ASTM E1820-2009e1 Standard Test Method for Measurement of Fracture Toughness《断裂韧性测定的标准试验方法》.pdf

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1、Designation: E1820 091Standard 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 A2.4.2, A2.4.2.2, and A3.5.2.2 were editorially corrected in July 2010.1. Scope1.1 This test method covers procedures and guidelines forthe determin

3、ation of fracture toughness of metallic materialsusing the following parameters: K, J, 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 recommend

4、ed specimens are single-edge bend,SE(B), compact, C(T), and disk-shaped compact, DC(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 throug

5、h consideration of material tough-ness, material flow strength, and the individual qualificationrequirements 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 no

6、t 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.NOTE 1Other standard methods for the det

7、ermination of fracturetoughness using the parameters K, J, and CTOD are contained in TestMethods E399, E813, E1152, E1290, and E1737. This test method wasdeveloped to provide a common method for determining all applicabletoughness parameters from a single test.2. Referenced Documents2.1 ASTM Standar

8、ds:2E4 Practices for Force Verification of Testing MachinesE8 Test Methods for Tension Testing of Metallic MaterialsE21 Test Methods for Elevated Temperature Tension Testsof Metallic MaterialsE399 Test Method for Linear-Elastic Plane-Strain FractureToughness KIcof Metallic MaterialsE813 Test Method

9、for JIc,AMeasure of FractureToughnessE1152 Test Method for Determining-J-R-CurvesE1290 Test Method for Crack-Tip Opening Displacement(CTOD) Fracture Toughness MeasurementE1737 Test Method for J-Integral Characterization of Frac-ture Toughness (Discontinued 1998)3E1823 Terminology Relating to Fatigue

10、 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 Mechanics Testing3. Terminology3.1 Terminology E1823 is applicable to this test m

11、ethod.3.2 Definitions: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 condition.3.2.2.1 D

12、iscussionIn 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 that is madeavail

13、able at the front of an ideal crack in an elastic solid duringa virtual increment of forward crack extension.3.2.5 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 fie

14、lds, and is often also termed crack size ordepth.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. 1, 2009. Published December 2009. Originallyapproved in

15、 1996. Last previous edition approved in 2008 as E1820 08a.DOI:10.1520/E1820-09.2For 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

16、onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.5.1 DiscussionIn practice, the value of a is obtainedfrom procedure

17、s for measurement of physical crack size, ap,original crack size, ao, and effective crack size, ae, as appro-priate to the situation being considered.3.2.6 crack-tip opening displacement (CTOD), d L,nthe crack displacement due to elastic and plastic deforma-tion at variously defined locations near t

18、he original crack 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 measurements made from the fo

19、rce versus displacementrecord.3.2.6.2 DiscussionIn CTOD testing, 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

20、 3.2.28)orpop-in (see 3.2.17) when Dap0.2mm (0.008 in.) + 0.7du. 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 t

21、esting, dc*L characterizesthe CTOD fracture toughness of materials 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

22、 that is independent of in-plane dimen-sions. However, there may be a dependence of toughness onthickness (length of crack front).3.2.7 effective thickness, BeL, nfor side-grooved speci-mens Be=B (BBN)2/B. This is used for the elasticunloading compliance measurement of crack size.3.2.7.1 DiscussionT

23、his definition is different from thedefinition of effective thickness in Test Method E813.3.2.8 effective yield strength, sYFL2, nan assumedvalue of uniaxial yield strength that represents the influence ofplastic yielding upon fracture test parameters.3.2.8.1 DiscussionIt is calculated as the averag

24、e of the0.2 % offset yield strength sYS, and the ultimate tensilestrength, sTSas follows:sY5sYS1sTS!2(1)3.2.8.2 DiscussionIn estimating sY, influences of testingconditions, such as loading rate and temperature, should beconsidered.3.2.9 J-integral, J FL1, na mathematical expression, aline or surface

25、 integral that encloses the crack front from onecrack surface to the other, used to characterize the localstress-strain field around the crack front.3.2.9.1 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 integ

26、ral as follows:J 5*GSWdy 2 T uxdsD(2)where: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

27、= rectangular coordinates, andNOTE 1Construction 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 For

28、ce versus Clip Gage Displacement RecordsE1820 0912Tuxds= rate of work input from the stress field intothe area enclosed by G.3.2.9.2 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

29、mens) caution is needed to adequately consider loadinginterior to G such as from rapid motion of the crack or theservice component, and from residual or thermal stress.3.2.9.3 DiscussionIn elastic (linear or nonlinear) solids,the J-integral equals the crack-extension force, G. (See crackextension fo

30、rce.)3.2.10 JcFL1The property Jcdetermined by this testmethod characterizes the fracture 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-

31、ity without significant stable crack extension that is indepen-dent of in-plane dimensions; however, there may be a depen-dence of toughness on thickness (length of crack front).3.2.11 JuFL1The quantity Judetermined by this testmethod measures fracture instability after the onset of signifi-cant sta

32、ble tearing crack extension. It may be size-dependentand a function of test specimen geometry. It can be useful todefine limits on ductile fracture behavior.3.2.12 net thickness, BNL, ndistance between the rootsof the side grooves in side-grooved specimens.3.2.13 original crack size, aoL, nthe physi

33、cal crack sizeat the start of testing.3.2.13.1 DiscussionIn this test method, aoqis used todenote original crack size estimated from compliance.3.2.14 original remaining ligament, boL, ndistancefrom the original crack front to the back edge of the specimen,that is (bo=Wao).3.2.15 physical crack size

34、, 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 the load-line o

35、r the centerline of a specimenor plate. The reference plane is defined prior to specimendeformation.3.2.16 plane-strain fracture toughness, KIcFL3/2, JIcFL1, KJIcFL3/2 , nthe crack-extension resistance underconditions of crack-tip plane-strain.3.2.16.1 DiscussionFor example, in Mode I for slow rates

36、of loading and negligible plastic-zone adjustment, plane-strainfracture toughness is the value of the stress-intensity factordesignated KIcFL3/2 as measured using the operationalprocedure (and satisfying all of the qualification requirements)specified in this test method, which provides for the meas

37、ure-ment of crack-extension resistance at the start of crack exten-sion and provides operational definitions of crack-tip sharp-ness, start of crack extension, and crack-tip plane-strain.3.2.16.2 DiscussionFor example, in Mode I for slow ratesof loading and substantial plastic deformation, plane-str

38、ainfracture 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-extension resistance near the onset of stable crack extens

39、ion.3.2.16.3 DiscussionFor example, in Mode I for slow ratesof loading, plane-strain fracture toughness is the value of thestress intensity designated KJIcFL3/2 calculated from JIcusing the equation (and satisfying all of the qualificationrequirements) specified in this test method, that provides fo

40、rthe measurement of crack-extension resistance near the onsetof stable crack extension under dominant elastic condi-tions.(1)43.2.17 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 info

41、rce. Subsequently, the displacement and force increase toabove their respective values at pop-in.3.2.18 R-curve or J-R curve, na plot of crack extensionresistance as a function of stable crack extension, Dapor Dae.3.2.18.1 DiscussionIn this test method, the J-R curve is aplot of the far-field J-inte

42、gral 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 crack.3.2.19 remaining ligament, b L, ndistance from thephysical crack front to the back edge of the specimen, that is(b=Wap).3.2.20 specimen cente

43、r of pin hole distance, H* L, nthedistance between the center of the pin holes on a pin-loadedspecimen.3.2.21 specimen gage length, d L, nthe distance be-tween the points of displacement measure (for example, clipgage, gage length).3.2.22 specimen span, S L, nthe distance betweenspecimen supports.3.

44、2.23 specimen thickness, B L, nthe side-to-side di-mension of the specimen being tested.3.2.24 specimen width, W L, na physical dimension ona test specimen measured from a reference position such as thefront edge in a bend specimen or the load-line in the compactspecimen to the back edge of the spec

45、imen.3.2.25 stable crack extension L, na displacement-controlled crack extension beyond the stretch-zone width (see3.2.27). The extension stops when the applied displacement isheld constant.3.2.26 stress-intensity factor, K, K1,K2,K3,KI,KII,KIIIFL3/2, nthe magnitude of the ideal-crack-tip stress fie

46、ld(stress-field singularity) for a particular mode in a homoge-neous, linear-elastic body.3.2.26.1 DiscussionValues of K for the Modes 1, 2, and 3are given by the following equations:K15r0limsyy2pr!1/2# (3)K25r0limtxy2pr!1/2# (4)K35r0limtyz2pr!1/2# (5)where r = distance directly forward from the cra

47、ck tip to a locationwhere the significant stress is calculated.4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.E1820 09133.2.26.2 DiscussionIn this test method, Mode 1 or ModeI is assumed. See Terminology E1823 for definition of mode.3.2.27 stretch-zon

48、e width, SZW L, nthe length of crackextension that occurs during crack-tip blunting, for example,prior to the onset of unstable brittle crack extension, pop-in, orslow stable crack extension. The SZW is in the same plane asthe original (unloaded) fatigue precrack and refers to anextension beyond the

49、 original crack size.3.2.28 unstable crack extension L, nan abrupt crackextension that occurs with or without prior stable crackextension in a standard test specimen under crosshead or clipgage displacement control.4. Summary of Test Method4.1 The objective of this test method is to load a fatigueprecracked test specimen to induce either or both of thefollowing responses (1) unstable crack extension, includingsigni