ASTM_C_1421_-_16.pdf

Designation:C142116Standard Test Methods forDetermination of Fracture Toughness of Advanced Ceramicsat Ambient Temperature1This standard is issued under the fixed designation C1421;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 These test methods cover the fracture toughness,KIc,determination of advanced ceramics at ambient temperature.The methods determine KIpb(precracked beam test specimen),KIsc(surface crack in flexure),and KIvb(chevron-notched beamtest specimen).The fracture toughness values are determinedusing beam test specimens with a sharp crack.The crack iseither a straight-through crack formed via bridge flexure(pb),or a semi-elliptical surface crack formed via Knoop indentation(sc),or it is formed and propagated in a chevron notch(vb),asshown in Fig.1.NOTE1The terms bend(ing)and flexure are synonymous in these testmethods.1.2 These test methods are applicable to materials witheither flat or with rising R-curves.Differences in test procedureand analysis may cause the values from each test method to bedifferent.For many materials,such as the silicon nitrideStandard Reference Material 2100,the three methods giveidentical results at room temperature in ambient air.1.3 The fracture toughness values for a material can befunctions of environment,test rate and temperature.These testmethods give fracture toughness values for specific conditionsof environment,test rate and temperature.1.4 These test methods are intended primarily for use withadvanced ceramics that are macroscopically homogeneous andmicrostructurally dense.Certain whisker-or particle-reinforced ceramics may also meet the macroscopic behaviorassumptions.Single crystals may also be tested.1.5 This standard begins with a main body that providesinformation on fracture toughness testing in general.It isfollowed by annexes and appendices with specific informationfor the particular test methods.Main BodySectionScope1Referenced Documents2Terminology(including definitions,orientation and symbols)3Summary of Test Methods4Significance and Use5Interferences6Apparatus7Test Specimen Configurations,Dimensions and Preparations8General Procedures9Report(including reporting tables)10Precision and Bias11Keywords12Summary of ChangesAnnexesTest Fixture GeometriesAnnex A1Procedures and Special Requirements for Precracked BeamMethodAnnex A2Procedures and Special Requirements for Surface Crack inFlexure MethodAnnex A3Procedures and Special Requirements for Chevron Notch FlexureMethodAnnex A4AppendicesPrecrack Characterization,Surface Crack in Flexure MethodAppendixX1Complications in Interpreting Surface Crack in Flexure PrecracksAppendixX2Alternative Precracking Procedure,Surface Crack in FlexureMethodAppendixX3Chamfer Correction Factors,Surface Crack in Flexure Method OnlyAppendixX4Crack OrientationAppendixX51.6 Values expressed in these test methods are in accordancewith the International System of Units(SI)and PracticeIEEE/ASTM SI 10.1.7 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1This test method is under the jurisdiction of ASTM Committee C28 onAdvanced Ceramics and is the direct responsibility of Subcommittee C28.01 onMechanical Properties and Performance.Current edition approved Jan.1,2016.Published March 2016.Originallyapproved in 1999.Last previous edition approved in 2015 as C1421 15.DOI:10.1520/C1421-16.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 1.8 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2C1161 Test Method for Flexural Strength of AdvancedCeramics at Ambient TemperatureC1322 Practice for Fractography and Characterization ofFracture Origins in Advanced CeramicsE4 Practices for Force Verification of Testing MachinesE112 Test Methods for Determining Average Grain SizeE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE337 Test Method for Measuring Humidity with a Psy-chrometer(the Measurement of Wet-and Dry-Bulb Tem-peratures)E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE740 Practice for Fracture Testing with Surface-Crack Ten-sion SpecimensE1823 Terminology Relating to Fatigue and Fracture TestingIEEE/ASTM SI 10 Standard for Use of the InternationalSystem of Units(SI)(The Modern Metric System)2.2 Reference Material:NIST SRM 2100 Fracture Toughness of Ceramics33.Terminology3.1 Definitions:3.1.1 The terms described in