ASTM E1820-2018a Standard Test Method for Measurement of Fracture Toughness.pdf

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1、Designation: E1820 18E1820 18aStandard 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

2、in parentheses 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 for the determination of fracture toughness of metallic materials usingthe following paramet

3、ers: K, J, and CTOD (). Toughness can be measured in the R-curve format or as a point value. The fracturetoughness determined in accordance with this test method is for the opening mode (Mode I) of loading.NOTE 1Until this version, KIc could be evaluated using this test method as well as by using Te

4、st Method E399. To avoid duplication, the evaluationof KIc has been removed from this test method and the user is referred to Test Method E399.1.2 The recommended specimens are single-edge bend, SE(B), compact, C(T), and disk-shaped compact, DC(T). Allspecimens contain notches that are sharpened wit

5、h fatigue cracks.1.2.1 Specimen dimensional (size) requirements vary according to the fracture toughness analysis applied. The guidelines areestablished through consideration of material toughness, material flow strength, and the individual qualification requirements ofthe toughness value per values

6、 sought.NOTE 2Other standard methods for the determination of fracture toughness using the parameters K, J, and CTOD are contained inTest Methods E399,E1290, and E1921. This test method was developed to provide a common method for determining all applicable toughness parameters from a single test.1.

7、3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.1.4 This standard does 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 ap

8、propriate safety, health, and environmental practices and determine the applicability ofregulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Devel

9、opment of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E4 Practices for Force Verification of Testing MachinesE8/E8M Test Methods for Tension Testing of Metallic Materi

10、alsE21 Test Methods for Elevated Temperature Tension Tests of Metallic MaterialsE23 Test Methods for Notched Bar Impact Testing of Metallic MaterialsE399 Test Method for Linear-Elastic Plane-Strain Fracture Toughness KIc of Metallic MaterialsE1290 Test Method for Crack-Tip Opening Displacement (CTOD

11、) Fracture Toughness Measurement (Withdrawn 2013)3E1823 Terminology Relating to Fatigue and Fracture TestingE1921 Test Method for Determination of Reference Temperature, To, for Ferritic Steels in the Transition RangeE1942 Guide for Evaluating Data Acquisition Systems Used in Cyclic Fatigue and Frac

12、ture Mechanics TestingE2298 Test Method for Instrumented Impact Testing of Metallic Materials2.2 ASTM Data Set:4E1820/1DS1(2015) Standard data set to evaluate computer algorithms for evaluation of JIc using, Annex A9 of E18201 This test method is under the jurisdiction of ASTM Committee E08 on Fatig

13、ue and Fracture and is the direct responsibility of Subcommittee E08.07 on FractureMechanics.Current edition approved May 1, 2018Nov. 1, 2018. Published July 2018February 2019. Originally approved in 1996. Last previous edition approved in 20172018 asE1820 17a.E1820 18. DOI: 10.1520/E1820-1810.1520/

14、E1820-18A2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 The last approved version of this historical stand

15、ard is referenced on www.astm.org.4 This data set is available for download from ASTM at https:/www.astm.org/COMMITTEE/E08.htm, under the heading, Additional Information.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes h

16、ave been made to 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 d

17、ocument.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 Terminology E1823 is applicable to this test method. Only items that are exclusive to Test Method E1820, or that havespecific discussion items associated, are l

18、isted in this section.3.2 Definitions of Terms Specific to This Standard:3.2.1 compliance LF1, nthe ratio of displacement increment to force increment.3.2.2 crack opening displacement (COD) L, nforce-induced separation vector between two points at a specific gage length.The direction of the vector i

19、s normal to the crack plane.3.2.2.1 DiscussionIn this practice, displacement, v, is the total displacement measured by clip gages or other devices spanning the crack faces.3.2.3 crack extension, a L, nan increase in crack size.3.2.4 crack-extension force, G FL1 or FLL2, nthe elastic energy per unit

20、of new separation area that is made availableat the front of an ideal crack in an elastic solid during a virtual increment of forward crack extension.3.2.5 crack-tip opening displacement (CTOD), L, ncrack displacement resulting from the total deformation (elastic plusplastic) at variously defined lo

21、cations near the original (prior to force application) crack tip.3.2.5.1 DiscussionIn this test method, CTOD is the displacement of the crack surfaces normal to the original (unloaded) crack plane at the tip of thefatigue precrack, ao. In this test method, CTOD is calculated at the original crack si

22、ze, ao, from measurements made from the forceversus displacement record.3.2.5.2 DiscussionIn CTOD testing, Ic L is a value of CTOD near the onset of slow stable crack extension, here defined as occurring at ap = 0.2mm (0.008 in.) + 0.7Ic.3.2.5.3 DiscussionIn CTOD testing, c L is the value of CTOD at

23、 the onset of unstable crack extension (see 3.2.36) or pop-in (see 3.2.22) whenap 0.2 mm (0.008 in.) + 0.7u. The u corresponds to the force Pu and the clip gage displacement vu (seeFig. 1). It may be size-dependent and a function of test specimen geometry. It can be useful to define limits on ductil

24、e fracturebehavior.3.2.5.5 DiscussionIn CTOD testing, c* L characterizes the CTOD fracture toughness of materials at fracture instability prior to the onset ofsignificant stable tearing crack extension. The value of c* determined by this test method represents a measure of fracturetoughness at insta

25、bility without significant stable crack extension that is independent of in-plane dimensions. However, there maybe a dependence of toughness on thickness (length of crack front).3.2.6 dial energy, KV FLabsorbed energy as indicated by the impact machine encoder or dial indicator, as applicable.3.2.7

26、dynamic stress intensity factor, KJdThe dynamic equivalent of the stress intensity factor KJ, calculated from J using theequation specified in this test method.3.2.8 effective thickness, Be L , nfor side-grooved specimens Be = B (B BN)2/B. This is used for the elastic unloadingcompliance measurement

27、 of crack size.3.2.9 effective yield strength, Y FL2,nan assumed value of uniaxial yield strength that represents the influence of plasticyielding upon fracture test parameters.3.2.9.1 DiscussionIt is calculated as the average of the 0.2 % offset yield strength YS, and the ultimate tensile strength,

28、 TS as follows:Y 5 YS1TS2 (1)3.2.9.2 DiscussionIn estimating Y, influences of testing conditions, such as loading rate and temperature, should be considered.3.2.9.3 DiscussionThe dynamic effective yield strength, Yd, is the dynamic equivalent of the effective yield strength.3.2.10 general yield forc

29、e, Pgy Fin an instrumented impact test, applied force corresponding to general yielding of thespecimen ligament. It corresponds to Fgy, as used in Test Method E2298.3.2.11 J-integral, J FL1, na mathematical expression, a line or surface integral that encloses the crack front from one cracksurface to

30、 the other, used to characterize the local stress-strain field around the crack front.3.2.11.1 DiscussionThe J-integral expression for a two-dimensional crack, in the x-z plane with the crack front parallel to the z-axis, is the line integralas follows:J 5* SWdy2Tux dsD (2)where:W = loading work per

31、 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 vector at ds,x, y, z = rectangular coordinates, andTux ds = rate of work input fro

32、m the stress field into the area enclosed by .E1820 18a33.2.11.2 DiscussionThe value of J obtained from this equation is taken to be path-independent in test specimens commonly used, but in servicecomponents (and perhaps in test specimens) caution is needed to adequately consider loading interior to

33、 such as from rapidmotion of the crack or the service component, and from residual or thermal stress.3.2.11.3 DiscussionIn elastic (linear or nonlinear) solids, the J-integral equals the crack-extension force, G. (See crack extension force.)3.2.11.4 DiscussionIn elastic (linear and nonlinear) solids

34、 for which the mathematical expression is path independent, the J-integral is equal to thevalue obtained from two identical bodies with infinitesimally differing crack areas each subject to stress. The parameter J is thedifference in work per unit difference in crack area at a fixed value of displac

35、ement or, where appropriate, at a fixed value of force(1)5.3.2.11.5 DiscussionThe dynamic equivalent of Jc isJcd,X, with X = order of magnitude of J-integral rate.3.2.12 Jc FL1 The property Jc determined by this test method characterizes the fracture toughness of materials at fractureinstability pri

36、or to the onset of significant stable tearing crack extension. The value of Jc determined by this test method representsa measure of fracture toughness at instability without significant stable crack extension that is independent of in-plane dimensions;however, there may be a dependence of toughness

37、 on thickness (length of crack front).3.2.13 Ju FL1The quantity Ju determined by this test method measures fracture instability after the onset of significantstable tearing crack extension. It may be size-dependent and a function of test specimen geometry. It can be useful to define limitson ductile

38、 fracture behavior.3.2.13.1 DiscussionThe dynamic equivalent of Ju is Jud,X, with X = order of magnitude of J-integral rate.3.2.14 J-integral rate, J FL21T21#derivative of J with respect to time.3.2.15 machine capacity, MC FLmaximum available energy of the impact testing machine.3.2.16 maximum force

39、, Pmax Fin an instrumented impact test, maximum value of applied force. It corresponds to Fm, asused in Test Method E2298.3.2.17 net thickness, BN L,ndistance between the roots of the side grooves in side-grooved specimens.3.2.18 original crack size, ao L , nthe physical crack size at the start of t

40、esting.3.2.18.1 DiscussionIn this test method, aoq is used to denote original crack size estimated from compliance.3.2.19 original remaining ligament, bo L,ndistance from the original crack front to the back edge of the specimen, that is(bo = W ao).3.2.20 physical crack size, ap L , nthe distance fr

41、om a reference plane to the observed crack front. This distance mayrepresent an average of several measurements along the crack front. The reference plane depends on the specimen form, and it isnormally taken to be either the boundary, or a plane containing either the load-line or the centerline of

42、a specimen or plate. Thereference plane is defined prior to specimen deformation.3.2.21 plane-strain fracture toughness, JIc FL1, KJIc FL3/2 , nthe crack-extension resistance under conditions ofcrack-tip plane-strain.5 The boldface numbers in parentheses refer to the list of references at the end of

43、 this standard.E1820 18a43.2.21.1 DiscussionFor example, in Mode I for slow rates of loading and substantial plastic deformation, plane-strain fracture toughness is the valueof the J-integral designated JIc FL1 as measured using the operational procedure (and satisfying all of the qualificationrequi

44、rements) specified in this test method, that provides for the measurement of crack-extension resistance near the onset of stablecrack extension.3.2.21.2 DiscussionFor example, in Mode I for slow rates of loading, plane-strain fracture toughness is the value of the stress intensity designated KJIccal

45、culated from JIc using the equation (and satisfying all of the qualification requirements) specified in this test method, thatprovides for the measurement of crack-extension resistance near the onset of stable crack extension under dominant elasticconditions (2).3.2.21.3 DiscussionThe dynamic equiva

46、lent of JIc is JIcd,X , with X = order of magnitude of J-integral rate.3.2.22 pop-in, na discontinuity in the force versus clip gage displacement record. The record of a pop-in shows a suddenincrease in displacement and, generally a decrease in force. Subsequently, the displacement and force increas

47、e to above theirrespective values at pop-in.3.2.23 R-curve or J-R curve, na plot of crack extension resistance as a function of stable crack extension, ap or ae.3.2.23.1 DiscussionIn this test method, the J-R curve is a plot of the far-field J-integral versus the physical crack extension, ap. It is

48、recognized thatthe far-field value of J may not represent the stress-strain field local to a growing crack.3.2.24 remaining ligament, b L, ndistance from the physical crack front to the back edge of the specimen, that is(b = W ap).3.2.25 specimen center of pin hole distance, H* L, nthe distance betw

49、een the center of the pin holes on a pin-loadedspecimen.3.2.26 specimen gage length, d L, nthe distance between the points of displacement measure (for example, clip gage, gagelength).3.2.27 specimen span, S L, nthe distance between specimen supports.3.2.28 specimen thickness, B L, nthe side-to-side dimension of the specimen being tested.3.2.29 specimen width, W L, na physical dimension on a test spec