Advances in Fatigue and Fracture Mechanics Analyse

April2000NASA/TM-2000-210084AdvancesinFatigueandFractureMechanicsAnalysesforMetallicAircraftStructuresJ.C.Newman,Jr.LangleyResearchCenter,Hampton,VirginiaTheNASASTIProgramOffice...inProfileSinceitsfounding,NASAhasbeendedicatedtotheadvancementofaeronauticsandspacescience.TheNASAScientificandTechnicalInformation(STI)ProgramOfficeplaysakeypartinhelpingNASAmaintainthisimportantrole.TheNASASTIProgramOfficeisoperatedbyLangleyResearchCenter,theleadcenterforNASAÕsscientificandtechnicalinformation.TheNASASTIProgramOfficeprovidesaccesstotheNASASTIDatabase,thelargestcollectionofaeronauticalandspacescienceSTIintheworld.TheProgramOfficeisalsoNASAÕsinstitutionalmechanismfordisseminatingtheresultsofitsresearchanddevelopmentactivities.TheseresultsarepublishedbyNASAintheNASASTIReportSeries,whichincludesthefollowingreporttypes:·TECHNICALPUBLICATION.ReportsofcompletedresearchoramajorsignificantphaseofresearchthatpresenttheresultsofNASAprogramsandincludeextensivedataortheoreticalanalysis.Includescompilationsofsignificantscientificandtechnicaldataandinformationdeemedtobeofcontinuingreferencevalue.NASAcounterpartofpeer-reviewedformalprofessionalpapers,buthavinglessstringentlimitationsonmanuscriptlengthandextentofgraphicpresentations.·TECHNICALMEMORANDUM.Scientificandtechnicalfindingsthatarepreliminaryorofspecializedinterest,e.g.,quickreleasereports,workingpapers,andbibliographiesthatcontainminimalannotation.Doesnotcontainextensiveanalysis.·CONTRACTORREPORT.ScientificandtechnicalfindingsbyNASA-sponsoredcontractorsandgrantees.·CONFERENCEPUBLICATION.Collectedpapersfromscientificandtechnicalconferences,symposia,seminars,orothermeetingssponsoredorco-sponsoredbyNASA.·SPECIALPUBLICATION.Scientific,technical,orhistoricalinformationfromNASAprograms,projects,andmissions,oftenconcernedwithsubjectshavingsubstantialpublicinterest.·TECHNICALTRANSLATION.English-languagetranslationsofforeignscientificandtechnicalmaterialpertinenttoNASAÕsmission.SpecializedservicesthatcomplementtheSTIProgramOfficeÕsdiverseofferingsincludecreatingcustomthesauri,buildingcustomizeddatabases,organizingandpublishingresearchresults...evenprovidingvideos.FormoreinformationabouttheNASASTIProgramOffice,seethefollowing:·AccesstheNASASTIProgramHomePageat·[e-mail]·FaxyourquestiontotheNASASTIHelpDeskat(301)621-0134·PhonetheNASASTIHelpDeskat(301)621-0390·Writeto:NASASTIHelpDeskNASACenterforAeroSpaceInformation7121StandardDriveHanover,MD21076-1320NationalAeronauticsandSpaceAdministrationLangleyResearchCenterHampton,Virginia23681-2199April2000NASA/TM-2000-210084AdvancesinFatigueandFractureMechanicsAnalysesforMetallicAircraftStructuresJ.C.Newman,Jr.LangleyResearchCenter,Hampton,VirginiaAvailablefrom:NASACenterforAeroSpaceInformation(CASI)NationalTechnicalInformationService(NTIS)7121StandardDrive5285PortRoyalRoadHanover,MD21076-1320Springfield,VA22161-2171(301)621-0390(703)605-6000ADVANCESINFATIGUEANDFRACTUREMECHANICSANALYSESFORMETALLICAIRCRAFTSTRUCTURESJ.C.Newman,Jr.*Thispaperreviewssomeoftheadvancesthathavebeenmadeinstressanalysesofcrackedaircraftcomponents,intheunderstandingofthefatigueandfatigue-crackgrowthprocess,andinthepredictionofresidualstrengthofcomplexaircraftstructureswithwidespreadfatiguedamage.Finite-elementanalysesofcrackedmetallicstructuresarenowusedtodetermineaccuratestress-intensityfactorsforcracksatstructuraldetails.Observationsofsmall-crackbehavioratopenandrivet-loadedholesandthedevelopmentofsmall-cracktheoryhasleadtothepredictionofstress-lifebehaviorforcomponentswithstressconcentrationsunderaircraftspectrumloading.Fatigue-crackgrowthundersimulatedaircraftspectracannowbepredictedwiththecrack-closureconcept.Residualstrengthofcrackedpanelswithsevereout-of-planedeformations(buckling)inthepresenceofstiffenersandmultiple-sitedamagecanbepredictedwithadvancedelastic-plasticfinite-elementanalysesandthecriticalcrack-tip-openingangle(CTOA)fracturecriterion.Theseadvancesarehelpingtoassurecontinuedsafetyofaircraftstructures.INTRODUCTIONIn1969,SchijveintheSecondFrederikJ.PlantemaMemorialLecture[1]statedthat“fatigueinaircraftstructuresisaproblemforwhichquantitativeandgenerallyacceptedsolutionsarenotavailable.”Duringthepast30years,manyadvanceshavebeenmadeinthestressanalysesofcrackedaircraftcomponents,inunderstandingthefatigueandfatigue-crackgrowthbehaviorinmetallicmaterials,andinthepredictionofresidualstrengthofcomplexbuilt-upaircraftstructureswithwidespreadfatiguedamage.Althoughthefailurerateinaircraftstructuresduetofatigueandstructuralfailurehasdroppedsignificantly[2]fromthemid-1950’s,thefatigueandfracturecommunitymuststayalert.Thetechnicalcommunityshouldcontinuetoimprovetheunderstandingofthefatigueandfractureprocessandtousetheadvancedanalysistoolstosafeguardthepublicagainstunexpectedfailuremodes,suchastheAlohaAirlinesfuselagefailurein1988duetowidespreadfatiguedamage.Swift,intheEleventhPlantemaLecture[3],discussedhowmultiple-sitedamagecrackingcouldreducetheresidualstrengthoffuselagestructures.TheSeventeenthP