Designation:G39−99(Reapproved2011)StandardPracticeforPreparationandUseofBent-BeamStress-CorrosionTestSpecimens1ThisstandardisissuedunderthefixeddesignationG39;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thispracticecoversproceduresfordesigning,preparing,andusingbent-beamstress-corrosionspecimens.1.2Differentspecimenconfigurationsaregivenforusewithdifferentproductforms,suchassheetorplate.Thispracticeapplicabletospecimensofanymetalthatarestressedtolevelslessthantheelasticlimitofthematerial,andtherefore,theappliedstresscanbeaccuratelycalculatedormeasured(seeNote1).Stresscalculationsbythispracticearenotapplicabletoplasticallystressedspecimens.NOTE1—Itisthenatureofthesepracticesthatonlytheappliedstresscanbecalculated.Sincestress-corrosioncrackingisafunctionofthetotalstress,forcriticalapplicationsandproperinterpretationofresults,theresidualstress(beforeapplyingexternalstress)orthetotalelasticstress(afterapplyingexternalstress)shouldbedeterminedbyappropriatenondestructivemethods,suchasX-raydiffraction(1).21.3Testproceduresaregivenforstress-corrosiontestingbyexposuretogaseousandliquidenvironments.1.4Thebent-beamtestisbestsuitedforflatproductforms,suchassheet,strip,andplate.Forplatematerialthebent-beamspecimenismoredifficulttousebecausemoreruggedspeci-menholdersmustbebuilttoaccommodatethespecimens.Adouble-beammodificationofafour-pointloadedspecimentoutilizeheaviermaterialsisdescribedin10.5.1.5Theexposureofspecimensinacorrosiveenvironmentistreatedonlybrieflysinceotherpracticesdealwiththisaspect,forexample,SpecificationD1141,andPracticesG30,G36,G44,G50,andG85.TheexperimenterisreferredtoASTMSpecialTechnicalPublication425(2).1.6Thebent-beampracticegenerallyconstitutesaconstantstrain(deflection)test.Oncecrackinghasinitiated,thestateofstressatthetipofthecra...
