Standard Test Method for Measurement of Fracture Toughness

SIGNIFICANCE AND USE
Assuming the presence of a preexisting, sharp, fatigue crack, the material fracture toughness values identified by this test method characterize its resistance to: (1) fracture of a stationary crack, (2) fracture after some stable tearing, (3) stable tearing onset, and (4) sustained stable tearing. This test method is particularly useful when the material response cannot be anticipated before the test. Application of procedures in Test Method E 1921 is recommended for testing ferritic steels that undergo cleavage fracture in the ductile-to-brittle transition.
5.1.1 These fracture toughness values may serve as a basis for material comparison, selection, and quality assurance. Fracture toughness can be used to rank materials within a similar yield strength range.  
5.1.2 These fracture toughness values may serve as a basis for structural flaw tolerance assessment. Awareness of differences that may exist between laboratory test and field conditions is required to make proper flaw tolerance assessment.
The following cautionary statements are based on some observations.
5.2.1 Particular care must be exercised in applying to structural flaw tolerance assessment the fracture toughness value associated with fracture after some stable tearing has occurred. This response is characteristic of ferritic steel in the transition regime. This response is especially sensitive to material inhomogeneity and to constraint variations that may be induced by planar geometry, thickness differences, mode of loading, and structural details.
5.2.2 The J-R curve from bend-type specimens recommended by this test method (SE(B), C(T), and DC(T)) has been observed to be conservative with respect to results from tensile loading configurations.  
5.2.3 The values of δc, δu, Jc, and Ju   may be affected by specimen dimensions.
SCOPE
1.1 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). Toughness can be measured in 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.
1.2 The recommended specimens are single-edge bend, [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 according to the fracture toughness analysis applied. The guidelines are established through consideration of material toughness, material flow strength, and the individual qualification requirements of the 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 purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Note 1—Other standard methods for the determination of fracture toughness using the parameters K, J, and CTOD are contained in Test Methods E 399, E 813, E 1152, E 1290, and E 1737. This test method was developed to provide a common method for determining all applicable toughness parameters from a single test.

General Information

Status
Historical
Publication Date
30-Jun-2006
Technical Committee
Drafting Committee
Current Stage
Ref Project

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ASTM E1820-06e1 - Standard Test Method for Measurement of Fracture Toughness
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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e1
Designation: E 1820 – 06
Standard Test Method for
1
Measurement of Fracture Toughness
This standard is issued under the fixed designation E1820; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1
e NOTE—Equation A3.11 was editorially corrected in May 2007.
1. Scope E8 Test Methods for Tension Testing of Metallic Materials
E21 Test Methods for Elevated Temperature Tension Tests
1.1 This test method covers procedures and guidelines for
of Metallic Materials
the determination of fracture toughness of metallic materials
E399 Test Method for Linear-Elastic Plane-Strain Fracture
using the following parameters: K, J, and CTOD (d). Tough-
Toughness K of Metallic Materials
Ic
nesscanbemeasuredintheR-curveformatorasapointvalue.
E1290 Test Method for Crack-Tip Opening Displacement
The fracture toughness determined in accordance with this test
(CTOD) Fracture Toughness Measurement
method is for the opening mode (Mode I) of loading.
E1823 Terminology Relating to Fatigue and Fracture Test-
1.2 The recommended specimens are single-edge bend,
ing
[SE(B)], compact, [C(T)], and disk-shaped compact, [DC(T)].
E1921 Test Method for Determination of Reference Tem-
All specimens contain notches that are sharpened with fatigue
perature, T , for Ferritic Steels in the Transition Range
o
cracks.
E1942 Guide for Evaluating Data Acquisition Systems
1.2.1 Specimen dimensional (size) requirements vary ac-
Used in Cyclic Fatigue and Fracture Mechanics Testing
cording to the fracture toughness analysis applied. The guide-
lines are established through consideration of material tough-
3. Terminology
ness, material flow strength, and the individual qualification
3.1 Terminology E1823 is applicable to this test method.
requirements of the toughness value per values sought.
3.2 Definitions:
1.3 The values stated in SI units are to be regarded as the
−1
3.2.1 compliance [LF ], n—the ratio of displacement in-
standard. The values given in parentheses are for information
crement to force increment.
only.
3.2.2 crack displacement [L], n—the separation vector be-
1.4 This standard does not purport to address all of the
tween two points (on the surfaces of a deformed crack) that
safety concerns, if any, associated with its use. It is the
were coincident on the surfaces of an ideal crack in the
responsibility of the user of this standard to establish appro-
undeformed condition.
priate safety and health practices and determine the applica-
3.2.2.1 Discussion—In this practice, displacement, v, is the
bility of regulatory limitations prior to use.
total displacement measured by clip gages or other devices
NOTE 1—Other standard methods for the determination of fracture
spanning the crack faces.
toughness using the parameters K, J, and CTOD are contained in Test
3.2.3 crack extension, Da [L], n—an increase in crack size.
MethodsE399,E813,E1152,E1290,andE1737.Thistestmethodwas
−1 −2
3.2.4 crack-extension force, G [FL or FLL ], n—the
developed to provide a common method for determining all applicable
elastic energy per unit of new separation area that is made
toughness parameters from a single test.
availableatthefrontofanidealcrackinanelasticsolidduring
2. Referenced Documents
a virtual increment of forward crack extension.
2
3.2.5 crack size, a [L], n—a lineal measure of a principal
2.1 ASTM Standards:
planar dimension of a crack. This measure is commonly used
E4 Practices for Force Verification of Testing Machines
in the calculation of quantities descriptive of the stress and
displacement fields, and is often also termed crack size or
1
This test method is under the jurisdiction ofASTM Committee E08 on Fatigue
depth.
and Fracture and is the direct responsibility of Subcommittee E08.07 on Fracture
3.2.5.1 Discussion—In practice, the value of a is obtained
Mechanics.
from procedures for measurement of physical crack size, a ,
CurrenteditionapprovedJuly1,2006.PublishedJuly2006.Originallyapproved p
in 1996. Last previous edition approved in 2005 as E1820–05a.
original crack size, a , and effective crack size, a , as appro-
o e
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
priate to the situation being considered.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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E1820–06
3.2.6 crack-tip opening displacement (CTOD), d [L], 3.2.7.1
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