1、Designation: E1820 112E1820 13Standard 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 NOTE3.2.2 and Note A13.3 were editorially revised in March 2013.2 NOTEEq X2.4 and Eq X2.6 were editorially corrected in June 2013.1. Scope1.1 This test
3、method covers procedures and guidelines for the determination of fracture toughness of metallic materials usingthe following parameters: 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
4、 the opening mode (Mode I) of loading.NOTE 1Until this version, KIc could be evaluated using this test method as well as by using Test 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 speci
5、mens are single-edge bend, SE(B), compact, C(T), and disk-shaped compact, DC(T). Allspecimens contain notches that are sharpened with fatigue cracks.1.2.1 Specimen dimensional (size) requirements vary according to the fracture toughness analysis applied. The guidelines areestablished through conside
6、ration of material toughness, material flow strength, and the individual qualification requirements ofthe toughness value per values 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 purpor
7、t to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.NOTE 2Other standard methods for the determination
8、 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.2. Referenced Documents2.1 ASTM Standards:2E4 Practices for
9、Force Verification of Testing MachinesE8/E8M Test Methods for Tension Testing of Metallic MaterialsE21 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 Fractu
10、re Toughness KIc of Metallic MaterialsE1290 Test Method for Crack-Tip Opening Displacement (CTOD) 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 Tra
11、nsition RangeE1942 Guide for Evaluating Data Acquisition Systems Used in Cyclic Fatigue and Fracture Mechanics TestingE2298 Test Method for Instrumented Impact Testing of Metallic Materials3. Terminology3.1 Terminology E1823 is applicable to this test method. Only items that are exclusive to Test Me
12、thod E1820, or that havespecific discussion items associated, are listed in this section.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 May 1, 2011Nov. 15
13、, 2013. Published August 2011January 2014. Originally approved in 1996. Last previous edition approved in 20092011 asE1820 09E1820 11 12. DOI: 10.1520/E1820-11E02.10.1520/E1820-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org.
14、 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 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 stand
15、ard 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
16、 is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2 Definitions of Terms Specific to This Standard:3.2.1 compliance LF1, nthe ratio of displacement increment to force increment.3.2.2 crack op
17、ening displacement (COD) L, nforce-induced separation vector between two points at a specific gage length.The direction of the vector 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
18、 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 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 siz
19、e, a L, na lineal measure of a principal planar dimension of a crack. This measure is commonly used in thecalculation of quantities 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 procedu
20、res for measurement of physical crack size, ap, original crack size, ao, andeffective crack size, ae , as appropriate to the situation being considered.3.2.6 crack-tip opening displacement (CTOD), L, nthe crack displacement resulting from the total deformation (elasticplus plastic) at variously defi
21、ned locations near the original crack tip.3.2.6.1 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 size, ao, from measureme
22、nts made from the forceversus displacement record.3.2.6.2 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.3.2.6.3 DiscussionNOTE 1Construction lines drawn parallel to the elastic loading slo
23、pe 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 132In CTOD testing, c L is the value of CTOD at th
24、e onset of unstable crack extension (see 3.2.39) or pop-in (see 3.2.25) 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 ductile f
25、racturebehavior.3.2.6.5 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 instabil
26、ity 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).3.2.7 dial energy, KV FLabsorbed energy as indicated by the impact machine encoder or dial indicator, as applicable.3.2.8 dyn
27、amic stress intensity factor, KJdThe dynamic equivalent of the stress intensity factor KJ, calculated from J using theequation specified in this test method.3.2.9 dynamic ultimate tensile strength, TSd FL-2dynamic equivalent of the ultimate tensile strength, measured at theequivalent strain rate of
28、the fracture toughness test.3.2.10 dynamic yield strength, YSd FL-2dynamic equivalent of the yield strength, measured at the equivalent strain rate ofthe fracture toughness test.3.2.11 effective thickness, Be L , nfor side-grooved specimens Be = B (B BN)2/B. This is used for the elastic unloadingcom
29、pliance measurement of crack size.3.2.12 effective yield strength, Y FL2,nan assumed value of uniaxial yield strength that represents the influence of plasticyielding upon fracture test parameters.3.2.12.1 DiscussionIt is calculated as the average of the 0.2 % offset yield strength YS, and the ultim
30、ate tensile strength, TS as follows:Y 5 YS1TS2 (1)3.2.12.2 DiscussionIn estimating Y, influences of testing conditions, such as loading rate and temperature, should be considered.3.2.12.3 DiscussionThe dynamic effective yield strength, Yd, is the dynamic equivalent of the effective yield strength, a
31、nd is calculated as the averageof the dynamic yield strength and dynamic ultimate tensile strength.3.2.13 general yield force, Pgy F in an instrumented impact test, applied force corresponding to general yielding of thespecimen ligament. It corresponds to Fgy, as used in Test Method E2298.3.2.14 J-i
32、ntegral, J FL1, na mathematical expression, a line or surface integral that encloses the crack front from one cracksurface to the other, used to characterize the local stress-strain field around the crack front.3.2.14.1 DiscussionThe J-integral expression for a two-dimensional crack, in the x-z plan
33、e with the crack front parallel to the z-axis, is the line integralas follows:J 5* SWdy2Tux dsD (2)E1820 133where: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
34、,T = outward traction vector on ds,u = displacement vector at ds,x, y, z = rectangular coordinates, andTux ds = rate of work input from the stress field into the area enclosed by .3.2.14.2 DiscussionThe value of J obtained from this equation is taken to be path-independent in test specimens commonly
35、 used, but in servicecomponents (and perhaps in test specimens) caution is needed to adequately consider loading interior to such as from rapidmotion of the crack or the service component, and from residual or thermal stress.3.2.14.3 DiscussionIn elastic (linear or nonlinear) solids, the J-integral
36、equals the crack-extension force, G. (See crack extension force.)3.2.14.4 DiscussionIn elastic (linear and nonlinear) 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 ea
37、ch subject to stress. The parameter J is thedifference in work per unit difference 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 Jc isJcd,X, with X = order of magnitude of J-integral rate.3.2.15 Jc FL1
38、 The property Jc determined by this test method characterizes the fracture toughness of materials at fractureinstability 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 s
39、ignificant stable crack extension that is independent of in-plane dimensions;however, there may be a dependence of toughness on thickness (length of crack front).3.2.15.1 DiscussionThe dynamic equivalent of Jc isJcd,X, with X = order of magnitude of J-integral rate.3.2.16 Ju FL1The quantity Ju deter
40、mined 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 fracture behavior.3.2.16.1 DiscussionThe dynamic equivalent of Ju is Ju
41、d,X, with X = order of magnitude of J-integral rate.3.2.17 J-integral rate, J FL21T21#derivative of J with respect to time.3.2.18 machine capacity, MC FLmaximum available energy of the impact testing machine.3.2.19 maximum force, Pmax Fin an instrumented impact test, maximum value of applied force.
42、It corresponds to Fm, asused in Test Method E2298.3.2.20 net thickness, BN L,ndistance between the roots of the side grooves in side-grooved specimens.3.2.21 original crack size, ao L , nthe physical crack size at the start of testing.4 The boldface numbers in parentheses refer to the list of refere
43、nces at the end of this standard.E1820 1343.2.21.1 DiscussionIn this test method, aoq is used to denote original crack size estimated from compliance.3.2.22 original remaining ligament, bo L,ndistance from the original crack front to the back edge of the specimen, that is(bo = W ao ).3.2.23 physical
44、 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 form, and it isnormally taken to be either the boundary, or a plane containing either
45、 the load-line or the centerline of a specimen or plate. Thereference plane is defined prior to specimen deformation.3.2.24 plane-strain fracture toughness, KIc FL3/2, JIc FL1, KJIc FL3/2 , nthe crack-extension resistance underconditions of crack-tip plane-strain.3.2.24.1 DiscussionFor example, in M
46、ode I for slow rates of loading and negligible plastic-zone adjustment, plane-strain fracture toughness is thevalue of the stress-intensity factor designated KIc as measured using the operational procedure (and satisfying all of thequalification requirements) specified in this test method, which pro
47、vides for the measurement of crack-extension resistance at thestart of crack extension and provides operational definitions of crack-tip sharpness, start of crack extension, and crack-tipplane-strain.3.2.24.1 DiscussionFor example, in Mode I for slow rates of loading and substantial plastic deformat
48、ion, plane-strain fracture toughness is the valueof the J-integral designated JIc FL1 as measured using the operational procedure (and satisfying all of the qualificationrequirements) specified in this test method, that provides for the measurement of crack-extension resistance near the onset of sta
49、blecrack extension.3.2.24.2 DiscussionFor example, in Mode I for slow rates of loading, plane-strain fracture toughness is the value of the stress intensity designated 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 und
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