1、DRAFT FOR DEVELOPMENT DD CEN/TS 14425-1:2003 Advanced technical ceramics Test methods for determination of fracture toughness of monolithic ceramics Part 1: Guide to test method selection ICS 81.060.30 DD CEN/TS 14425-1:2003 This Draft for Development was published under the authority of the Standar
2、ds Policy and Strategy Committee on 23 March 2003 BSI 23 March 2003 ISBN 0 580 45661 7 National foreword This Draft for Development is the official English language version of CEN/TS 14425-1:2003. This publication is not to be regarded as a British Standard. It is being issued in the Draft for Devel
3、opment series of publications and is of a provisional nature because it is considered that a further experience is required in its application before it is converted to a European and hence British Standard. It should be applied on this provisional basis, so that information and experience of its pr
4、actical application may be obtained. Comments arising from the use of this Draft for Development are requested so that UK experience can be reported to the European organization responsible for its conversion to a European Standard. A review of this publication will be initiated 2 years after its pu
5、blication by the European organization so that a decision can be taken on its status at the end of its 3-year life. Notification of the start of the review period will be made in an announcement in the appropriate issue of Update Standards. According to the replies received by the end of the review
6、period, the responsible BSI Committee will decide whether to support the conversion into a European Standard, to extend the life of the Technical Specification or to withdraw it. Comments should be sent in writing to the Secretary of BSI Technical Committee RPI/13, Advanced technical ceramics, at Br
7、itish Standards House, 389 Chiswick High Road, London W4 4AL, giving the document reference and clause number and proposing, where possible, an appropriate revision of the text. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The Br
8、itish Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards O
9、nline. Summary of pages This document comprises a front cover, an inside front cover, the CEN/TS title page, pages 2 to 13 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsTECH
10、NICALSPECIFICATION SPCIFICATIONTECHNIQUE TECHNISCHESPEZIFIKATION CEN/TS144251 July2003 ICS81.060.30 Englishversion AdvancedtechnicalceramicsTestmethodsfordetermination offracturetoughnessofmonolithicceramicsPart1:Guideto testmethodselection Cramiquestechniquesavances HochleistungskeramikPrfverfahren
11、zurBestimmungder BruchzhigkeitvonmonolithischerKeramikTeil1: LeitliniezurAuswahldesPrfverfahrens ThisTechnicalSpecification(CEN/TS)wasapprovedbyCENon19January2003forprovisionalapplication. TheperiodofvalidityofthisCEN/TSislimitedinitiallytothreeyears.AftertwoyearsthemembersofCENwillberequested tosub
12、mittheir comments,particularlyonthequestionwhethertheCEN/TScanbeconvertedintoaEuropeanStandard. CENmembersarerequiredtoannouncetheexistenceofthisCEN/TSinthesamewayasforanENandtomaketheCEN/TSavailable .It ispermissibletokeepconflictingnationalstandardsinforce(inparalleltotheCEN/TS)untilthefinaldecisi
13、onaboutthep ossible conversionoftheCEN/TSintoanENisreached. CENmembersarethenationalstandardsbodiesofAustria,Belgium,CzechRepublic,Denmark,Finland,France,Germany,Greece, Hungary,Iceland,Ireland,Italy,Luxembourg,Malta,Netherlands,Norway,Portugal,Slovakia,Spain,Sweden,SwitzerlandandUn ited Kingdom. EU
14、ROPEANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2003CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwideforCENnationalMembers. Ref.No.CEN/TS144251:2003E 3002:152441ST/NEC/NECTS52441:1(3002E) 2 Con
15、tents Page Foreword3 1 Scope 3 2 Normativereferences 3 3 Termsanddefinitions. .4 4 Significanceanduse .5 5 Testmethods 5 5.1 Background 5 5.2 Testmethods 5 5.3 Testpiecemicrostructure. 8 5.4 Testpiecemachining 8 5.5 Scatteroftestresults . .8 6 Criteriaforselectionofanapparentfracturetoughnesstestmet
16、hod.9 Bibliography 12 CEN/TS144251:2003/NECTS52441:1(3002E) 3 Foreword Thisdocument(CEN/TS144251:2003)hasbeenpreparedbyTechnicalCommitteeCEN/TC 184“Advanced technicalceramics”,thesecretariatofwhichisheldbyBSI. ThisdocumenthasbeenpreparedunderamandategiventoCENbytheEuropeanCommissionandtheEuropean Fr
17、eeTradeAssociation. AccordingtotheCEN/CENELECInternalRegulations,thenationalstandardsorganizationsofthefollowing countriesareboundtoannouncethisTechnicalSpecification:Austria,Belgium,CzechRepublic,Denmark, Finland,France,Germany,Greece,HungaryIceland,Ireland,Italy,Luxembourg,Malta,Netherlands,Norway
18、, Portugal,Slovakia,Spain,Sweden,SwitzerlandandtheUnitedKingdom. CEN/TS14425AdvancedtechnicalceramicsTestmethodsfordeterminationoffracturetoughnessofmonolithic ceramicsconsistsoffiveparts: Part1: Guidetotestmethodselection Part2: Singleedgeprecrackedbeam(SEPB)method Part3: Chevronnotchedbeam(CNB)met
19、hod Part4: Surfacecrackinflexure(SCF)method Part5: Singleedgeveenotchbeam(SEVNB)method 1Scope 1.1 ThispartofCEN/TS14425providesinformationonthecomparativevalue,andguidanceontheselection,of testmethodsfordeterminingtheapparentfracturetoughnessofmonolithicadvancedtechnicalceramics.Forthe purposesofthi
20、sTechnicalSpecification,thetermmonolithicincludesparticle,plateletandwhiskerreinforced advancedtechnicalceramicswhichcanberegardedasmacroscopicallyhomogeneous.Itdoesnotincludelong fibrereinforcedceramics. 1.2 ReferenceismadeinthispartofCEN/TS14425tospecifictestmethodsdescribedinotherpartsofthis Tech
21、nicalSpecification. 2 Normativereferences ThisTechnicalSpecificationincorporatesbydatedorundatedreference,provisionsfromotherpublications.These normativereferencesarecitedattheappropriateplacesinthetextandthepublicationsarelistedhereafter.For datedreferences,subsequentamendmentstoorrevisionsofanyoft
22、hesepublicationsapplytothisTechnical Specificationonlywhenincorporatedinitbyamendmentorrevision.Forundatedreferencesthelatesteditionof thepublicationreferredtoapplies(includingamendments). EN8431 AdvancedtechnicalceramicsMonolithicceramicsMechanicalpropertiesatroomtemperature:Part 1:Determinationoff
23、lexuralstrength. CEN/TS144251:2003/NECTS52441:1(3002E) 4 3 Termsanddefinitions ForthepurposesofthisTechnicalSpecification,thefollowingtermsanddefinitionsapply. 3.1 stressintensityfactor( K) magnitudeofthefactordeterminingtheidealcracktipstressfield(astressfieldsingularity)foraparticularmodein ahomog
24、eneouslinearelasticbody.ThisTechnicalSpecificationdealsprimarilywithopeningmodebehaviour, K I . 3.2 criticalstressintensityfactor( K c ) magnitudeofthestressintensityfactorrequiredtocauseacracktopropagateathighvelocity. 3.3 crackextensionresistance resistancetopropagationofacrackexpressedaseither(1)
25、thestressintensityfactorforcrackpropagation (commonlyreferredtoasfracturetoughness),or(2)theforceperunitcrackwidthrequiredtoextendacrack,or(3) thevalueof J,thesocalledJintegral. 3.4 fracturetoughness resistancedisplayedbyamaterialtothepropagationofacrackthroughit. NOTE Thistermshouldnormallybequalif
26、iedwiththeconditionsunderwhichthetestisperformedsincethevalue obtainedmaydependonthecracksize,geometry,stressfield,crackvelocityandtestmethod. 3.5 apparentfracturetoughness fracturetoughnessdeterminedbyaparticularmethodundertheconditionsimposedbythatmethod. 3.6 workoffracture externalmechanicalworkp
27、erformedonatestpiecetoproduceunitareaofnewmacroscopiccrackface. 3.7 planestrainfracturetoughness fracturetoughnessunderconditionsofcracktipplanestrain,i.e.whereallstrainsareconfinedtoaplanenormalto thecrackfrontandcontainingthecrackpropagationdirection. 3.8 stablecrackgrowth growthofacrackunderknown
28、andcontrolledconditionsbyvirtueoftheexperimentaltechniqueemployed. 3.9 unstablecrackgrowth growthofacrackunderconditionswheretheaccelerationofthecrackfrontisuncontrolledbyvirtueofthe experimentaltechniqueemployed. 3.10 popin suddenjumpofapreexistingcrackfrontfromaninitialpositionorthedevelopmentofan
29、ewcracktoastable positiononapplicationofaforcewithoutcatastrophicfailureofthetestpiece. 3.11 Rcurve plotofcrackextensionresistanceasafunctionofstablecrackextension. CEN/TS144251:2003/NECTS52441:1(3002E) 5 4 Significanceanduse Thetoughnessofabrittle,nominallycrackfreematerialisnotanengineeringdesignp
30、arameterinthesamesense asmightbethecaseformoreductilematerials.Thereasonisthatthemicroscopicflaws,suchasgrain boundaries,largegrains,pores,inclusionsorprocessingdefects,aretoosmalltobemeasurednondestructivelyin ameaningfulway.Despitethis,thetoughnessofrelativelybrittlematerialsisanimportantguidetoot
31、her mechanicalproperties,suchasdefecttolerance,abrasivewearanderosionresistance,impactresistance,fatigue resistance,andthermalshockdamageresistance. 5Test methods 5.1Background Itisrecognisedthattheapparentplanestrainfracturetoughnessofadvancedtechnicalceramicsmaynotbea uniquematerialproperty.Thenum
32、ericalvalueobtainedinanyparticulartestmaybecontrolledbyfactors associatedwiththetestmethod,bythelengthofthecrack,andbythevelocityatwhichthecrackpropagates.Thus theresultsfromdifferenttypesoftestmaynotbenumericallyequivalent.Someoftheimportantfactorsintest methodselectionaregivenbelow. NOTE TheBiblio
33、graphycontainsalistoffracturetoughnessmethodassessmentsforadvancedtechnicalceramics. 5.2Test methods 5.2.1 Thewidevarietyofpossibletestmethodsfordeterminingopeningmodeapparentfracturetoughness( K Ic ) fallintotwogroups: 1) thosewhichareconsideredtogivegoodqualitydeterminationsofcriticalstressintensi
34、tyfactorwith accurateandreliablecalibrations; 2) thosewhichareinwidespreadusebutwhichareconsideredtohaveconsiderablecalibration uncertaintiesassociatedwiththem,orwherethecrackcannotbewellcharacterised,orisprestressedby themethodbywhichitisintroduced;suchtestsmightbeusedforcomparativepurposesonly. 5.
35、2.2 ThisTechnicalSpecificationcoversatotalofsixmethodswhichcanbeappliedtoflexuraltestpiecesas describedinEN8431.Someoftheseareconsideredtobehaveinaccordancewiththefirstgroup,andsomein accordancewiththesecondgroup.Table1liststhemethodsandtheirlevelofqualityforapparentfracture toughnessdetermination.F
36、igure1illustratesschematicallythetestpieceandcrackgeometries. 5.2.3 Methodswhichinvolveprecracksordevelopingcrackslongerthanafewtensofmicrometresmaybe influencedbysocalledrisingcrackresistance(Rcurve)behaviour.Thisoccursparticularlyinmaterialsinwhich crackfaceseparationisincompletebehindthedevelopin
37、gcrack.Thishasbeenfoundtooccurincoarsegrained materialssuchasalumina,andinmaterialscontainingwhiskersorplateletreinforcement,andinmaterials containingmetallicphasereinforcement.Theeffectmayalsobefoundinmaterialswhichundergophase transformationclosetothecracktipasthecrackpropagates,e.g.insomezirconia
38、s.TheRcurveeffectmaybe testpiecegeometrydependent,andisnotauniquelyquantifiablematerialcharacteristic. CEN/TS144251:2003/NECTS52441:1(3002E) 6 SEPB CNB SCF SEVNB IF IS Figure1Schematicdiagramsoftherangeofapparentfracturetoughnesstestmethods. Forabbreviationsseetable1 CEN/TS144251:2003/NECTS52441:1(3
39、002E) 7 Table1Apparentfracturetoughnesstestsperformedonsmalltestpieces Method Description Calibrations Uncertaintiesordifficulties Singleedgepre crackedbeam (SEPB) (CEN/TS144252) * Aflexuraltestona beamintothetensile sideofwhichashort straightsharpcrack hasbeenintroduced Accuratecalibrations availab
40、leforwide rangeofprecrack lengths;toughnessat adefinedcracklength Precrackingrequiressomeskill toobtainstraightfrontedcracks. Resultsareinfluencedbyrising crackresistancebehaviour Chevronnotched beam(CNB) (CEN/TS144253) * Aflexuraltestona beamwithtwo coplanarangled notchesleavinga sharptippedtriangu
41、lar shapedregionto fracture Accuratecalibrations Toughnessatanilldefined cracklength;crackinitiation difficultinsomematerials;result influencedbyrisingcrack resistancebehaviour Surfacecrackin flexure(SCF) (CEN/TS144254) * Aflexuraltestona beaminwhichasmall semicircularflawhas beenintroducedby indent
42、ationonthe tensileside,andwith theindentation damageremoved. Accuratecalibrations, assumingthepre crackshape approximatestoan ellipseafterremovalof surfacedamaged region. Requiresobservationand measurementofprecrack dimensions,whichmaynot alwaysbeclearlyvisible;limited tomaterialsinwhichindentation
43、producesgoodqualitycracks. Resulttypicalforsmallcracks. Singleedgevee notchbeam (SEVNB) (CEN/TS144255) * Aflexuraltestona beaminwhicha narrownotchhas beenmadeonthe tensileside,withthe notchtipsharpened byhoningwith diamondpaste. Accuratecalibrations assumingasharp crack(sameas SEPB). Assumesthatifth
44、etipradiusof thesharpnotchisoftheorder thegrainsizethenotchis equivalenttoasharpcrackand theSEPBcalibrationcanbe used. Indentationfracture (IF) Atestinwhichthe lengthofcracks emanatingfromthe cornersofaVickers hardnessindentation ismeasured Poorcalibrations owingtouncertainties instressfields developedby indentationmethodsof cracking.Widevariety ofdifferentcalibrations available. Effectiveonlyinmaterialswhich donotchipo
