ASTM E399-90(1997)
(Test Method)Standard Test Method for Plane-Strain Fracture Toughness of Metallic Materials
Standard Test Method for Plane-Strain Fracture Toughness of Metallic Materials
SCOPE
1.1 This test method covers the determination of the plane-strain fracture toughness (KIc) of metallic materials by tests using a variety of fatigue-cracked specimens having a thickness of 0.063 in. (1.6 mm) or greater. The details of the various specimen and test configurations are shown in Annexes A1 through A7 and A9. Note 1-Plane-strain fracture toughness tests of thinner materials that are sufficiently brittle (see 7.1) can be made with other types of specimens (1). There is no standard test method for testing such thin materials.
1.2 This test method also covers the determination of the specimen strength ratio Rsx where x refers to the specific specimen configuration being tested. This strength ratio is a function of the maximum load the specimen can sustain, its initial dimensions and the yield strength of the material.
1.3 Measured values of plane-strain fracture toughness stated in inch-pound units are to be regarded as standard.
1.4 This test method is divided into two main parts. The first part gives general information concerning the recommendations and requirements for Ic testing. The second part is composed of annexes that give the displacement gage design, fatigue cracking procedures, and special requirements for the various specimen configurations covered by this method. In addition, an annex is provided for the specific procedures to be followed in rapid-load plane-strain fracture toughness tests. General information and requirements common to all specimen types are listed as follows: Sections Referenced Documents 2 Terminology 3 Stress-Intensity Factor 3.1.1 Plane-Strain Fracture Toughness 3.1.2 Summary of Test Method 4 Significance and Use 5 Precautions 5.1.1 to 5.1.3 Practical Applications 5.2 Apparatus 6 Loading Fixtures 6.2 Displacement Gage Design Annex A1 Displacement Measurements 6.3 Sections Specimens Size, Configurations, and Preparation 7 Specimen Size Estimates 7.1 Standard and Alternative Specimen Configurations 7.2 Forms of Fatigue Crack Starter Notch 7.3.1 Fatigue Cracking Annex A2 Crack Extension Beyond Starter 7.3.2.2 Measurements before Testing Thickness 8.2.1 Width 8.2.3 Starter Notch Root Radius 7.3.1 Specimen Testing Loading Rate 8.3 Test Record 8.4 Measurements after Testing Crack Length 8.2.2 Crack Plane Angle 8.2.4 Calculation and Interpretation of Results 9 Analysis of Test Record 9.1 Validity Requirements on Pmax/PQ 9.1.2 Validity Requirements on Specimen Size 9.1.3 Crack Plane Orientation Designations 9.2 Fracture Appearance Descriptions 9.3 Reporting 10 Precision and Bias 11 Special Requirements for Rapid Load K1c (t) Tests Annex A7 Bend Specimen SE(B) Annex A3 Compact Specimen C(T) Annex A4 Arc-Shaped Tension Specimen A(T) Annex A5 Disk-Shaped Compact Specimen DC(T) Annex A6 Arc-Shaped Bend Specimen Annex A9
1.5 Special requirements for the various specimen configurations appear in the following order:
1.6 This standard does not purport to address the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E 399 – 90 (Reapproved 1997)
Standard Test Method for
Plane-Strain Fracture Toughness of Metallic Materials
This standard is issued under the fixed designation E399; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope Generalinformationandrequirementscommontoallspecimen
types are listed as follows:
1.1 This test method covers the determination of the plane-
Sections
strain fracture toughness (K ) of metallic materials by tests
Ic
using a variety of fatigue-cracked specimens having a thick-
Referenced Documents 2
ness of 0.063 in. (1.6 mm) or greater. The details of the
Terminology 3
Stress-Intensity Factor 3.1.1
various specimen and test configurations are shown in Annex
Plane-Strain Fracture Toughness 3.1.2
A1-Annex A7 and Annex A9.
Summary of Test Method 4
Significance and Use 5
NOTE 1—Plane-strain fracture toughness tests of thinner materials that
Precautions 5.1.1-5.1.3
aresufficientlybrittle(see7.1)canbemadewithothertypesofspecimens
Practical Applications 5.2
(1). There is no standard test method for testing such thin materials.
Apparatus 6
Loading Fixtures 6.2
1.2 This test method also covers the determination of the
Displacement Gage Design Annex A1
specimen strength ratio R where x refers to the specific Displacement Measurements 6.3
sx
Specimen Size, Configurations, and Prepara- 7
specimen configuration being tested. This strength ratio is a
tion
function of the maximum load the specimen can sustain, its
Specimen Size Estimates 7.1
initial dimensions and the yield strength of the material. Standard and Alternative Specimen Configu- 7.2
rations
1.3 Measured values of plane-strain fracture toughness
Forms of Fatigue Crack Starter Notch 7.3.1
stated in inch-pound units are to be regarded as standard.
Fatigue Cracking Annex A2
1.4 Thistestmethodisdividedintotwomainparts.Thefirst Crack Extension Beyond Starter 7.3.2.2
Measurements before Testing
part gives general information concerning the recommenda-
Thickness 8.2.1
tions and requirements for K testing. The second part is
Ic Width 8.2.3
composed of annexes that give the displacement gage design, Starter Notch Root Radius 7.3.1
Specimen Testing
fatigue cracking procedures, and special requirements for the
Loading Rate 8.3
various specimen configurations covered by this method. In
Test Record 8.4
addition, an annex is provided for the specific procedures to be Measurements after Testing
Crack Length 8.2.2
followed in rapid-load plane-strain fracture toughness tests.
Crack Plane Angle 8.2.4
Calculation and Interpretation of Results 9
Analysis of Test Record 9.1
Validity Requirements on P /P 9.1.2
max Q
This test method is under the jurisdiction ofASTM Committee E-8 on Fatigue
Validity Requirements on Specimen Size 9.1.3
and Fracture and is the direct responsibility of Subcommittee E08.07 on Lin-
Crack Plane Orientation Designations 9.2
ear–Elastic Fracture.
Fracture Appearance Descriptions 9.3
Current edition approved Nov. 30, 1990. Published April 1991. Originally
Reporting 10
published as E399–70T. Last previous edition E399–83.
2 Precision and Bias 11
For additional information relating to the fracture toughness testing of alumi-
Special Requirements for Rapid Load K (t) Annex A7
Ic
inum alloys, see Method B645.
Tests
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this test method.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 399 – 90 (1997)
1.5 Special requirements for the various specimen configu- 3.1.2.2 Discussion—See also definitions of crack-
rations appear in the following order: extension resistance, crack-tip plane strain, and mode.
3.1.2.3 Discussion—Inthistestmethod,mode1isassumed.
Bend Specimen SE(B) Annex A3
Compact Specimen C(T) Annex A4
3.1.3 crack plane orientation—anidentificationoftheplane
Arc-Shaped Tension Specimen A(T) Annex A5
anddirectionofafractureinrelationtoproductgeometry.This
Disk-Shaped Compact Specimen DC(T) Annex A6
identification is designated by a hyphenated code with the first
Arc-Shaped Bend Specimen A(B) Annex A9
letter(s) representing the direction normal to the crack plane
1.6 This standard does not purport to address all of the
and the second letter(s) designating the expected direction of
safety concerns, if any, associated with its use. It is the
crack propagation.
responsibility of the user of this standard to establish appro-
3.1.3.1 Discussion—The fracture toughness of a material
priate safety and health practices and determine the applica-
usuallydependsontheorientationanddirectionofpropagation
bility of regulatory limitations prior to use.
of the crack in relation to the anisotropy of the material, which
depends, in turn, on the principal directions of mechanical
2. Referenced Documents
working or grain flow. The orientation of the crack plane
2.1 ASTM Standards:
should be identified wherever possible in accordance with the
E8 TestMethodsforTensionTestingofMetallicMaterials
followingsystems(11).Inaddition,theproductformshouldbe
E337 Test Method for Measuring Humidity with a Psy-
identified(forexample,straight-rolledplate,cross-rolledplate,
chrometer (the Measurement of Wet- and Dry-Bulb Tem-
pancake forging, etc.).
peratures)
3.1.3.2 Discussion—For rectangular sections, the reference
E338 Test Method of Sharp-Notch Tension Testing of
directions are identified as in Fig. 1 and Fig. 2, which give
High-Strength Sheet Materials
examples for a rolled plate. The same system would be useful
E616 Terminology Relating to Fracture Testing
for sheet, extrusions, and forgings with nonsymmetrical grain
flow.
3. Terminology
3.1 Definitions—Terminology E616 is applicable to this
L = direction of principal deformation (maximum grain
test method.
−3/2 flow),
3.1.1 stress-intensity factor, K, K , K , K [FL ]—the
1 2 3
T = direction of least deformation, and
magnitude of the ideal-crack-tip stress field (a stress-field
S = third orthogonal direction.
singularity) for a particular mode in a homogeneous, linear-
3.1.3.3 Discussion—Using a two letter code, the first letter
elastic body.
designates the direction normal to the crack plane, and the
3.1.1.1 Discussion—Values of K for modes 1, 2, and 3 are
second letter the expected direction of crack propagation. For
given by:
example,inFig.1theT–Lspecimenhasafractureplanewhose
1 2
/
K 5limit[s ~2pr! #, (1)
1 y normal is in the width direction of a plate and an expected
direction of crack propagation coincident with the direction of
r→o
maximum grain flow or longitudinal direction of the plate.
1 2
/
K 5limit[t ~2pr! #,and
2 xy
3.1.3.4 Discussion—For specimens that are tilted in respect
r→o
totwoofthereferenceaxes,Fig.2,theorientationisidentified
1 2
/
by a three-letter code.The code L–TS, for example, means that
K 5limit[t [p ~2pr! #,
3 yz yz
the crack plane is perpendicular to the direction of principal
r→o
deformation (L direction), and the expected fracture direction
wherer= adistancedirectlyforwardfromthecracktiptoalocation
is intermediate between T and S. The code TS–L means the
where the significant stress is calculated.
crack plane is perpendicular to a direction intermediate be-
3.1.1.2 Discussion—Inthistestmethod,mode1isassumed.
tween T and S, and the expected fracture direction is in the L
3.1.2 plane-strain fracture toughness—the crack-extension
direction.
resistance under conditions of crack-tip plane strain.
3.1.3.5 Discussion—For certain cylindrical sections where
3.1.2.1 Discussion—For example, in mode 1 for slow rates
the direction of principal deformation is parallel to the longi-
of loading and negligible plastic-zone adjustment, plane-strain
tudinal axis of the cylinder, the reference directions are
fracture toughness is the value of stress-intensity factor desig-
identified as in Fig. 3, which gives examples for a drawn bar.
−3/2
nated K [FL ] as measured using the operational procedure
Thesamesystemwouldbeusefulforextrusionsorforgedparts
Ic
(andsatisfyingallofthevalidityrequirements)specifiedinthis
having circular cross section.
test method, which provides for the measurement of crack-
extensionresistanceatthestartofcrackextensionandprovides
L = direction of maximum grain flow,
operational definitions of crack-tip sharpness, start of crack
R = radial direction, and
extension, and crack-tip plane strain.
C = circumferential or tangential direction.
4. Summary of Test Method
4.1 This test method involves testing of notched specimens
Annual Book of ASTM Standards, Vol 03.01.
Annual Book of ASTM Standards, Vol 11.03. that have been precracked in fatigue by loading either in
E 399 – 90 (1997)
FIG. 1 Crack Plane Orientation Code for Rectangular Sections
FIG. 2 Crack Plane Orientation Code for Rectangular Sections
Where Specimens are Tilted with Respect to the Reference
Directions
FIG. 3 Crack Plane Orientation Code for Bar and Hollow Cylinder
tension or three-point bending. Load versus displacement
across the notch at the specimen edge is recorded autographi-
cally. The load corresponding to a 2% apparent increment of
crackextensionisestablishedbyaspecifieddeviationfromthe
5. Significance and Use
linear portion of the record. The K value is calculated from
Ic
5.1 The property K determined by this test method char-
Ic
this load by equations that have been established on the basis
acterizes the resistance of a material to fracture in a neutral
of elastic stress analysis of specimens of the types described in
environment in the presence of a sharp crack under severe
this method. The validity of the determination of the K
value
Ic
tensile constraint, such that the state of stress near the crack
by this test method depends upon the establishment of a
frontapproachestritensileplanestrain,andthecrack-tipplastic
sharp-crack condition at the tip of the fatigue crack, in a
region is small compared with the crack size and specimen
specimen of adequate size. To establish a suitable crack-tip
dimensions in the constraint direction. A K value is believed
Ic
condition, the stress intensity level at which the fatigue
to represent a lower limiting value of fracture toughness. This
precracking of the specimen is conducted is limited to a
value may be used to estimate the relation between failure
relatively low value.
stress and defect size for a material in service wherein the
4.2 The specimen size required for testing purposes in-
conditions of high constraint described above would be ex-
creases as the square of the ratio of toughness to yield strength pected. Background information concerning the basis for
of the material; therefore a range of proportional specimens is
development of this test method in terms of linear elastic
provided. fracture mechanics may be found in Refs (1) and (2).
E 399 – 90 (1997)
5.1.1 The K value of a given material is a function of 6.3 Displacement Gage—The displacement gage output
Ic
testing speed and temperature. Furthermore, cyclic loads can shallindicatetherelativedisplacementoftwopreciselylocated
cause crack extension at K values less than the K value. gage positions spanning the crack starter notch mouth. Exact
I Ic
Crack extension under cyclic or sustained load will be in- and positive positioning of the gage on the specimen is
creased by the presence of an aggressive environment. There- essential, yet the gage must be released without damage when
fore, application of K in the design of service components the specimen breaks. A recommended design for a self-
Ic
shouldbemadewithawarenesstothedifferencethatmayexist supporting, releasable gage is shown in Fig. 4 and described in
between the laboratory tests and field conditions. AnnexA1.Thestraingagebridgearrangementisalsoshownin
5.1.2 Plane-strain crack toughness testing is unusual in that Fig. 4.
there can be no advance assurance that a valid K will be 6.3.1 The specimen must be provided with a pair of accu-
Ic
determined in a particular test. Therefore it is essential that all rately machined knife edges that support the gage arms and
of the criteria concerning validity of results be carefully serve as the displacement reference points. These knife edges
considered as described herein. can be machined integral with the specimen as shown in Fig. 4
5.1.3 Clearly it will not be possible to determine K if any andFig.5ortheymaybeseparatepiecesfixedtothespecimen.
Ic
dimension of the available stock of a material is insufficient to Asuggesteddesignforsuchattachableknifeedgesisshownin
provide a specimen of the required size. In such a case the Fig. 6. This design is based on a knife edge spacing of 0.2 in.
specimen strength ratio determined by this method will often (5.1mm).Theeffectivegagelengthisestablishedbythepoints
have useful significance. However, this ratio, unlike K ,isnot of contact between the screw and the hole threads. For the
Ic
a concept of linear elastic fracture mechanics, but can be a design shown, the major diameter of the screw has been used
usefulcomparativemeasureofthetoughnessofmaterialswhen insettingthisgagelength.ANo.2screwwillpermittheuseof
the specimens are of the same form and size, and that size is attachable knife edges for specimens having W > 1 in. (25
insufficient to provide a valid K determination, but sufficient mm).
Ic
that the maximum load results from pronounced crack propa- 6.3.2 Each gage shall be checked for linearity using an
gation rather than plastic instability. extensometer calibrator or other suitable device; the resettabil-
5.1.3.1 The strength ratio for center-cracked plate speci- ity of the calibrator at each displacement interval should be
mens tested in uniaxial tension may be determined by Test within+0.000020 in. (0.00050 mm). Readings shall be taken
Method E338. at ten equally spaced intervals over the working range of the
5.2 This test method can serve the following purposes: gage (see Annex A1). This calibration procedure should be
5.2.1 In research and development to establish, in quantita- performed three times, removing and reinstalling the gage in
tive terms, significant to service performance, the effects of the calibration fixture between each run.The required linearity
metallurgical variables such as composition or heat treatment, shall correspond to a maximum deviation of+0.0001 in.
or of fabricating operations such as welding or forming, on the (0.0025 mm) of the individual displaceme
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