ASTM E2472-12(2018)e2
(Test Method)Standard Test Method for Determination of Resistance to Stable Crack Extension under Low-Constraint Conditions
Standard Test Method for Determination of Resistance to Stable Crack Extension under Low-Constraint Conditions
SIGNIFICANCE AND USE
5.1 This test method characterizes a metallic material’s resistance to stable crack extension in terms of crack-tip-opening angle (CTOA), ψ and/or crack-opening displacement (COD), δ5 under the laboratory or application environment of interest. This method applies specifically to fatigue pre-cracked specimens that exhibit low constraint and that are tested under slowly increasing displacement.
5.2 When conducting fracture tests, the user must consider the influence that the loading rate and laboratory environment may have on the fracture parameters. The user should perform a literature review to determine if loading rate effects have been observed previously in the material at the specific temperature and environment being tested. The user should document specific information pertaining to their material, loading rates, temperature, and environment (relative humidity) for each test.
5.3 The results of this characterization include the determination of a critical, lower-limiting value, of CTOA (ψc) or a resistance curve of δ5, a measure of crack-opening displacement against crack extension, or both.
5.4 The test specimens are the compact, C(T), and middle-crack-tension, M(T), specimens.
5.5 Materials that can be evaluated by this standard are not limited by strength, thickness, or toughness, if the crack-size-to-thickness (a/B) ratio or ligament-to-thickness (b/B) ratio are equal to or greater than 4, which ensures relatively low and similar global crack-front constraint for both the C(T) and M(T) specimens (2, 3).
5.6 The values of CTOA and COD (δ5) determined by this test method may serve the following purposes:
5.6.1 In research and development, CTOA (ψc) or COD (δ5), or both, testing can show the effects of certain parameters on the resistance to stable crack extension of metallic materials significant to service performance. These parameters include, but are not limited to, material thickness, material composition, thermo-mechanical processing,...
SCOPE
1.1 This standard covers the determination of the resistance to stable crack extension in metallic materials in terms of the critical crack-tip-opening angle (CTOA), ψc and/or the crack-opening displacement (COD), δ5 resistance curve (1).2 This method applies specifically to fatigue pre-cracked specimens that exhibit low constraint (crack-size-to-thickness and un-cracked ligament-to-thickness ratios greater than or equal to 4) and that are tested under slowly increasing remote applied displacement. The test specimens are the compact, C(T), and middle-crack-tension, M(T), specimens. The fracture resistance determined in accordance with this standard is measured as ψc (critical CTOA value) and/or δ5 (critical COD resistance curve) as a function of crack extension. Both fracture resistance parameters are characterized using either a single-specimen or multiple-specimen procedures. These fracture quantities are determined under the opening mode (Mode I) of loading. Influences of environment and rapid loading rates are not covered in this standard, but the user must be aware of the effects that the loading rate and laboratory environment may have on the fracture behavior of the material.
1.2 Materials that are evaluated by this standard are not limited by strength, thickness, or toughness, if the crack-size-to-thickness (a/B) ratio and the ligament-to-thickness (b/B) ratio are greater than or equal to 4, which ensures relatively low and similar global crack-front constraint for both the C(T) and M(T) specimens (2, 3).
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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, health, and environmental practices and determine the applicability of regulatory lim...
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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
´2
Designation: E2472 − 12 (Reapproved 2018)
Standard Test Method for
Determination of Resistance to Stable Crack Extension
under Low-Constraint Conditions
This standard is issued under the fixed designation E2472; the number immediately following the designation indicates the year of
original 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 reapproval.
ε NOTE—Sections 7.4.1, 7.4.2, 9.3.1.4, A1.1.3, A2.1.3, and Fig. 7 were editorially corrected in May 2020.
ε NOTE—Section A2.1.3 was editorially corrected in June 2023.
1. Scope 1.3 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
1.1 This standard covers the determination of the resistance
standard.
to stable crack extension in metallic materials in terms of the
1.4 This standard does not purport to address all of the
critical crack-tip-opening angle (CTOA), ψ and/or the crack-
c
2 safety concerns, if any, associated with its use. It is the
opening displacement (COD), δ resistance curve (1). This
responsibility of the user of this standard to establish appro-
method applies specifically to fatigue pre-cracked specimens
priate safety, health, and environmental practices and deter-
that exhibit low constraint (crack-size-to-thickness and un-
mine the applicability of regulatory limitations prior to use.
cracked ligament-to-thickness ratios greater than or equal to 4)
1.5 This international standard was developed in accor-
and that are tested under slowly increasing remote applied
dance with internationally recognized principles on standard-
displacement. The test specimens are the compact, C(T), and
ization established in the Decision on Principles for the
middle-crack-tension, M(T), specimens. The fracture resis-
Development of International Standards, Guides and Recom-
tance determined in accordance with this standard is measured
mendations issued by the World Trade Organization Technical
as ψ (critical CTOA value) and/or δ (critical COD resistance
c 5
Barriers to Trade (TBT) Committee.
curve) as a function of crack extension. Both fracture resis-
tance parameters are characterized using either a single-
2. Referenced Documents
specimen or multiple-specimen procedures. These fracture
2.1 ASTM Standards:
quantities are determined under the opening mode (Mode I) of
E4 Practices for Force Calibration and Verification of Test-
loading. Influences of environment and rapid loading rates are
ing Machines
not covered in this standard, but the user must be aware of the
E8/E8M Test Methods for Tension Testing of Metallic Ma-
effects that the loading rate and laboratory environment may
terials
have on the fracture behavior of the material.
E399 Test Method for Linear-Elastic Plane-Strain Fracture
1.2 Materials that are evaluated by this standard are not Toughness of Metallic Materials
limited by strength, thickness, or toughness, if the crack-size- E561 Test Method for K Curve Determination
R
to-thickness (a/B) ratio and the ligament-to-thickness (b/B) E647 Test Method for Measurement of Fatigue Crack
ratio are greater than or equal to 4, which ensures relatively Growth Rates
E1290 Test Method for Crack-Tip Opening Displacement
low and similar global crack-front constraint for both the C(T)
and M(T) specimens (2, 3). (CTOD) Fracture Toughness Measurement (Withdrawn
2013)
E1820 Test Method for Measurement of Fracture Toughness
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 Fracture
Mechanics. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2018. Published December 2018. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ε1
approved in 2006. Last previous edition approved in 2012 as E2472–12 . DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E2472-12R18E02. the ASTM website.
2 4
The boldface numbers in parentheses refer to the list of references at the end of The last approved version of this historical standard is referenced on
this standard. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´2
E2472 − 12 (2018)
E1823 Terminology Relating to Fatigue and Fracture Testing the vector is normal to the crack plane (normal to the facing
E2309 Practices for Verification of Displacement Measuring surfaces of a crack) at a specified gage length. In this standard,
Systems and Devices Used in Material Testing Machines δ is measured at the fatigue precrack tip location over a gage
length of 5-mm as the crack stably tears.
2.2 ISO Standards:
ISO 22889:2007 Metallic Materials—Method of Test for the
3.2.6 crack-tip-opening displacement (CTOD), δ [L],
Determination of Resistance to Stable Crack Extension
n—relative displacement of crack surfaces resulting from the
Using Specimens of Low Constraint
total deformation (elastic plus plastic) measured (or calculated)
ISO 12135 Metallic Materials—Unified Method of Test for
at 1- mm behind the current crack tip as the crack stably tears.
the Determination of Quasistatic Fracture Toughness
3.2.7 critical crack-tip-opening displacement (CTOD ), δ
c 1c
[L], n—steady-state relative displacement of crack surfaces
3. Terminology
resulting from the total deformation (elastic plus plastic)
3.1 Terminology E1823 is applicable to this test standard.
measured (or calculated) at 1-mm behind the current crack tip
3.2 Definitions: as the crack stably tears.
3.2.1 crack extension, Δa [L], n—an increase in crack size.
3.2.8 crack extension resistance curve (R curve),
3.2.1.1 Discussion—It should be noted that in thin-sheet and
n—variation of δ with crack extension, Δa.
thick-plate materials under low constraint conditions, the crack
-2
3.2.9 effective yield strength, σ [FL ], n—an assumed
Y
extension observed on the surface of the specimen may be
value of uniaxial yield strength that represents the influence of
significantly less than that in the interior of the specimen due
plastic yielding upon fracture test parameters.
to the effects of crack tunneling. This must be considered if
3.2.9.1 Discussion—Effective yield strength is calculated as
direct optical techniques are used to monitor and measure
the average of the 0.2 % offset yield strength σ , and the
YS
free-surface crack extension. Indirect crack extension measure-
ultimate tensile strength, σ as follows:
TS
ment techniques such as unloading compliance and electric-
σ 5 σ 1σ /2 (1)
potential drop method may be used in place of (or to comple- ~ !
Y YS TS
NOTE 1—The yield and ultimate tensile strength are determined from
ment) the direct optical techniques to provide a measure of
Test Methods E8/E8M.
average crack extension. (See Test Method E647 for compli-
ance methods for C(T) and M(T) specimens; and ISO 12135
3.2.9.2 Discussion—In estimating σ , influences of testing
Y
and Test Method E647 for electric potential-drop methods for
conditions, such as loading rate and temperature, should be
C(T) specimens.)
considered.
3.2.2 crack size, a [L], n—principal linear dimension used
3.2.10 final crack size, a [L], n—crack extension at end of
f
in the calculation of fracture mechanics parameters for through
stable tearing (a = a + Δa ).
f o f
thickness cracks.
3.2.11 final remaining ligament, b [L], n—distance from
f
3.2.2.1 Discussion—A measure of the crack size after the
the tip of the final crack size to the back edge of the specimen,
fatigue pre-cracking stage is denoted as the original crack size,
that is b = W – a .
f f
a . The value for a may be obtained using surface
o o
3.2.12 force, P [F], n—force applied to a test specimen or to
measurement, unloading compliance, electric-potential drop or
a component.
other methods where validation procedures for the measure-
ments are available. 3.2.13 minimum crack extension, Δa [L], n—crack exten-
min
sion beyond which ψ is nearly constant.
c
3.2.3 crack-tip-opening angle (CTOA), ψ [deg], n—relative
angle of crack surfaces resulting from the total deformation 3.2.14 maximum crack extension, Δa [L], n—crack ex-
max
(elastic plus plastic) measured (or calculated) at 1-mm behind tension limit for ψ and δ controlled crack extension.
c 5
–1
the current crack tip as the crack stably tears, where ψ = 2 tan
3.2.15 maximum fatigue force, P [F] , n—maximum fatigue
f
(δ /2).
force applied to specimen during pre-cracking stage.
-2
3.2.4 critical crack-tip-opening angle (CTOA ), ψ [deg],
c c
3.2.16 modulus of elasticity, E [FL ], n—the ratio of stress
n—steady-state relative angle of crack surfaces resulting from
to corresponding strain below the proportional limit.
the total deformation (elastic plus plastic) measured (or calcu-
3.2.17 notch size, a [L], n—distance from a reference plane
n
lated) at 1-mm behind the current crack tip as the crack stably
to the front of the machined notch, such as the force line in the
–1
tears, where ψ = 2 tan (δ /2).
c 1c
compact specimen to the notch front or from the center line in
3.2.4.1 Discussion—Critical CTOA value tends to approach
the middle-crack-tension specimen to the notch front.
a constant, steady-state value after a small amount of crack
3.2.18 original crack size, a [L], n—the physical crack size
extension (associated with crack tunneling and transition from
o
at the start of testing.
flat-to-slant crack extension).
3.2.19 original ligament, b [L], n—distance from the origi-
3.2.5 crack-opening displacement, (COD) δ [L]—force-
5 o
nal crack front to the back edge of the specimen, that is b = W
induced separation vector between two points. The direction of
o
– a .
o
3.2.20 remaining ligament, b [L], n—distance from the
Available from International Organization for Standardization (ISO), 1, ch. de
physical crack front to the back edge of the specimen, that is b
la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http://
www.iso.ch. = W – a.
´2
E2472 − 12 (2018)
3.2.21 specimen thickness, B [L], n—distance between the specimens that exhibit low constraint and that are tested under
parallel sides of a test specimen or component. Side grooving slowly increasing displacement.
is not allowed.
5.2 When conducting fracture tests, the user must consider
3.2.22 specimen width, W [L], n—distance from a reference
the influence that the loading rate and laboratory environment
position (for example, the force line of a compact specimen or
may have on the fracture parameters. The user should perform
center line in the middle-crack-tension specimen) to the rear
a literature review to determine if loading rate effects have
surface of the specimen. (Note that the total width of the M(T)
been observed previously in the material at the specific
specimen is defined as 2W.)
temperature and environment being tested. The user should
document specific information pertaining to their material,
4. Summary of Test Method
loading rates, temperature, and environment (relative humid-
4.1 The objective of this standard is to induce stable crack
ity) for each test.
extension in a fatigue pre-cracked, low-constraint test speci-
5.3 The results of this characterization include the determi-
men while monitoring and measuring the COD at the original
nation of a critical, lower-limiting value, of CTOA (ψ ) or a
c
fatigue pre-crack-tip location (4, 5) or the CTOA (or CTOD) at
resistance curve of δ , a measure of crack-opening displace-
1-mm behind the stably tearing crack tip (6, 7), or both. The
ment against crack extension, or both.
resistance curve associated with the δ measurements and the
5.4 The test specimens are the compact, C(T), and middle-
critical limiting value of the CTOA measurements are used to
crack-tension, M(T), specimens.
characterize the corresponding resistance to stable crack ex-
tension. In contrast, the CTOD values determined from Test
5.5 Materials that can be evaluated by this standard are not
Method E1290 (high-constraint bend specimens) are values at
limited by strength, thickness, or toughness, if the crack-size-
one or more crack extension events, such as the CTOD at the
to-thickness (a/B) ratio or ligament-to-thickness (b/B) ratio are
onset of brittle crack extension with no significant stable crack
equal to or greater than 4, which ensures relatively low and
extension.
similar global crack-front constraint for both the C(T) and
M(T) specimens (2, 3).
4.2 Either of the fatigue pre-cracked, low-constraint test
specimen configurations specified in this standard [C(T) or
5.6 The values of CTOA and COD (δ ) determined by this
M(T)] may be used to measure or calculate either of the
test method may serve the following purposes:
fracture resistance parameters considered. The fracture resis-
5.6.1 In research and development, CTOA (ψ ) or COD
c
tance parameters, CTOA (or CTOD) and δ , may be charac-
5 (δ ), or both, testing can show the effects of certain parameters
terized using either a single-specimen or multiple-specimen
on the resistance to stable crack extension of metallic materials
procedure. In all cases, tests are performed by applying slowly
significant to service performance. These parameters include,
increasing displacements to the test specimen and measuring
but are not limited to, material thickness, material composition,
the forces, displacements, crack extension and angles realized
thermo-mechanical processing, welding, and thermal stress
during the test. The forces, displacements and angles are then
relief.
used in conjunction with certain pre-test and post-test specimen
5.6.2 For specifications of acceptance and manufacturing
measurements to determine the material’s resistance to stable
quality control of base materials.
crack extension.
5.6.3 For inspection and flaw assessment criteria, when used
in conjunction with fracture mechanics analyses. Awareness of
4.3 Four procedures for measuring crack extension are:
differences that may exist between laboratory test and field
surface visual, unloading compliance, electrical potential, and
conditions is required to make proper flaw assessment.
multiple specimens.
5.6.4 The critical CTOA (ψ ) has been used with the
c
4.4 Two techniques are presented for measuring CTOA:
elastic-plastic finite-element method to accurately predict
optical microscopy (OM) (8) and digital image correlation
structural
...
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´2
Designation: E2472 − 12 (Reapproved 2018)
Standard Test Method for
Determination of Resistance to Stable Crack Extension
under Low-Constraint Conditions
This standard is issued under the fixed designation E2472; the number immediately following the designation indicates the year of
original 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 reapproval.
ε NOTE—Sections 7.4.1, 7.4.2, 9.3.1.4, A1.1.3, A2.1.3, and Fig. 7 were editorially corrected in May 2020.
ε NOTE—Section A2.1.3 was editorially corrected in June 2023.
1. Scope 1.3 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
1.1 This standard covers the determination of the resistance
standard.
to stable crack extension in metallic materials in terms of the
1.4 This standard does not purport to address all of the
critical crack-tip-opening angle (CTOA), ψ and/or the crack-
c
safety concerns, if any, associated with its use. It is the
opening displacement (COD), δ resistance curve (1). This
responsibility of the user of this standard to establish appro-
method applies specifically to fatigue pre-cracked specimens
priate safety, health, and environmental practices and deter-
that exhibit low constraint (crack-size-to-thickness and un-
mine the applicability of regulatory limitations prior to use.
cracked ligament-to-thickness ratios greater than or equal to 4)
1.5 This international standard was developed in accor-
and that are tested under slowly increasing remote applied
dance with internationally recognized principles on standard-
displacement. The test specimens are the compact, C(T), and
ization established in the Decision on Principles for the
middle-crack-tension, M(T), specimens. The fracture resis-
Development of International Standards, Guides and Recom-
tance determined in accordance with this standard is measured
mendations issued by the World Trade Organization Technical
as ψ (critical CTOA value) and/or δ (critical COD resistance
c 5
Barriers to Trade (TBT) Committee.
curve) as a function of crack extension. Both fracture resis-
tance parameters are characterized using either a single-
2. Referenced Documents
specimen or multiple-specimen procedures. These fracture
2.1 ASTM Standards:
quantities are determined under the opening mode (Mode I) of
E4 Practices for Force Calibration and Verification of Test-
loading. Influences of environment and rapid loading rates are
ing Machines
not covered in this standard, but the user must be aware of the
E8/E8M Test Methods for Tension Testing of Metallic Ma-
effects that the loading rate and laboratory environment may
terials
have on the fracture behavior of the material.
E399 Test Method for Linear-Elastic Plane-Strain Fracture
1.2 Materials that are evaluated by this standard are not
Toughness of Metallic Materials
limited by strength, thickness, or toughness, if the crack-size-
E561 Test Method for K Curve Determination
R
to-thickness (a/B) ratio and the ligament-to-thickness (b/B)
E647 Test Method for Measurement of Fatigue Crack
ratio are greater than or equal to 4, which ensures relatively
Growth Rates
low and similar global crack-front constraint for both the C(T)
E1290 Test Method for Crack-Tip Opening Displacement
and M(T) specimens (2, 3).
(CTOD) Fracture Toughness Measurement (Withdrawn
2013)
E1820 Test Method for Measurement of Fracture Toughness
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 Fracture
Mechanics. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2018. Published December 2018. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ε1
approved in 2006. Last previous edition approved in 2012 as E2472–12 . DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E2472-12R18E02. the ASTM website.
2 4
The boldface numbers in parentheses refer to the list of references at the end of The last approved version of this historical standard is referenced on
this standard. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´2
E2472 − 12 (2018)
E1823 Terminology Relating to Fatigue and Fracture Testing the vector is normal to the crack plane (normal to the facing
E2309 Practices for Verification of Displacement Measuring surfaces of a crack) at a specified gage length. In this standard,
Systems and Devices Used in Material Testing Machines δ is measured at the fatigue precrack tip location over a gage
length of 5-mm as the crack stably tears.
2.2 ISO Standards:
ISO 22889:2007 Metallic Materials—Method of Test for the
3.2.6 crack-tip-opening displacement (CTOD), δ [L],
Determination of Resistance to Stable Crack Extension
n—relative displacement of crack surfaces resulting from the
Using Specimens of Low Constraint
total deformation (elastic plus plastic) measured (or calculated)
ISO 12135 Metallic Materials—Unified Method of Test for
at 1- mm behind the current crack tip as the crack stably tears.
the Determination of Quasistatic Fracture Toughness
3.2.7 critical crack-tip-opening displacement (CTOD ), δ
c 1c
[L], n—steady-state relative displacement of crack surfaces
3. Terminology
resulting from the total deformation (elastic plus plastic)
3.1 Terminology E1823 is applicable to this test standard.
measured (or calculated) at 1-mm behind the current crack tip
3.2 Definitions: as the crack stably tears.
3.2.1 crack extension, Δa [L], n—an increase in crack size.
3.2.8 crack extension resistance curve (R curve),
3.2.1.1 Discussion—It should be noted that in thin-sheet and
n—variation of δ with crack extension, Δa.
thick-plate materials under low constraint conditions, the crack
-2
3.2.9 effective yield strength, σ [FL ], n—an assumed
Y
extension observed on the surface of the specimen may be
value of uniaxial yield strength that represents the influence of
significantly less than that in the interior of the specimen due
plastic yielding upon fracture test parameters.
to the effects of crack tunneling. This must be considered if
3.2.9.1 Discussion—Effective yield strength is calculated as
direct optical techniques are used to monitor and measure
the average of the 0.2 % offset yield strength σ , and the
YS
free-surface crack extension. Indirect crack extension measure-
ultimate tensile strength, σ as follows:
TS
ment techniques such as unloading compliance and electric-
σ 5 σ 1σ /2 (1)
potential drop method may be used in place of (or to comple- ~ !
Y YS TS
NOTE 1—The yield and ultimate tensile strength are determined from
ment) the direct optical techniques to provide a measure of
Test Methods E8/E8M.
average crack extension. (See Test Method E647 for compli-
ance methods for C(T) and M(T) specimens; and ISO 12135
3.2.9.2 Discussion—In estimating σ , influences of testing
Y
and Test Method E647 for electric potential-drop methods for
conditions, such as loading rate and temperature, should be
C(T) specimens.)
considered.
3.2.2 crack size, a [L], n—principal linear dimension used
3.2.10 final crack size, a [L], n—crack extension at end of
f
in the calculation of fracture mechanics parameters for through
stable tearing (a = a + Δa ).
f o f
thickness cracks.
3.2.11 final remaining ligament, b [L], n—distance from
f
3.2.2.1 Discussion—A measure of the crack size after the
the tip of the final crack size to the back edge of the specimen,
fatigue pre-cracking stage is denoted as the original crack size,
that is b = W – a .
f f
a . The value for a may be obtained using surface
o o
3.2.12 force, P [F], n—force applied to a test specimen or to
measurement, unloading compliance, electric-potential drop or
a component.
other methods where validation procedures for the measure-
3.2.13 minimum crack extension, Δa [L], n—crack exten-
ments are available.
min
sion beyond which ψ is nearly constant.
c
3.2.3 crack-tip-opening angle (CTOA), ψ [deg], n—relative
angle of crack surfaces resulting from the total deformation 3.2.14 maximum crack extension, Δa [L], n—crack ex-
max
(elastic plus plastic) measured (or calculated) at 1-mm behind tension limit for ψ and δ controlled crack extension.
c 5
–1
the current crack tip as the crack stably tears, where ψ = 2 tan
3.2.15 maximum fatigue force, P [F] , n—maximum fatigue
f
(δ /2).
force applied to specimen during pre-cracking stage.
3.2.4 critical crack-tip-opening angle (CTOA ), ψ [deg], -2
c c
3.2.16 modulus of elasticity, E [FL ], n—the ratio of stress
n—steady-state relative angle of crack surfaces resulting from
to corresponding strain below the proportional limit.
the total deformation (elastic plus plastic) measured (or calcu-
3.2.17 notch size, a [L], n—distance from a reference plane
n
lated) at 1-mm behind the current crack tip as the crack stably
–1 to the front of the machined notch, such as the force line in the
tears, where ψ = 2 tan (δ /2).
c 1c
compact specimen to the notch front or from the center line in
3.2.4.1 Discussion—Critical CTOA value tends to approach
the middle-crack-tension specimen to the notch front.
a constant, steady-state value after a small amount of crack
3.2.18 original crack size, a [L], n—the physical crack size
extension (associated with crack tunneling and transition from
o
at the start of testing.
flat-to-slant crack extension).
3.2.19 original ligament, b [L], n—distance from the origi-
3.2.5 crack-opening displacement, (COD) δ [L]—force-
o
nal crack front to the back edge of the specimen, that is b = W
induced separation vector between two points. The direction of
o
– a .
o
3.2.20 remaining ligament, b [L], n—distance from the
Available from International Organization for Standardization (ISO), 1, ch. de
physical crack front to the back edge of the specimen, that is b
la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http://
www.iso.ch. = W – a.
´2
E2472 − 12 (2018)
3.2.21 specimen thickness, B [L], n—distance between the specimens that exhibit low constraint and that are tested under
parallel sides of a test specimen or component. Side grooving slowly increasing displacement.
is not allowed.
5.2 When conducting fracture tests, the user must consider
3.2.22 specimen width, W [L], n—distance from a reference
the influence that the loading rate and laboratory environment
position (for example, the force line of a compact specimen or
may have on the fracture parameters. The user should perform
center line in the middle-crack-tension specimen) to the rear
a literature review to determine if loading rate effects have
surface of the specimen. (Note that the total width of the M(T)
been observed previously in the material at the specific
specimen is defined as 2W.)
temperature and environment being tested. The user should
document specific information pertaining to their material,
4. Summary of Test Method
loading rates, temperature, and environment (relative humid-
4.1 The objective of this standard is to induce stable crack
ity) for each test.
extension in a fatigue pre-cracked, low-constraint test speci-
5.3 The results of this characterization include the determi-
men while monitoring and measuring the COD at the original
nation of a critical, lower-limiting value, of CTOA (ψ ) or a
c
fatigue pre-crack-tip location (4, 5) or the CTOA (or CTOD) at
resistance curve of δ , a measure of crack-opening displace-
1-mm behind the stably tearing crack tip (6, 7), or both. The
ment against crack extension, or both.
resistance curve associated with the δ measurements and the
5.4 The test specimens are the compact, C(T), and middle-
critical limiting value of the CTOA measurements are used to
crack-tension, M(T), specimens.
characterize the corresponding resistance to stable crack ex-
tension. In contrast, the CTOD values determined from Test
5.5 Materials that can be evaluated by this standard are not
Method E1290 (high-constraint bend specimens) are values at
limited by strength, thickness, or toughness, if the crack-size-
one or more crack extension events, such as the CTOD at the
to-thickness (a/B) ratio or ligament-to-thickness (b/B) ratio are
onset of brittle crack extension with no significant stable crack
equal to or greater than 4, which ensures relatively low and
extension.
similar global crack-front constraint for both the C(T) and
M(T) specimens (2, 3).
4.2 Either of the fatigue pre-cracked, low-constraint test
specimen configurations specified in this standard [C(T) or
5.6 The values of CTOA and COD (δ ) determined by this
M(T)] may be used to measure or calculate either of the
test method may serve the following purposes:
fracture resistance parameters considered. The fracture resis-
5.6.1 In research and development, CTOA (ψ ) or COD
c
tance parameters, CTOA (or CTOD) and δ , may be charac-
(δ ), or both, testing can show the effects of certain parameters
terized using either a single-specimen or multiple-specimen
on the resistance to stable crack extension of metallic materials
procedure. In all cases, tests are performed by applying slowly
significant to service performance. These parameters include,
increasing displacements to the test specimen and measuring
but are not limited to, material thickness, material composition,
the forces, displacements, crack extension and angles realized
thermo-mechanical processing, welding, and thermal stress
during the test. The forces, displacements and angles are then
relief.
used in conjunction with certain pre-test and post-test specimen
5.6.2 For specifications of acceptance and manufacturing
measurements to determine the material’s resistance to stable
quality control of base materials.
crack extension.
5.6.3 For inspection and flaw assessment criteria, when used
in conjunction with fracture mechanics analyses. Awareness of
4.3 Four procedures for measuring crack extension are:
differences that may exist between laboratory test and field
surface visual, unloading compliance, electrical potential, and
conditions is required to make proper flaw assessment.
multiple specimens.
5.6.4 The critical CTOA (ψ ) has been used with the
c
4.4 Two techniques are presented for measuring CTOA:
elastic-plastic finite-element method to accurately predict
optical microscopy (OM) (8) and digital image correlation
structural response and force carrying capacity of simple and
(DIC) (9).
complex cracked structural components, see Appendix X1.
4.5 Three
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it 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 version
of the standard as published by ASTM is to be considered the official document.
´2 ´2
Designation: E2472 − 12 (Reapproved 2018) E2472 − 12 (Reapproved 2018)
Standard Test Method for
Determination of Resistance to Stable Crack Extension
under Low-Constraint Conditions
This standard is issued under the fixed designation E2472; the number immediately following the designation indicates the year of
original 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 reapproval.
ε NOTE—Sections 7.4.1, 7.4.2, 9.3.1.4, A1.1.3, A2.1.3, and Fig. 7 were editorially corrected in May 2020.
ε NOTE—Section A2.1.3 was editorially corrected in June 2023.
1. Scope
1.1 This standard covers the determination of the resistance to stable crack extension in metallic materials in terms of the critical
crack-tip-opening angle (CTOA), ψ and/or the crack-opening displacement (COD), δ resistance curve (1). This method applies
c 5
specifically to fatigue pre-cracked specimens that exhibit low constraint (crack-size-to-thickness and un-cracked ligament-to-
thickness ratios greater than or equal to 4) and that are tested under slowly increasing remote applied displacement. The test
specimens are the compact, C(T), and middle-crack-tension, M(T), specimens. The fracture resistance determined in accordance
with this standard is measured as ψ (critical CTOA value) and/or δ (critical COD resistance curve) as a function of crack
c 5
extension. Both fracture resistance parameters are characterized using either a single-specimen or multiple-specimen procedures.
These fracture quantities are determined under the opening mode (Mode I) of loading. Influences of environment and rapid loading
rates are not covered in this standard, but the user must be aware of the effects that the loading rate and laboratory environment
may have on the fracture behavior of the material.
1.2 Materials that are evaluated by this standard are not limited by strength, thickness, or toughness, if the crack-size-to-thickness
(a/B) ratio and the ligament-to-thickness (b/B) ratio are greater than or equal to 4, which ensures relatively low and similar global
crack-front constraint for both the C(T) and M(T) specimens (2, 3).
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
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 Fracture
Mechanics.
ε1
Current edition approved Nov. 1, 2018. Published December 2018. Originally approved in 2006. Last previous edition approved in 2012 as E2472–12 . DOI:
10.1520/E2472-12R18E01.10.1520/E2472-12R18E02.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
For 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 page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´2
E2472 − 12 (2018)
E4 Practices for Force Calibration and Verification of Testing Machines
E8/E8M Test Methods for Tension Testing of Metallic Materials
E399 Test Method for Linear-Elastic Plane-Strain Fracture Toughness of Metallic Materials
E561 Test Method for K Curve Determination
R
E647 Test Method for Measurement of Fatigue Crack Growth Rates
E1290 Test Method for Crack-Tip Opening Displacement (CTOD) Fracture Toughness Measurement (Withdrawn 2013)
E1820 Test Method for Measurement of Fracture Toughness
E1823 Terminology Relating to Fatigue and Fracture Testing
E2309 Practices for Verification of Displacement Measuring Systems and Devices Used in Material Testing Machines
2.2 ISO Standards:
ISO 22889:2007 Metallic Materials—Method of Test for the Determination of Resistance to Stable Crack Extension Using
Specimens of Low Constraint
ISO 12135 Metallic Materials—Unified Method of Test for the Determination of Quasistatic Fracture Toughness
3. Terminology
3.1 Terminology E1823 is applicable to this test standard.
3.2 Definitions:
3.2.1 crack extension, Δa [L],n—an increase in crack size.
3.2.1.1 Discussion—
It should be noted that in thin-sheet and thick-plate materials under low constraint conditions, the crack extension observed on the
surface of the specimen may be significantly less than that in the interior of the specimen due to the effects of crack tunneling.
This must be considered if direct optical techniques are used to monitor and measure free-surface crack extension. Indirect crack
extension measurement techniques such as unloading compliance and electric-potential drop method may be used in place of (or
to complement) the direct optical techniques to provide a measure of average crack extension. (See Test Method E647 for
compliance methods for C(T) and M(T) specimens; and ISO 12135 and Test Method E647 for electric potential-drop methods for
C(T) specimens.)
3.2.2 crack size, a [L], n—principal linear dimension used in the calculation of fracture mechanics parameters for through
thickness cracks.
3.2.2.1 Discussion—
A measure of the crack size after the fatigue pre-cracking stage is denoted as the original crack size, a . The value for a may be
o o
obtained using surface measurement, unloading compliance, electric-potential drop or other methods where validation procedures
for the measurements are available.
3.2.3 crack-tip-opening angle (CTOA), ψ [deg],n—relative angle of crack surfaces resulting from the total deformation (elastic
–1
plus plastic) measured (or calculated) at 1-mm behind the current crack tip as the crack stably tears, where ψ = 2 tan (δ /2).
3.2.4 critical crack-tip-opening angle (CTOA ),ψ [deg],n—steady-state relative angle of crack surfaces resulting from the total
c c
deformation (elastic plus plastic) measured (or calculated) at 1-mm behind the current crack tip as the crack stably tears, where
–1
ψ = 2 tan (δ /2).
c 1c
3.2.4.1 Discussion—
Critical CTOA value tends to approach a constant, steady-state value after a small amount of crack extension (associated with crack
tunneling and transition from flat-to-slant crack extension).
3.2.5 crack-opening displacement, (COD) δ [L]—force-induced separation vector between two points. The direction of the vector
is normal to the crack plane (normal to the facing surfaces of a crack) at a specified gage length. In this standard, δ is measured
at the fatigue precrack tip location over a gage length of 5-mm as the crack stably tears.
3.2.6 crack-tip-opening displacement (CTOD), δ [L],n—relative displacement of crack surfaces resulting from the total
deformation (elastic plus plastic) measured (or calculated) at 1- mm behind the current crack tip as the crack stably tears.
The last approved version of this historical standard is referenced on www.astm.org.
Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http://www.iso.ch.
´2
E2472 − 12 (2018)
3.2.7 critical crack-tip-opening displacement (CTOD ), δ [L], n—steady-state relative displacement of crack surfaces resulting
c 1c
from the total deformation (elastic plus plastic) measured (or calculated) at 1-mm behind the current crack tip as the crack stably
tears.
3.2.8 crack extension resistance curve (R curve), n—variation of δ with crack extension, Δa.
-2
3.2.9 effective yield strength, σ [FL ],n—an assumed value of uniaxial yield strength that represents the influence of plastic
Y
yielding upon fracture test parameters.
3.2.9.1 Discussion—
Effective yield strength is calculated as the average of the 0.2 % offset yield strength σ , and the ultimate tensile strength, σ as
YS TS
follows:
σ 5 ~σ 1σ !/2 (1)
Y YS TS
NOTE 1—The yield and ultimate tensile strength are determined from Test Methods E8/E8M.
3.2.9.2 Discussion—
In estimating σ , influences of testing conditions, such as loading rate and temperature, should be considered.
Y
3.2.10 final crack size, a [L],n—crack extension at end of stable tearing (a = a + Δa ).
f f o f
3.2.11 final remaining ligament, b [L],n—distance from the tip of the final crack size to the back edge of the specimen, that is
f
b = W – a .
f f
3.2.12 force, P [F], n—force applied to a test specimen or to a component.
3.2.13 minimum crack extension, Δa [L],n—crack extension beyond which ψ is nearly constant.
min c
3.2.14 maximum crack extension, Δa [L],n—crack extension limit for ψ and δ controlled crack extension.
max c 5
3.2.15 maximum fatigue force, P [F] , n—maximum fatigue force applied to specimen during pre-cracking stage.
f
-2
3.2.16 modulus of elasticity, E [FL ],n—the ratio of stress to corresponding strain below the proportional limit.
3.2.17 notch size, a [L],n—distance from a reference plane to the front of the machined notch, such as the force line in the
n
compact specimen to the notch front or from the center line in the middle-crack-tension specimen to the notch front.
3.2.18 original crack size, a [L],n—the physical crack size at the start of testing.
o
3.2.19 original ligament, b [L],n—distance from the original crack front to the back edge of the specimen, that is b = W – a .
o o o
3.2.20 remaining ligament, b [L], n—distance from the physical crack front to the back edge of the specimen, that is b = W – a.
3.2.21 specimen thickness, B [L], n—distance between the parallel sides of a test specimen or component. Side grooving is not
allowed.
3.2.22 specimen width, W [L], n—distance from a reference position (for example, the force line of a compact specimen or center
line in the middle-crack-tension specimen) to the rear surface of the specimen. (Note that the total width of the M(T) specimen
is defined as 2W.)
4. Summary of Test Method
4.1 The objective of this standard is to induce stable crack extension in a fatigue pre-cracked, low-constraint test specimen while
monitoring and measuring the COD at the original fatigue pre-crack-tip location (4, 5) or the CTOA (or CTOD) at 1-mm behind
the stably tearing crack tip (6, 7), or both. The resistance curve associated with the δ measurements and the critical limiting value
´2
E2472 − 12 (2018)
of the CTOA measurements are used to characterize the corresponding resistance to stable crack extension. In contrast, the CTOD
values determined from Test Method E1290 (high-constraint bend specimens) are values at one or more crack extension events,
such as the CTOD at the onset of brittle crack extension with no significant stable crack extension.
4.2 Either of the fatigue pre-cracked, low-constraint test specimen configurations specified in this standard [C(T) or M(T)] may
be used to measure or calculate either of the fracture resistance parameters considered. The fracture resistance parameters, CTOA
(or CTOD) and δ , may be characterized using either a single-specimen or multiple-specimen procedure. In all cases, tests are
performed by applying slowly increasing displacements to the test specimen and measuring the forces, displacements, crack
extension and angles realized during the test. The forces, displacements and angles are then used in conjunction with certain
pre-test and post-test specimen measurements to determine the material’s resistance to stable crack extension.
4.3 Four procedures for measuring crack extension are: surface visual, unloading compliance, electrical potential, and multiple
specimens.
4.4 Two techniques are presented for measuring CTOA: optical microscopy (OM) (8) and digital image correlation (DIC) (9).
4.5 Three techniques are presented for measuring COD: δ clip gage (5), optical microscopy (OM) (8), and digital image
correlation (DIC) (9).
4.6 Data generated following the procedures and guidelines contained in this standard are labeled qualified data and are insensitive
to in-plane dimensions and specimen type (tension or bending forces), but are dependent upon sheet or plate thickness.
5. Significance and Use
5.1 This test method characterizes a metallic material’s resistance to stable crack extension in terms of crack-tip-opening angle
(CTOA), ψ and/or crack-opening displacement (COD), δ under the laboratory or application environment of interest. This method
applies specifically to fatigue pre-cracked specimens that exhibit low constraint and that are tested under slowly increasing
displacement.
5.2 When conducting fracture tests, the user must consider the influence that the loading rate and laboratory environment may
have on the fracture parameters. The user should perform a literature review to determine if loading rate effects have been observed
previously in the material at the specific temperature and environment being tested. The user should document specific information
pertaining to their material, loading rates, temperature, and environment (relative humidity) for each test.
5.3 The results of this characterization include the determination of a critical, lower-limiting value, of CTOA (ψ ) or a resistance
c
curve of δ , a measure of crack-opening displacement against crack extension, or both.
5.4 The test specimens are the compact, C(T), and middle-crack-tension, M(T), specimens.
5.5 Materials that can be evaluated by this standard are not limited by strength, thickness, or toughness, if the crack-size-to-
thickness (a/B) ratio or ligament-to-thickness (b/B) ratio are equal to or greater than 4, which ensures relatively low and similar
global crack-front constraint for both the C(T) and M(T) specimens (2, 3).
5.6 The value
...
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