1、Designation: E2472 061 E2472 12Standard 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 ca
2、se 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 NOTE3.2.16 was editorially revised in May 2010.1. Scope1.1 This standard covers the determination of
3、 the resistance to stable crack extension in metallic materials in terms of the criticalcrack-tip-opening angle (CTOA(CTOA),c), c and/or the crack-opening displacement (COD), 5 resistance curve (1).2 Thismethod applies specifically to fatigue pre-cracked specimens that exhibit low constraint (crack-
4、length-to-thickness(crack-size-to-thickness and un-cracked ligament-to-thickness ratios greater than or equal to 4) and that are tested under slowly increasing remoteapplied displacement. The recommendedtest specimens are the compact-tension,compact, C(T), and middle-crack-tension, M(T),specimens. T
5、he fracture resistance determined in accordance with this standard is measured as c (critical CTOA value) and/or5 (critical COD resistance curve) as a function of crack extension. Both fracture resistance parameters are characterized usingeither a single-specimen or multiple-specimen procedures. The
6、se fracture quantities are determined under the opening mode (ModeI) of loading. Influences of environment and rapid loading rates are not covered in this standard, but the user must be aware ofthe effects that the loading rate and laboratory environment may have on the fracture behavior of the mate
7、rial.1.2 Materials that are evaluated by this standard are not limited by strength, thickness, or toughness, if the crack-length-to-thicknesscrack-size-to-thickness (a/B) ratio and the ligament-to-thickness (b/B) ratio are greater than or equal to 4, which ensuresrelatively low and similar global cr
8、ack-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 as the standard. The values given in parentheses (English) are for informationpurposes only.standard. No other units of measurement are included in this standard.1.4 This standard do
9、es not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Stand
10、ards:3E4 Practices for Force Verification of Testing MachinesE8E8/E8M Test Methods for Tension Testing of Metallic MaterialsE399 Test Method for Linear-Elastic Plane-Strain Fracture Toughness KIc of Metallic MaterialsE561 Test Method forK-R Curve DeterminationE647 Test Method for Measurement of Fati
11、gue Crack Growth RatesE1290 Test Method for Crack-Tip Opening Displacement (CTOD) Fracture Toughness MeasurementE1820 Test Method for Measurement of Fracture ToughnessE1823 Terminology Relating to Fatigue and Fracture TestingE2309 Practices for Verification of Displacement Measuring Systems and Devi
12、ces Used in Material Testing Machines1 This test method is under the jurisdiction of ASTM Committee E08 on Fatigue and Fracture and is the direct responsibility of Subcommittee E08.07 on FractureMechanics.Current edition approved June 15, 2006July 1, 2012. Published August 2006January 2013. Original
13、ly approved in 2006. Last previous edition approved in 2006 asE2472061. DOI: 10.1520/E2472-06E01.10.1520/E2472-12.2 The boldface numbers in parentheses refer to the list of references at the end of this standard.3 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM C
14、ustomer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to
15、 the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyrigh
16、t ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.2 ISO Standards:4ISO/TC164/SC4-N413.4 ISO 22889:2007 Metallic MaterialsMethod of Test for the Determination of Resistance to StableCrack Extension Using Specimens of Low ConstraintISO 12135 Me
17、tallic MaterialsUnified Method of Test for the 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 length.size.3.2.1.1 DiscussionIt should be noted that in thin-sheet a
18、nd thick-plate materials under low constraint conditions, the crack extension observed on thesurface of the specimen may be significantly less than that in the interior of the specimen due to the effects of crack tunneling.This must be considered if direct optical techniques are used to monitor and
19、measure free-surface crack extension. Indirect crackextension measurement techniques such as unloading compliance and electric-potential drop method may be used in place of (orto augment)complement) the direct optical techniques to provide a measure of average crack extension. (See Test Method E647f
20、or compliance methods for C(T) and M(T) specimens; and ISO 12135 and Test Method E647 for electric potential-drop methodsfor C(T) specimens.)3.2.2 crack length,size, a L, na linear measure of a principal planar dimension of a crack. This measure is commonlyprincipal linear dimension used in the calc
21、ulation of quantities descriptive of the stress and displacement fields of crackedspecimens.fracture mechanics parameters for through thickness cracks.3.2.2.1 DiscussionA measure of the crack lengthsize after the fatigue pre-cracking stage is denoted as the original crack length,size, ao. The valuef
22、or ao may be obtained using surface measurement, unloading compliance, electric-potential drop or other methods wherevalidation procedures for the measurements are available.3.2.3 crack-tip-opening angle (CTOA), deg,nrelative angle of the crack surfaces crack surfaces resulting from the totaldeforma
23、tion (elastic plus plastic) measured (or calculated) at 1-mm behind the current crack tip, tip as the crack stably tears, where = 2 tan-11 (CTOD/2). (1/2).3.2.4 critical crack-tip-opening angle (CTOAc),cdeg,nsteady-state value of CTOA relative angle of crack surfacesresulting from the total deformat
24、ion (elastic plus plastic) measured (or calculated) at 1-mm behind the current crack tip, whereCTOAtip as the crack stably tears, where c = = 2 tan1 (CTOD (c1c/2).3.2.4.1 DiscussionThe critical Critical CTOA value tends to approach a constant, steady-state value after a small amount of crack extensi
25、on(associated with crack tunneling and transition from flat-to-slant crack extension).3.2.5 crack-opening displacement, 5L,nrelative displacement of the crack surfaces normal to the original (un-deformed)crack plane at the tip of the fatigue pre-crack length,force-induced separation vector between t
26、wo points (normal to the facingsurfaces of a crack) at a aspecifiedo. gage length. In this standard, 5 is measured at the original crack lengthsize location over agage length of 5-mm as the crack stably tears.3.2.6 crack-tip-opening displacement (CTOD), 1 L,nrelative displacement of crack surfaces r
27、esulting from the totaldeformation (elastic plus plastic) at variously defined locations near the original (prior to force application) crack tip.measured (orcalculated) at 1- mm behind the current crack tip as the crack stably tears.3.2.7 critical crack-tip-opening displacement (CTODc), c1c L, nste
28、ady-state value of CTOD relative displacement of cracksurfaces resulting from the total deformation (elastic plus plastic) measured (or calculated) at 1-mm behind current crack-tiplocation.the current crack tip as the crack stably tears.3.2.8 crack extension resistance curve (R curve), nvariation of
29、 5 with crack extension, a.3.2.9 effective yield strength, YFL-2,nan assumed value of uniaxial yield strength that represents the influence of plasticyielding upon fracture test parameters.4 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036.In
30、ternational Organization for Standardization (ISO), 1,ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.E2472 1223.2.9.1 DiscussionEffective yield strength is calculated as the average of the 0.2 % offset yield strength YS, and the ultimate tensile strength, T
31、S asfollows:Y 5YS1TS!/2 (1)NOTE 1The yield and ultimate tensile strength are determined from Test Methods E8E8/E8M.3.2.9.2 DiscussionIn estimating Y, influences of testing conditions, such as loading rate and temperature, should be considered.3.2.10 final crack length,size, af L L, , ncrack extensio
32、n at end of stable tearing (af = ao + af).3.2.11 final remaining ligament, bf L L, , ndistance from the tip of the final crack lengthsize to the back edge of thespecimen, that is bf = W af.3.2.12 force, P F, nforce applied to specimen.a test specimen or to a component.3.2.13 minimum crack extension,
33、 amin L,ncrack extension beyond which c is nearly constant.3.2.14 maximum crack extension, amax L,ncrack extension limit for c and 5 controlled crack extension.3.2.15 maximum fatigue force, Pf F , nmaximum fatigue force applied to specimen during pre-cracking stage.3.2.16 modulus of elasticity, E FL
34、-2,nthe rationratio of stress to corresponding strain below the proportional limit.3.2.17 notch length,size, an L L, , nthe distance from a reference plane to the tipfront of the machined notch, such as theloadforce line in the compact-tensioncompact specimen to the notch tipfront or from the center
35、 line in the middle-crack tensionmiddle-crack-tension specimen to the notch tip.front.3.2.18 original crack length,size, ao L L, , nthe physical crack lengthsize at the start of testing.3.2.19 original remaining ligament, bo L L, , ndistance from the original crack front to the back edge of the spec
36、imen, thatis bo = W ao.3.2.20 remaining ligament, b L, ndistance from the physical crack front to the back edge of the specimen, that is b = W a.3.2.21 specimen thickness, B L, nthe side-to-side dimension of the specimen being tested (sidedistance between the parallelsides of a test specimen or comp
37、onent. Side grooving is not allowed).allowed.3.2.22 specimen width, W L, na physical dimension on a test specimen measured distance from a reference position, suchas the load line in the compact-tension specimen or the position (for example, the force line of a compact specimen or center linein the
38、middle-crack tension specimen middle-crack-tension specimen) to the edge rear surface of the specimen. (Note that the totalwidth of the M(T) specimen is defined as 2W.)4. Summary of Test Method4.1 The objective of this standard is to induce stable crack extension in a fatigue pre-cracked, low-constr
39、aint test specimen whilemonitoring and measuring the COD at the original fatigue pre-crack tip pre-crack-tip location (4, 5) or the CTOA (or CTOD) at1-mm behind the stably tearing crack tip (6, 7), or both. The resistance curve associated with the 5 measurements and the criticallimiting value of the
40、 CTOA measurements are used to characterize the corresponding resistance to stable crack extension. Incontrast, the CTOD values determined from Test Method E1290 (high-constraint bend specimens) are values at one or more crackextension events, such as the CTOD at the onset of brittle crack extension
41、 with no significant stable crack extension.4.2 Either of the fatigue pre-cracked, low-constraint test specimen configurations specified in this standard (C(T)C(T) orM(T)M(T) may be used to measure or calculate either of the fracture resistance parameters considered. The fracture resistanceparameter
42、s, CTOA (or CTOD) and 5, may be characterized using either a single-specimen or multiple-specimen procedure. In allcases, tests are performed by applying slowly increasing displacements to the test specimen and measuring the forces,displacements, crack extension and angles realized during the test.
43、The forces, displacements and angles are then used inconjunction with certain pre-test and post-test specimen measurements to determine the materials resistance to stable crackextension.4.3 Four procedures for measuring crack extension are: surface visual, unloading compliance, electrical potential,
44、 and multiplespecimens.4.4 Two techniques are presented for measuring CTOA: optical microscopy (OM) (8) and digital image correlation (DIC) (9).4.5 Three techniques are presented for measuring COD: 5 clip gage (5), optical microscopy (OM) (8), and digital imagecorrelation (DIC) (9).E2472 1234.6 Data
45、 generated following the procedures and guidelines contained in this standard are labeled qualified data and areinsensitive to in-plane dimensions and specimen type (tension or bending forces), but are dependent upon sheet or plate thickness.5. Significance and Use5.1 This test method characterizes
46、a metallic materials resistance to stable crack extension in terms of crack-tip-opening angle(CTOA), and/or crack-opening displacement (COD), 5 under the laboratory or application environment of interest. This methodapplies specifically to fatigue pre-cracked specimens that exhibit low constraint an
47、d that are tested under slowly increasingdisplacement.5.2 When conducting fracture tests, the user must consider the influence that the loading rate and laboratory environment mayhave on the fracture parameters. The user should perform a literature review to determine if loading rate effects have be
48、en observedpreviously in the material at the specific temperature and environment being tested. The user should document specific informationpertaining to their material, loading rates, temperature, and environment (relative humidity) for each test.5.3 The results of this characterization include th
49、e determination of a critical, lower-limiting value, of CTOA (c) or a resistancecurve of 5, a measure of crack-opening displacement against crack extension, or both.5.4 The recommendedtest specimens are the compact-tension,compact, C(T), and middle-crack-tension, M(T), specimens.5.5 Materials that can be evaluated by this standard are not limited by strength, thickness, or toughness, if the crack-length-to-thicknesscrack-size-to-thickness (a/B
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