ASTM E1820-2015a Standard Test Method for Measurement of Fracture Toughness《测量断裂韧度的标准试验方法》.pdf

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1、Designation: E1820 15E1820 15aStandard 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.1.3 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 es

7、tablish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.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

8、developed to provide a common method for determining all applicable toughness parameters from a single test.2. Referenced Documents2.1 ASTM Standards:2E4 Practices for Force Verification of Testing MachinesE8/E8M Test Methods for Tension Testing of Metallic MaterialsE21 Test Methods for Elevated Tem

9、perature 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) Fracture Toughness Measurement (Wi

10、thdrawn 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 Fracture Mechanics TestingE2298 Test Met

11、hod for Instrumented Impact Testing of Metallic Materials3. 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 listed in this section.3.2 Definitions of Terms Specific to This S

12、tandard:3.2.1 compliance LF1, nthe ratio of displacement increment to force increment.1 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 1, 2015Oct. 15,

13、2015. Published September 2015November 2015. Originally approved in 1996. Last previous edition approved in 20132015as E1820 13E1820 15.1. DOI: 10.1520/E1820-1510.1520/E1820-15A2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. Fo

14、r 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 standard is referenced on www.astm.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard

15、 an indication of what changes have 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

16、 to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.2 crack opening displacement (COD) L, nforce-induced separation vector between two points at a specific gage length.The direction of the vecto

17、r is 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 un

18、it 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 size, a L, na lineal measure of a principal planar dimension of a crack. This measure is commonly used in thecalculation of quantities

19、descriptive of the stress and displacement fields, and is often also termed crack length or depth.3.2.5.1 DiscussionIn practice, the value of a is obtained from procedures for measurement of physical crack size, ap, original crack size, ao, andeffective crack size, ae, as appropriate to the situatio

20、n being considered.3.2.5 crack-tip opening displacement (CTOD), L, nthe crack displacement resulting from the total deformation (elasticplus plastic) at variously defined locations near the original (prior to force application) crack tip.3.2.5.1 DiscussionIn this test method, CTOD is the displacemen

21、t 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 size, ao, from measurements made from the forceversus displacement record.3.2.5.2 DiscussionIn CTOD testing, Ic L is a value of C

22、TOD 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 the onset of unstable crack extension (see 3.2.393.2.38) or pop-in (see3.2.253.2.24) when ap 0.2 mm (0.008 in.) + 0.7u. The u

23、corresponds to the force Pu and the clip gagedisplacement vu (see Fig. 1). It may be size-dependent and a function of test specimen geometry. It can be useful to define limitson ductile fracture behavior.3.2.5.5 DiscussionIn CTOD testing, c* L characterizes the CTOD fracture toughness of materials a

24、t 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 instability without significant stable crack extension that is independent of in-plane dimensions. However, there maybe

25、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 dynamic stress intensity factor, KJdThe dynamic equivalent of the stress intensity factor KJ, calculated from J usi

26、ng theequation specified in this test method.3.2.8 dynamic ultimate tensile strength, TSd FL-2dynamic equivalent of the ultimate tensile strength, measured at theequivalent strain rate of the fracture toughness test.3.2.9 dynamic yield strength, YSd FL-2dynamic equivalent of the yield strength, meas

27、ured at the equivalent strain rate ofthe fracture toughness test.3.2.10 effective thickness, Be L , nfor side-grooved specimens Be = B (B BN)2/B. This is used for the elastic unloadingcompliance measurement of crack size.3.2.11 effective yield strength, Y FL2,nan assumed value of uniaxial yield stre

28、ngth that represents the influence of plasticyielding upon fracture test parameters.3.2.11.1 DiscussionIt is calculated as the average of the 0.2 % offset yield strength YS, and the ultimate tensile strength, TS as follows:Y 5 YS1TS2 (1)3.2.11.2 DiscussionIn estimating Y, influences of testing condi

29、tions, such as loading rate and temperature, should be considered.3.2.11.3 DiscussionThe dynamic effective yield strength, Yd, is the dynamic equivalent of the effective yield strength, and is calculated as the averageof the dynamic yield strength and dynamic ultimate tensile strength.3.2.12 general

30、 yield force, Pgy Fin an instrumented impact test, applied force corresponding to general yielding of thespecimen ligament. It corresponds to Fgy, as used in Test Method E2298.3.2.13 J-integral, J FL1, na mathematical expression, a line or surface integral that encloses the crack front from one crac

31、ksurface to the other, used to characterize the local stress-strain field around the crack front.3.2.13.1 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 = loadi

32、ng work per unit volume or, for elastic bodies, strain energy density, = path of the integral, that encloses (that is, contains) the crack tip,E1820 15a3ds = increment of the contour path,T = outward traction vector on ds,u = displacement vector at ds,x, y, z = rectangular coordinates, andTux ds = r

33、ate of work input from the stress field into the area enclosed by .3.2.13.2 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

34、interior to such as from rapidmotion of the crack or the service component, and from residual or thermal stress.3.2.13.3 DiscussionIn elastic (linear or nonlinear) solids, the J-integral equals the crack-extension force, G. (See crack extension force.)3.2.13.4 DiscussionIn elastic (linear and nonlin

35、ear) solids 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

36、 of displacement or, where appropriate, at a fixed value of force(1)4.3.2.13.5 DiscussionThe dynamic equivalent of Jc isJcd,X, with X = order of magnitude of J-integral rate.3.2.14 Jc FL1 The property Jc determined by this test method characterizes the fracture toughness of materials at fractureinst

37、ability prior 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 o

38、f toughness on thickness (length of crack front).3.2.15 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 limit

39、son ductile fracture behavior.3.2.15.1 DiscussionThe dynamic equivalent of Ju is Jud,X, with X = order of magnitude of J-integral rate.3.2.16 J-integral rate, J FL21T21#derivative of J with respect to time.3.2.17 machine capacity, MC FLmaximum available energy of the impact testing machine.3.2.18 ma

40、ximum force, Pmax Fin an instrumented impact test, maximum value of applied force. It corresponds to Fm, asused in Test Method E2298.3.2.19 net thickness, BN L,ndistance between the roots of the side grooves in side-grooved specimens.3.2.20 original crack size, ao L , nthe physical crack size at the

41、 start of testing.3.2.20.1 DiscussionIn this test method, aoq is used to denote original crack size estimated from compliance.3.2.21 original remaining ligament, bo L,ndistance from the original crack front to the back edge of the specimen, that is(bo = W ao).4 The boldface numbers in parentheses re

42、fer to the list of references at the end of this standard.E1820 15a43.2.22 physical crack size, ap L , nthe distance from 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 fo

43、rm, and it isnormally taken to be either the boundary, or a plane containing either the load-line or the centerline of a specimen or plate. Thereference plane is defined prior to specimen deformation.3.2.23 plane-strain fracture toughness, JIc FL1, KJIc FL3/2 , nthe crack-extension resistance under

44、conditions ofcrack-tip plane-strain.3.2.23.1 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 qualifi

45、cationrequirements) specified in this test method, that provides for the measurement of crack-extension resistance near the onset of stablecrack extension.3.2.23.2 DiscussionFor example, in Mode I for slow rates of loading, plane-strain fracture toughness is the value of the stress intensity designa

46、ted KJIccalculated 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).3.2.23.3 DiscussionThe dyn

47、amic equivalent of JIc is JIcd,X , with X = order of magnitude of J-integral rate.3.2.24 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 fo

48、rce increase to above theirrespective values at pop-in.3.2.25 R-curve or J-R curve, na plot of crack extension resistance as a function of stable crack extension, ap or ae.3.2.25.1 DiscussionIn this test method, the J-R curve is a plot of the far-field J-integral versus the physical crack extension,

49、 ap. It is recognized thatthe far-field value of J may not represent the stress-strain field local to a growing crack.3.2.26 remaining ligament, b L, ndistance from the physical crack front to the back edge of the specimen, that is(b = W ap).3.2.27 specimen center of pin hole distance, H* L, nthe distance between the center of the pin holes on a pin-loadedspecimen.3.2.28 specimen gage length, d L, n