T型板焊缝处埋藏式裂纹扩展特性研究

T型板焊缝处埋藏式裂纹扩展特性研究T型板焊缝处埋藏式裂纹扩展特性研究摘要：本文研究了T型板焊缝处埋藏式裂纹扩展特性。首先描述了T型板焊接结构及其力学特性，然后详细阐述了裂纹扩展机理及其影响因素，并对T型板焊缝处埋藏式裂纹扩展特性进行了系统的分析和研究。实验结果表明，焊缝处埋藏式裂纹的扩展速率随着载荷增大而加速，且随着裂纹长度的增加而减小，同时焊缝的振动方向对裂纹扩展有一定的影响。本文的研究结果可为T型板焊接结构设计提供参考。关键词：T型板；焊缝；埋藏式裂纹；扩展特性；影响因素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