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INTERNATIONALISOSTANDARD23146Secondedition2012-12-15Fineceramics(advancedceramics,advancedtechnicalceramics)—Testmethodsforfracturetoughnessofmonolithicceramics—Single-edgeV-notchbeam(SEVNB)methodCéramiquestechniques—Méthodesd’essaipourladéterminationdelaténacitéàlarupturedescéramiquesmonolithiques—MéthodesuréprouvetteàentailleenVsuruneseuleface(MéthodeSEVNB)ReferencenumberISO23146:2012(E)--`,,```,,,,````-`-`,,`,,`,`,,`---CopyrightInternationalOrganizationforStandardization©ISO2012ProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)--`,,```,,,,````-`-`,,`,,`,`,,`---COPYRIGHTPROTECTEDDOCUMENT© ISO2012Allrightsreserved.Unlessotherwisespecified,nopartofthispublicationmaybereproducedorutilizedinanyformorbyanymeans,electronicormechanical,includingphotocopyingandmicrofilm,withoutpermissioninwritingfromeitherISOattheaddressbeloworISO’smemberbodyinthecountryoftherequester.ISOcopyrightofficeCasepostale56•CH-1211Geneva20Tel.+41227490111Fax+41227490947E-mailcopyright@iso.orgWebwww.iso.orgPublishedinSwitzerlandii©ISO2012–AllrightsreservedCopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)ContentsPageForeword........................................................................................................................................................................................................................................iv1Scope.................................................................................................................................................................................................................................12Normativereferences......................................................................................................................................................................................13Termsanddefinitions.....................................................................................................................................................................................14Principle........................................................................................................................................................................................................................15Apparatus.....................................................................................................................................................................................................................26Testpiecepreparation....................................................................................................................................................................................36.1Numberoftestpieces.......................................................................................................................................................................36.2Test-piecedimensions......................................................................................................................................................................46.3PreparingtheV-notchbyhand.................................................................................................................................................46.4PreparingtheV-notchesbymachine(optional)........................................................................................................76.5Determinationofnotch-rootradius.....................................................................................................................................77Testprocedure........................................................................................................................................................................................................8--`,,```,,,,````-`-`,,`,,`,`,,`---7.1Dimensionsoftestpiece.................................................................................................................................................................87.2Flexural-strengthtest........................................................................................................................................................................87.3Measurementofnotchdepth......................................................................................................................................................97.4Calculationoffracturetoughness...........................................................................................................................................98Precisionandbias............................................................................................................................................................................................119Testreport................................................................................................................................................................................................................11AnnexA(informative)Notchhoningbymachine................................................................................................................................12AnnexB(informative)InterlaboratoryevaluationoftheSEVNBfracturetoughnesstestprocedures...................................................................................................................................................................................................14AnnexC(informative)Correctionsforeffectivecracklengthgreaterthannotchdepth............................16Bibliography.............................................................................................................................................................................................................................17©ISO2012–AllrightsreservediiiCopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)ForewordISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies(ISOmemberbodies).TheworkofpreparingInternationalStandardsisnormallycarriedoutthroughISOtechnicalcommittees.Eachmemberbodyinterestedinasubjectforwhichatechnicalcommitteehasbeenestablishedhastherighttoberepresentedonthatcommittee.Internationalorganizations,governmentalandnon-governmental,inliaisonwithISO,alsotakepartinthework.ISOcollaboratescloselywiththeInternationalElectrotechnicalCommission(IEC)onallmattersofelectrotechnicalstandardization.InternationalStandardsaredraftedinaccordancewiththerulesgivenintheISO/IECDirectives,Part2.ThemaintaskoftechnicalcommitteesistoprepareInternationalStandards.DraftInternationalStandardsadoptedbythetechnicalcommitteesarecirculatedtothememberbodiesforvoting.PublicationasanInternationalStandardrequiresapprovalbyatleast75%ofthememberbodiescastingavote.Attentionisdrawntothepossibilitythatsomeoftheelementsofthisdocumentmaybethesubjectofpatentrights.ISOshallnotbeheldresponsibleforidentifyinganyorallsuchpatentrights.ISO23146waspreparedbyTechnicalCommitteeISO/TC206,Fineceramics.Thissecondeditioncancelsandreplacesthefirstedition(ISO23146:2008),ofwhichitconstitutesaminorrevision.--`,,```,,,,````-`-`,,`,,`,`,,`---iv©ISO2012–AllrightsreservedCopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale INTERNATIONALSTANDARDISO23146:2012(E)Fineceramics(advancedceramics,advancedtechnicalceramics)—Testmethodsforfracturetoughnessofmonolithicceramics—Single-edgeV-notchbeam(SEVNB)method1ScopeThisInternationalStandardspecifiesamethodforthedeterminationofthefracturetoughnessofadvancedtechnicalceramics.Theproceduremakesuseofsingle-edgeV-notchedbars,whichareloadedinfour-pointbendinguntilfailure.Itisapplicabletomonolithicceramicswithagrainsizeormajormicrostructuralfeaturesizelargerthanabout1µm.TheuseofthisInternationalStandardforyttriatetragonalzirconiapolycrystalmaterial(Y-TZP)isnotrecommended.ThemethodmightalsobeunsuitableforsomeotherverytoughorsoftceramicsinwhichasharpcrackdoesnotformattherootoftheV-notch.2NormativereferencesThefollowingreferenceddocumentsareindispensablefortheapplicationofthisdocument.Fordatedreferences,onlytheeditioncitedapplies.Forundatedreferences,thelatesteditionofthereferenceddocument(includinganyamendments)applies.ISO3611,Geometricalproductspecifications(GPS)—Dimensionalmeasuringinstruments;Micrometersforexternalmeasurements—DesignandmetrologicalcharacteristicsISO7500-1,Metallicmaterials—Verificationofstaticuniaxialtestingmachines—Part1:Tension/compressiontestingmachines—Verificationandcalibrationoftheforce-measuringsystemISO14704,Fineceramics(advancedceramics,advancedtechnicalceramics)—TestmethodforflexuralstrengthofmonolithicceramicsatroomtemperatureISO15732,Fineceramics(advancedceramics,advancedtechnicalceramics)—Testmethodforfracturetoughnessofmonolithicceramicsatroomtemperaturebysingleedgeprecrackedbeam(SEPB)method3TermsanddefinitionsForthepurposesofthisdocument,thetermsanddefinitionsgiveninISO15732apply.4PrincipleThismethodofconductingafracturetoughnesstestisbasedonthepreparationandfractureofbartestpiecesinwhichasharp-tippednotchismachined.Usingthetechniqueofareciprocatingrazorbladeanddiamondpaste,anarrownotchcanbehonedintoatestpieceusingeitheramanualmethodorasimplemachine.Underwell-controlledconditions,anotch-tipradiusintherangeof1µmto20µmcanbeprepareddependingonthegrainsizeofthetestmaterial.Formanymaterials,thisisacloseapproximationtoasharpcrack,andthemethodhasbeenfoundtogivefracturetoughnessvaluesveryclosetothoseofothermethodssuchasthesingle-edgeprecrackedbeammethod(ISO15732)orthesurfacecrackinflexuremethod(ISO18756),providedthatasharpcrackformsattherootofthenotcheitherduringitspreparationorduringthesubsequentfracturesequence.Themethodhastheadvantageofsimplicityofnotchproductioncomparedwithusingasharp-tippeddiamondsaworadiamondimpregnatedwireinwhichthetipradiusisnormallygreaterthan50µm.Themethodisoften--`,,```,,,,````-`-`,,`,,`,`,,`---©ISO2012–Allrightsreserved1CopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)easiertoundertakecomparedwithothermethodsofprecrackingandisapplicabletoawiderrangeofmaterialsoutsidethescopeofthesemethods.Themethodhasbeenextensivelyresearched(seetheBibliography)andhasbeenevaluatedinanESIS(EuropeanStructuralIntegritySociety)/VAMAS(VersaillesAgreementonAdvancedMaterialsandStandards)roundrobin,theresultsofwhicharesummarizedinAnnexB.ThisrecommendedpracticeisbasedupontheESIS/VAMASSEVNBroundrobin.Themethodmayhavesomelimitationsformaterialswithgrainsizesoflessthan1µm,forwhichtheassumptionthatthenotchapproximatestoasharpcrackmaynotbevalid(seeAnnexC).Usersshouldstrivetominimizethenotch-rootradiusinthetestpieces.ThisInternationalStandardplacesaprovisionalcriterionthatthenotch-rootradiusshouldbesimilartoorlessthantwicetheaveragegrainsizeofthematerial.ThemethodiscomplementarytoothermethodsofmeasuringfracturetoughnessdescribedinISO15732(single-edgeprecrackedbeammethod),ISO18756(surfacecrackinflexuremethod),andISO24370(chevronnotchmethod);seetheBibliography.5Apparatus5.1Ordinaryrazorblades,preferablywithasupportalongoneedgebutalternativelyinsertedinasuitableholder.NOTE1Razorbladesthinnerthanabout0,2mmarenotidealforthistaskunlessstiffenedbyasupport,suchasbygluingorscrewingbetweentwosteelplates,leavingonlyabout2mmofedgeshowing.Arazorbladewithatipangleof30°orsmallerisideal.NOTE2Althoughitispossibletomachinethenotchesentirelybyhand,theuseofasimpledeviceinwhichthetestpiecesaremountedandinwhicharazorbladeprimedwithdiamondpasteismovedinareciprocatingmotionacrossthemountedtestpieceshasadistinctadvantage,asthisprovidescontrolledloadinganddirectionalstabilitytotherazorblade,andsharpernotchesareproduced.AnexampleisshowninAnnexA.5.2Metallographicdiamondpaste,inaviscousorganiccarrierandoffinegrainsize,typically1µmto3µm.5.3Lubricant,alightlubricatingoilforlubricatingtherazorblade,e.g.clockoil.5.4Testpiecesupport,consistingofaflatplateorothersuitabledeviceformountingtestpiecesduringnotchhoning.5.5Flexural-strengthtestfixture,preferablyafour-pointflexural-strengthtestfixtureoperatinginaccordancewiththerequirementsofISO14704,i.e.either1/4-pointflexure(preferred)or1/3-pointflexure.Alternatively,athree-pointflexural-strengthtestjigmayalsobeused,butthealignmentoftheV-notchwiththecentralloadingrollerismorecritical.Thetestpieceissupportedontwobearingedgesperpendiculartoitslength.Theouter-supportbearingedgesshallbeparallelrollersofdiameter5,0mm±0,2mmandshallbecapableofrollingoutwardonflatsupportsurfaces.Preferably,oneoftherollersshalladditionallybecapableofrotatingaboutanaxisparalleltothelengthofthetestpiecesuchthattorsionalloadingisminimised.Thetworollersshall--`,,```,,,,````-`-`,,`,,`,`,,`---bepositionedinitiallywiththeircentres40,0mm±0,5mm(1/4-pointflexure)or30mm±0,5mm(1/3-pointflexure)apartwiththeiraxesparalleltowithin1°.Theseparationofthecentresoftherollersintheirstartingpositionsshallbemeasuredtothenearest0,1mmwithatravellingmicroscope.Therollersshallbemadefromhardenedsteelorotherhardmaterialwithahardnessgreaterthan40HRC(RockwellC-scale).Therollersshallhaveasmoothburr-freesurfacefinishwithroughnesslessthan0,5µmRaandshallhaveadiameteruniformto±0,02mm.Forfour-pointflexure,thetwoloadingrollersarelocatedatthe1/4-points(or1/3-points),withaninnerspanof20mm±0,2mm(or10mm±0,2mmfor1/3-pointflexure)andarefreetorollinwards.The2©ISO2012–AllrightsreservedCopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)rollersarefreetorotateseparatelyaboutanaxisparalleltothelengthofthetestpiecetoallowalignment.Forthree-pointflexure,thesingleloadingroller,whichneednotrotate,shallbepositionedcentrallybetweentheouter-supportrollers.Thedistancesbetweentherollersshallbemeasuredtothenearest0,1mmalongthelengthofthespecimenperpendiculartothedirectionofloading,usingatravellingmicroscopeorothersuitabledevice.Theloadingrollersinfour-pointflexureshallbesymmetricallypositionedtowithin±0,1mm.Thearrangementforloadingshallensurethatequalforcesareappliedtothetwoloadingrollers.Thesingleloadingrollerinthree-pointflexureshallbecentrallylocatedtowithin±0,2mm.5.6Mechanicaltestingmachine,capableofapplyingaforceataconstantrateofdisplacementorconstantloadingratetothetestpieceintheflexural-strengthtestjigandofrecordingtheforceatwhichthetestpiecefractures.TheforcemeasuringdeviceshallbeinaccordancewithISO7500-1andshallhaveanaccuracyof≤1%.NOTEThetestfacilitycan,withadvantage,beequippedwithacapabilityforrecordingtheforce/displacementbehaviourofthetestpiece,ideallyasensitivesystemdirectlycontactingthetestpiece.Providedthattheload-trainstiffnessissufficient,machinedisplacementrecordingcanbeadequate.5.7Ultrasoniccleaningbath,forcleaningthetestpiecesafternotching,suitableforinsertionofabeakerorotherreceptaclecontainingsolvent.5.8Calibratedmicrometer,similartotheoneinaccordancewithISO3611,butcapableofbeingreadtoaprecisionof0,002mmusingavernierorelectronicreadout.5.9Opticalmicroscope,withcalibratedmagnificationsovertherange50×to500×,suitableforobservingthenotch-tipshape,andfittedwithphotomicrographicfacilities.--`,,```,,,,````-`-`,,`,,`,`,,`---5.10Notch-measuringdevice,acalibrateddeviceformeasuringthedepthofthesawnnotchafterfracturewithareadingprecisionof0,002mm.NOTEThiscanbeachievedbytheuseofanappropriatetravellingmicroscope,oraconventionalmetallurgicalmicroscopewithcalibratedstagemovement,oramicroscopewithacalibratedmicrometereyepiece.5.11Dryingoven,capableofmaintaining120°C±5°Cfordryingtestpiecesaftercleaning.5.12Diamondslittingsaworslittingmachine,capableofpreparingashallownotchinasetoftestpiecesofwidthnomorethan0,5mmanddepthofabout0,5mm.See6.3forguidance.6Testpiecepreparation6.1NumberoftestpiecesAtleastseventestpiecesshallbepreparedfornotching,ofwhichfivearerequiredfortestingandtwoaredummytestpiecesforprotectingtheothersduringnotchpreparation.NOTEIfamachineisusedforpreparingtheV-notches,itmightnotbenecessarytoemploythedummytestpiecestoprotectatestsetoffivetestpieces.OperatorswithnoexperienceofpreparingthesharpV-notchesusedinthismethodarehighlyrecommendedtotryoutthetechniqueandequipmentfirstwithsurplustestpieces.©ISO2012–Allrightsreserved3CopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)6.2Test-piecedimensionsPreparebartestpiecesofrectangularcross-section,preferablyinaccordancewiththerequirementsofISO14704.Figure1showstheshapeandmaindimensionsofthetestpiecespreparedinaccordancewiththisInternationalStandard.NOTE1ThechamferingorroundingrequirementsinISO14704arenotessentialfortheV-notchtest,andcanbeignored.NOTE2Othersizesoftestpieces,e.g.(2×2,5×>25mm),canoptionallybeusedwithappropriatelysizedflexural-strengthfixtures.KeyL>45mm(1/4-pointflexure)or>35mm(1/3-pointflexure)W4,0mm±0,2mmB3,0mm±0,2mmFigure1—TestpiecedimensionsinaccordancewithISO147046.3PreparingtheV-notchbyhandMountthetestpiecessidebysideonthetest-piecesupportusinganappropriatetemporaryadhesive,asinFigure2.Mounttestpiecesanddummiesasclosetogetheraspossible.Ensurethatthetopsurfacesofthetestpiecesarelevel.Drawapencillineacrossthesetoftestpiecesatthemid-pointoftheirlengthtoindicatewherethenotchistobeprepared.Bendingthetestpieceswhilemountingontheholderistobeavoided.--`,,```,,,,````-`-`,,`,,`,`,,`---4©ISO2012–AllrightsreservedCopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)Key1mountingplate2dummytestpieces3testpiecesfortesting4pencillineasaguideforintroducingadiamond-sawnstarternotchFigure2—MountingprocedureforthesetoftestpiecesMounttheholderonadiamondsaw.Sawastarternotchalongthepencillineofwidth≤0,5mm.Thenotchshouldhavethesamedepthofabout0,5mmoveritsentirelength.Figure3showsaschematicarrangementforsawing.Aftersawing,cleantheholder,testpieces,andespeciallythenotch.Dimensionsinmillimetres--`,,```,,,,````-`-`,,`,,`,`,,`---a)Testpiecesarrangedonthetestpiecesupportb)MachiningastarternotchwithathindiamondsawbladeKeyAtensilesurfaceBholderCdiamondsawbladeDsawnnotchXdummytestpiecesFigure3—SchematicdiagramsforsawingNOTE1Itishelpfulifthethicknessofthediamondsawbladeisonlyalittlelargerthanthethicknessoftherazorbladeusedfornotchhoning.Otherwise,therazor-bladetipmightskateoverthesurfaceofthepre-sawnnotchanditmightbedifficulttostartpolishingtheV-notch.V-shapingthesaw-bladetipcanhelpifavailablesawbladesaresignificantlythickerthantherazorblades.Fixthetest-pieceholderinaviceorothersuitableclamp.FillthestarternotchwiththefinediamondpasteasshowninFigure4a).©ISO2012–Allrightsreserved5CopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)Toprotectthefingers,placearazorbladeinaholderorapplyaheavyself-adhesivetapeasshowninFigure4b).Puttheexposededgeoftherazorbladeinthestarternotchandapplyalightforce.NOTE2Excessiveforcecanbecounter-productive,causingtherazor-bladetiptobluntmorequickly.Usingaforceofabout5Nto10Nontherazorbladewhilepolishingisnormallysufficient.HonetheV-notchwiththerazorbladewithasmoothgentleback-and-forthmotion[whitearrowsinFigure4b)].Movetherazorbladeasuprightandlevelaspossible.NOTE3Adropoflubricatingoilplacedinthenotchreducesanytendencyfortherazorbladetojerkorbindwhilehoning.a)Applyingdiamondpastefromasyringetothesawnnotchb)ReciprocatingarazorbladeinthesawnnotchKey1heavyprotectiontape2razorbladeFigure4—PositioningarazorbladeinthesawnnotchExaminethedepthoftheV-notchperiodicallywithanopticalmicroscopeatbothendsoftheV-notch.Ifpossible,donotremovethetestpiecesfromthetest-pieceholderforexamination.Ifitisnecessarytoremovethemandfurtherhoningisrequired,remountthetestpiecesontheholderwitharazorbladeinsertedintheV-notchtoactasaguide.IfthetotalV-notchdepthislessthan0,8mm,continuetohone.ThetotalfinalV-notchdepthshouldbebetween0,8mmand1,2mm.NOTE4Honingbyhandwitha4µmdiamondpasteproducesaV-notchwidthSofapproximately20µm.Usingafinerdiamondpaste,e.g.a1µmone,usuallydoesnotdecreasethewidth.IftheV-notchwidthSislargerthanabout30µm,itissuggestedthatanewrazorbladeordifferentrazor-bladebrandbeemployed.Incoarse-grainedmaterials,largegrainsmightpopoutintothenotchduringhoningandlimittheabilitytoobtainasharpV-notch.--`,,```,,,,````-`-`,,`,,`,`,,`---6©ISO2012–AllrightsreservedCopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)NOTE5Differentmaterialswilltakedifferentperiodsoftimetopreparethenotch.Generally,harderortougherceramicstakelongerthansofter,moreeasilymachinedceramics.PolishingV-notchesintoaluminatestpieceswilltaketypicallyapproximately30minandintosiliconnitrideonestypicallyapproximately4h,forfivetestpiecesandtwodummies.Removethetestpiecesfromtheholderwhileavoidingbendingthem.Carefullycleanthetestpieceswithacetoneinasmallpowerfulultrasonicbath.Takecarenottodamagethetestpieceswhilecleaning,e.g.byallowingthemtocomeintocontactduringultrasoniccleaning.Drythetestpiecesintheovenforatleast1hat120°C.NOTE6CleaningoftheV-notchcanbedifficult,especiallywhenthetipradiusissmall.Alternativestepsmightbenecessarytoflushorscrapeoutthediamondgrains.6.4PreparingtheV-notchesbymachine(optional)ThetaskofhoningV-notchescanbeautomated.AnexampleofamachineanditsprincipalrequirementsareshowninAnnexA.NOTE1Withamachineofsufficientrigidityemployinga1µmdiamondpasteforthefinalstagesofnotching,thenotchwidthcanbereducedtypicallyto1µmforceramicswithagrainsizeofabout1µmto2µm.NOTE2Bycommencingthenotchingdirectlyontheflattest-piecesurfacesusingarazorbladeandmediumgritsizediamondpaste,typically10µm,itispossibletoavoidsaw-notchingthetestpiecesfirst.Whenthenotchisdeepenough,thenotchtipissharpenedusinganewbladeandfinegritpaste,aftercleaningoutthemediumgritfromthenotch.6.5Determinationofnotch-rootradiusSelecttwotestpiecesfromthesetoffivefortesting.PhotographtheV-notchononesideofeachoftheselectedtestpiecesusingamagnificationofabout50×,orgreaterifthenotchtipisnotresolvedatthismagnification.ControltheV-notchgeometrywiththehelpofthephotograph.ReportanydeviationfromthegeometryshowninFigure5.PhotographtheV-notchtiponthesametwotestpieceswithamagnificationapproximately300×.MeasuretheV-notchangleandwidthinaccordancewithFigure5.ReporttheV-notchangleβandwidthS.Thenotchwidthshallbeofthesameorderas,orsmallerthan,twicetheaveragegrainsizeofthetestmaterial.Notchesofwidthgreaterthan20µmarenotacceptableinanytestmaterialirrespectiveofgrainsize.NOTE1LinearinterceptmethodsfordeterminingtheaveragegrainsizearedescribedinASTME112[8]orEN623-3[9].NOTE2Itishelpfultodeterminetheacceptabilityofthenotchwidthontheoutermosttestpiecesbeforeremovingthemfromthemountingplate.Thisallowsthenotchhoningprocesstobecontinuedifthenotchwidthistoolarge.--`,,```,,,,````-`-`,,`,,`,`,,`---a)Notchwidthandanglemeasurement©ISO2012–Allrightsreserved7CopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)b)Interpretationofnotch-rootshapeKeya0,8upto1,2mmbapproximately0,5mmcwidthofrazorblade,a−b>cβapproximately30°orassmallaspossibleSV-notchwidthFigure5—SchematicgeometryofV-notches7Testprocedure7.1DimensionsoftestpieceMeasurethedepthWandwidthB(seeFigure1)ofeachtestpieceadjacenttothenotchusingthemicrometercallipers.Readeachvaluetothenearest0,002mm.7.2Flexural-strengthtestPlacethetestpieceinthetestjigonits3mmwidthface,withtheV-notchedfacerestingontheouter-supportrollers.Centralisethenotchbetweenthesupportrollers.Ifthree-pointflexureisemployed,ensurethatthenotchisimmediatelyundertheloadingrollertowithin±0,1mm.Loadthetestpiecesuchthatthetimetofractureisbetween5sand15s.NOTE1Thiscorrespondswithamachinedisplacementrateoftypically0,5mm/min.Recordthefractureload(maximumload)tothreesignificantfigures.Thetestsshouldbeperformedinairatroomtemperature.Ifsubcriticalcrackgrowthisexpected,thetestsmayalsobeconductedinadrynitrogenatmosphere.Reportthetemperatureandpercentagerelativehumidity(%RH)duringthetestsorthemediuminwhichthetestshavebeenconducted.Inspecttheload/displacementcurveforanyevidenceofsubcriticalcrackgrowthorcrackpop-in,particularlyindicatedbyadownwardcurvaturecommencingjustbeforefracture.--`,,```,,,,````-`-`,,`,,`,`,,`---NOTE2Theabilitytodetectsubcriticalcrackgrowthcanbestronglyinfluencedbythetestfixtureandload-trainstiffness.Theuseoftest-piece-displacementmeasurementmadedirectlyonthetestpieceusingasensitivedisplacementtransducersystem,orasensitivestraingaugeplacedonthetest-piecesurfaceoppositethenotch,assistswithdetection.8©ISO2012–AllrightsreservedCopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)7.3MeasurementofnotchdepthThedepthoftheV-notchesismeasuredbyobservingthefracturedsurface(seeFigure6)usingamicroscopewithcalibratedstagemovementandwithamagnification≥50×.Readthedepthsa1,a2,anda3tothreesignificantfigures.CheckifthefracturestartedatthebottomoftheV-notchoveritsentirelength;ifnot,thetestisnotvalid.NOTE1Withwhitematerial,itmightbedifficulttomeasuretheV-notchdepth.Inordertohighlightthebrokenedges,typicaltechniquesthatcanbeusedincludegrazingincidenceilluminationfromafibre-opticlight-sourceorapplyingacoloureddyetotheV-notchbeforefracture.Inspecttheregionoffractureclosetothenotchtipathighermagnificationandatangledorgrazingincidenceillumination.Ifevidencecanbeseenofanarrowzone(3inFigure6)wherethecrackhasdevelopedfromthenotchrootorwherethiscrackhaspropagatedsubcriticallybeforefastfracture,determinethewidthofthiszone,δa1,δa2,andδa3,inthesamethreepositionsasshowninFigure6,andaddthesevaluestothenotchlengthsa1,a2,anda3,respectively.NOTE2Itmightnotbepossibletoseeclearlytheinitialcrackgrowthregioninalltestmaterials.Key1fracturedsurface2V-notchedsurface3subcriticalcrackgrowthzoneofwidthδaFigure6—SchematicdiagramoffracturedV-notchedtestpieceandthepositionsatwhichnotchdepthsaremeasured7.4CalculationoffracturetoughnessTheaveragedepthoftheV-notchiscalculatedusingFormula(1).TheaveragerelativeV-notchdepthα,calculatedinaccordancewithFormula(3),shallbebetween0,2and0,3andshallsatisfyFormula(2).aa=+()12aa+3/3(1)()aamaxm−≤in/,a01(2)--`,,```,,,,````-`-`,,`,,`,`,,`---©ISO2012–Allrightsreserved9CopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)α=aW/(3)Forfour-pointflexure,computethefracturetoughnessKlc,SEVNBusingFormulae(4)and(5)(fromISO15732):FSS12−3αKlc,SEVNB=⋅⋅32/⋅Y*(4)BWW21()−αwhere2(,3490−+,,68αα1351)(αα−)Y*,=−198871,326α−(5)2()1+α--`,,```,,,,````-`-`,,`,,`,`,,`---Forthree-pointflexureusinga40mmspan,with4mmdeeptestpieces(i.e.S1/W=10),computethefracturetoughnessKlc,SEVNBusingFormulae(6)and(7)(fromISO15732):FS13αKlc,SEVNB=⋅⋅32/⋅Y*(6)BWW21()−αwhere2345Y*,=−194725,,0247αα+−118954180635,,αα+−1459864,6896α(7)Forthree-pointflexureusinga30mmspan,with4mmdeeptestpieces(i.e.S1/W=7,5),computethefracturetoughnessKlc,SEVNBusingFormulae(6)and(8)(fromISO15732),where:234Y*,=−19642,,837αα+−13771423250,,αα+24129(8)whereKlc,SEVNBisthefracturetoughness,inMPa•m1/2;Fisthefractureload,inMN;Bisthetest-piecewidth,inm;Wisthetest-piecedepth,inm;S1isthesupportspan,inm;S2istheloadingspan(S1>S2),inm;aistheaverageV-notchdepth,inm;amaxisthemaximumamonga1,a2,a3,inm;aministheminimumamonga1,a2,a3,inm;αistherelativeV-notchdepth;Y*isthestressintensityshapefactor.NOTE1Theabovecalculationsareconsideredvalidfor0,3599,8%>99,9%BayerN3208PressedsinteredpostCIPaairCIPaairgas-pressuregas-pressureHPbHIPedGrainsize>10µm≈1,7µm<1µm,elonga-7µmtionDensity3,86Mg/m33,97Mg/m33,23Mg/m33,15Mg/m3Strength342MPac350MPac>920MPacaColdisostaticpressed.bHotpressed.cFour-pointbending.Theseceramicshaddifferentdegreesofdifficultyintheapplicationofthistestmethod.Veryconsistentresultswereobtainedforthealumina-998.Thefracturetoughnessforthe135validtestsinfour-pointflexureonsizeBtestpiecesfrom28participantswas3,57±0,22MPa·m1/2(mean,standarddeviation).Reasonablyconsistentresultswereobtainedforthealumina-999.Thefracturetoughnessforthe102validtestsfrom21participantswas3,74±0,40MPa·m1/2.ConsistentresultswereobtainedfortheGPSSN.Thefracturetoughnessforthe129validtestsacceptedfrom27participantswas5,36±0,34MPa·m1/2.VeryconsistentresultswereobtainedfortheSSiC.Thefracturetoughnessforthe56validtestsacceptedfrom12participantswas2,61±0,18MPa·m1/2.Asmallernumberoftestswerealsoundertakenonyttriatetragonalzirconiapolycrystalmaterial(Y-TZP).Theseshowedaclearevidenceofnotch-rootradiusdependenceofoutcome,andalloutcomesgavehighervaluesoftoughnesscomparedwiththesurfacecrackinflexure(SCF)method.Noneoftheparticipantswereabletoachieveasufficientlysmallnotch-rootradius.Themethodisthereforenotrecommendedforthismaterial.Todeterminetherepeatability(within-laboratory)andreproducibility(between-laboratories)oftheSEVNBfracturetoughnessmeasurementmethod,ISO5725-2(Reference[2]intheBibliography)wasusedintheround-robinanalysis.ThestatisticalresultsareshowninTableB.2andarecomparedwithresultsonthesamematerialsfromanearlierVAMASroundrobinwiththeSCFmethod(Reference[3]intheBibliography).TheprecisionandbiasstatementsfortheSCFmethodwerecomputedonthesamebasisbutinaccordancewithASTME691(Reference[4]intheBibliography),inwhichrepeatabilityandreproducibilityarecomputedinanidenticalmanner.(NotethatinISO5725-2,thecriterionforanoutlieris1%,whereasinASTME691,itis0,5%.)14--`,,```,,,,````-`-`,,`,,`,`,,`---©ISO2012–AllrightsreservedCopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)DetailsoftheapplicabilityofthemethodtosmalltestpiecesmaybefoundinReference[5]intheBibliography.TableB.2—RepeatabilityandreproducibilitycoefficientofvarianceandstandarddeviationoftheSEVNBmethod[1]comparedwiththeSCFmethodmeasuredonhot-pressedSi3N4[earlierVAMASroundrobin(Reference[3]intheBibliography)]TotalnumberofRepeatabilityReproducibility(within-labora-(between-laborato-tory)ries)MaterialMethodparticipantstestpiecesStandardCVStandardCVdeviationdeviationMPa∙m1/2%MPa∙m1/2%Alumina-998SEVNB281350,174,60,226,1Alumina-999SEVNB211020,236,20,4010,7GPSSNSEVNB271290,285,30,346,3SSiCSEVNB12560,124,50,186,8Hot-pressedSi3N4SCF191020,245,40,316,8Hot-iso-pressedSi3N4SCF151000,387,70,458,9--`,,```,,,,````-`-`,,`,,`,`,,`---©ISO2012–Allrightsreserved15CopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)AnnexC(informative)CorrectionsforeffectivecracklengthgreaterthannotchdepthTheassumptioninthemathematicalanalysisinthisInternationalStandardisthattheeffectivecracklengthequalsthenotchdepth.Inpractice,asharpcrackhastodevelop(i.e.growsubcriticallyor“pop-in”)fromthehoningdamageatthetipofthenotchforfracturetooccur,sothatthetruecracklengthatthepeakforceappliedtothetestpieceislikelytobelongerthanthatestimatedfromthenotchdepth,givinganunderestimateofthetruefracturetoughness.Thepresenceofsubcriticalcrackextensionbeforefracturemaybedetectedasanonlinearityintheforce/deflectioncurveofthetestpieceimmediatelybeforethepeakforceisattained.Theextentofthesubcriticalextensionofacrack-likeflawbelowthenotcheitherhastobemeasured,e.g.fromfractographicobservation,orassumedfrom,forexample,thegrainsizeofthematerial,whichmayactasaflawlengthlimiter.Inordertoprovideanimprovedestimateoffracturetoughness,ananalysisgiveninReference[6]intheBibliographymaybefollowed.AssumingthatthetestmaterialshowsnoR-curvebehaviouroverthecrackpropagationdistancebetweenthenotchrootandthecrackextensionpositionatthepointoffastfracture,Reference[6]showsthatthereisanegligibledifferencebetweentruetoughnessandthetoughnesscomputedusingtheextendedcracklength(i.e.a0+δa)ifδa/R≥1,5foraplanarcrackorforasemi-ellipticalcrackextendingfromthenotchtip,whereδaisthelengthofthecrackfromthenotchtipandRisthenotch-rootradius.Inthiscondition,thenominaltoughnesscomputedwiththenotchdepthcanbecorrectedusingtheexpression:KK*/lc,SEVNB≈+lc,SEVNB1δδaa00{}Fa()+aW//Fa(/0W)(C.1)whereF=Y*inthree-pointflexureorY*/(1−α)1,5infour-pointflexure.Ifthecrackextensioncanbeseenusingfractographicmethodsanditslengthmeasured,thisexpressioncanvalidlybeusedwhenδa/R≥1,5.Iftheconditionisδa/R<1,5,i.e.whenthecracktipstressisstronglyinfluencedbytheradiusofthenotch,thenthereisanincreasingerrorinusingtheaboveapproachwithdecreasingδaorincreasingR.Animprovedapproximationisgivenby:KK**lc,SEVNB=*(lc,SEVNBtanh2,243δaR/)(C.2)forastraightcrackbeneaththenotch,orKK**lc,SEVNB=*[lc,SEVNBtanh2,243ga(/δδRa)/R](C.3)forasemi-ellipticalcrackbeneaththenotch,whereg(δa/R)=0,6667+0,178[1−exp(−1,64δa/R)](C.4)Incaseswherenoobviouscrackextensionregioncanbeidentifiedfractographically,Damanietal.[10]suggestassumingthattheextensionshouldbeaccountedfor,asbeingatleastonegrainsizeinlength.Forfine-grainedmaterials,thismaymakeanegligiblecorrection,butforcoarsergrainedmaterials,itmaybeverysignificant.TheactiontakenbytheuserofthisInternationalStandardshouldbereportedinthetestreport.--`,,```,,,,````-`-`,,`,,`,`,,`---16©ISO2012–AllrightsreservedCopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)Bibliography[1]KÜBLER.J.,(1999).FracturetoughnessofceramicsusingtheSEVNBmethod:roundrobin,VAMASReportNo.37(ISSN1016-2186)andESISDocumentD2-99,EMPA-Dübendorf,Switzerland,1998[2]ISO5725-2:1994,Accuracy(truenessandprecision)ofmeasurementmethodsandresults—Part2:Basicmethodforthedeterminationofrepeatabilityandreproducibilityofastandardmeasurementmethod[3]QUINN.G.,GETTINGS,R.andKÜBLER,J.(1996).Fractographyandthesurfacecrackinflexure(SCF)methodforevaluatingfracturetoughnessofceramics,in:FractographyofGlassesandCeramicsIII:CeramicTransactions,64,editedbyVarner,J.R.,Fréchette,V.C.andQuinn,G.D.,Amer.Ceram.Soc.,Westerville,USA,pp.107-44[4]ASTME691,StandardPracticeforConductinganInterlaboratoryStudytoDeterminethePrecisionofaTestMethod[5]KUEBLER.In:J.,FractureToughnessofCeramicsusingtheSEVNBMethod:FromaPreliminaryStudytoaStandardTestMethod,FractureResistanceTestingofMonolithicandCompositeBrittleMaterials,ASTMSTP1409.(SalemJ.A.,JenkinsM.G.,QuinnG.D.eds.).AmericanSocietyforTestingandMaterials,WestConshohocken,PA,2001[6]ASTMC1421-99,StandardTestMethodsforDeterminationofFractureToughnessofAdvancedCeramicsatAmbientTemperatures[7]FETT.T.,Influenceofafinitenotchrootradiusonfracturetoughness.J.Eur.Ceram.Soc.2005,25pp.543–547[8]ASTME112,StandardTestMethodsforDeterminingAverageGrainSize[9]EN623-3,Advancedtechnicalceramics—Monolithicceramics—Generalandtexturalproperties—Part3:Determinationofgrainsizeandsizedistribution(characterizedbythelinearinterceptmethod)--`,,```,,,,````-`-`,,`,,`,`,,`---[10]DAMANI.R.J.,SCHUSTER,C.andDANZER,R.PolishednotchmodificationofSENB-Sfracturetoughnesstesting.J.Eur.Ceram.Soc.1997,17(14)pp.1685–1689[11]LeBac.VerfahrenzumFeinkerbenvonkeramischenKörpern,Patent146416,GermanDemocraticRepublic1979-81[12]NISHIDA.T.,HANAKI,Y.andPEZZOTTI,G.Effectofnotch-rootradiusonthefracturetoughnessofafine-grainedalumina.J.Am.Ceram.Soc.1994,77(2)pp.606–608[13]AWAJI.H.andSAKAIDA,Y.V-notchtechniqueforsingleedgenotchedbeamandchevronnotchmethods.J.Am.Ceram.Soc.1990,76(11)pp.3522–3525[14]ISO18756:2003,Fineceramics(advancedceramics,advancedtechnicalceramics)—Determinationoffracturetoughnessofmonolithicceramicsatroomtemperaturebythesurfacecrackinflexure(SCF)method[15]ISO24370:2005,Fineceramics(advancedceramics,advancedtechnicalceramics)—Testmethodforfracturetoughnessofmonolithicceramicsatroomtemperaturebychevron-notchedbeam(CNB)method©ISO2012–Allrightsreserved17CopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale ISO23146:2012(E)ICS 81.060.30Pricebasedon17pages--`,,```,,,,````-`-`,,`,,`,`,,`---©ISO2012–AllrightsreservedCopyrightInternationalOrganizationforStandardizationProvidedbyIHSunderlicensewithISONoreproductionornetworkingpermittedwithoutlicensefromIHSNotforResale
