ASTM E1221-12A(2018)e1
(Test Method)Standard Test Method for Determining Plane-Strain Crack-Arrest Fracture Toughness, KIa, of Ferritic Steels
Standard Test Method for Determining Plane-Strain Crack-Arrest Fracture Toughness, <emph type="bdit">K<inf>Ia</inf></emph>, of Ferritic Steels
SIGNIFICANCE AND USE
5.1 In structures containing gradients in either toughness or stress, a crack may initiate in a region of either low toughness or high stress, or both, and arrest in another region of either higher toughness or lower stress, or both. The value of the stress intensity factor during the short time interval in which a fast-running crack arrests is a measure of the ability of the material to arrest such a crack. Values of the stress intensity factor of this kind, which are determined using dynamic methods of analysis, provide a value for the crack-arrest fracture toughness which will be termed KA in this discussion. Static methods of analysis, which are much less complex, can often be used to determine K at a short time (1 to 2 ms) after crack arrest. The estimate of the crack-arrest fracture toughness obtained in this fashion is termed K a. When macroscopic dynamic effects are relatively small, the difference between KA and Ka is also small (1-4). For cracks propagating under conditions of crack-front plane-strain, in situations where the dynamic effects are also known to be small, KIa determinations using laboratory-sized specimens have been used successfully to estimate whether, and at what point, a crack will arrest in a structure (5, 6). Depending upon component design, loading compliance, and the crack jump length, a dynamic analysis of a fast-running crack propagation event may be necessary in order to predict whether crack arrest will occur and the arrest position. In such cases, values of K Ia determined by this test method can be used to identify those values of K below which the crack speed is zero. More details on the use of dynamic analyses can be found in Ref (4).
5.2 This test method can serve at least the following additional purposes:
5.2.1 In materials research and development, to establish in quantitative terms significant to service performance, the effects of metallurgical variables (such as composition or heat treatment) or fabrication o...
SCOPE
1.1 This test method employs a side-grooved, crack-line-wedge-loaded specimen to obtain a rapid run-arrest segment of flat-tensile separation with a nearly straight crack front. This test method provides a static analysis determination of the stress intensity factor at a short time after crack arrest. The estimate is denoted Ka. When certain size requirements are met, the test result provides an estimate, termed KIa, of the plane-strain crack-arrest toughness of the material.
1.2 The specimen size requirements, discussed later, provide for in-plane dimensions large enough to allow the specimen to be modeled by linear elastic analysis. For conditions of plane-strain, a minimum specimen thickness is also required. Both requirements depend upon the crack arrest toughness and the yield strength of the material. A range of specimen sizes may therefore be needed, as specified in this test method.
1.3 If the specimen does not exhibit rapid crack propagation and arrest, Ka cannot be determined.
1.4 The values stated in SI units are to be regarded as the standards. The values given in parentheses are provided for information only.
1.5 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.
1.6 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.
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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.
ϵ1
Designation: E1221 − 12a (Reapproved 2018)
Standard Test Method for
Determining Plane-Strain Crack-Arrest Fracture Toughness,
K , of Ferritic Steels
Ia
This standard is issued under the fixed designation E1221; 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 (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Editorial changes were made throughout in May 2020.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method employs a side-grooved, crack-line-
wedge-loadedspecimentoobtainarapidrun-arrestsegmentof E8/E8MTest Methods for Tension Testing of Metallic Ma-
terials
flat-tensile separation with a nearly straight crack front. This
test method provides a static analysis determination of the E23Test Methods for Notched Bar Impact Testing of Me-
tallic Materials
stress intensity factor at a short time after crack arrest. The
estimate is denoted K . When certain size requirements are E208Test Method for Conducting Drop-Weight Test to
a
Determine Nil-Ductility Transition Temperature of Fer-
met, the test result provides an estimate, termed K ,ofthe
Ia
plane-strain crack-arrest toughness of the material. ritic Steels
E399Test Method for Linear-Elastic Plane-Strain Fracture
1.2 The specimen size requirements, discussed later, pro-
Toughness of Metallic Materials
vide for in-plane dimensions large enough to allow the speci-
E616Terminology Relating to Fracture Testing (Withdrawn
men to be modeled by linear elastic analysis. For conditions of
1996)
plane-strain, a minimum specimen thickness is also required.
E1304Test Method for Plane-Strain (Chevron-Notch) Frac-
Both requirements depend upon the crack arrest toughness and
ture Toughness of Metallic Materials
the yield strength of the material. A range of specimen sizes
E1823TerminologyRelatingtoFatigueandFractureTesting
may therefore be needed, as specified in this test method.
3. Terminology
1.3 Ifthespecimendoesnotexhibitrapidcrackpropagation
and arrest, K cannot be determined.
a
3.1 Definitions:
3.1.1 Definitions in Terminology E1823 are applicable to
1.4 The values stated in SI units are to be regarded as the
this test method.
standards. The values given in parentheses are provided for
3.2 Definitions of Terms Specific to This Standard:
information only.
3.2.1 conditional value of the plane-strain crack-arrest
1.5 This standard does not purport to address all of the
−3/2
fracturetoughness,K (FL )—theconditionalvalueofK
Qa Ia
safety concerns, if any, associated with its use. It is the
calculated from the test results and subject to the validity
responsibility of the user of this standard to establish appro-
criteria specified in this test method.
priate safety, health, and environmental practices and deter-
3.2.1.1 Discussion—Inthistestmethod,side-groovedspeci-
mine the applicability of regulatory limitations prior to use.
mensareused.Thecalculationof K isbaseduponmeasure-
Qa
1.6 This international standard was developed in accor-
ments of both the arrested crack size and of the crack-mouth
dance with internationally recognized principles on standard-
openingdisplacementpriortoinitiationofafast-runningcrack
ization established in the Decision on Principles for the
and shortly after crack arrest.
Development of International Standards, Guides and Recom-
−3/2
3.2.2 crack-arrest fracture toughness, K (FL )—the
mendations issued by the World Trade Organization Technical A
value of the stress intensity factor shortly after crack arrest as
Barriers to Trade (TBT) Committee.
determined from dynamic methods of analysis.
1 2
This test method is under the jurisdiction ofASTM Committee E08 on Fatigue For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and Fracture and is the direct responsibility of Subcommittee E08.07 on Fracture contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Mechanics. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Nov. 1, 2018. Published December 2018. Originally the ASTM website.
approved in 1988. Last previous edition approved in 2012 as E1221–12a. DOI: The last approved version of this historical standard is referenced on
10.1520/E1221-12AR18E01. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
ϵ1
E1221 − 12a (2018)
3.2.2.1 Discussion—The in-plane specimen dimensions crackarrest.Theestimateofthecrack-arrestfracturetoughness
must be large enough for adequate enclosure of the crack-tip obtained in this fashion is termed K . When macroscopic
a
plastic zone by a linear-elastic stress field. dynamiceffectsarerelativelysmall,thedifferencebetween K
A
−3/2
and K is also small (1-4). For cracks propagating under
a
3.2.3 crack-arrest fracture toughness, K (FL )—the
a
conditions of crack-front plane-strain, in situations where the
value of the stress intensity factor shortly after crack arrest, as
dynamiceffectsarealsoknowntobesmall,K determinations
Ia
determined from static methods of analysis.
using laboratory-sized specimens have been used successfully
3.2.3.1 Discussion—The in-plane specimen dimensions
to estimate whether, and at what point, a crack will arrest in a
must be large enough for adequate enclosure of the crack-tip
structure (5, 6). Depending upon component design, loading
plastic zone by a linear-elastic stress field.
compliance, and the crack jump length, a dynamic analysis of
3.2.4 plane-strain crack-arrest fracture toughness, K
Ia
a fast-running crack propagation event may be necessary in
−3/2
(FL )—the value of crack-arrest fracture toughness, K , for
a
order to predict whether crack arrest will occur and the arrest
acrackthatarrestsunderconditionsofcrack-frontplane-strain.
position. In such cases, values of K determined by this test
Ia
3.2.4.1 Discussion—The requirements for attaining condi-
method can be used to identify those values of K below which
tions of crack-front plane-strain are specified in the procedures
the crack speed is zero. More details on the use of dynamic
of this test method.
analyses can be found in Ref (4).
−3/2
3.2.5 stressintensityfactoratcrackinitiation,K (FL )—
o
5.2 This test method can serve at least the following
the value of K at the onset of rapid fracturing.
additional purposes:
3.2.5.1 Discussion—In this test method, only a nominal
5.2.1 In materials research and development, to establish in
estimate of the initial driving force is needed. For this reason,
quantitative terms significant to service performance, the
K is calculated on the basis of the original (machined) crack
o
effects of metallurgical variables (such as composition or heat
(or notch) size and the crack-mouth opening displacement at
treatment) or fabrication operations (such as welding or form-
the initiation of a fast-running crack.
ing) on the ability of a new or existing material to arrest
running cracks.
4. Summary of Test Method
5.2.2 In design, to assist in selection of materials for, and
4.1 This test method estimates the value of the stress
determine locations and sizes of, stiffeners and arrestor plates.
intensity factor, K, at which a fast running crack will arrest.
This test method is made by forcing a wedge into a split-pin,
6. Apparatus
whichappliesanopeningforceacrossthecrackstarternotchin
6.1 The procedure involves testing of modified compact
a modified compact specimen, causing a run-arrest segment of
specimens that have been notched by machining. To minimize
crack extension.The rapid run-arrest event suggests need for a
the introduction of additional energy into the specimen during
dynamic analysis of test results. However, experimental obser-
4 the run-arrest event, the loading system must have a low
vations (1, 2) indicate that, for this test method, an adjusted
compliance compared with the test specimen. For this reason a
static analysis of test results provides a useful estimate of the
wedge and split-pin assembly is used to apply a force on the
value of the stress intensity factor at the time of crack arrest.
crack line. This loading arrangement does not permit easy
4.2 Calculationofanominalstressintensityatinitiation,K ,
o
measurement of opening forces. Consequently, opening dis-
is based on measurements of the machined notch size and the
placement measurements in conjunction with crack size and
crack-mouth opening displacement at initiation. The value of
compliance calibrations are used for calculating K and K .
o a
K is based on measurements of the arrested crack size and the
a
6.2 Loading Arrangement:
crack-mouth opening displacements prior to initiation and
6.2.1 Atypical loading arrangement is shown in Fig. 1.The
shortly after crack arrest.
specimen is placed on a support block whose thickness should
be adequate to allow completion of the test without interfer-
5. Significance and Use
ence between the wedge and the lower crosshead of the testing
5.1 In structures containing gradients in either toughness or
machine. The support block should contain a hole that is
stress, a crack may initiate in a region of either low toughness
aligned with the specimen hole, and whose diameter should be
or high stress, or both, and arrest in another region of either
between 1.05 and 1.15 times the diameter of the hole in the
higher toughness or lower stress, or both. The value of the
specimen.The force that pushes the wedge into the split-pin is
stress intensity factor during the short time interval in which a
transmitted through a force transducer.
fast-running crack arrests is a measure of the ability of the
6.2.1.1 The surfaces of the wedge, split-pin, support block,
material to arrest such a crack. Values of the stress intensity
and specimen hole should be lubricated. Lubricant in the form
factor of this kind, which are determined using dynamic
of thin (0.13 mm or 0.005 in.) strips of TFE-fluorocarbon is
methods of analysis, provide a value for the crack-arrest
preferred. Molybdenum disulfide (both dry and in a grease
fracture toughness which will be termed K in this discussion.
A
vehicle) and high-temperature lubricants can also be used.
Static methods of analysis, which are much less complex, can
6.2.1.2 A low-taper-angle wedge and split-pin arrangement
often be used to determine K at a short time (1 to 2 ms) after
is used. If grease or dry lubricants are used, a matte finish (grit
blasted) on the sliding surfaces may be helpful in avoiding
galling. The split-pin must be long enough to contact the full
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this test method. specimen thickness, and the radius must be large enough to
ϵ1
E1221 − 12a (2018)
satisfactory. It is necessary to attach the gage in a fashion such
that seating contact with the specimen is not altered by the
jump of the crack. Two methods that have proven satisfactory
for doing this are shown in Fig. 4. Other gages can be used so
long as their accuracy is within 2%.
7. Specimen Configuration, Dimensions, and Preparation
7.1 Standard Specimen:
7.1.1 The configuration of a compact-crack-arrest (CCA)
specimen that is satisfactory for low- and intermediatestrength
steels is shown in Fig. 5. (In this context, an intermediate-
strength steel is considered to be one whose static yield stress,
σ , is of the order of 700 MPa (100 ksi) or less.)
YS
7.1.1.1 The thickness, B, shall be either full product plate
thickness or a thickness sufficient to produce a condition of
plane-strain, as specified in 9.3.3.
7.1.1.2 SidegroovesofdepthB/8persideshallbeused.For
alloys that require notch-tip embrittlement (see 7.1.3.2) the
sidegroovesshouldbeintroducedafterdepositionofthebrittle
weld.
7.1.1.3 Thespecimenwidth,W,shallbewithintherange2B
≤ W ≤ 8B.
7.1.1.4 The displacement gage shall measure opening dis-
placementsatanoffsetfromtheloadlineof0.25W,awayfrom
the crack tip.
7.1.2 Specimen Dimensions:
7.1.2.1 In order to limit the extent of plastic deformation in
thespecimenpriortocrackinitiation,certainsizerequirements
must be met. These requirements depend upon the material
FIG. 1 Schematic Pictorial and Sectional Views Showing the yieldstrength.Theyalsodependupon K ,andthereforethe K
a o
Standard Arrangement of the Wedge and Split-Pin Assembly, the
needed to achieve an appropriate run-arrest event.
Test Specimen, and the Support Block
7.1.2.2 The in-plane specimen dimensions must be large
enoughtoallowforthelinearelasticanalysisemployedbythis
testmethod.Theserequirementsaregivenin9.3.2and9.3.4,in
avoidplasticindentationsofthetestspecimen.Inallcasesitis
terms of allowable crack jump lengths.
recommended that the diameter of the split-pin should be 0.13
7.1.2.3 For a test result to be termed plane-strain (K )by
mm(0.005in.)lessthanthediameterofthespecimenhole.The Ia
this test method, the specimen thickness, B, should meet the
wedgemustbelongenoughtodevelopthemaximumexpected
requirement given in 9.3.3.
opening displacement. Any air or oil hardening tool steel is
7.1.3 Starting Notch:
suitableformakingthewedgeandsplit-pins.Ahardnessinthe
7.1.3.1 Thefunctionofthestartingnotchistoproducecrack
rangefromR 45toR 55hasbeenusedsuccessfully.Withthe
C C
initiation at an opening displacement (or wedging force) that
recommended wedge angle and proper lubrication, a loading
1 1
machine producing ⁄5 to ⁄10 the expected maximum opening will permit an appropriate length of crack extension prior to
crack arrest. Different materials require different starter notch
force is adequate. The dimensions of a wedge and split-pin
assembly suitable for use with a 25.4-mm (1.0-in.) diameter preparation procedures.
loading hole are shown in Fig. 2. The dimensions should be 7.1.3.2 The recommended starter notch for low- and
scaled when other hole diameters are used.Ahole diameter of intermediate-strength steels is a notched brittle weld, as shown
1.0 in. has been found satisfactory for specimens having 125 < in Fig. 6. It is produced by depositing a weld across the
W < 170 mm (5 < W < 6.7 in.). specimen thickness. Guidelines on welding procedures are
given in Appendix X1.
NOTE 1—Specimens tested with the arrangement shown in Fig. 1 may
7.1.3.3 Alternative crack starter configurations (8) and em-
not exhibit an adequate segment of run-arrest fracturing, for example, at
brittlement methods may also be used. Examples of both
testing temperatures well above the NDT temperature. I
...
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
´1
Designation: E1221 − 12a (Reapproved 2018)
Standard Test Method for
Determining Plane-Strain Crack-Arrest Fracture Toughness,
K , of Ferritic Steels
Ia
This standard is issued under the fixed designation E1221; 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—Editorial changes were made throughout in May 2020.
1. Scope 2. Referenced Documents
1.1 This test method employs a side-grooved, crack-line- 2.1 ASTM Standards:
E8/E8M Test Methods for Tension Testing of Metallic Ma-
wedge-loaded specimen to obtain a rapid run-arrest segment of
flat-tensile separation with a nearly straight crack front. This terials
E23 Test Methods for Notched Bar Impact Testing of Me-
test method provides a static analysis determination of the
stress intensity factor at a short time after crack arrest. The tallic Materials
E208 Test Method for Conducting Drop-Weight Test to
estimate is denoted K . When certain size requirements are
a
met, the test result provides an estimate, termed K , of the Determine Nil-Ductility Transition Temperature of Fer-
Ia
ritic Steels
plane-strain crack-arrest toughness of the material.
E399 Test Method for Linear-Elastic Plane-Strain Fracture
1.2 The specimen size requirements, discussed later, pro-
Toughness of Metallic Materials
vide for in-plane dimensions large enough to allow the speci-
E616 Terminology Relating to Fracture Testing (Withdrawn
men to be modeled by linear elastic analysis. For conditions of
1996)
plane-strain, a minimum specimen thickness is also required.
E1304 Test Method for Plane-Strain (Chevron-Notch) Frac-
Both requirements depend upon the crack arrest toughness and
ture Toughness of Metallic Materials
the yield strength of the material. A range of specimen sizes
E1823 Terminology Relating to Fatigue and Fracture Testing
may therefore be needed, as specified in this test method.
1.3 If the specimen does not exhibit rapid crack propagation 3. Terminology
and arrest, K cannot be determined.
a
3.1 Definitions:
3.1.1 Definitions in Terminology E1823 are applicable to
1.4 The values stated in SI units are to be regarded as the
this test method.
standards. The values given in parentheses are provided for
3.2 Definitions of Terms Specific to This Standard:
information only.
3.2.1 conditional value of the plane-strain crack-arrest
1.5 This standard does not purport to address all of the
−3/2
fracture toughness, K (FL ) —the conditional value of K
Qa Ia
safety concerns, if any, associated with its use. It is the
calculated from the test results and subject to the validity
responsibility of the user of this standard to establish appro-
criteria specified in this test method.
priate safety, health, and environmental practices and deter-
3.2.1.1 Discussion—In this test method, side-grooved speci-
mine the applicability of regulatory limitations prior to use.
mens are used. The calculation of K is based upon measure-
Qa
1.6 This international standard was developed in accor-
ments of both the arrested crack size and of the crack-mouth
dance with internationally recognized principles on standard-
opening displacement prior to initiation of a fast-running crack
ization established in the Decision on Principles for the
and shortly after crack arrest.
Development of International Standards, Guides and Recom-
−3/2
3.2.2 crack-arrest fracture toughness, K (FL )—the
mendations issued by the World Trade Organization Technical
A
value of the stress intensity factor shortly after crack arrest as
Barriers to Trade (TBT) Committee.
determined from dynamic methods of analysis.
1 2
This test method is under the jurisdiction of ASTM Committee E08 on Fatigue For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and Fracture and is the direct responsibility of Subcommittee E08.07 on Fracture contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Mechanics. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Nov. 1, 2018. Published December 2018. Originally the ASTM website.
approved in 1988. Last previous edition approved in 2012 as E1221 – 12a. DOI: The last approved version of this historical standard is referenced on
10.1520/E1221-12AR18E01. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
ϵ1
E1221 − 12a (2018)
3.2.2.1 Discussion—The in-plane specimen dimensions crack arrest. The estimate of the crack-arrest fracture toughness
must be large enough for adequate enclosure of the crack-tip obtained in this fashion is termed K . When macroscopic
a
plastic zone by a linear-elastic stress field. dynamic effects are relatively small, the difference between K
A
−3/2
and K is also small (1-4). For cracks propagating under
a
3.2.3 crack-arrest fracture toughness, K (FL )—the
a
conditions of crack-front plane-strain, in situations where the
value of the stress intensity factor shortly after crack arrest, as
dynamic effects are also known to be small, K determinations
Ia
determined from static methods of analysis.
using laboratory-sized specimens have been used successfully
3.2.3.1 Discussion—The in-plane specimen dimensions
to estimate whether, and at what point, a crack will arrest in a
must be large enough for adequate enclosure of the crack-tip
structure (5, 6). Depending upon component design, loading
plastic zone by a linear-elastic stress field.
compliance, and the crack jump length, a dynamic analysis of
3.2.4 plane-strain crack-arrest fracture toughness, K
Ia
a fast-running crack propagation event may be necessary in
−3/2
(FL )—the value of crack-arrest fracture toughness, K , for
a
order to predict whether crack arrest will occur and the arrest
a crack that arrests under conditions of crack-front plane-strain.
position. In such cases, values of K determined by this test
Ia
3.2.4.1 Discussion—The requirements for attaining condi-
method can be used to identify those values of K below which
tions of crack-front plane-strain are specified in the procedures
the crack speed is zero. More details on the use of dynamic
of this test method.
analyses can be found in Ref (4).
−3/2
3.2.5 stress intensity factor at crack initiation, K (FL )—
o
5.2 This test method can serve at least the following
the value of K at the onset of rapid fracturing.
additional purposes:
3.2.5.1 Discussion—In this test method, only a nominal
5.2.1 In materials research and development, to establish in
estimate of the initial driving force is needed. For this reason,
quantitative terms significant to service performance, the
K is calculated on the basis of the original (machined) crack
o
effects of metallurgical variables (such as composition or heat
(or notch) size and the crack-mouth opening displacement at
treatment) or fabrication operations (such as welding or form-
the initiation of a fast-running crack.
ing) on the ability of a new or existing material to arrest
running cracks.
4. Summary of Test Method
5.2.2 In design, to assist in selection of materials for, and
4.1 This test method estimates the value of the stress
determine locations and sizes of, stiffeners and arrestor plates.
intensity factor, K, at which a fast running crack will arrest.
This test method is made by forcing a wedge into a split-pin,
6. Apparatus
which applies an opening force across the crack starter notch in
6.1 The procedure involves testing of modified compact
a modified compact specimen, causing a run-arrest segment of
specimens that have been notched by machining. To minimize
crack extension. The rapid run-arrest event suggests need for a
the introduction of additional energy into the specimen during
dynamic analysis of test results. However, experimental obser-
the run-arrest event, the loading system must have a low
vations (1, 2) indicate that, for this test method, an adjusted
compliance compared with the test specimen. For this reason a
static analysis of test results provides a useful estimate of the
wedge and split-pin assembly is used to apply a force on the
value of the stress intensity factor at the time of crack arrest.
crack line. This loading arrangement does not permit easy
4.2 Calculation of a nominal stress intensity at initiation, K ,
o measurement of opening forces. Consequently, opening dis-
is based on measurements of the machined notch size and the
placement measurements in conjunction with crack size and
crack-mouth opening displacement at initiation. The value of
compliance calibrations are used for calculating K and K .
o a
K is based on measurements of the arrested crack size and the
a
6.2 Loading Arrangement:
crack-mouth opening displacements prior to initiation and
6.2.1 A typical loading arrangement is shown in Fig. 1. The
shortly after crack arrest.
specimen is placed on a support block whose thickness should
be adequate to allow completion of the test without interfer-
5. Significance and Use
ence between the wedge and the lower crosshead of the testing
5.1 In structures containing gradients in either toughness or
machine. The support block should contain a hole that is
stress, a crack may initiate in a region of either low toughness
aligned with the specimen hole, and whose diameter should be
or high stress, or both, and arrest in another region of either
between 1.05 and 1.15 times the diameter of the hole in the
higher toughness or lower stress, or both. The value of the
specimen. The force that pushes the wedge into the split-pin is
stress intensity factor during the short time interval in which a
transmitted through a force transducer.
fast-running crack arrests is a measure of the ability of the
6.2.1.1 The surfaces of the wedge, split-pin, support block,
material to arrest such a crack. Values of the stress intensity
and specimen hole should be lubricated. Lubricant in the form
factor of this kind, which are determined using dynamic
of thin (0.13 mm or 0.005 in.) strips of TFE-fluorocarbon is
methods of analysis, provide a value for the crack-arrest
preferred. Molybdenum disulfide (both dry and in a grease
fracture toughness which will be termed K in this discussion.
A
vehicle) and high-temperature lubricants can also be used.
Static methods of analysis, which are much less complex, can
6.2.1.2 A low-taper-angle wedge and split-pin arrangement
often be used to determine K at a short time (1 to 2 ms) after
is used. If grease or dry lubricants are used, a matte finish (grit
blasted) on the sliding surfaces may be helpful in avoiding
4 galling. The split-pin must be long enough to contact the full
The boldface numbers in parentheses refer to the list of references at the end of
this test method. specimen thickness, and the radius must be large enough to
ϵ1
E1221 − 12a (2018)
satisfactory. It is necessary to attach the gage in a fashion such
that seating contact with the specimen is not altered by the
jump of the crack. Two methods that have proven satisfactory
for doing this are shown in Fig. 4. Other gages can be used so
long as their accuracy is within 2 %.
7. Specimen Configuration, Dimensions, and Preparation
7.1 Standard Specimen:
7.1.1 The configuration of a compact-crack-arrest (CCA)
specimen that is satisfactory for low- and intermediatestrength
steels is shown in Fig. 5. (In this context, an intermediate-
strength steel is considered to be one whose static yield stress,
σ , is of the order of 700 MPa (100 ksi) or less.)
YS
7.1.1.1 The thickness, B, shall be either full product plate
thickness or a thickness sufficient to produce a condition of
plane-strain, as specified in 9.3.3.
7.1.1.2 Side grooves of depth B/8 per side shall be used. For
alloys that require notch-tip embrittlement (see 7.1.3.2) the
side grooves should be introduced after deposition of the brittle
weld.
7.1.1.3 The specimen width, W, shall be within the range 2B
≤ W ≤ 8B.
7.1.1.4 The displacement gage shall measure opening dis-
placements at an offset from the load line of 0.25W, away from
the crack tip.
7.1.2 Specimen Dimensions:
7.1.2.1 In order to limit the extent of plastic deformation in
the specimen prior to crack initiation, certain size requirements
must be met. These requirements depend upon the material
FIG. 1 Schematic Pictorial and Sectional Views Showing the yield strength. They also depend upon K , and therefore the K
a o
Standard Arrangement of the Wedge and Split-Pin Assembly, the
needed to achieve an appropriate run-arrest event.
Test Specimen, and the Support Block
7.1.2.2 The in-plane specimen dimensions must be large
enough to allow for the linear elastic analysis employed by this
test method. These requirements are given in 9.3.2 and 9.3.4, in
avoid plastic indentations of the test specimen. In all cases it is
terms of allowable crack jump lengths.
recommended that the diameter of the split-pin should be 0.13
7.1.2.3 For a test result to be termed plane-strain (K ) by
mm (0.005in.) less than the diameter of the specimen hole. The
Ia
this test method, the specimen thickness, B, should meet the
wedge must be long enough to develop the maximum expected
requirement given in 9.3.3.
opening displacement. Any air or oil hardening tool steel is
7.1.3 Starting Notch:
suitable for making the wedge and split-pins. A hardness in the
7.1.3.1 The function of the starting notch is to produce crack
range from R 45 to R 55 has been used successfully. With the
C C
recommended wedge angle and proper lubrication, a loading initiation at an opening displacement (or wedging force) that
1 1
will permit an appropriate length of crack extension prior to
machine producing ⁄5 to ⁄10 the expected maximum opening
force is adequate. The dimensions of a wedge and split-pin crack arrest. Different materials require different starter notch
preparation procedures.
assembly suitable for use with a 25.4-mm (1.0-in.) diameter
loading hole are shown in Fig. 2. The dimensions should be 7.1.3.2 The recommended starter notch for low- and
scaled when other hole diameters are used. A hole diameter of intermediate-strength steels is a notched brittle weld, as shown
1.0 in. has been found satisfactory for specimens having 125 < in Fig. 6. It is produced by depositing a weld across the
specimen thickness. Guidelines on welding procedures are
W < 170 mm (5 < W < 6.7 in.).
given in Appendix X1.
NOTE 1—Specimens tested with the arrangement shown in Fig. 1 may
7.1.3.3 Alternative crack starter configurations (8) and em-
not exhibit an adequate segment of run-
...
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.
´1
Designation: E1221 − 12a (Reapproved 2018) E1221 − 12a (Reapproved 2018)
Standard Test Method for
Determining Plane-Strain Crack-Arrest Fracture Toughness,
K , of Ferritic Steels
Ia
This standard is issued under the fixed designation E1221; 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—Editorial changes were made throughout in May 2020.
1. Scope
1.1 This test method employs a side-grooved, crack-line-wedge-loaded specimen to obtain a rapid run-arrest segment of
flat-tensile separation with a nearly straight crack front. This test method provides a static analysis determination of the stress
intensity factor at a short time after crack arrest. The estimate is denoted K . When certain size requirements are met, the test result
a
provides an estimate, termed K , of the plane-strain crack-arrest toughness of the material.
Ia
1.2 The specimen size requirements, discussed later, provide for in-plane dimensions large enough to allow the specimen to be
modeled by linear elastic analysis. For conditions of plane-strain, a minimum specimen thickness is also required. Both
requirements depend upon the crack arrest toughness and the yield strength of the material. A range of specimen sizes may
therefore be needed, as specified in this test method.
1.3 If the specimen does not exhibit rapid crack propagation and arrest, K cannot be determined.
a
1.4 The values stated in SI units are to be regarded as the standards. The values given in parentheses are provided for
information only.
1.5 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.
1.6 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:
E8/E8M Test Methods for Tension Testing of Metallic Materials
E23 Test Methods for Notched Bar Impact Testing of Metallic Materials
E208 Test Method for Conducting Drop-Weight Test to Determine Nil-Ductility Transition Temperature of Ferritic Steels
E399 Test Method for Linear-Elastic Plane-Strain Fracture Toughness of Metallic Materials
E616 Terminology Relating to Fracture Testing (Withdrawn 1996)
E1304 Test Method for Plane-Strain (Chevron-Notch) Fracture Toughness of Metallic Materials
E1823 Terminology Relating to Fatigue and Fracture Testing
3. Terminology
3.1 Definitions:
3.1.1 Definitions in Terminology E1823 are applicable to this test method.
3.2 Definitions of Terms Specific to This Standard:
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.
Current edition approved Nov. 1, 2018. Published December 2018. Originally approved in 1988. Last previous edition approved in 2012 as E1221 – 12a. DOI:
10.1520/E1221-12AR18.10.1520/E1221-12AR18E01.
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.
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. United States
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E1221 − 12a (2018)
−3/2
3.2.1 conditional value of the plane-strain crack-arrest fracture toughness, K (FL ) —the conditional value of K
Qa Ia
calculated from the test results and subject to the validity criteria specified in this test method.
3.2.1.1 Discussion—
In this test method, side-grooved specimens are used. The calculation of K is based upon measurements of both the arrested
Qa
crack size and of the crack-mouth opening displacement prior to initiation of a fast-running crack and shortly after crack arrest.
−3/2
3.2.2 crack-arrest fracture toughness, K (FL )—the value of the stress intensity factor shortly after crack arrest as
A
determined from dynamic methods of analysis.
3.2.2.1 Discussion—
The in-plane specimen dimensions must be large enough for adequate enclosure of the crack-tip plastic zone by a linear-elastic
stress field.
−3/2
3.2.3 crack-arrest fracture toughness, K (FL )—the value of the stress intensity factor shortly after crack arrest, as
a
determined from static methods of analysis.
3.2.3.1 Discussion—
The in-plane specimen dimensions must be large enough for adequate enclosure of the crack-tip plastic zone by a linear-elastic
stress field.
−3/2
3.2.4 plane-strain crack-arrest fracture toughness, K (FL )—the value of crack-arrest fracture toughness, K , for a crack
Ia a
that arrests under conditions of crack-front plane-strain.
3.2.4.1 Discussion—
The requirements for attaining conditions of crack-front plane-strain are specified in the procedures of this test method.
−3/2
3.2.5 stress intensity factor at crack initiation, K (FL )—the value of K at the onset of rapid fracturing.
o
3.2.5.1 Discussion—
In this test method, only a nominal estimate of the initial driving force is needed. For this reason, K is calculated on the basis of
o
the original (machined) crack (or notch) size and the crack-mouth opening displacement at the initiation of a fast-running crack.
4. Summary of Test Method
4.1 This test method estimates the value of the stress intensity factor, K, at which a fast running crack will arrest. This test
method is made by forcing a wedge into a split-pin, which applies an opening force across the crack starter notch in a modified
compact specimen, causing a run-arrest segment of crack extension. The rapid run-arrest event suggests need for a dynamic
analysis of test results. However, experimental observations (1, 2) indicate that, for this test method, an adjusted static analysis
of test results provides a useful estimate of the value of the stress intensity factor at the time of crack arrest.
4.2 Calculation of a nominal stress intensity at initiation, K , is based on measurements of the machined notch size and the
o
crack-mouth opening displacement at initiation. The value of K is based on measurements of the arrested crack size and the
a
crack-mouth opening displacements prior to initiation and shortly after crack arrest.
5. Significance and Use
5.1 In structures containing gradients in either toughness or stress, a crack may initiate in a region of either low toughness or
high stress, or both, and arrest in another region of either higher toughness or lower stress, or both. The value of the stress intensity
factor during the short time interval in which a fast-running crack arrests is a measure of the ability of the material to arrest such
a crack. Values of the stress intensity factor of this kind, which are determined using dynamic methods of analysis, provide a value
for the crack-arrest fracture toughness which will be termed K in this discussion. Static methods of analysis, which are much less
A
complex, can often be used to determine K at a short time (1 to 2 ms) after crack arrest. The estimate of the crack-arrest fracture
toughness obtained in this fashion is termed K . When macroscopic dynamic effects are relatively small, the difference between
a
K and K is also small (1-4). For cracks propagating under conditions of crack-front plane-strain, in situations where the dynamic
A a
The boldface numbers in parentheses refer to the list of references at the end of this test method.
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E1221 − 12a (2018)
effects are also known to be small, K determinations using laboratory-sized specimens have been used successfully to estimate
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whether, and at what point, a crack will arrest in a structure (5, 6). Depending upon component design, loading compliance, and
the crack jump length, a dynamic analysis of a fast-running crack propagation event may be necessary in order to predict whether
crack arrest will occur and the arrest position. In such cases, values of K determined by this test method can be used to identify
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those values of K below which the crack speed is zero. More details on the use of dynamic analyses can be found in Ref (4).
5.2 This test method can serve at least the following additional purposes:
5.2.1 In materials research and development, to establish in quantitative terms significant to service performance, the effects of
metallurgical variables (such as composition or heat treatment) or fabrication operations (such as welding or forming) on the ability
of a new or existing material to arrest running cracks.
5.2.2 In design, to assist in selection of materials for, and determine locations and sizes of, stiffeners and arrestor plates.
6. Apparatus
6.1 The procedure involves testing of modified compact specimens that have been notched by machining. To minimize the
introduction of additional energy into the specimen during the run-arrest event, the loading system must have a low compliance
compared with the test specimen. For this reason a wedge and split-pin assembly is used to apply a force on the crack line. This
loading arrangement does not permit easy measurement of opening forces. Consequently, opening displacement measurements in
conjunction with crack size and compliance calibrations are used for calculating K and K .
o a
6.2 Loading Arrangement:
6.2.1 A typical loading arrangement is shown in Fig. 1. The specimen is placed on a support block whose thickness should be
adequate to allow completion of the test without interference between the wedge and the lower crosshead of the testing machine.
The support block should contain a hole that is aligned with the specimen hole, and whose diameter should be between 1.05 and
1.15 times the diameter of the hole in the specimen. The force that pushes the wedge into the split-pin is transmitted through a
force transducer.
6.2.1.1 The surfaces of the wedge, split-pin, support block, and specimen hole should be lubricated. Lubricant in the form of
thin (0.13 mm or 0.005 in.) strips of TFE-fluorocarbon is preferred. Molybdenum disulfide (both dry and in a grease vehicle) and
high-temperature lubricants can also be used.
FIG. 1 Schematic Pictorial and Sectional Views Showing the Standard Arrangement of the Wedge and Split-Pin Assembly, the Test
Specimen, and the Support Block
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E1221 − 12a (2018)
6.2.1.2 A low-taper-angle wedge and split-pin arrangement is used. If grease or dry lubricants are used, a matte finish (grit
blasted) on the sliding surfaces may be helpful in avoiding galling. The split-pin must be long enough to contact the full specimen
thickness, and the radius must be large enough to avoid plastic indentations of the test specimen. In all cases it is recommended
that the diameter of the split-pin should be 0.13 mm (0.005in.) less than the diameter of the specimen hole. The wedge must be
long enough to develop the maximum expected opening displacement. Any air or oil hardening tool steel is suitable for making
the wedge and split-pins. A hardness in the range from R 45 to R 55 has been used successfully. With the recommended wedge
C C
1 1
angle and proper lubrication, a loading machine producing ⁄5 to ⁄10 the expected maximum opening force is adequate. The
dimensions of a wedge and split-pin assembly suitable for use with a 25.4-mm (1.0-in.) diameter loading hole are shown in Fig.
2. The dimensions should be scaled when other hole diameters are used. A hole diameter of 1.0 in. has been found satisfactory for
specimens having 125 < W < 170 mm (5 < W < 6.7 in.).
NOTE 1—Specimens tested with the arrangement shown in Fig. 1 may not exhibit an adequate segment of run-arrest fracturing, for example, at testing
temperatures well above the NDT temperature. In these circumstances, the use of the loading arrangement shown in Fig. 3 has been found to be helpful
(2, 7) and may be employed.
6.3 Displacement Gages—Displacement gages are used to measure the crack-mouth opening displacement at 0.25W from the
load-line. Accuracy within 2 % over the working range is required. Either the gage recommended in Test Method E399 or a similar
gage modified to accommodate conical seats is satisfactory. It is necessary to attach the gage in a fashion such that seating contact
with the specimen is not altered by the jump of the crack. Two methods that have proven satisfactory for doing this are shown in
Fig. 4. Other gages can be used so long as their accuracy is within 2 %.
7. Specimen Configuration, Dimensions, and Preparation
7.1 Standard Specimen:
7.1.1 The configuration of a compact-crack-arrest (CCA) specimen that is satisfactory for low- and intermediatestrength steels
is shown in Fig. 5. (In this context, an intermediate-strength steel is considered to be one whose static yield stress, σ , is of the
YS
order of 700 MPa (100 ksi) or less.)
7.1.1.1 The thickness, B, shall be either full product plate thickness or a thickness sufficient to produce a condition of
plane-strain, as specified in 9.3.3.
7.1.1.2 Side grooves of depth B/8 per side shall be used. For alloys that require notch-tip embrittlement (see 7.1.3.2) the side
grooves should be introduced after deposition of the brittle weld.
7.1.1.3 The specimen width, W, shall be within the range 2B ≤ W ≤ 8B.
mm in.
A 203 8.00
B 8.4 0.33
D 25.1 0.99
E 25.4 1.00
F 57.2 2.25
G 50.8 2.00
H 1.50 38.1
NOTE 1—The dimensions given are suitable for use with a 25.4 mm (1.0 in.) diameter loading hole in a 50.8 mm (2.0 in.) thick test specimen. These
dimensions should be scaled appropriately when other hole diameters and specimen thicknesses are used.
FIG. 2 Suggested Geometry and Dimensions of a Wedge and Split-Pin Assembly
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E1221 − 12a (2018)
FIG. 3 Sectional View of a Loading Arrangement That May Be Helpful When Testing Specimens at Hi
...
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