283-paper-Effects of the Striking Edge Radius on t

SECRETARIATUSE;Headershouldbeblank.SECRETARIATUSE;FootershouldbeblankEffectsoftheStrikingEdgeRadiusontheCharpyImpactTestatDifferentTemperatureLIHepingZHOUXingXUWeichengWANGHongxin(ManufacturingDepartment,BaosteelBranch,BaoshanIron&SteelCo.LTD.Shanghai200941,China)Abstract:Therearetwodifferenttypesofstrikers,withradiusof2mmand8mm.DifferenteffectsofthesestrikingedgeradiusontheCharpyimpacttestinlowershelfzone,transitionzoneanduppershelfzoneofabsorbedenergyandthecurveasafunctionoftemperaturearedescribedinthispaper.AnopiniontorisetheacceptedcriterionforordinarystrengthshipsteeltestedaccordingtoISOorGBstandardisputforward.Keywords:Charpyimpacttest,lowershelfzone,transitionzone,uppershelfzone0IntroductionCharpynotched-barimpacttestisusedwidelytodeterminethetendencyofamaterialtobehaveinabrittlemanner.TherearetwotypesofCharpyimpactmachines:oneisaccordingtoASTMstandardwith8mmradiusstriker,anotherisaccordingtoISO(includedGB,JIS,DIN,etc.)standardwith2mmradiusstriker.Forsamematerialthesetwotypemachineswillgivedifferentabsorbedenergy.Thedifferencemustbeconsideredfortheacceptedcriterion.Aspecialandveryimportantexampleisordinarystrengthhullsteel.DuringWorldWarIIagreatdealofattentionwasdirectedtothebrittlefailureofweldedLibertyShipsandT-2Tankers.Abroadresearchprogramwasundertakentofindthecausesofthesefailuresandtoprescribetheremediesfortheirfutureprevention.A15ft-lb(20.3J)Charpyabsorbedenergytransitiontemperaturehasbecomeanacceptedcriterionforlow-strengthhullsteel[1].Theseresearchworksarethebaseofrecentrequirementsonabsorbedenergyforordinarystrengthhullsteels.Thereisafactthatit’swidelyignored:itis8mmradiusstrikermachinewasusedfortheseresearchworks.Withoutdistinction,theacceptedcriteriononCharpyabsorbedenergycanbefoundinrulesofdifferentBureausofShipping[2-4]while2mmradiusstrikermachineisrequiredforCharpyimpacttest.It’sreportedthatinuppershelfzonetheabsorbedenergyobtainedfromISOstandardmachinesislowerthanthatfromASTMstandardmachines[5].Asacceptedcriterionofabsorbedenergylevelisintransitionzoneformildsteels,whetherthisresultisstillrightintransitionzoneshouldbemoreimportantthaninuppershelfzone.ToinvestigatetheeffectsofstrikerradiusonCharpyimpactabsorbedenergysystematically,aserialcomparisiontestswithASTMstandardmachineandISOstandardmachineinlowershelftemperaturezone,transitiontemperaturezoneanduppershelftemperaturezonehavebeendone.Someconclusionswhichconflictwiththerulesbeenusedforalongtimehavebeeninferred.1ExperimentandResultsTobeconvenientforcalculatinguncertaintyofmeasurement,thefollowingtestingstepsareSECRETARIATUSE;Headershouldbeblank.SECRETARIATUSE;Footershouldbeblanktakenwith8mmradiusstrikermachineand2mmradiusstrikermachine:(1)test2piecesreferenceV-notchspecimenat19ºCtemperature;(2)test6piecesSS400steelV-notchspecimenat19ºCtemperature;(3)test6piecesSS400steelV-notchspecimenat-20ºCtemperature;(4)test6piecesSS400steelV-notchspecimenat-40ºCtemperature;(5)test2piecesreferenceV-notchspecimenat19ºCtemperature.TheseSS400steelV-notchspecimensaretakenfromsameplateinanearbyarea.Afterthesetestings,itisnoticedthatthelowershelfzoneofabsorbedenergyhavenotappeared.Togetdatainlowershelfzoneofabsorbedenergy,someadditionalSS400steelV-notchspecimensaremadeandtestedat-60ºC,-70ºCand-80ºC.Ateachtemperature,6piecesSS400steelspecimenaretestedwith8mmradiusstrikermachineand6pieceswith2mmradiusmachine.Accordingtothetests,thetendencyofabsorbedenergywithSS400steelV-notchspecimensobtainedisshowedinfig.1.Fig.1:AbsorbedenergyofISOandASTMstrikersatdifferenttemperature2UncertaintyofMeasurement2.1ArithmeticmeanvaluesandstandarddeviationofV-notchquasireferencespecimenSimilarastensiletest[6],therearemanyfactorswhichinfluenceuncertaintyofCharpypendulumimpacttest,andsomeofthemcannotbequantified.ToevaluatetheuncertaintyofCharpypendulumimpacttestreliably,itisnecessarytousereferencespecimensorquasireferencespecimens.Inthispaper,theauthorsuseamethodsimilartoISO/DIS6507[7]toevaluatemeasurementuncertaintyforCharpypendulumimpacttest.TheV-notchquasireferencespecimensaremadeaccordingtoaChinesepatent[8-9]asreferencematerial.25V-notchquasireferencespecimenswith7.5mminwidtharetestedby2mmstrikerand8mmstrikerofCharpyimpactmachinesrespectively.Thearithmeticmeanvalueofall25quasireferencespecimenstestedby2mmstrikermachineis202jouleswithastandarddeviation6.17joules.Thearithmeticmeanvalueofall25quasireferencespecimenstestedby8mmstrikermachineis231jouleswithastandarddeviation6.69joules.After1datumiseliminatedfrom25dataaccordingtoGrubbsrule,thearithmeticmeanvalueofall24quasiSECRETARIATUSE;Headershouldbeblank.SECRETARIATUSE;Footershouldbeblankreferencespecimenstestedby2mmstrikermachineis201jouleswithastandarddeviation4.99joules.Thearithmeticmeanvalueofall24quasireferencespecimenstestedby8mmstrikermachineis232jouleswithastandarddeviation5.45joules.2.2CalculatetheuncertaintyTheauthorstrytousequasi-referencematerialtoestimateuncertaintyofmeasurementinCharpyimpacttestandusethemethodsimilartoISO/CD6507tocalculatetheuncertaintyofmeasurementonabsorbedenergy.Togetreliableuncertaintyofmeas