Effectoflocalwallthinningonthecollapsebehaviorofpipeelbowssubjectedtoacombinedinternalpressureandin-planebendingloadOriginalResearchArticle

Theobjectiveofthisstudywastoinvestigatetheeffectoflocalwallthinningonthecollapsebehaviorofpipeelbowssubjectedtoacombinedinternalpressureandin-planebendingload.Thisstudyevaluatedtheglobaldeformationbehaviorandcollapsemomentoftheelbows,whichcontainedvarioustypesoflocalwall-thinningdefectsattheirintradosorextrados,usingthree-dimensionalelastic–plasticfiniteelementanalysis.Theanalysisresultsshowedthattheglobaldeformationbehavioroflocallywall-thinnedelbowswaslargelygovernedbythemodeofthebendingandtheelbowgeometryratherthanthewall-thinningparameters,exceptforelbowswithconsiderablylargeanddeepwallthinningthatshowedplasticinstabilitiesinducedbylocalbucklingandplasticcollapsinginthethinnedarea.Thereductioninthecollapsemomentwithwall-thinningdepthwasconsiderablewhenlocalbucklingoccurredinthethinnedareas,whereastheeffectofthethinningdepthwassmallwhenovalizationoccurred.Theeffectsofthecircumferentialthinningangleandthinninglengthonthecollapsemomentofelbowswerenotmajorforshallowwall-thinningcases.Fordeeperwall-thinningcases,however,theireffectsweresignificantandthedependenceofcollapsemomentontheaxialthinninglengthwasgovernedbythestresstypeappliedtothewall-thinnedarea.Typically,thereductioninthecollapsemomentduetolocalwallthinningwasclearerwhenthethinningdefectwaslocatedattheintradosratherthantheextrados,anditwasapparentforelbowswithlargerbendradius.