1、Designation: E1820 131Standard 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 paren
2、theses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTESections A6.2.2 and A6.3.2 were editorially revised in May 2015.1. Scope1.1 This test method covers procedures and guidelines forthe determination of fractur
3、e toughness of metallic materialsusing the following parameters: K, J, and CTOD (). 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.NOTE 1Until this version, KIccould
4、 be evaluated using this testmethod as well as by using Test Method E399. To avoid duplication, theevaluation of KIchas been removed from this test method and the user isreferred to Test Method E399.1.2 The recommended specimens are single-edge bend,SE(B), compact, C(T), and disk-shaped compact, DC(
5、T).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 materialtoughness, material flow strength, and the individual qua
6、lifi-cation requirements 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
7、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.NOTE 2Other standard methods for the determination of fracturetoughness using the parameters K, J, and CTOD are contained in
8、 TestMethods 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 Testin
9、g of Metallic Ma-terialsE21 Test Methods for ElevatedTemperatureTensionTests ofMetallic MaterialsE23 Test Methods for Notched Bar Impact Testing of Me-tallic MaterialsE399 Test Method for Linear-Elastic Plane-Strain FractureToughness KIcof Metallic MaterialsE1290 Test Method for Crack-Tip Opening Di
10、splacement(CTOD) Fracture Toughness Measurement (Withdrawn2013)3E1823 Terminology Relating to Fatigue and Fracture TestingE1921 Test Method for Determination of ReferenceTemperature, To, for Ferritic Steels in the TransitionRangeE1942 Guide for Evaluating DataAcquisition Systems Usedin Cyclic Fatigu
11、e and Fracture 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.
12、3.2 Definitions of Terms Specific to This Standard:3.2.1 compliance LF1, nthe ratio of displacement in-crement to force increment.3.2.2 crack opening displacement (COD) L, nforce-induced separation vector between two points at a specific gagelength. The direction of the vector is normal to the crack
13、 plane.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 Nov. 15, 2013. Published January 2014. Originallyapproved in 1996. Last previous edition approved in 2
14、011 as E1820 112. DOI:10.1520/E1820-13E01.2For 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.3The last approved
15、version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.2.1 DiscussionIn this practice, displacement, v, is thetotal displacement measured by clip gages or other devicesspan
16、ning the crack faces.3.2.3 crack extension, a L, nan increase in crack size.3.2.4 crack-extension force, G FL1or FLL2, ntheelastic energy per unit of new separation area that is madeavailable at the front of an ideal crack in an elastic solid duringa virtual increment of forward crack extension.3.2.
17、5 crack size, a L, na lineal measure of a principalplanar dimension of a crack. This measure 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
18、procedures for measurement of physical crack size, ap,original crack size, ao, and effective crack size, ae,asappropriate to the situation being considered.3.2.6 crack-tip opening displacement (CTOD), L, nthecrack displacement resulting from the total deformation (elasticplus plastic) at variously d
19、efined locations near the originalcrack tip.3.2.6.1 DiscussionIn this test method, CTOD 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 measure
20、ments made from the force versus displacementrecord.3.2.6.2 DiscussionIn CTOD testing, IcL is a value ofCTOD near the onset of slow stable crack extension, heredefined as occurring at ap= 0.2 mm (0.008 in.) + 0.7Ic.3.2.6.3 DiscussionIn CTOD testing, cL is the value ofCTOD at the onset of unstable cr
21、ack extension (see 3.2.39)orpop-in (see 3.2.25) when ap0.2 mm(0.008 in.) + 0.7u. The ucorresponds to the force Puand theclip 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 Disc
22、ussionIn CTOD testing, c*L characterizesthe CTOD fracture toughness of materials at fracture instabilityprior to the onset of significant stable tearing crack extension.The value of c*determined by this test method represents ameasure of fracture toughness at instability without significantstable cr
23、ack extension that is independent of in-plane dimen-sions. However, there may 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, KJd
24、The dynamicequivalent of the stress intensity factor KJ, calculated from Jusing the equation specified in this test method.3.2.9 dynamic ultimate tensile strength, TSdFL-2dynamic equivalent of the ultimate tensile strength, measuredat the equivalent strain rate of the fracture toughness test.3.2.10
25、dynamic yield strength, YSdFL-2dynamicequivalent of the yield strength, measured at the equivalentstrain rate of the fracture toughness test.3.2.11 effective thickness, BeL,nfor side-groovedspecimens Be=B(BBN)2/B. This is used for the elasticunloading compliance measurement of crack size.3.2.12 effe
26、ctive yield strength, YFL2, nan assumedvalue of uniaxial yield strength 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 YS, and the ultimate tensilestrength, TSas follows:NOTE 1Constru
27、ction 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 RecordsE18
28、20 1312Y5YS1TS2(1)3.2.12.2 DiscussionIn estimating Y, influences of testingconditions, such as loading rate and temperature, should beconsidered.3.2.12.3 DiscussionThe dynamic effective yield strength,Yd, is the dynamic equivalent of the effective yield strength,and is calculated as the average of t
29、he dynamic yield strengthand dynamic ultimate tensile strength.3.2.13 general yield force, PgyF in 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 express
30、ion, aline or surface integral that encloses the crack front from 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-a
31、xis, is the line integral as follows:J 5 *SWdy 2 TuxdsD(2)where:W = loading work per unit volume or, for elastic bodies,strain energy density, = 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 v
32、ector at ds,x, y, z = rectangular coordinates, andTuxds= rate of work input from the stress field into the areaenclosed by .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 testspeci
33、mens) caution is needed to adequately consider loadinginterior to 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 for
34、ce.)3.2.14.4 DiscussionIn elastic (linear and nonlinear) solidsfor 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
35、per unitdifference in crack area at a fixed value of displacement or,where appropriate, at a fixed value of force (1)4.3.2.14.5 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 fra
36、cture toughness of materials atfracture instability prior to 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 dim
37、ensions; however, there may be a depen-dence of toughness on 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 specime
38、n geometry. It can be useful todefine limits on ductile fracture 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, JFL21T21#derivative of J withrespect to time.3.2.18 machine capacity, MC FLmaximum availableenergy
39、of the impact testing machine.3.2.19 maximum force, PmaxFin 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,
40、aoL,nthe physical crack sizeat the start of testing.3.2.21.1 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 physi
41、cal crack size, apL,nthe distance from areference plane to 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 th
42、e load-line or the centerline of a specimenor plate. The reference plane is defined prior to specimendeformation.3.2.24 plane-strain fracture toughness, JIcFL1, KJIcFL3/2,nthe crack-extension resistance under conditionsof crack-tip plane-strain.3.2.24.1 DiscussionFor example, in Mode I for slow rate
43、sof loading and substantial plastic deformation, plane-strainfracture toughness is the value of the J-integral designated JIcFL1 as measured using the operational procedure (andsatisfying all of the qualification requirements) specified in thistest method, that provides for the measurement of crack-
44、extension resistance near the onset of stable crack extension.3.2.24.2 DiscussionFor example, in Mode I for slow ratesof loading, plane-strain fracture toughness is the value of thestress intensity designated KJIccalculated from JIcusing theequation (and satisfying all of the qualification requireme
45、nts)specified in this test method, that provides for the measurementof crack-extension resistance near the onset of stable crackextension under dominant elastic conditions (2).3.2.24.3 DiscussionThe dynamic equivalent of JIcis JIcd,X, with X = order of magnitude of J-integral rate.4The boldface numb
46、ers in parentheses refer to the list of references at the end ofthis standard.E1820 13133.2.25 pop-in, na discontinuity in the force versus clipgage displacement record. The record of a pop-in shows asudden increase in displacement and, generally a decrease inforce. Subsequently, the displacement an
47、d force increase toabove their respective values at pop-in.3.2.26 R-curve or J-R curve, na plot of crack extensionresistance as a function of stable crack extension, apor ae.3.2.26.1 DiscussionIn this test method, the J-R curve is aplot of the far-field J-integral versus the physical crackextension,
48、 ap. It is recognized that the far-field value of J maynot represent the stress-strain field local to a growing crack.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, nthedistanc
49、e 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 between speci-men supports.3.2.31 specimen thickness, B L, nthe side-to-side di-mension of the specimen being tested.3.2.32 specimen width, W L, na physical dimen
