ASTM_E_2472_-_12e1.pdf

Designation:E2472121Standard Test Method forDetermination of Resistance to Stable Crack Extensionunder Low-Constraint Conditions1This standard is issued under the fixed designation E2472;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.1NOTE3.2.5 and 3.2.6 were editorially revised in March 2013.1.Scope1.1 This standard covers the determination of the resistanceto stable crack extension in metallic materials in terms of thecritical crack-tip-opening angle(CTOA),cand/or the crack-opening displacement(COD),5resistance curve(1).2Thismethod applies specifically to fatigue pre-cracked specimensthat exhibit low constraint(crack-size-to-thickness and un-cracked ligament-to-thickness ratios greater than or equal to 4)and that are tested under slowly increasing remote applieddisplacement.The test specimens are the compact,C(T),andmiddle-crack-tension,M(T),specimens.The fracture resis-tance determined in accordance with this standard is measuredas c(critical CTOA value)and/or 5(critical COD resistancecurve)as a function of crack extension.Both fracture resis-tance parameters are characterized using either a single-specimen or multiple-specimen procedures.These fracturequantities are determined under the opening mode(Mode I)ofloading.Influences of environment and rapid loading rates arenot covered in this standard,but the user must be aware of theeffects that the loading rate and laboratory environment mayhave on the fracture behavior of the material.1.2 Materials that are evaluated by this standard are notlimited by strength,thickness,or toughness,if the crack-size-to-thickness(a/B)ratio and the ligament-to-thickness(b/B)ratio are greater than or equal to 4,which ensures relativelylow and similar global crack-front constraint for both the C(T)and M(T)specimens(2,3).1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.4 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:3E4 Practices for Force Verification of Testing MachinesE8/E8M Test Methods for Tension Testing of Metallic Ma-terialsE399 Test Method for Linear-Elastic Plane-Strain FractureToughness KIcof Metallic MaterialsE561 Test Method forK-R Curve DeterminationE647 Test Method for Measurement of Fatigue CrackGrowth RatesE1290 Test Method for Crack-Tip Opening Displacement(CTOD)Fracture Toughness Measurement(Withdrawn2013)4E1820 Test Method for Measurement of Fracture ToughnessE1823 Terminology Relating to Fatigue and Fracture TestingE2309 Practices for Verification of Displacement MeasuringSystems and Devices Used in Material Testing Machines2.2 ISO Standards:5ISO 22889:2007 Metallic MaterialsMethod of Test for theDetermination of Resistance to Stable Crack ExtensionUsing Specimens of Low ConstraintISO 12135 Metallic MaterialsUnified Method of Test forthe Determination of Quasistatic Fracture Toughness3.Terminology3.1 Terminology E1823 is applicable to this test standard.3.2 Definitions:3.2.1 crack extension,a L,nan increase in crack size.1This test method is under the jurisdiction of ASTM Committee E08 on Fatigueand Fracture and is the direct responsibility of Subcommittee E08.07 on FractureMechanics.Current edition approved July 1,2012.Published January 2013.Originallyapproved in 2006.Last previous edition approved in 2006 as E2472061.DOI:10.1520/E2472-12E01.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.4The last approved version of this historical standard is referenced onwww.astm.org.5Available from International Organization for Standardization(ISO),1,ch.dela Voie-Creuse,Case postale 56,CH-1211,Geneva 20,Switzerland,http:/www.iso.ch.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.2.1.1 DiscussionIt should be noted that in thin-sheet andthick-plate materials under low constraint conditions,the crackextension observed on the surface of the specimen may besignificantly less than that in the interior of the specimen dueto the effects of crack tunneling.This must be considered ifdirect optical techniques are used to monitor and measurefree-surface crack extension.Indirect crack extension measure-ment techniques such as unloading compliance and elec