ASTM E1304-97(2020)
(Test Method)Standard Test Method for Plane-Strain (Chevron-Notch) Fracture Toughness of Metallic Materials
Standard Test Method for Plane-Strain (Chevron-Notch) Fracture Toughness of Metallic Materials
SIGNIFICANCE AND USE
5.1 The fracture toughness determined by this test method characterizes the resistance of a material to fracture by a slowly advancing steady-state crack (see 3.2.5) in a neutral environment under severe tensile constraint. The state of stress near the crack front approaches plane strain, and the crack-tip plastic region is small compared with the crack size and specimen dimensions in the constraint direction. A KIv or KIvj value may be used to estimate the relation between failure stress and defect size when the conditions described above would be expected, although the relationship may differ from that obtained from a KIc value (see Note 1). Background information concerning the basis for development of this test method in terms of linear elastic fracture mechanics may be found in Refs (6-15).
5.1.1 The KIv, KIvj, or KIvM value of a given material can be a function of testing speed (strain rate) and temperature. Furthermore, cyclic forces can cause crack extension at KI values less than KIv, and crack extension can be increased by the presence of an aggressive environment. Therefore, application of KIv in the design of service components should be made with an awareness of differences that may exist between the laboratory tests and field conditions.
5.1.2 Plane-strain fracture toughness testing is unusual in that there can be no advance assurance that a valid KIv, KIvj, or KIvM will be determined in a particular test. Therefore, it is essential that all the criteria concerning the validity of results be carefully considered as described herein.
5.2 This test method can serve the following purposes:
5.2.1 To establish the effects of metallurgical variables such as composition or heat treatment, or of fabricating operations such as welding or forming, on the fracture toughness of new or existing materials.
5.2.2 For specifications of acceptance and manufacturing quality control, but only when there is a sound basis for specification of minimum ...
SCOPE
1.1 This test method covers the determination of plane-strain (chevron-notch) fracture toughnesses, KIv or KIvM, of metallic materials. Fracture toughness by this method is relative to a slowly advancing steady state crack initiated at a chevron-shaped notch, and propagating in a chevron-shaped ligament (Fig. 1). Some metallic materials, when tested by this method, exhibit a sporadic crack growth in which the crack front remains nearly stationary until a critical load is reached. The crack then becomes unstable and suddenly advances at high speed to the next arrest point. For these materials, this test method covers the determination of the plane-strain fracture toughness, KIvj or KIvM, relative to the crack at the points of instability.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
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Standards Content (Sample)
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: E1304 − 97 (Reapproved 2020)
Standard Test Method for
Plane-Strain (Chevron-Notch) Fracture Toughness of
Metallic Materials
This standard is issued under the fixed designation E1304; 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.
1. Scope priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.1 This test method covers the determination of plane-
1.5 This international standard was developed in accor-
strain (chevron-notch) fracture toughnesses, K or K ,of
Iv IvM
dance with internationally recognized principles on standard-
metallic materials. Fracture toughness by this method is
ization established in the Decision on Principles for the
relative to a slowly advancing steady state crack initiated at a
Development of International Standards, Guides and Recom-
chevron-shaped notch, and propagating in a chevron-shaped
mendations issued by the World Trade Organization Technical
ligament (Fig. 1). Some metallic materials, when tested by this
Barriers to Trade (TBT) Committee.
method, exhibit a sporadic crack growth in which the crack
front remains nearly stationary until a critical load is reached.
2. Referenced Documents
The crack then becomes unstable and suddenly advances at
2.1 ASTM Standards:
highspeedtothenextarrestpoint.Forthesematerials,thistest
E4Practices for Force Calibration and Verification of Test-
method covers the determination of the plane-strain fracture
toughness, K or K , relative to the crack at the points of ing Machines
Ivj IvM
E8/E8MTest Methods for Tension Testing of Metallic Ma-
instability.
terials
NOTE 1—One difference between this test method and Test Method
E399Test Method for Linear-Elastic Plane-Strain Fracture
E399 (which measures K ) is that Test Method E399 centers attention on
Ic
Toughness of Metallic Materials
the start of crack extension from a fatigue precrack. This test method
E1823TerminologyRelatingtoFatigueandFractureTesting
makes use of either a steady state slowly propagating crack, or a crack at
the initiation of a crack jump. Although both methods are based on the
principles of linear elastic fracture mechanics, this difference, plus other
3. Terminology
differences in test procedure, may cause the values from this test method
tobelargerthan K valuesinsomematerials.Therefore,toughnessvalues 3.1 Definitions:
Ic
determined by this test method cannot be used interchangeably with K .
Ic 3.1.1 The terms described in Terminology E1823 are appli-
cable to this test method.
1.2 This test method uses either chevron-notched rod speci-
−3/2
3.1.2 stress-intensity factor, K [FL ]—the magnitude of
mens of circular cross section, or chevron-notched bar speci- I
the mathematically ideal crack-tip stress field (stress-field
mens of square or rectangular cross section (Figs. 1-10). The
singularity) for mode I in a homogeneous linear-elastic body.
terms “short rod” and “short bar” are used commonly for these
3.1.2.1 Discussion—Valuesof Kformode Iaregivenbythe
types of chevron-notched specimens.
following equation:
1.3 The values stated in inch-pound units are to be regarded
½
K 5 limit σ 2πr
@ #
I y x
as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only r →0
x
and are not considered standard.
where:
1.4 This standard does not purport to address all of the
r = distance from the crack tip to a location where the
x
safety concerns, if any, associated with its use. It is the
stress is calculated and
responsibility of the user of this standard to establish appro-
σ = the principal stress r normal to the crack plane.
y x
3.2 Definitions of Terms Specific to This Standard:
This test method is under the jurisdiction ofASTM 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 May 15, 2020. Published May 2020. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1989. Last previous edition approved in 2014 as E1304–97(2014). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/E1304-97R20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1304 − 97 (2020)
longerchangewithfurthercrackextension.Althoughcrack-tip
conditions can be a function of crack velocity, the steady-state
crack-tip conditions for metals have appeared to be indepen-
dent of the crack velocity within the range attained by the
loading rates specified in this test method.
3.2.6 effective unloading slope ratio, r—the ratio of an
effective unloading slope to that of the initial elastic loading
slope on a test record of force versus specimen mouth opening
displacement.
3.2.6.1 Discussion—This unloading slope ratio provides a
methodofdeterminingthecracklengthatvariouspointsonthe
NOTE 1—The crack commences at the tip of the chevron-shaped
test record and therefore allows evaluation of stress intensity
ligament and propagates (shaded area) along the ligament, and has the
coefficient Y* (see 3.2.11). The effective unloading slope ratio
length “a” shown. (Not to scale.)
is measured by performing unloading-reloading cycles during
FIG. 1 Schematic Diagrams of Chevron-Notched Short Rod (a)
thetestasindicatedschematicallyinFig.4andFig.5.Foreach
and Short Bar (b) Specimens
unloading-reloading trace, the effective unloading slope ratio,
r, is defined in terms of the tangents of two angles:
3.2.1 plane-strain (chevron-notch) fracture toughness, K
Iv
−3/2
r 5 tan θ/tanθ
o
or K [FL ]—under conditions of crack-tip plane strain in a
Ivj
chevron-notched specimen: K relates to extension resistance
Iv
where:
with respect to a slowly advancing steady-state crack. K
Ivj
tan θ = the slope of the initial elastic line, and
o
relates to crack extension resistance with respect to a crack
tan θ = the slope of an effective unloading line.
which advances sporadically.
Theeffectiveunloadinglineisdefinedashavinganoriginat
3.2.1.1 Discussion—For slow rates of loading the fracture
the high point where the displacement reverses direction on
toughness, K or K , is the value of stress-intensity factor as
Iv Ivj
unloading (slot mouth begins to close) and joining the low
measuredusingtheoperationalprocedure(andsatisfyingallof
point on the reloading line where the force is one half that at
the validity requirements) specified in this test method.
the high point.
3.2.2 plane-strain (chevron-notch) fracture toughness, K
IvM
3.2.6.2 Discussion—For a brittle material with linear elastic
−3/2
[FL ]—determined similarly to K or K (see 3.2.1) using
Iv Ivj
behavior the unloading-reloading lines of an unloading-
the same specimen, or specimen geometries, but using a
reloading cycle would be linear and coincident. For many
simpler analysis based on the maximum test force. The
engineering materials, deviations from linear elastic behavior
analysisisdescribedinAnnexA1.Unloading-reloadingcycles
and hysteresis are commonly observed to a varying degree.
as described in 3.2.6 are not required in a test to determine
These effects require an unambiguous method of obtaining an
K . 3
IvM
effective unloading slope from the test record (6-5).
3.2.3 smooth crack growth behavior—generally,thattypeof
3.2.6.3 Discussion—Although r is measured only at those
crack extension behavior in chevron-notch specimens that is
crack positions where unloading-reloading cycles are
characterized primarily by slow, continuously advancing crack
performed, r is nevertheless defined at all points during a
growth, and a relatively smooth force displacement record
chevron-notch specimen test. For any particular point it is the
(Fig. 4). However, any test behavior not satisfying the condi-
value that would be measured for r if an unloading-reloading
tions for crack jump behavior is automatically characterized as
cycle were performed at that point.
smooth crack growth behavior.
3.2.7 critical slope ratio, r —the unloading slope ratio at
c
3.2.4 crack jump behavior—in tests of chevron-notch
the critical crack length.
specimens, that type of sporadic crack growth which is
3.2.8 critical crack length—the crack length in a chevron-
characterizedprimarilybyperiodsduringwhichthecrackfront
notch specimen at which the specimen’s stress-intensity factor
is nearly stationary until a critical force is reached, whereupon
coefficient, Y* (see 3.2.11 and Table 3), is a minimum, or
the crack becomes unstable and suddenly advances at high
equivalently, the crack length at which the maximum force
speed to the next arrest point, where it remains nearly station-
would occur in a purely linear elastic fracture mechanics test.
ary until the force again reaches a critical value, etc. (see Fig.
At the critical crack length, the width of the crack front is
5).
approximately one third the dimension B (Figs. 2 and 3).
3.2.4.1 Discussion—A chevron-notch specimen is said to
3.2.9 high point, High—the point on a force-displacement
have a crack jump behavior when crack jumps account for
plot, at the start of an unloading-reloading cycle, at which the
more than one half of the change in unloading slope ratio (see
displacement reverses direction, that is, the point at which the
3.2.6) as the unloading slope ratio passes through the range
specimen mouth begins closing due to unloading (see points
from0.8r to1.2r (see3.2.6and3.2.7,and8.3.5.2).Onlythose
c c
labeled High in Figs. 4 and 5).
sudden crack advances that result in more than a 5% decrease
inforceduringtheadvancearecountedascrackjumps(Fig.5).
3.2.5 steady-state crack—a crack that has advanced slowly
The boldface numbers in parentheses refer to the list of references at the end
until the crack-tip plastic zone size and crack-tip sharpness no of this standard.
E1304 − 97 (2020)
NOTE 1—See Table 1 for tolerances and other details.
FIG. 2 Rod Specimens Standard Proportions
NOTE 1—See Table 2 for tolerances and other details.
FIG. 3 Bar Specimens Standard Proportions
3.2.10 low point, Low—thepointonthereloadingportionof displacement of the specimen mouth.An autographic record is
an unloading-reloading cycle where the force is one half the made of the load versus mouth opening displacement and the
high point force (see points labeled Low in Figs. 4 and 5).
slopes of periodic unloading-reloading cycles are used to
calculate the crack length based on compliance techniques.
3.2.11 stress-intensity factor coeffıcient, Y*—a dimension-
These crack lengths are expressed indirectly as slope ratios.
less parameter that relates the applied force and specimen
Thecharacteristicsoftheforceversusmouthopeningdisplace-
geometry to the resulting crack-tip stress-intensity factor in a
chevron-notch specimen test (see 9.6.3). ment trace depend on the geometry of the specimen, the
3.2.11.1 Discussion—Values of Y* can be found from the specimen plasticity during the test, any residual stresses in the
graphsinFig.10,orfromthetabulationsinTable4orfromthe specimen, and the crack growth characteristics of the material
polynominal expressions in Table 5. beingtested.Ingeneral,twotypesofforceversusdisplacement
traces are recognized, namely, smooth behavior (see3.2.3) and
3.2.12 minimum stress-intensity factor coeffıcient, Y* —the
m
crack jump behavior (see 3.2.4).
minimum value of Y*(Table 3).
4.1.1 In metals that exhibit smooth crack behavior (3.2.3),
4. Summary of Test Method
thecrackinitiatesatalowforceatthetipofasufficientlysharp
chevron, and each incremental increase in its length corre-
4.1 Thistestmethodinvolvestheapplicationofaloadtothe
mouth of a chevron-notched specimen to induce an opening sponds to an increase in crack front width and requires further
E1304 − 97 (2020)
R# 0.010B
φ # 60°
s
t# 0.03B
NOTE 1—These requirements are satisfied by slots with a round bottom
whenever t ≤ 0.020B.
FIG. 6 Slot Bottom Configuration
FIG. 4 Schematic of a Load-Displacement Test Record for
Smooth Crack Growth Behavior, with Unloading/Reloading
Cycles, Data Reduction Constructions, and Definitions of Terms
FIG. 5 Schematic of a Load-Displacement Test Record for Crack
NOTE 1—Machine finish all over equal to or better than 64 µin.
Jump Behavior, with Unloading/Reloading Cycles, Data Reduc-
tion Constructions, and Definitions of Terms NOTE 2—Unless otherwise specified, dimensions 60.010B; angles
62°.
NOTE 3—Grip hardness should be RC=45 or greater.
increase in force. This force increase continues until a point is FIG. 7 Suggested Loading Grip Design
reached where further increases in force provide energy in
excess of that required to advance the crack. This maximum
forcepointcorrespondstoawidthofcrackfrontapproximately toughness determined by this procedure is termed K .An
Iv
one third the specimen diameter or thickness. If the loading alternative procedure, described in Annex A1, omits the
systemissufficientlystiff,thecrackcanbemadetocontinueits unloading cycles and uses the maximum test force to calculate
smooth crack growth under decreasing force. Two unloading- a plane-strain fracture toughness K , where M signifies the
IvM
reloadingcyclesareperformedtodeterminethelocationofthe use of the maximum force. Values of K versus K are
Iv IvM
crack, the force used to calculate K , and to provide validity discussed in Annex A1.
Iv
checks on the test. The fracture toughness is calculated from 4.1.2 A modified procedure is used to determine K when
Ivj
theforcerequiredtoadvancethecrackwhenthecrackisatthe crack jump behavior is encountered. In this procedure,
critical crack length (see 3.2.8). The plane-strain fracture unloading-reloading cycles are used to determine the crack
E1304 − 97 (2020)
NOTE 1—Compiled from Refs (1), (2), (3), and (4).
FIG. 10 Normalized Stress-Intensity Factor Coefficients as a
Function of Slope Ratio (r) for Chevron-Notch Specimens
TABLE 1 Rod Dimensions
NOTE 1—All surfaces to be 64-µin. finish or better.
NOTE 2—Side grooves may be made with a plunge cut with a circular
blade, such that the sides of the chevron ligament have curved profiles,
provided that the
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