationwithlowmeltingtemperature,butporosityisseriousinthefirstweldseamthatismainlycomposedofequiaxialgrainswithunevensizes.Asthepoorpositionofthewholeweldedjoint,fusionzonehasbigandcoarsegrains,unevenmicrostructures;Inquenchingzone,thereexistalotofsoakedmicrostructuresthatcocrystallizationwithlowmeltingtemperaturesoluteintomatrix,thusstrengtheningthemetalinthiszone;Inexcessiveagingzone,muchmorephasesthatdistributeevenlywillbeseparatedfromthematrix;Outsidethiszone,propertiesandmicrostructuresofthemetalarebasicallysimilartomatrixduetotherelativelylowtemperatureorunaffectedheatinthezoneduringwelding.

简介：ThefatiguebehaviorofweldedstructuresiscurrentlydeterminedbymeansofrecommendationsdefinedintermsofS-Ncurvecorrespondingtothedetailclassesofweldedjointswithouttakingaccountoftheactualgeometryoftheweld.AnewfatiguestrengthassessmentmethodbasedonDangVanmultiaxialfatiguelimitcriterionwasintroduced,whichisnamedthelocalapproachandpresentedbyInstitutdeSoudurerecently.Thelocalapproachhasadvantagesintakingweldingresidualstressesandthegeometryoftheweldtoeandweldrootintoconsideration.TheapplicationofthelocalapproachtothefatiguestrengthassessmentoflowcarbonsteelQ235Bweldedjointswasstudied.ThefatiguetestsandfiniteelementanalysisresultsshowthatthelocalapproachparametersrecommendedbyInstitutdeSoudurewereincorrectlyforlowcarbonsteelQ235Bweldedjoints.Withaluminumalloyweldedjointsbeingusedwidely,theparametersofthelocalapproachusedforaluminumalloyweldedjointswereobtainedandverifiedonbasesofthefatiguetestsandfiniteelementanalysis.

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简介：Themostsignificantdifferencesbetweencontinuousweldedrails(CWRs)andgeneralsplit-typeconnectorsareaxialcompressioninthelongitudinaldirection,bucklingstabilityandotherissuesgeneratedundertheinfluenceofthermaleffect.Underthermaleffect,adynamicalbehaviorsimilartothatofabeamfixedontwosidesoccursinthecentrallockedareaoftheweldedrail,asthereisaxialcompressionbutnopossibilityofsliding.Continuousweldedrailsdonotcontractorexpand,andaresupportedbythedynamicalsystemmadeupofballastsandrailclips.Therail-supportsystemmentionedabovehasthefeaturesofnon-uniformmaterialdistributionanduncertaintyofconstructionquality.Duetothesefacts,thedynamicsmethodbasedonthelinearelastichypothesiscannotcorrectlyevaluatetherail'sbucklingconditions.ThisstudyisaimedatapplyingFiniteDifferenceMethod(FDM)andMonteCarloRandomNormalVariablesMethodtotheanalysisofweldedrail'sbucklingbehaviorduringthetrain'saccelerationanddeceleration,underthermaleffectanduncertainfactorsofballastandrailclips.Theanalysisresultshowedthatbucklingoccursunderthecombinedeffectofthermaleffectandthetrain'sdecelerationforceco-effectandthevarianceratioofballastandrailclipsisover0.85,orunderthecombinedeffectofthermaleffectandthetrain'saccelerationforcewhenthevarianceratioisover0.88.

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简介：Structuralintegrityisstatedasthescienceandtechnologyofmarginbetweensafetyanddisaster.Systematicpredictionofstructuralintegrityofcriticalstructuressuchascombustionchambers,pressurevessels,nuclearreactorcomponents,boilersetc.,ensuresthehumansafety,environmentalprotection,andtheeconomicalconsiderations.Thepresentworkaimsatpredictionoffatiguebehaviourofsymmetricstructureslikepressurevesselsinthepresenceofcommonweldingdefectssuchaslackoffusion(LOF),lackofpenetration(LOP)andporosity.Aringtypespecimenwhichreplicatesthestresspatterninthepressurevesselisconsideredforthestudyofseverityofweldimperfections.InitialdimensionsofwelddefectsarearrivedbyperformingNDTinspection.Crackgrowthanalysisiscarriedouttodeterminetheremaininglifeoftheweldedjointwithdefects.

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简介：Fordifferentstrengthmatching,thereliabilityindexandfailureprobabilityofweldedpressurepipewithcircumferentialsurfacecrackwerecalculatedusingthreedimensionalstochasticfiniteelementmethod.Thismethodhasovercometheshortcomingsofconservativeresultsinsafetyassessmentwithdeterministicfracturemechanicsmethod.Theeffectsofexternalmomentandthedepthofthecircumferentialsurfacecrack(a)onthereliabilityofpressurepipewerealsocalculatedanddiscussed.Thecalculationresultsindicatethatthestrengthmatchinghascertaineffectonthereliabilityoftheweldedpressurepipewithcircumferentialsurfacecrack.Thefailureprobabilityofweldedpressurepipewithhighstrengthmatchingislowerthanthatwithlowstrengthmatchingatthesameconditions.Theeffectsofstrengthmatchingonthefailureprobabilityandreliabilityindexincreasedbyaddingexternalmoment(M)andthedepthofthecircumferentialsurfacecrack(a).

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简介：Numericalsimulationconcerningtheformingandweldingprocessofspiralweldedpipewasconducted,whichincludedthreesteps:thefirststepwasthestressanalysiswhenthespiralwasformed,andthenthestresswasregardedasinitialconditionofmeldingduringthetemperaturefieldanalysisintheprocessofwelding,thelaststepwasthethermalstressanalysisoftheweldseamaftertheweldingwasover.Moreover,whenthesteelstripwaspushed,thestresswasalsocalculatedbynon-linearitycontacttechnologyusingAbaqusSoftware.Byfiniteelementmodelingandcalculatingoftheformingandweldingprocessofthespiralweldedpipe,thekeypointsofthemulti-fieldssyntheticsimulatingwerestudiedanddiscussed.

简介：Thispaperdescribesthealloydesignphilosophyfortheimprovementoflong-termcreepstrengthoftemperedmartensitic9Crsteel,includingweldedjoints.Thecreeplifetrisinverselyproportionaltotheminimumcreeprateεmintimestheincreaseincreepratebystraindlnε/dεintheaccelerationregionastr=1.5/[(εmin)（dlnε/dε）].Theparametersεminanddlnε/dεarecloselycorrelatedwiththetimetominimumcreepratetmandthestraintominimumcreeprateεm,whichcharacterizethecreepdeformationbehaviorinthetransientregion.Theboundaryandsub-boundaryhardeningisshowntobethemostimportantstrengtheningmechanismincreepof9Crsteelandisenhancedbyfinedispersionsofprecipitatesalongboundaries.TheadditionofboronreducesthecoarseningrateofM23C6carbidesalongboundariesnearprioraustenitegrainboundariesduringcreep.Theenhancementofboundaryandsub-boundaryhardeningincreasesthetmanddecreasestheεmin,whichimprovesthecreeplife.Theboundaryandsub-boundaryhardeningissignificantlyreducedinfine-grainedregionofheataffected-zone（HAZ）ofconventionalsteelP92weldedjoints,promotingTypeⅣfracture.InNIMS9Crboronsteelweldedjoints,thedistributionofcarbonitridesalongboundariesaresubstantiallythesamebetweentheHAZandbasemetal,suppressingtheTypeⅣfracture.

简介：Asameansofsurfacemodificationprocess,metalsurfacenanocrystallization(MSN)hasattractedwidespreadattentionandenjoyedagreatprospect.However,currentlylittleresearchiscarriedoutregardingMSNofweldedjoint.Theprocessesofhighenergyshotpeening(HESP)technologyandultrasonicimpacttreatment(UIT)werecarriedouttoachievejointsurfacenanocrystallization.ThegrainsizeofbeforeandaftertheweldedjointsurfacenanocrystallizationwerecomparativelyanalyzedwithX-raydiffractometer,thesurfacedeformationlayerthicknessofbeforeandaftertheweldedjointsurfacenanocrystallizationwerecomparativelyanalyzedwithopticalmicroscopy,thesurfacehardnessofbeforeandaftertheweldedjointsurfacenanocrystallizationwerecomparativelyanalyzedwithmicrohardnessmachine.TheresultsshowthatbothoftheprocessescanachieveweldedjointsurfacenanocrystallizationandtheweldafterHESPhavesmallergrainsize,largerdeformationlayerthicknessandhigherhardnessvaluesthanthoseafterUIT.However,HESPisrestrainedbytheshapesandsizesofweldingmaterials,sotheUITprocessispreferredtouseinthegeneralengineeringpracticalapplications.

简介：Theobjectiveofthisworkistoanalyzethefatiguereliabilityofcomplexweldedstructurescomposedofmultipleweb-framejoints,accountingforcorrelationeffects.Athree-dimensionalfiniteelementmodelusingthe20-nodesolidelementsisgenerated.Alinearelasticfiniteelementanalysiswasperformed,hotspotstressesinaweb-framejointwereanalyzedandfatiguedamagewasquantifiedemployingtheS-Napproach.Thestatisticaldescriptorsofthefatiguelifeofanon-correlatedweb-framejointcontainingseveralcriticalhotspotswereestimated.Thefatiguereliabilityofaweb-framejointwasmodeledasaseriessystemofcorrelatedcomponentsusingtheDitlevsenbounds.Thefatiguereliabilityoftheentireweldedstructurewithmultipleweb-framejoints,modeledasaparallelsystemofnon-correlatedweb-framejointswasalsocalculated.

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简介：Crackopeningdisplacement(COD)wasappliedtocharacterizethefractureinitiationofthetoughhighdensitypolyethylene.Normalsinglesidenotchedthree-pointbendspecimensandsilicarubberreplicatechniqueswereusedtostudythecharacteristicCODofhigh-densitypolyethylenepipeanditsbutt-fusionjointsincludingtheweldfusionzoneandheataffectedzoneatdifferenttemperaturefrom-78℃to20℃.TestingresultsshowthatthecharacteristicCODappearstodependonthestructuralfeaturesthataredeterminedbyweldingprocessandthetestingtemperature.Asthetemperatureislowered,thecharacteristicCODofallzonesstudieddecreases.Becausetheweldingprocesssignificantlychangessomestructuralfeatureofthematerial,characteristicCODoftheweldfusionzoneisthesmallestoneamongthoseofthethreezones.TheresultscanbeusedfortheengineeringdesignandfailureanalysisofHDPEpipe.

简介：Theweldedjointofdissimilarheat-resistingsteels20Crl2MoV(F12)and12Cr2MoWVTiB(102)generallyworksaround600°C.Inthispaperthreekindsofferriticelectrodesareusedfortesting.TheyareR817high-strengthelectrode(CrllMoVNi),R347low-strengthelectrode(Cr2MoVWB)andnewly-developedR507MoNbmedium-strengthelectrode.Thestudyontheinfluenceofthosethreedifferentelectrodesoncarbonmigration,HICandhy-drogendiffusionshowsthatmedium-strengthelectrodescanwellcontrolthecarbonmigration,andthatthetendencytoHICinthejointformedbyR817issmallerthanthatbyR347instead.Consideringtheeffectofweldmetaltransfor-mationontherestraintstressandhydrogenconcentrationofajoint,thehydro-gendistributionintheheat-affectedzone(HAZ)iscalculatedbyusingfiniteele-mentmethod(FEM)withstressandstrainchanging,andsotheeffectofthetransformationbehaviouronHICisrevealed.Inaddition,newly-developedR507MoNbelectrodes,testedtheelevated-temperatureproperty,oxidationre-sistanceandcreeprupturestrength,havefulfilledthetechnicalstandardscon-cernedandpassedtheexaminationofon-the-spotoperation.

简介：Veryhighcyclefatigue(VHCF)behaviorsofbridgesteel(Q345)weldedjointswereinvestigatedusinganultrasonicfatiguetestsystematroomtemperaturewithastressratioR=-1.Theresultsshowthatthefatiguestrengthofweldedjointsisdroppedbyanaverageof60%comparingtothebasemetalandthefatiguefailurestilloccurredbeyond10~7cycles.Thefatiguefractureofweldedjointsinthelowcycleregimegenerallyoccurredatthesolderwhileattheheat-affectedzone(HAZ)intheveryhighcycleregime.Thefatiguefracturesurfacewasanalyzedwithscanningelectronmicroscopy(SEM),showingweldingdefectssuchaspore,micro-crackandinclusionwerethemainfactorsondecreasingthefatiguepropertiesofweldedjoints.Theeffectofweldingdefectsonthefatiguebehaviorsofweldedjointswasdiscussedintermsofexperimentalresultsandfiniteelementsimulations.

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