ASTM-E290弯曲试验英文作业指导书

OperationInstructionofBendTestingofMaterialforDuctilityDocumentCodeZYZDS-30StateControlledOperationNameStandardTestMethodsforBendTestingofMaterialforDuctilityRefereneeStandardASTME290-97aScopeThesetestmethodscoverbendtestingforductilityofmaterials.Includedintheproceduresarefourconditionsofconstraintonthebentportionofthespecimen;aguided-bendtestusingamandrelorplungerofdefineddimensionstoforcethemid-lengthofthespecimenbetweentwosupportsseparatedbyadefinedspace;asemi-guided-bendtestinwhichthespecimenisbent,whileincontactwithamandrel,throughaspecifiedangleortoaspecifiedinsideradius(r)ofcurvature,measuredwhileunderthebendingforce;afree-bendtestinwhichtheendsofthespecimenarebroughttowardeachother,butinwhichnotransverseforceisappliedtothebenditselfandthereisnocontactoftheconcaveinsidesurfaceofthebendwithothermaterial;abendandflattentest,inwhichatransverseforceisappliedtothebendsuchthatthelegsmakecontactwitheachotheroverthelengthofthespecimen.t.Afterbending,theconvexsurfaceofthebendisexaminedforevideneeofacrackorsurfaceirregularity.Ifthespecimenfractures,thematerialhasfailedthetesWhencompletefracturedoesnotoccur,thecriterionforfailureisthenumberandsizeofcracksorothersurfaceirregularityvisibletotheunaidedeyeoccurringontheconvexsurfaceofthespecimenafterbending,asspecifiedbytheproductstandard.Anycrackswithinonethicknessoftheedgeofthespecimenarenotconsideredabendtestfailure.Cracksoccurringinthecornersofthebentportionshallnotbeconsideredsignificantuniesstheyexceedthesizespecifiedforcornercracksintheproductstandard.t.ThevaluesstatedinSIunitsaretoberegardedasstandard.Inch-poundvaluesgiveninparentheseswereusedinestablishingtestparametersandareforinformationonly.ProcedureDirectionofTest:IntestsofIongitudinalspecimens,theaxisofthebendshallbe90°tothedirectionofrolling,forging,drawing,orextrusion.Intestsoftransversespecimens,theaxisofthebendshallbeparalleltothedirectionofrolling,forging,drawing,orextrusion.Forroundspecimensmachinedfromsectionsotherthanroundsections,thesurfaceofthespecimenshallbeparalleltothesurfaceoftheparentproduct.SurfaceSubjectedtoTension—Intestsofreducedthicknessspecimens,thetensionsurfaceshallbetheas-fabricatedsurfaceofthesection.ProcedurefortheGuided-BendTest:2.3.1Placethetworoundedaclearanee2.3.1Placethetworoundedaclearaneeequalto(才+3t), ±2),asshowninFig.3,wheret)isthespecimenthickness.ForceSDKimenSDKimen「…—Farce Forcet-2r* +t/2NOTE1—C=distaneebetweenlowersupports,r=radiusoftheendofthemandrelorplunger,t=sheetspecimenthickness,d=roundspecimendiameter,andw=sheetspecimenwidth.FIG.3SchematicFixturefortheGuided-BendTestBendthespecimenbyapplyingaforcethroughaplungerormandrelincontacwiththespecimenatthemid-lengthbetweensupports(C/2)ontheoppositesideofthespecimenfromtheendsupports.Applythebendingforcesmoothlyandwithoutshock.Continuebendinguntilfailureoccurs,oruntilthespecifiedangleofbend,ormaximumangleforthefixtureisachieved.Theangleofbendismeasuredwhilethespecimenisunderthebendingforce.WhentherequiredanglecannotbeachievedinthebendfixtureshowninFig.3,completethetestbypressingthespecimenbetweensuitableplatensuntilthespecifiedconditionsofbendareobtained,asshowninFig.4.Applytheforcesmoothly,withoutshock.Whenitisdesirednottoexceed180°ofbendwhilecompletingthebend,placebetweenthetwolegsofthespecimenaspacerhavingathicknesstwicetherequiredbendradius.ProceduresforSemi-GuidedBendTests:Theprocedureforperformingthetestshallfollowoneofthreemethods:A—HeldEnd,B—BendAreaSupported,orC—MandrelGuided.rarceForetFIG.4SchematicFixtureforCompletingtheGuided-BendTestStartedasShowninFig.3

242Held-End—ArrangementA:Securelyholdoneendofthespecimensothattheaxisofbendingliesonthcenterlineofthereactionpinorroller.2.422BendthespecimenbyemployingafixtureembodyingtheappropriatefeaturesshowninFig.5.FreeEndForceAppliedNearFreeEndForceAppliedNearApplythebendingforcesmoothly,withoutshock.Continuebendinguntilthespecifiedangleofbendisachievedwiththespecimeninthebendfixtureandunderthebendingforce,oruntilfailureoccurs.ArrangementIB—BendAreaSupported—ThinMaterial:Holdoneendofthespecimensecurelyagainstthebendsupportbyclamp,inavise,asshowninFig.6.Thesupportshallextendaminimumoftwospecimenwidthsbeyondtheclamp.Usingamallet,hammerthespecimenovertheroundededgeofthesupport.Donotstrikethespecimeninanareathatwillformanypartofthebend.FIG.6ArrangementBforSemi-Guided-BendTestofThinSpecimens—FIG.6ArrangementBforSemi-Guided-BendTestofThinSpecimens—OneEndHeldContinuebendinguntilthespecifiedangleofbendisachievedorfailureoccurs.Whenhammerblowsarethesourceofthebendingforce,theangleofbendshallbemeasuredundernoforce.Incaseofdispute,theHeld-EndArrangementAof2.4.2shallbeused.Mandrel-guidedBenc—ArrangementC:oneendasshowninFig.7.

oneendasshowninFig.7.forctrotationDcvjccFo-ceforctrotationDcvjccFo-ceFIG.7SchematicFixtureforSemi-Guided-BendTestArrangementC—OneEndHeld—ForceAppliedNearMandrelPlaceareactionpin,withthespecifiedbendradiusf)againstthespecimen.Ifthethicknessofthespecimenhasbeenreducedbymachining,themachinedsurfaceistobeplacedagainstthepin.Forbendanglesof180orless,aradiusedsurfacemaybesubstitutedforthepin.2.443Holdasecondmandrelincontactwiththeoppositesurfaceofthespecimenandrotatethismandrelunderforceinanarctomaintaintheinsideofthebendsurfaceagainstthefirstmandrel.Theradiusofthesecondmandrelisnotcriticalandcanbeofanyconvenientsize.Thesecondmandrelcanemployarollerasthecontactsurfacewiththespecimen.Continuebendinguntilthematerialsuccessfullyreachesthespecifiedangleoruntilfailureinthebendoccurs.Theangleofbendismeasuredwhilethespecimenisunderthebendingforce.ProceduresforFree-BendTests:Initiatethebendbygraspingthespecimenneareachendandbringingtheendstowardeachother,providedthematerialissufficientlyductile.Ifthematerialdoesnotbendeasily,useadevicesuchasthatshowninFig.8toinitiatethebend.FIG.8Free-BendSupportandForce「丄?TForteFIG.8Free-BendSupportandForce「丄?TType1-Free-BendTest—ContinuebendingthespecimenunderforceinaclampingdeviceuntilthetwolegsareparallelasshowninFig.9.ThiscompletestheType1,180,f°e-bendtest.Type2-Free-BendTest—Ifthetestrequirementisthatthetwolegsbeincontact,theforceoftheclampingdeviceiscontinueduntiltheconditionshowninFig.10isreached,withoutapplyingforceatanylocationlessthanonespecimenwidthfromtheouterendofthebend.ThisisreferredtoasaType2,flat-on-itself,free-bendtest.ProcedurefortheBendandFlattenTest:Formaninitialbendtoanangleofapproximately180°usingtheprocedureoutlinedin2.5.1.?orceFgrceFIG.10Type2Flat-on-ItselfFree-BendPlacethespecimenbetweentwoplatensthatwillcoverthebentportionofthespecimen.ApplyforceuntilthespecimenisflattenedasshowninFig.11.FaresFIG.11BendandFlattenTheflatteningoperationmaydevelopIongitudinalstrainsexceedingtheforminglimitofthematerial.Thisisdependentonthematerialandthespecimenthickness.Bendingfollowedbyflatteningimposesextremeouterfiberstressesandthe

materialmayshowexternalcrackinginthebendortheremaybecompressivefailuroftheinsidesurfaceoftheeyeofthebend.2.632Theouterfiberstrainisreducedwhentheinsideofthebendcollapses,asshowninFig.12,sincethisreducestheamountofstretchingoftheoutersurface.Thismaybesufficienttoavoidsurfacecracksontheoutersurfaceofthebend.HL*viewHL*viewQefiG- orthewndFIG.12BendofMaterial(EyeoftheBendCollapsed)2.633Iftheinsideofthebenddoesnotcollapse,itispossibleforexcessivestrainstodevelopthatcausetheoutersurfaceofthebendtocrack,asshowninFig.13.ExaminationoftheSurfaceoftheBend—Thebendspecimenmayberemovedaanytimeduringthebendingoperationforinspectionoftheconvexsurfaceofthebendforthepreseneeofcracksorirregularities.Subsequentbendingshallbecontinuedimmediatelyfollowingtheexamination.viwviw调呗-如律r 駅色and电创或“共碎FIG.13BendandFlattenBendofMaterial(EyeoftheBendDidNotCollapse)AngleofBend—Theangleofbendisdeterminedbytheprojectionoflineswiththeflatsurfacesofthespecimenoutsideofthebendregionandistheintersectingangleoftheselines.Whenthebendingiscompleted,theradiusofthebendthroughoutthebendregion,undernoforceuniessspecifiedotherwise,shallnotbesmallerthantherequiredvaluespecifiedintheproductstandard.Springback,whenthebendingforceisreleased,willcausetheradiusandangofbendtoincrease.Noadjustmentinthebendangleshallbemadetoadjustforspringback.Ifthematerialcollapsesbyalocalizedkink,thetestisnotvalid.Analternativeprocedureshallbeusedtocontroltheinsidebendradius.Thetestiscompletewhenthespecifiedconditionsofbendareachieved.Ifsignificantcracksappearintheoutersurfaceofthebendwhilethebendingforceisbeingapplied,thetestshallbestoppedandthematerialshallbeevaluatedaccordintotheappropriateproductstandard.Cracksoccurringinthecornersofthebentportionshallnotbeconsideredsignificantuniesstheyexceedthesizespecifiedforcornercracks.Ifnocracksizeisspecified,cornercracksnotexceedingthenominalthicknessofthespecimenshallnotbeconsideredafailure.2.8.5Inteststhetestbeconsidered2.8.5Inteststhetestbeconsideredcompletedwhentheacceptaneeconditionshavebeenmet.SpeedofBending—Therateofmotioninformingabendshallconformtothatoftheanticipatedprocessapplicationofthematerialbeingtested.Whennorateisspecified,thetestshallbeconductedatarateconsistentwithsafepracticeforthemethod.AmbientconditionsforISO7438testingonly.Testingisconductedbetween10°Cand35°Cuniessotherwisespecifiedintheapplicablestandard.ControlledconditionsforISO7438testingonly.Testingisconductedbetween18°Cand28CAnyareasofmaterialaffectedbyshearing,flamecuttingandsimilaroperationsareremoved.Testingspecimenwheretheaffectedpartshavenotbeenremovedisacceptableprovidedtheresultsaresatisfactory.EvaluationExaminetheconvexsurfaceofthebentspecimenforcracksorotheropendefects,usingtheunaidedeye(withoutmagnification).Edgecracksassociatedwithsamplepreparationshallnotbeconsideredduringtheevaluation.Whenthetestisconductedasanacceptancecriterion,theallowablecracksizshallbespecifiedbythecodeorspecificationrequiringthetest.Materialthatissusceptibletoagehardeningshallbetestedwithinthetimeallowedbytheproductspecification.Surfaceirregularities,lossofcoatingadherence,or