【astm標準】e 1820 - 15a

1、Designation: E1820 ? 15aStandard Test Method for Measurement of Fracture Toughness1This standard is issued under the fixed designation E1820; the number immediately following the designation indicates the year of origina

2、l adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or re

3、approval.1. Scope1.1 This test method covers procedures and guidelines for the determination of fracture toughness of metallic materials using the following parameters: K, J, and CTOD (δ). Tough- ness can be measured in

4、the R-curve format or as a point value. The fracture toughness determined in accordance with this test method is for the opening mode (Mode I) of loading.NOTE 1—Until this version, KIc could be evaluated using this test

5、method as well as by using Test Method E399. To avoid duplication, the evaluation of 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 b

6、end, [SE(B)], compact, [C(T)], and disk-shaped compact, [DC(T)]. All specimens contain notches that are sharpened with fatigue cracks. 1.2.1 Specimen dimensional (size) requirements vary ac- cording to the fracture tough

7、ness analysis applied. The guide- lines are established through consideration of material toughness, material flow strength, and the individual qualifi- cation requirements of the toughness value per values sought.1.3 Th

8、e 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 i

9、ts use. It is the responsibility 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 2—Other standard methods

10、for the determination of fracture toughness using the parameters K, J, and CTOD are contained in Test Methods E399, E1290, and E1921. This test method was developed to provide a common method for determining all applicab

11、le toughness parameters from a single test.2. Referenced Documents2.1 ASTM Standards:2E4 Practices for Force Verification of Testing Machines E8/E8M Test Methods for Tension Testing of Metallic Ma- terialsE21 Test Method

12、s for Elevated Temperature Tension Tests of Metallic MaterialsE23 Test Methods for Notched Bar Impact Testing of Me- tallic MaterialsE399 Test Method for Linear-Elastic Plane-Strain Fracture Toughness KIc of Metallic Mat

13、erialsE1290 Test Method for Crack-Tip Opening Displacement (CTOD) Fracture Toughness Measurement (Withdrawn 2013)3E1823 Terminology Relating to Fatigue and Fracture Testing E1921 Test Method for Determination of Referenc

14、e Temperature, To, for Ferritic Steels in the Transition RangeE1942 Guide for Evaluating Data Acquisition Systems Used in Cyclic Fatigue and Fracture Mechanics TestingE2298 Test Method for Instrumented Impact Testing of

15、Metallic Materials3. Terminology3.1 Terminology E1823 is applicable to this test method. Only items that are exclusive to Test Method E1820, or that have specific discussion items associated, are listed in this section.3

16、.2 Definitions of Terms Specific to This Standard: 3.2.1 compliance [LF?1], n—the ratio of displacement in- crement to force increment.3.2.2 crack opening displacement (COD) [L], n—force- induced separation vector betwee

17、n two points at a specific gage length. The direction of the vector is normal to the crack plane.1 This test method is under the jurisdiction of ASTM Committee E08 on Fatigue and Fracture and is the direct responsibility

18、 of Subcommittee E08.07 on Fracture Mechanics. Current edition approved Oct. 15, 2015. Published November 2015. Originally approved in 1996. Last previous edition approved in 2015 as E1820 – 15. DOI: 10.1520/E1820-15A2 F

19、or referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary pag

20、e on the ASTM website. 3 The last approved version of this historical standard is referenced on www.astm.org.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Unit

21、ed States13.2.12 general yield force, Pgy [F]—in an instrumented impact test, applied force corresponding to general yielding of the specimen ligament. It corresponds to Fgy, as used in Test Method E2298.3.2.13 J-integra

22、l, J [FL?1], n—a mathematical expression, a line or surface integral that encloses the crack front from one crack surface to the other, used to characterize the local stress-strain field around the crack front. 3.2.13.1

23、Discussion—The 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 integral as follows:J 5 * ΓS Wdy 2 T ¯ ·]u ¯]x dsD (2)where:W =

24、loading work per unit volume or, for elastic bodies, strain energy density, Γ = path of the integral, that encloses (that is, contains) the crack tip, ds = increment of the contour path, T ¯ = outward traction vecto

25、r on ds, u ¯ = displacement vector at ds, x, y, z = rectangular coordinates, andT ¯ · ]u ¯]x ds = rate of work input from the stress field into the area enclosed by Γ.3.2.13.2 Discussion—The value of

26、J obtained from this equation is taken to be path-independent in test specimens commonly used, but in service components (and perhaps in test specimens) caution is needed to adequately consider loading interior to Γ such

27、 as from rapid motion of the crack or the service component, and from residual or thermal stress. 3.2.13.3 Discussion—In elastic (linear or nonlinear) solids, the J-integral equals the crack-extension force, G. (See crac

28、k extension force.) 3.2.13.4 Discussion—In elastic (linear and nonlinear) solids for which the mathematical expression is path independent, the J-integral is equal to the value obtained from two identical bodies with inf

29、initesimally differing crack areas each subject to stress. The parameter J is the difference in work per unit difference in crack area at a fixed value of displacement or, where appropriate, at a fixed value of force (1)

30、4. 3.2.13.5 Discussion—The dynamic equivalent of Jc is Jcd,X, with X = order of magnitude of J-integral rate.3.2.14 Jc [FL?1] —The property Jc determined by this test method characterizes the fracture toughness of materi

31、als at fracture instability prior to the onset of significant stable tearing crack extension. The value of Jc determined by this test method represents a measure of fracture toughness at instabil- ity without significant

32、 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).3.2.15 Ju [FL?1]—The quantity Ju determined by this test method

33、 measures fracture instability after the onset of signifi- cant stable tearing crack extension. It may be size-dependentand a function of test specimen geometry. It can be useful to define limits on ductile fracture beha

34、vior. 3.2.15.1 Discussion—The 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 [FL]—

35、maximum available energy of the impact testing machine.3.2.18 maximum force, Pmax [F]—in an instrumented im- pact test, maximum value of applied force. It corresponds to Fm, as used in Test Method E2298.3.2.19 net thickn

36、ess, BN [L], n—distance between the roots of the side grooves in side-grooved specimens.3.2.20 original crack size, ao [L] , n—the physical crack size at the start of testing. 3.2.20.1 Discussion—In this test method, aoq

37、 is used to denote original crack size estimated from compliance.3.2.21 original remaining ligament, bo [L], n—distance from the original crack front to the back edge of the specimen, that is (bo = W ? ao).3.2.22 physica

38、l crack size, ap [L] , n—the distance from a reference plane to the observed crack front. This distance may represent an average of several measurements along the crack front. The reference plane depends on the specimen

39、form, and it is normally taken to be either the boundary, or a plane containing either the load-line or the centerline of a specimen or plate. The reference plane is defined prior to specimen deformation.3.2.23 plane-str

40、ain fracture toughness, JIc [FL?1], KJIc [FL?3/2] , n—the crack-extension resistance under conditions of crack-tip plane-strain. 3.2.23.1 Discussion—For example, in Mode I for slow rates of loading and substantial plasti

41、c deformation, plane-strain fracture toughness is the value of the J-integral designated JIc [FL?1] as measured using the operational procedure (and satisfying all of the qualification requirements) specified in this tes

42、t method, that provides for the measurement of crack- extension resistance near the onset of stable crack extension. 3.2.23.2 Discussion—For example, in Mode I for slow rates of loading, plane-strain fracture toughness i

43、s the value of the stress intensity designated KJIc calculated from JIc using the equation (and satisfying all of the qualification requirements) specified in this test method, that provides for the measurement of crack-

44、extension resistance near the onset of stable crack extension under dominant elastic conditions (2). 3.2.23.3 Discussion—The dynamic equivalent of JIc is JIcd,X , with X = order of magnitude of J-integral rate.3.2.24 pop

45、-in, n—a discontinuity in the force versus clip gage displacement record. The record of a pop-in shows a sudden increase in displacement and, generally a decrease in force. Subsequently, the displacement and force increa

46、se to above their respective values at pop-in.3.2.25 R-curve or J-R curve, n—a plot of crack extension resistance as a function of stable crack extension, ?ap or ?ae. 3.2.25.1 Discussion—In this test method, the J-R curv