ASTM E1221-23

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.
Designation: E1221 − 23
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.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method employs a side-grooved, crack-line-
E8/E8M Test Methods for Tension Testing of Metallic Ma-
wedge-loaded specimen to obtain a rapid run-arrest segment of
terials
flat-tensile separation with a nearly straight crack front. This
E23 Test Methods for Notched Bar Impact Testing of Me-
test method provides a static analysis determination of the
tallic Materials
stress intensity factor at a short time after crack arrest. The
E208 Test Method for Conducting Drop-Weight Test to
estimate is denoted K . When certain size requirements are
a
Determine Nil-Ductility Transition Temperature of Fer-
met, the test result provides an estimate, termed K , of the
Ia
ritic Steels
plane-strain crack-arrest toughness of the material.
E399 Test Method for Linear-Elastic Plane-Strain Fracture
Toughness of Metallic Materials
1.2 The specimen size requirements, discussed later, pro-
E1304 Test Method for Plane-Strain (Chevron-Notch) Frac-
vide for in-plane dimensions large enough to allow the speci-
ture Toughness of Metallic Materials
men to be modeled by linear elastic analysis. For conditions of
E1823 Terminology Relating to Fatigue and Fracture Testing
plane-strain, a minimum specimen thickness is also required.
Both requirements depend upon the crack arrest toughness and
3. Terminology
the yield strength of the material. A range of specimen sizes
3.1 Definitions:
may therefore be needed, as specified in this test method.
3.1.1 Definitions in Terminology E1823 are applicable to
1.3 If the specimen does not exhibit rapid crack propagation this test method.
and arrest, K cannot be determined. 3.2 Definitions of Terms Specific to This Standard:
a
3.2.1 conditional value of the plane-strain crack-arrest
1.4 The values stated in SI units are to be regarded as the
−3/2
fracture toughness, K (FL ) —the conditional value of K
Qa Ia
standards. The values given in parentheses are provided for
calculated from the test results and subject to the validity
information only.
criteria specified in this test method.
3.2.1.1 Discussion—In this test method, side-grooved speci-
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the mens are used. The calculation of K is based upon measure-
Qa
ments of both the arrested crack size and of the crack-mouth
responsibility of the user of this standard to establish appro-
opening displacement prior to initiation of a fast-running crack
priate safety, health, and environmental practices and deter-
and shortly after crack arrest.
mine the applicability of regulatory limitations prior to use.
−3/2
3.2.2 crack-arrest fracture toughness, K (FL )—the
1.6 This international standard was developed in accor- A
value of the stress intensity factor shortly after crack arrest as
dance with internationally recognized principles on standard-
determined from dynamic methods of analysis.
ization established in the Decision on Principles for the
3.2.2.1 Discussion—The in-plane specimen dimensions
Development of International Standards, Guides and Recom-
must be large enough for adequate enclosure of the crack-tip
mendations issued by the World Trade Organization Technical
plastic zone by a linear-elastic stress field.
Barriers to Trade (TBT) Committee.
−3/2
3.2.3 crack-arrest fracture toughness, K (FL )—the
a
value of the stress intensity factor shortly after crack arrest, as
determined from static methods of analysis.
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, 2023. Published December 2023. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ɛ1
approved in 1988. Last previous edition approved in 2018 as E1221 – 18 . DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E1221-23. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1221 − 23
3.2.3.1 Discussion—The in-plane specimen dimensions using laboratory-sized specimens have been used successfully
must be large enough for adequate enclosure of the crack-tip to estimate whether, and at what point, a crack will arrest in a
plastic zone by a linear-elastic stress field. structure (5, 6). Depending upon component design, loading
compliance, and the crack jump length, a dynamic analysis of
3.2.4 plane-strain crack-arrest fracture toughness, K
Ia
−3/2
a fast-running crack propagation event may be necessary in
(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
5. Significance and Use be adequate to allow completion of the test without interfer-
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
crack arrest. The estimate of the crack-arrest fracture toughness
blasted) on the sliding surfaces may be helpful in avoiding
obtained in this fashion is termed K . When macroscopic
a
galling. The split-pin must be long enough to contact the full
dynamic effects are relatively small, the difference between K
A
specimen thickness, and the radius must be large enough to
and K is also small (1-4). For cracks propagating under
a
avoid plastic indentations of the test specimen. In all cases it is
conditions of crack-front plane-strain, in situations where the
recommended that the diameter of the split-pin should be 0.13
dynamic effects are also known to be small, K determinations
Ia
mm (0.005 in.) 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
The boldface numbers in parentheses refer to the list of references at the end of
this test method. steel is suitable for making the wedge and split-pins. A
E1221 − 23
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
yield strength. They also depend upon K , and therefore the K
a o
needed to achieve an appropriate run-arrest event.
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
FIG. 1 Schematic Pictorial and Sectional Views Showing the
Standard Arrangement of the Wedge and Split-Pin Assembly, the
terms of allowable crack jump lengths.
Test Specimen, and the Support Block
7.1.2.3 For a test result to be termed plane-strain (K ) by
Ia
this test method, the specimen thickness, B, should meet the
requirement given in 9.3.3.
hardness in the range from R 45 to R 55 has been used
7.1.3 Starting Notch:
C C
successfully. With the recommended wedge angle and proper
7.1.3.1 The function of the starting notch is to produce crack
1 1
lubrication, a loading machine producing ⁄5 to ⁄10 the expected
initiation at an opening displacement (or wedging force) that
maximum opening force is adequate. The dimensions of a
will permit an appropriate length of crack extension prior to
wedge and split-pin assembly suitable for use with a 25.4 mm
crack arrest. Different materials require different starter notch
(1.0 in.) diameter loading hole are shown in Fig. 2. The
preparation procedures.
dimensions should be scaled when other hole diameters are
7.1.3.2 The recommended starter notch for low- and
used. A hole diameter of 1.0 in. has been found satisfactory for
intermediate-strength steels is a notched brittle weld, as shown
specimens having 125 < W < 170 mm (5 < W < 6.7 in.).
in Fig. 6. It is produced by depositing a weld across the
NOTE 1—Specimens tested with the arrangement shown in Fig. 1 may
specimen thickness. Guidelines on welding procedures are
not exhibit an adequate segment of run-arrest fracturing, for example, at
given in Appendix X1.
testing temperatures well above the NDT temperature. In these
7.1.3.3 Alternative crack starter configurations (8) and em-
circumstances, the use of the loading arrangement shown in Fig. 3 has
brittlement methods may also be used. Examples of both
been found to be helpful (2, 7) and may be employed.
alternative configurations and alternative test methods are also
6.3 Displacement Gages—Displacement gages are used to
described in Appendix X1.
measure the crack-mouth opening displacement at 0.25W from
7.1.3.4 While it is expected that a values for the starting
the load-line. Accuracy within 2 % over the working range is
o
notch will typically lie in the range 0.30 W ≤ a ≤ 0.40 W, it is
required. Either the gage recommended in Test Method E399
o
sometimes useful to utilize values as low as 0.20 W. The lower
or a similar gage modified to accommodate conical seats is
initial value of a /W results in a greater and quicker drop in the
satisfactory. It is necessary to attach the gage in a fashion such
o
crack driving force as the crack extends. This may aid in
that seating contact with the specimen is not altered by the
jump of the crack. Two methods that have proven satisfactory arresting the running crack at a shorter final crack length and
could be useful for conditions where the crack extension is too
for doing this are shown in Fig. 4. Other gages can be used so
long as their accuracy is within 2 %. great with larger initial a /W values.
o
E1221 − 23
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
temperatures to be reached without difficulty. To minimize
temperature gradients through the specimen thickness, it is
necessary to surround the specimen with a good thermal
insulator. Prior to starting the test, the specimen should be held
at the test temperature for a time sufficient to allow the
specimen to attain a uniform temperature (to within 5 °F
(3 °C)).
8.3.2 Measure the specimen temperature with a thermo-
couple welded to the top surface of the specimen at a location
near the side groove, about 25 mm (1 in.) ahead of the starter
FIG. 3 Sectional View of a Loading Arrangement That May Be
notch. In reporting the test results, the test temperature shall be
Helpful When Testing Specimens at Higher Temperatures
the temperature measured on the specimen at the time of the
rapid run-arrest event.
8. Procedure
8.4 Loading Procedure:
8.1 Number of Tests—It is recommended that at least three
8.4.1 The test method calls for the use of a cyclic loading
valid test results be obtained at a single test temperature.
technique. In this technique, force is applied to the wedge until
a rapid crack initiates, or until the crack-mouth opening
8.2 Specimen Measurement—Measure the specimen
displacement (measured by the clip gage) reaches a predeter-
thickness, B, and the net thickness, B , to 61 % of B. Measure
N
mined value. If a rapid fracture has not initiated prior to the
the specimen width, W, to 61 % of W.
recommended maximum displacement being reached, the
8.3 Temperature Control and Measurement:
specimen is unloaded until the wedge loses contact with the
8.3.1 Specimens may be heated or cooled to the selected test
split-pin. The specimen is then reloaded in the same manner as
temperature by any appropriate method. A method that has
before and force application is once again terminated either by
been used successfully for elevated-temperature tests employs
initiation of a rapid crack or upon the opening displacement
electric-resistance heating tapes in combination with a variable
reaching a specified value. Successively higher values of the
power source. Tests at subambient temperatures have been
recommended maximum opening displacement are allowed on
conducted using cooling coils embedded in the specimen
each loading cycle, until a rapid crack initiates or until the test
support block (see Fig. 7); a controlled flow of liquid nitrogen
or other suitable coolant through the cooling coils permits low is discontinued.
E1221 − 23
(a) (b)
NOTE 1— Dimension A should be 0.002–0.010 in. (0.05–0.25 mm) less than the thickness of the clip gage arm.
NOTE 2—The knife edge can be attached to the specimen with mechanical fasteners or adhesives.
NOTE 3—The clip gage is installed by sliding it into the gap.
FIG. 4 Two Alternative Clip Gage Seating Arrangements Using (a) Knife Edges and (b) Using Conical Mounts
H = 0.6 W ± 0.005 W
S = (B − B )/2 ± 0.01 B
N
h # W/10
0.15 W # L # 0.25 W
0.20 W # a # 0.40 W
o
0.125 W ± 0.005 W # D # 0.250 W ± 0.005 W
FIG. 5 Geometry and Dimensions of a Crack-Line-Wedge-Loaded Compact-Crack-Arrest (CCA) Test Specimen that is Satisfactory for
Low and Medium Strength Steels
8.4.2 The loading technique of this test method does not plete strain reversal in the plastic zone near the root of the
allow direct measurement of the opening forces applied to the starter notch. The purpose of the cyclic loading technique is to
specimen by the wedge and split-pin assembly. The force identify and estimate the magnitude of these contributions.
applied to the specimen is therefore obtained from measure- 8.4.3 The effects of load train seating and weld bead
ments of the crack-mouth opening displacement. Components cracking can essentially be limited to the first loading cycle by
of the opening displacement that do not contribute to the an appropriate limit on the maximum opening displacement
opening force can occur. These have their origin primarily in imposed in that cycle. This limit is designed to keep the first
seating of the load train and clip gage, local cracking in the loading cycle linear elastic in a global sense. These influences
brittle weld, and interference with crack closure due to incom- can then be eliminated, with some degree of conservatism, by
E1221 − 23
0.69 σ W =B /B
YS N
δo 5 (1)
@~ ! #
1 max
E f a /W
~ !
o
where:
σ = static yield strength of the specimen material (or, in
YS
the case of the duplex specimen, of the crack-starter-
section material).
The other terms are as defined in 9.2. The testing machine
should be operated in displacement control, with a free-running
crosshead speed of 2 mm/min to 12 mm/min (0.1 in. ⁄min to 0.5
in./min).
NOTE 2—Rapid fracture initiation on the first loading cycle is unlikely
in the brittle weld CCA specimen. However, if a run-arrest event does
NOTE 1—Dimension h must be large enough to allow entry of the
occur, proceed with the calculations of K and K in the same manner as
o a
welding electrode being used.
if sequential load-unload cycling had been used. In subsequent tests of
FIG. 6 Details of the Notched Brittle Weld that is Recommended
replicate specimens, the first cycle displacement limit should be reduced
for Use as a Crack Starter for Low and Medium Strength Steels
sufficiently so that the first loading cycle can be completed without
intervention of a rapid fracture.
8.4.7 Unload the specimen by extracting the wedge in
preparation for a second loading cycle. The clip gage should
excluding the zero-force displacement offset recorded at the
remain in place during unloading and wedge removal to
end of the first loading cycle from the displacement used to
maintain a record of the displacement offset that occurs upon a
calculate K .
a
return to zero force.
8.4.4 The second undesirable contribution to the total mea-
sured crack opening displacement is due to the local yielding
NOTE 3—Wedge extraction and cyclic loading can be simplified greatly
by the use of the arrangement shown schematically in Fig. 7. Key features
that occurs around the root of the starter notch prior to
include a hold-down plate and a wedge that is fastened to the loading ram.
initiation of a rapid fracture. The formation and growth of this
However, the hold-down plate may not be required when using lubricant
plastic zone can be regarded as being mainly responsible for
in the form of TFE-fluorocarbon strips (see 6.2.1.1).
the zero-force displacement offsets that are recorded after
8.4.8 Without re-zeroing the recorder, reinsert and apply
completion of the first loading cycle, that is, between Cycles 2
force to the wedge at the same displacement rate as on the first
and 3, 3 and 4, etc. The influence of this effect could be
cycle. Continue loading until a rapid crack jump occurs or until
eliminated in its entirety by excluding all of the zero-force
the displacement measured with the clip gage reaches a
offset in opening displacement measured prior to the start of
predetermined value. The recommended maximum opening
the loading cycle during which the run-arrest event occurs.
displacement on the second and subsequent cycles can be
However, there is evidence to suggest that such a step may be
calculated from
overly conservative. Model tests have shown that, when the
plastic zone is well enclosed by the linear elastic stress field in
0.69 σ W =B /B
YS N
the specimen, nearly all of the offset in the zero-force displace- @ δ # 5 @1.010.25 n 2 1 #F G (2)
~ ! ~ !
o
n max
E f ~a /W!
o
ment is recovered if the plastic zone is severed by a saw cut or
where:
by a brittle crack (9). The degree to which this component of
the strain energy stored in the specimen is recovered in time to n = cycle number.
influence the run-arrest behavior of the rapid crack is unclear at
The other terms are the same as in (Eq 1). If an unstable
the present time. The K-calculation procedure of this test
crack is not initiated upon reaching the prescribed displace-
method therefore avoids the extremes of excluding all or none
ment limit, again unload and extract the wedge as specified in
of the zero-force displacement offsets which accumulate in the
8.4.7. Label the force/displacement record with the appropriate
second and subsequent loading cycles, and excludes one half of
cycle number and repeat 8.4.8.
these effects.
8.4.5 An autographic record of wedge-force versus crack-
NOTE 4—If a large number of load/unload cycles are required, it may be
necessary to relubricate the wedge and split-pin assembly. Increased
mouth-opening-displacement should be obtained. The recorder
friction will be indicated by an increased slope in the force-displacement
should not be re-zeroed between loading cycles since knowl-
record and the need for large reverse loads to extract the wedge.
edge of the accumulated zero-force displacement offset is
desired. It could also be useful to obtain information about the 8.4.9 To measure K , a segment of unstable crack extension
a
final segment of the opening-displacement versus time record must occur. The occurrence of unstable crack extension will
on an oscillograph or other high-rate recording device. This normally be apparent to the operator, both audibly and as an
would provide additional information about the nature of the abrupt force drop on the test record. (In the brittle weld CCA
run-arrest event. specimen, a force drop of 50 % to 60 % has been found to
8.4.6 Apply force to the wedge until the crack-mouth- indicate that a sufficient length of unstable fracturing has
opening-displacement measured by the clip gage reaches the occurred.) After the event, the operator should remove the
recommended maximum value given by: force on the wedge to avoid further crack propagation.
E1221 − 23
FIG. 7 Schematic Illustration of a Loading Arrangement that Facilitates Wedge Extraction When Using the Cyclic Loading Technique
8.4.10 If on subsequent loading cycles, it is observed that 8.5.2 After marking the crack front the specimen is broken
attempts to increase the opening displacement are accompanied completely in two. This can usually be done with the wedging
by a decrease in the applied wedge load, that is, stable tearing apparatus used in testing the specimen. The breaking open of
is occurring, it is unlikely that the specimen will exhibit rapid structural steel specimens is greatly facilitated by cooling them
run-arrest fracturing. It is recommended that under these in dry ice or liquid nitrogen.
circumstances, the test be discontinued. It may be helpful at
8.6 Measurement of Arrested Crack Size:
this point to remachine the specimen to remove the weld bead
8.6.1 The heat-tinted fracture surface should first be exam-
and the material ahead of the starter notch that has been
ined to determine whether it displays irregularities serious
subjected to plastic deformation. A fresh starter notch can then
enough to warrant exclusion of the test result. The occurrence
be prepared and the specimen retested at a lower temperature
of tunnelling, a failure to follow the side grooves on one or
(20 °C to 40 °C (35 °F to 70 °F) lower) in an attempt to obtain
both sides, and the presence of large, unbroken ligaments on
useful data from the specimen.
the fracture surface are all behaviors that may give erroneous
results for K . Annex A1 provides more detailed information
NOTE 5—A displacement limit beyond which the specimen is unlikely
a
to give successful results can be estimated from the following equation:
on this subject.
8.6.2 The average of three measurements defines the ar-
1.50 σ W =B /B
YS N
rested crack size, a . These measurements are to be made on
@δ # 5 (3) a
o limit
E f a /W
~ !
o
the heat-tinted fracture surface, to within 1 %, at the following
which is approximately twice the quantity calculated from (Eq 1).
positions: at the center (mid-thickness) of the specimen, and
NOTE 6—The quantity of material that must be removed from an
midway between the center and the bottom of the side groove
unsuccessful specimen can be approximated by the radius of the plastic
zone surrounding the starter notch under plane strain conditions, and on each side. Since crack front irregularities may make it
calculated from (K /σ ) /6π. A sufficient quantity of material must be
o YS difficult to determine the crack length at the specified locations,
machined out to remove any stable tearing that may have occurred.
it is suggested that the measurement be taken as a visual
8.5 Marking the Arrested Crack:
average across a strip of width, B /4, centered at each
N
8.5.1 The position of the arrested crack can be marked by
measurement location. Examples of sample crack size deter-
heat tinting. Heating at temperatures in the range 260 °C to
minations using this technique are also provided in Annex A1.
370 °C (500 °F to 700 °F) for 10 min to 90 min has proved
NOTE 7—It is recommended that a photographic record of the heat-
successful. Any time and temperature combination that clearly
tinted fracture surface be made a part of the test report, particularly if there
marks the arrested crack front is acceptable. The appearance of
are any unusual perturbations in the crack front contours. Descriptive
heat tinting on freshly machined (or ground and sanded) comments may also be helpful.
surfaces may provide a clue to the heat tinting progress on the
9. Calculation and Interpretation of Results
fracture surfaces. If a fractographic examination of the fracture
surfaces is to be performed, the use of lower heat tinting 9.1 Displacement Measurement:
temperatures or the marking of the arrested crack front by 9.1.1 From the autographic force-displacement record, sev-
means of fatigue may be desirable. eral displacement values should be determined. Fig. 8 is a
E1221 − 23
FIG. 8 Wedge-Force Versus Crack-Mouth-Opening-Displace-
ment Record for a Specimen Tested Using Cyclic Loading Techniques, that Displayed Rapid Run-Arrest Fracturing on the Fourth Load-
ing Cycle
typical force-displacement record for a specimen tested using from (Eq 5) for various values of x are given in Table 1. The
sequential load-unload cycling that did not exhibit unstable other terms in (Eq 4) are as follows:
cracking until the fourth loading cycle. The required displace-
E = Young’s modulus, MPa (ksi),
ments are as follows:
a = initial slot size, a , or final crack size, a , as deter-
o a
9.1.1.1 (δ ) = displacement offset at the end of the first load cycle
p 1
mined in 8.6, m (in.),
= δ in Fig. 8;
R 1
W = specimen width, m (in.),
9.1.1.2 (δ ) = total displacement offset at the end of the (n − 1) cycle
p n −1
= total displacement offset at the start of the last cycle
B = specimen thickness as shown in Fig. 5, m (in.),
= δ in Fig. 8;
R3
B = net thickness as shown in Fig. 5, m (in.), and
N
9.1.1.3 δ = displacement at the onset of unstable crack growth
o
δ = crack mouth opening displacement, m (in.).
= δ in Fig. 8;
P4
9.1.1.4 δ = displacement approximately 0.1 s after crack arrest
a
9.2.3 To calculate K , use a = a and δ = d . To calculate
o o o
= δ in Fig. 8;
P5
K , use a = a and δ = d . The quantities d and d are given
9.1.1.5 δ − δ = rapid increase in crack opening that frequently a a a o a
a o
accompanies the run-arrest event as follows:
= δ − δ in Fig. 8.
P5 P4
d 5 δ 2 δ , and (6)
~ !
o o p
n21
NOTE 8—The preferred interpretation of δ is the opening displacement
a
d 5 δ 2 δ 2 0.5 δ 2 δ 10.5 δ 2 δ (7)
~ ! @~ ! ~ ! # @ #
a o p p p a o
at about 2 ms after crack arrest. However, this measurement may not be 1 n21 1
possible with the instrumentation used. This testing practice assumes that
50.5@δ 1δ 2 ~δ ! 2 ~δ ! # (8)
o a p p
1 n21
δ at about 100 ms after crack arrest does not differ significantly from δ
a a
NOTE 9—The quantities in brackets in (Eq 7) both represent displace-
at 2 ms.
ment components whose exact contribution to the energy available to
9.1.2 In the brittle weld CCA specimen, a force drop of
50 % to 60 % has been found to indicate that a sufficient length
TABLE 1 Values of f(x) for use in (Eq 4)
of unstable fracture has occurred and that δ is a usable arrest
a
x f(x) x f(x) x f(x)
displacement value. See 9.3.2 and 9.3.4 for limitations on the
0.20 0.390 0.42 0.223 0.64 0.149
length of the run-arrest segment.
0.21 0.378 0.43 0.218 0.65 0.147
9.2 Calculation of K and K : 0.22 0.367 0.44 0.214 0.66 0.144
o Qa
0.23 0.357 0.45 0.210 0.67 0.141
9.2.1 Calculate K and K from the following:
o Qa
0.24 0.347 0.46 0.206 0.68 0.139
0.25 0.337 0.47 0.202 0.69 0.136
=B/B
N
0.26 0.328 0.48 0.198 0.70 0.133
K 5 E δ f x MPa=m ksi=in. (4)
~ ! ~ !
0.27 0.319 0.49 0.194 0.71 0.131
=W
0.28 0.310 0.50 0.191 0.72 0.128
0.29 0.302 0.51 0.188 0.73 0.125
where:
0.30 0.294 0.52 0.184 0.74 0.122
0.5
f ~x! 5 ~1 2 x! ~0.748 2 2.176 x (5) 0.31 0.287 0.53 0.181 0.75 0.119
0.32 0.280 0.54 0.178 0.76 0.117
2 3 4 0.33 0.273 0.55 0.175 0.77 0.114
13.56 x 2 2.55x 10.62 x ) and
0.34 0.266 0.56 0.172 0.78 0.111
0.35 0.260 0.57 0.169 0.79 0.108
x = a/W.
0.36 0.254 0.58 0.166 0.80 0.105
9.2.2 The expression for f(x) used here is based on a curve
0.37 0.248 0.59 0.163 0.81 0.102
fit to boundary value collocation results and an exact limit 0.38 0.243 0.60 0.160 0.82 0.098
0.39 0.237 0.61 0.158 0.83 0.095
solution (10). The curve fit is considered to be accurate within
0.40 0.232 0.62 0.155 0.84 0.092
1 % over the range 0.20 ≤ x ≤ 1, and is in close agreement with
0.41 0.227 0.63 0.152 0.85 0.088
experimental compliance results (11). Values of f(x) computed
E1221 − 23
drive the running crack is unclear at the present time. The rationale for the
10.1.2.3 Yield strength (offset − 0.2 %) as determined by
selection of the premultiplier of 0.5 for each of these quantities is
Test Methods E8/E8M, and
discussed in Ref (2). (Eq 8) is simply a mathematical simplification of (Eq
10.1.2.4 Dynamic yield strength used in 9.3.2 and 9.3.3.
7) and may be more convenient to use from a computational standpoint.
10.1.3 Test Temperature:
NOTE 10—If a rapid run-arrest event occurs on the first loading cycle,
(Eq 8) should be used with (δ ) and (δ ) set equal to zero.
10.1.4 Starter Notch:
p n −1 p 1
10.1.4.1 Type of brittle weld, if any,
9.3 Validity Requirements:
10.1.4.2 Notch height, h, and
9.3.1 The value of K calculated from (Eq 4) can be
Qa
considered a linear-elastic plane-strain value, K , provided the 10.1.4.3 Notch root radius, ρ.
Ia
criteria described in 9.3.2 – 9.3.4 and summarized in Table 2 10.1.5 Specimen Dimensions:
are satisfied. Comments on the adequacy of these requirements
10.1.5.1 Specimen thickness, B,
can be found in Refs (2) and (12). It should also be pointed out
10.1.5.2 Net thickness, B ,
N
that in some instances, the extrapolation of a combined set of
10.1.5.3 Thickness ratio, B /B, and
N
test results, including some which would be deemed invalid by
10.1.5.4 Width, W.
these criteria, may be useful in predicting the behavior of large
10.1.6 Crack Size Measurements:
structures.
10.1.6.1 Method used for marking the arrested crack front,
9.3.1.1 Use is made in the following of σ , a formal
Yd
10.1.6.2 Crack size at machined notch, a , and
o
dynamic yield strength estimate for appropriate loading times
10.1.6.3 Crack size at arrest,
at the test temperature. For structural steels, it is being assumed
(1) At mid-thickness, a ,
here that σ is 205 MPa (30 ksi ) greater than the yield
Yd
(2) At ⁄4 points of net thickness, a and a , and
1 3
strength, σ , measured by Test Methods E8/E8M.
YS
(3) Average crack size at arrest, a = (a + a + a )/3.
a 1 2 3
NOTE 11—The extremely high strain rates associated with yielding near 10.1.7 Test Record:
the tip of a fast running crack and the abrupt nature of crack arrest suggest
10.1.7.1 Force and displacement records and associated
that the true elevation of σ over σ should be much greater. The value
Yd YS
calculations,
of σ that is being used here is therefore thought to substantially
Yd
10.1.7.2 First cycle limiting displacement, [(δ ) ] ,
o 1 max
underestimate the actual effective resistance to plastic flow at crack arrest
10.1.7.3 Opening displacement increment for subsequent
(12).
cycles, (δ ) = 0.25 [(δ ) ] ,
o inc o 1 max
9.3.2 The unbroken ligament, W − a , must equal or exceed
a
10.1.7.4 Number of load/unload cycles, n,
both 0.15W and 1.25 (K /σ ) .
Qa Yd
10.1.7.5 Displacements measured from force-displacement
9.3.3 The thickness, B, must equal or exceed 1.0 (K
Qa
records,
/σ ) .
Yd
(1) Displacement offset at end of first loading cycle, (δ ) ,
9.3.4 The minimum crack jump, a − a , must be at least p 1
a o
(2) Total displacement offset accumulated prior to start of
twice the notch height, h, defined in Fig. 5, and greater than the
last loading cycle, (δ ) ,
plane-stress plastic zone radius associated with the initial p n −1
(3) Displacement at onset of unstable crack growth, δ ,
loading, (K /σ ) /2π. o
o YS
(4) Displacement at crack arrest, δ , and
a
NOTE 12—If a duplex specimen is used, the alternative requirement is
(5) Displacement increase accompanying the run-arrest
that the crack penetrate a distance equal to or greater than B into the test
N
event, δ − δ ,
a o
section.
10.1.7.6 Displacements used to calculate K and K ,
o Qa
(1) Displacement used to calculate K , d according to Eq 6
10. Report o 0
(2) Displacement used to calculate K , d according to Eq
a 0
10.1 Report the following information:
7 or Eq 8.
10.1.1 Test Identification:
10.1.7.7 Force drop as a percentage of P .
max
10.1.1.1 Date,
10.1.8 Calculated Values of K— and K (K ):
o Qa Ia
10.1.1.2 Specimen number, and
10.1.8.1 K— , and
o
10.1.1.3 Crack plane orientation in accordance with Termi-
10.1.8.2 K (K ) .
Qa Ia
nology E1823.
10.1.9 Validity Requirements (see Table 2):
10.1.2 Material:
10.1.9.1 Uncracked ligament length,
10.1.2.1 Material type,
(1) Compared to 0.15W, and
10.1.2.2 Young’s modulus,
(2) Compared to 1.25 (K /σ ) ,
Qa Yd
10.1.9.2 Thickness, compared to 1.0 (K /σ ) ,
Qa Yd
10.1.9.3 Crack jump length,
TABLE 2 Summary of Criteria Used to Ensure That K is a
Qa
(1) Compared to 2N, and
Linear Elastic, Plane-Strain Value 2
(2) Compared to (K /σ ) /2π.
o YS
Feature Criterion
10.1.10 Photographic Record of Fracture Surfaces and
Unbroken ligament (A) W − a $ 0.15W
a
Descriptive Comments (Optional):
Unbroken ligament (B) W − a $ 1.25 (K /σ )
a a Yd
Thickness (C) B $ 1.0 (K /σ )
a Yd
Crack-jump length (D) a − a $ 2h
a o 11. Precision and Bias
Crack-jump length (E) a − a $ (K /σ ) /2π
a o o YS
11.1 Precision:
E1221 − 23
TABLE 3 Grand Means and Standard Deviations for K for
11.1.1 The precision of a K determination by this test
Ia
Ia
Three Steels as Obtained From a Large Interlaboratory
method is a function of the precision and bias of the various
A
Round Robin Test Program
measurements of linear dimensions of the specimen and testing
B C D D
Material Tested A514 A588 A533B A533B
fixtures, the precision of the displacement measurements, the
Test Temperature −30 °C −30 °C 10 °C 25 °C
precision and bias of the recording devices used to produce the
No. of Test Results 12 40 30 28
force displacement record, and the precision and bias of the 88.4 61.5 78.2 83.4
Mean K , MPa m
Ia
œ
Standard Deviation, 10.2 6.4 9.7 10.6
measurements of the arrested crack size. It is not possible to
(12 %) (10 %) (12 %) (13 %)
MPa m and percent
œ
make meaningful statements concerning precision and bias for
A
A total of 21 laboratories reported test results from the program.
all of these measurements. However, it is possible to derive
B
Specimens were cut from 50.8 mm (2-in.) thick rolled plate and tested full
useful information concerning the precision of a K measure-
Ia
thickness in an L-T orientation; σ = 890 MPa (129 ksi); NDT = −50 °C (−58 °F);
YS
ment in a global sense from the results of an interlaboratory RT = −12 °C (10 °F ).
NDT
C
Specimens were cut from 50.8 mm (2 in.) thick rolled plate and tested full
round-robin test program that was conducted to evaluate the
thickness in an L-T orientation; σ = 330 MPa (48 ksi); NDT = −10 °C (14 °F);
YS
originally proposed test method on which this test method is
RT = −9 °C (16 °F ).
NDT
D
Specimens of 50.8 mm (2 in.) thickness were cut from 254 mm (10 in.) thick
based (2).
rolled plate and tested in an L-S orientation; σ = 480 MPa (70 ksi);
YS
11.1.2 The results from this program are summarized in
NDT = −12 °C (10 °F); RT = −2 °C (28 °F).
NDT
Table 3. It should be appreciated that the measures of precision
shown in Table 3 apply to tests conducted with materials that
exhibit strong transitional behavior in terms of temperature. A
exhibit significant inhomogeneity, and a size effect may be
larger degree of scatter in K measurements could therefore be
Ia
apparent when testing specimens of different sizes, with tests
expected in tests conducted higher in the transition range,
on smaller specimens being characterized by larger scatter than
although the coefficient of variation appears to be temperature
tests on larger specimens.
insensitive for some materials (6). The materials tested also
11.2 Bias—There is no accepted standard value for the
plane-strain crack-arrest fracture toughness of any material. In
Information on K round-robin data and the round-robin program is available
Ia
the absence of such a true value, any statement concerning bias
in Ref (2), a copy of which is available from ASTM Headquarters. Request
RR:E8-1003. is not meaningful.
ANNEX
(Mandatory Information)
A1. GUIDELINES FOR ASSESSING FRACTURE SURFACE ACCEPTABILITY AND PROCEDURES FOR
DETERMINING THE ARRESTED CRACK SIZE
A1.1 Introduction: intended to serve as a set of guidelines for the personnel
involved in obtaining crack-arrest toughness data.
A1.1.1 The idealized fracture surface of a crack arrest
specimen is flat, continuous, and straight-fronted. This ideal-
A1.1.3 The final decision as to which fracture surfaces will
ization can be closely approached in practice, as evidenced by
be classified as unacceptable presently rests primarily on the
Fig. A1.1 and Fig. A1.2. However, the fracture surfaces of
judgment of the individual (or individuals) performing and
crack-arrest specimens can be complicated by features that,
evaluating the test. This judgement should be based on
when present in excess, can lead to questionable results for the
experience, or on some knowledge of what is representative for
crack-arrest fracture toughness of the material being tested.
the particular steel and test temperature combination under
This annex provides guidelines for identifying, from the
consideration. Judgmental decisions of this nature are clearly
fracture surface appearance, test results that are probably not
undesirable from a standards viewpoint. However, the alterna-
representative of the bulk of the material being tested. It also
tive would be to disregard test results from all specimens with
provides guidelines for determining the arrested crack size, a ,
a
any degree of fracture surface irregularity. This would not only
for a specimen with an irregular crack front.
reduce the percentage of successful, valid tests to a very small
A1.1.2 Deviations from the ideal fracture surface appear-
number, but would also eliminate virtually all tests performed
ance generally fall into three broad categories. These are: the
under certain conditions, for example, at temperatures well into
presence of remaining ligaments, a lack of crack front
the transition range for a given material. As the testing
straightness, and crack propagation out of the plane of the side
technology involved here matures, it is anticipated that this
grooves. The extent to which one or more of these behaviors
annex will be updated to a more quantitative level.
can occur without adversely affecting the test result cannot be
easily quantified at the present time. The purpose of this annex
A1.2 Fracture Surface Acceptability:
is to provide a basis for the decision-making process that is
required in assessing fracture surface acceptability and it is A1.2.1 Remaining Ligaments:
E1221 − 23
A1.2.1.1 In a number of steels, portions of the surface curve determined using Methods E23.) As the test temperature
formed by a rapid fracture frequently remain unbroken. These increases to the limit at which a rapid fract
...