1、Designation: E1820 11Standard Test Method forMeasurement of Fracture Toughness1This standard is issued under the fixed designation E1820; 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 parent
2、heses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers procedures and guidelines forthe determination of fracture toughness of metallic materialsusing the following parameters: K, J,
3、 and CTOD (d). Tough-ness can be measured in the R-curve format or as a point value.The fracture toughness determined in accordance with this testmethod is for the opening mode (Mode I) of loading.1.2 The recommended specimens are single-edge bend,SE(B), compact, C(T), and disk-shaped compact, DC(T)
4、.All specimens contain notches that are sharpened with fatiguecracks.1.2.1 Specimen dimensional (size) requirements vary ac-cording to the fracture toughness analysis applied. The guide-lines are established through consideration of material tough-ness, material flow strength, and the individual qua
5、lificationrequirements of the toughness value per values sought.1.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is
6、 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.NOTE 1Other standard methods for the determination of fracturetoughness using the parameters K, J, and CTOD are contained in T
7、estMethods E399, E1290, and E1921. This test method was developed toprovide a common method for determining all applicable toughnessparameters from a single test.2. Referenced Documents2.1 ASTM Standards:2E4 Practices for Force Verification of Testing MachinesE8/E8M Test Methods for Tension Testing
8、of MetallicMaterialsE21 Test Methods for Elevated Temperature Tension Testsof Metallic MaterialsE23 Test Methods for Notched Bar Impact Testing ofMetallic MaterialsE399 Test Method for Linear-Elastic Plane-Strain FractureToughness KIcof Metallic MaterialsE1290 Test Method for Crack-Tip Opening Displ
9、acement(CTOD) Fracture Toughness MeasurementE1823 Terminology Relating to Fatigue and Fracture Test-ingE1921 Test Method for Determination of Reference Tem-perature, To, for Ferritic Steels in the Transition RangeE1942 Guide for Evaluating Data Acquisition SystemsUsed in Cyclic Fatigue and Fracture
10、Mechanics TestingE2298 Test Method for Instrumented Impact Testing ofMetallic Materials3. Terminology3.1 Terminology E1823 is applicable to this test method.Only items that are exclusive to Test Method E1820, or thathave specific discussion items associated, are listed in thissection.3.2 Definitions
11、 of Terms Specific to This Standard:3.2.1 compliance LF1, nthe ratio of displacement in-crement to force increment.3.2.2 crack displacement L, nthe separation vector be-tween two points (on the surfaces of a deformed crack) thatwere coincident on the surfaces of an ideal crack in theundeformed condi
12、tion.3.2.2.1 DiscussionIn this practice, displacement, v, is thetotal displacement measured by clip gages or other devicesspanning the crack faces.3.2.3 crack extension, Da L, nan increase in crack size.3.2.4 crack-extension force, G FL1or FLL2, ntheelastic energy per unit of new separation area tha
13、t is madeavailable at the front of an ideal crack in an elastic solid duringa virtual increment of forward crack extension.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 edi
14、tion approved May 1, 2011. Published August 2011. Originallyapproved in 1996. Last previous edition approved in 2009 as E1820 091. DOI:10.1520/E1820-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMSta
15、ndards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.5 crack size, a L, na lineal measure of a principalplanar dimension of a crack. This measu
16、re is commonly usedin the calculation of quantities descriptive of the stress anddisplacement fields, and is often also termed crack length ordepth.3.2.5.1 DiscussionIn practice, the value of a is obtainedfrom procedures for measurement of physical crack size, ap,original crack size, ao, and effecti
17、ve crack size, ae, as appro-priate to the situation being considered.3.2.6 crack-tip opening displacement (CTOD), d L,nthe crack displacement resulting from the total deformation(elastic plus plastic) at variously defined locations near theoriginal crack tip.3.2.6.1 DiscussionIn this test method, CT
18、OD is the dis-placement of the crack surfaces normal to the original (un-loaded) crack plane at the tip of the fatigue precrack, ao. In thistest method, CTOD is calculated at the original crack size, ao,from measurements made from the force versus displacementrecord.3.2.6.2 DiscussionIn CTOD testing
19、, dIcL is a value ofCTOD near the onset of slow stable crack extension, heredefined as occurring at Dap= 0.2 mm (0.008 in.) + 0.7dIc.3.2.6.3 DiscussionIn CTOD testing, dcL is the value ofCTOD at the onset of unstable crack extension (see 3.2.39)orpop-in (see 3.2.25) when Dap0.2mm (0.008 in.) + 0.7du
20、. The ducorresponds to the force Puandthe clip gage displacement vu(see Fig. 1). It may be size-dependent and a function of test specimen geometry. It can beuseful to define limits on ductile fracture behavior.3.2.6.5 DiscussionIn CTOD testing, dc*L characterizesthe CTOD fracture toughness of materi
21、als at fracture instabilityprior to the onset of significant stable tearing crack extension.The value of dc*determined by this test method represents ameasure of fracture toughness at instability without significantstable crack extension that is independent of in-plane dimen-sions. However, there ma
22、y be a dependence of toughness onthickness (length of crack front).3.2.7 dial energy, KV FLabsorbed energy as indicatedby the impact machine encoder or dial indicator, as applicable.3.2.8 dynamic stress intensity factor, KJdThe dynamicequivalent of the stress intensity factor KJ, calculated from Jus
23、ing the equation specified in this test method.3.2.9 dynamic ultimate tensile strength, sTSdFL-2dynamic equivalent of the ultimate tensile strength, measuredat the equivalent strain rate of the fracture toughness test.3.2.10 dynamic yield strength, sYSdFL-2dynamicequivalent of the yield strength, me
24、asured at the equivalentstrain rate of the fracture toughness test.3.2.11 effective thickness, BeL, nfor side-grooved speci-mens Be=B (BBN)2/B. This is used for the elasticunloading compliance measurement of crack size.3.2.12 effective yield strength, sYFL2, nan assumedvalue of uniaxial yield streng
25、th that represents the influence ofplastic yielding upon fracture test parameters.3.2.12.1 DiscussionIt is calculated as the average of the0.2 % offset yield strength sYS, and the ultimate tensilestrength, sTSas follows:sY5sYS1sTS2(1)3.2.12.2 DiscussionIn estimating sY, influences of testingconditio
26、ns, such as loading rate and temperature, should beconsidered.3.2.12.3 DiscussionThe dynamic effective yield strength,sYd, is the dynamic equivalent of the effective yield strength,and is calculated as the average of the dynamic yield strengthand dynamic ultimate tensile strength.NOTE 1Construction
27、lines drawn parallel to the elastic loading slope to give vp, the plastic component of total displacement, vg.NOTE 2In curves b and d, the behavior after pop-in is a function of machine/specimen compliance, instrument response, etc.FIG. 1 Types of Force versus Clip Gage Displacement RecordsE1820 112
28、3.2.13 general yield force, PgyFin an instrumentedimpact test, applied force corresponding to general yielding ofthe specimen ligament. It corresponds to Fgy, as used in TestMethod E2298.3.2.14 J-integral, J FL1, na mathematical expression, aline or surface integral that encloses the crack front fro
29、m onecrack surface to the other, used to characterize the localstress-strain field around the crack front.3.2.14.1 DiscussionThe J-integral expression for a two-dimensional crack, in the x-z plane with the crack front parallelto the z-axis, is the line integral as follows:J 5*GSWdy 2 T uxdsD(2)where
30、:W = loading work per unit volume or, for elasticbodies, strain energy density,G = path of the integral, that encloses (that is,contains) the crack tip,ds = increment of the contour path,T= outward traction vector on ds,u = displacement vector at ds,x, y, z = rectangular coordinates, andTuxds= rate
31、of work input from the stress field intothe area enclosed by G.3.2.14.2 DiscussionThe value of J obtained from thisequation is taken to be path-independent in test specimenscommonly used, but in service components (and perhaps in testspecimens) caution is needed to adequately consider loadinginterio
32、r to G such as from rapid motion of the crack or theservice component, and from residual or thermal stress.3.2.14.3 DiscussionIn elastic (linear or nonlinear) solids,the J-integral equals the crack-extension force, G. (See crackextension force.)3.2.14.4 DiscussionIn elastic (linear and nonlinear) so
33、lidsfor which the mathematical expression is path independent, theJ-integral is equal to the value obtained from two identicalbodies with infinitesimally differing crack areas each subject tostress. The parameter J is the difference in work per unitdifference in crack area at a fixed value of displa
34、cement or,where appropriate, at a fixed value of force (1)3.3.2.14.5 DiscussionThe dynamic equivalent of JcisJcd,X, with X = order of magnitude of J-integral rate.3.2.15 JcFL1The property Jcdetermined by this testmethod characterizes the fracture toughness of materials atfracture instability prior t
35、o the onset of significant stabletearing crack extension. The value of Jcdetermined by this testmethod represents a measure of fracture toughness at instabil-ity without significant stable crack extension that is indepen-dent of in-plane dimensions; however, there may be a depen-dence of toughness o
36、n thickness (length of crack front).3.2.16 JuFL1The quantity Judetermined by this testmethod measures fracture instability after the onset of signifi-cant stable tearing crack extension. It may be size-dependentand a function of test specimen geometry. It can be useful todefine limits on ductile fra
37、cture behavior.3.2.16.1 DiscussionThe dynamic equivalent of Juis Jud,X,with X = order of magnitude of J-integral rate.3.2.17 J-integral rate, JFL-1T-1derivative of J withrespect to time.3.2.18 machine capacity, MC FLmaximum availableenergy of the impact testing machine.3.2.19 maximum force, PmaxFin
38、an instrumented im-pact test, maximum value of applied force. It corresponds toFm, as used in Test Method E2298.3.2.20 net thickness, BNL, ndistance between the rootsof the side grooves in side-grooved specimens.3.2.21 original crack size, aoL, nthe physical crack sizeat the start of testing.3.2.21.
39、1 DiscussionIn this test method, aoqis used todenote original crack size estimated from compliance.3.2.22 original remaining ligament, boL, ndistancefrom the original crack front to the back edge of the specimen,that is (bo=Wao).3.2.23 physical crack size, apL, nthe distance from areference plane to
40、 the observed crack front. This distance mayrepresent an average of several measurements along the crackfront. The reference plane depends on the specimen form, andit is normally taken to be either the boundary, or a planecontaining either the load-line or the centerline of a specimenor plate. The r
41、eference plane is defined prior to specimendeformation.3.2.24 plane-strain fracture toughness, KIcFL3/2, JIcFL1, KJIcFL3/2 , nthe crack-extension resistance underconditions of crack-tip plane-strain.3.2.24.1 DiscussionFor example, in Mode I for slow ratesof loading and negligible plastic-zone adjust
42、ment, plane-strainfracture toughness is the value of the stress-intensity factordesignated KIcas measured using the operational procedure(and satisfying all of the qualification requirements) specifiedin this test method, which provides for the measurement ofcrack-extension resistance at the start o
43、f crack extension andprovides operational definitions of crack-tip sharpness, start ofcrack extension, and crack-tip plane-strain.3.2.24.2 DiscussionFor example, in Mode I for slow ratesof loading and substantial plastic deformation, plane-strainfracture toughness is the value of the J-integral desi
44、gnated JIcFL1 as measured using the operational procedure (andsatisfying all of the qualification requirements) specified in thistest method, that provides for the measurement of crack-extension resistance near the onset of stable crack extension.3.2.24.3 DiscussionFor example, in Mode I for slow ra
45、tesof loading, plane-strain fracture toughness is the value of thestress intensity designated KJIccalculated from JIcusing theequation (and satisfying all of the qualification requirements)specified in this test method, that provides for the measurementof crack-extension resistance near the onset of
46、 stable crackextension under dominant elastic conditions (2).3.2.24.4 DiscussionThe dynamic equivalent of JIcisJIcd,X, with X = order of magnitude of J-integral rate.3.2.25 pop-in, na discontinuity in the force versus clipgage displacement record. The record of a pop-in shows asudden increase in dis
47、placement and, generally a decrease in3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.E1820 113force. Subsequently, the displacement and force increase toabove their respective values at pop-in.3.2.26 R-curve or J-R curve, na plot of crack extensionres
48、istance as a function of stable crack extension, Dapor Dae.3.2.26.1 DiscussionIn this test method, the J-R curve is aplot of the far-field J-integral versus the physical crackextension, Dap. It is recognized that the far-field value of J maynot represent the stress-strain field local to a growing cr
49、ack.3.2.27 remaining ligament, b L, ndistance from thephysical crack front to the back edge of the specimen, that is(b=Wap).3.2.28 specimen center of pin hole distance, H* L, nthedistance between the center of the pin holes on a pin-loadedspecimen.3.2.29 specimen gage length, d L, nthe distance be-tween the points of displacement measure (for example, clipgage, gage length).3.2.30 specimen span, S L, nthe distance betweenspecime
