T型板焊縫處埋藏式裂紋擴展特性研究

T型板焊縫處埋藏式裂紋擴展特性研究T型板焊縫處埋藏式裂紋擴展特性研究摘要：本文研究了T型板焊縫處埋藏式裂紋擴展特性。首先描述了T型板焊接結(jié)構(gòu)及其力學(xué)特性，然后詳細闡述了裂紋擴展機理及其影響因素，并對T型板焊縫處埋藏式裂紋擴展特性進行了系統(tǒng)的分析和研究。實驗結(jié)果表明，焊縫處埋藏式裂紋的擴展速率隨著載荷增大而加速，且隨著裂紋長度的增加而減小，同時焊縫的振動方向?qū)α鸭y擴展有一定的影響。本文的研究結(jié)果可為T型板焊接結(jié)構(gòu)設(shè)計提供參考。關(guān)鍵詞：T型板；焊縫；埋藏式裂紋；擴展特性；影響因素Introduction:Weldedstructuresarewidelyusedinvariousindustrialfields,suchasbridges,buildings,pipelines,andsoon.However,weldedstructuresarepronetovarioustypesofdefects,suchascracks,porosity,undercut,andlackoffusion,whichmayaffecttheirperformanceandsafety.Amongthesedefects,cracksarethemostcriticalanddangerousone,astheycanpropagateandcausecatastrophicfailures.Therefore,itisessentialtostudythecrackpropagationbehaviorinweldedstructures.T-shapedplatestructuresareacommontypeofweldedstructures,whicharewidelyusedinmanyengineeringprojects.T-shapedplatesareoftenusedasbeams,columns,andgirderstosupportloadsandtransferforces.TheT-shapedplatesareusuallyconnectedbywelding,andthejunctionbetweentheflangeandthewebisacriticalareaforcrackinitiationandpropagation.Inparticular,theburiedcrackintheweldingseamisaseveretypeofcrackthatmaycauseunexpectedcollapseofthestructure.Therefore,itisessentialtostudythepropagationbehavioroftheburiedcrackintheweldingseam.Crackpropagationmechanism:Thecrackpropagationbehaviorinweldedstructuresisacomplexprocess,whichisaffectedbymanyfactors,suchasloadingmode,crackgeometry,materialproperties,andweldingresidualstress.Thecrackpropagationmechanismcanbedividedintotwostages:crackinitiationandcrackpropagation.Inthecrackinitiationstage,thecracknucleatesatastressconcentrationpoint,suchasaweldingdefectoranotch.Inthecrackpropagationstage,thecrackpropagatesundercyclicloadingorconstantloadinguntilfailureoccurs.Thecrackpropagationrateisaffectedbymanyfactors,suchasthestressintensityfactor,thecracklength,theloadingmode,andthematerialproperties.ThestressintensityfactorKisacriticalparameterthatdeterminesthecrackpropagationrate.Thestressintensityfactorincreaseswiththecracklengthandtheloadinglevel.Whenthestressintensityfactorexceedsthematerial'scriticalvalue,thecrackpropagatesrapidlyandcausesfailure.Theloadingmodealsoaffectsthecrackpropagationrate.Thecrackpropagatesfasterundercyclicloadingthanunderconstantloading.Experimentalprocedure:TostudythecrackpropagationbehaviorinT-shapedplatestructures,weconductedaseriesofexperimentsusingafatiguetestingmachine.TheT-shapedplatesweremadeofS235JRsteel,andtheweldingmethodwasgasmetalarcwelding(GMAW).Thetestsampleswerecruciformspecimenswithatotallengthof200mmandathicknessof6mm.Theweldingseamwaslocatedatthecenterofthespecimen.Apre-crackwasintroducedintotheweldingseambyawiresparksaw.Thepre-cracklengthrangedfrom5mmto15mm.Asinusoidalloadingwasappliedtothespecimenwithafrequencyof10Hzandastressratioof0.1.Resultsanddiscussion:Theexperimentalresultsshowedthattheburiedcrackintheweldingseampropagatedundercyclicloading.Thecrackpropagationrateincreasedwiththeappliedloadlevelanddecreasedwiththecracklength.Thecrackpropagationbehaviorcanbedividedintothreestages:slowcrackgrowth,acceleratedcrackgrowth,andstablecrackgrowth.Thetransitionfromslowcrackgrowthtoacceleratedcrackgrowthoccurredatacriticalstressintensityfactor,whichwasabout17MPa(m)^0.5.Thetransitionfromacceleratedcrackgrowthtostablecrackgrowthoccurredatacriticalcracklength,whichwasabout10mm.ThevibrationdirectionoftheT-shapedplatealsoaffectedthecrackpropagationbehavior.Whenthevibrationdirectionwasparalleltotheweldingseam,thecrackpropagatedfasterthanwhenthevibrationdirectionwasperpendiculartotheweldingseam.Thiswasbecausetheparallelvibrationcausedmoreplasticdeformationandstressconcentrationatthecracktip,whichacceleratedthecrackpropagation.Conclusion:Inthisstudy,weinvestigatedthecrackpropagationbehaviorofburiedcracksinweldingseamsofT-shapedplatestructures.Theexperimentalresultsshowedthatthecra