ASTM E2899-19
(Test Method)Standard Test Method for Measurement of Initiation Toughness in Surface Cracks Under Tension and Bending
Standard Test Method for Measurement of Initiation Toughness in Surface Cracks Under Tension and Bending
SIGNIFICANCE AND USE
5.1 Surface cracks are among the most common defects found in structural components. An accurate characterization and understanding of crack-front behavior is necessary to ensure successful operation of a structure containing surface cracks. The testing of laboratory specimens with surface cracks provides a means to understand and quantify surface crack behavior, but the test results must be interpreted correctly to ensure transferability between the laboratory specimen and the structure.
5.2 Transferability refers to the capacity of a fracture mechanics methodology to correlate the crack-tip stress and strain fields of different cracked bodies. Traditionally, the correlation has been based on the presence at fracture of a dominant, asymptotically singular, crack-tip field with amplitude set by the value of a single parameter, such as the stress intensity factor, KI, or the J-integral. For components and specimens with high crack-tip constraint, the singular crack-tip field dominates over microstructurally significant size scales for loads ranging from globally linear-elastic conditions to moderately large-scale plasticity. For specimens with low crack-tip constraint, a dominant single-parameter crack-tip field exists only at low levels of plasticity. At higher levels of plasticity, the opening mode stress of the low constraint specimen is lower than predicted by the single-parameter, asymptotically singular fields. Therefore, low constraint specimens often exhibit larger fracture toughness than do high constraint specimens. If feasible, users are strongly encouraged to generate high constraint fracture toughness data using methods such as Test Methods E399 or E1820 prior to testing the surface crack geometry.
5.2.1 To address this phenomenon, two-parameter fracture criteria are used to include the influence of crack-tip constraint. Crack-tip constraint has been quantified using various scalar parameters including the T-stress (10, 11, 12), Q (13, 14), stres...
SCOPE
1.1 This test method describes the method for testing fatigue-sharpened, semi-elliptically shaped surface cracks in rectangular flat panels subjected to monotonically increasing tension or bending. Tests quantify the crack-tip conditions at initiation of stable crack extension or immediate unstable crack extension.
1.2 This test method applies to the testing of metallic materials not limited by strength, thickness, or toughness. Materials are assumed to be essentially homogeneous and free of residual stress. Tests may be conducted at any appropriate temperature. The effects of environmental factors and sustained or cyclic loads are not addressed in this test method.
1.3 This test method describes all necessary details for the user to test for the initiation of crack extension in surface crack test specimens. Specific requirements and recommendations are provided for test equipment, instrumentation, test specimen design, and test procedures.
1.4 Tests of surface cracked, laboratory-scale specimens as described in this test method may provide a more accurate understanding of full-scale structural performance in the presence of surface cracks. The provided recommendations help to assure test methods and data are applicable to the intended purpose.
1.5 This test method prescribes a consistent methodology for test and analysis of surface cracks for research purposes and to assist in structural assessments. The methods described here utilize a constraint-based framework (1, 2)2 to evaluate the fracture behavior of surface cracks.
Note 1: Constraint-based framework. In the context of this test method, constraint is used as a descriptor of the three-dimensional stress and strain fields in the near vicinity of the crack tip, where material contractions due to the Poisson effect may be suppressed and therefore produce an elevated, tensile stress state (3, 4). (See further discussions in Terminology and Significance a...
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Designation: E2899 − 19
Standard Test Method for
Measurement of Initiation Toughness in Surface Cracks
1
Under Tension and Bending
This standard is issued under the fixed designation E2899; 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.
produce an elevated, tensile stress state (3, 4). (See further discussions in
1. Scope
TerminologyandSignificanceandUse.)Whenaparameterdescribingthis
1.1 This test method describes the method for testing
stress state, or constraint, is used with the standard measure of crack-tip
fatigue-sharpened, semi-elliptically shaped surface cracks in stress amplitude (K or J), the resulting two-parameter characterization
broadens the ability of fracture mechanics to accurately predict the
rectangular flat panels subjected to monotonically increasing
response of a crack under a wider range of loading. The two-parameter
tension or bending. Tests quantify the crack-tip conditions at
methodology produces a more complete description of the crack-tip
initiationofstablecrackextensionorimmediateunstablecrack
conditions at the initiation of crack extension.The effects of constraint on
extension.
measured fracture toughness are material dependent and are governed by
the effects of the crack-tip stress-strain state on the micromechanical
1.2 This test method applies to the testing of metallic
failure processes specific to the material. Surface crack tests conducted
materials not limited by strength, thickness, or toughness.
with this test method can help to quantify the material sensitivity to
Materials are assumed to be essentially homogeneous and free
constraint effects and to establish the degree to which the material
toughness correlates with a constraint-based fracture characterization.
of residual stress. Tests may be conducted at any appropriate
temperature.Theeffectsofenvironmentalfactorsandsustained
1.6 This test method provides a quantitative framework to
or cyclic loads are not addressed in this test method.
categorize test specimen conditions into one of three regimes:
(I)alinear-elasticregime,(II)anelastic-plasticregime,or(III)
1.3 This test method describes all necessary details for the
a field-collapse regime. Based on this categorization, analysis
usertotestfortheinitiationofcrackextensioninsurfacecrack
techniques and guidelines are provided to determine an appli-
test specimens. Specific requirements and recommendations
cable crack-tip parameter for the linear-elastic regime (K or J)
areprovidedfortestequipment,instrumentation,testspecimen
or the elastic-plastic regime (J), and an associated constraint
design, and test procedures.
parameter. Recommendations are provided to assess the test
1.4 Tests of surface cracked, laboratory-scale specimens as
data in the context of a toughness-constraint locus (2). For
described in this test method may provide a more accurate
tension loading, a computer program referred to as TASC
understanding of full-scale structural performance in the pres-
V1.0.2 (Tool for Analysis of Surface Cracks) may be used to
ence of surface cracks.The provided recommendations help to
perform the analytical assessments in Section 9, Analysis of
assure test methods and data are applicable to the intended
Results. The user is directed to other resources for evaluation
purpose.
of the test specimen in the field-collapse regime when exten-
1.5 This test method prescribes a consistent methodology
sive plastic deformation in the specimen eliminates the iden-
fortestandanalysisofsurfacecracksforresearchpurposesand
tifiable crack-front fields of fracture mechanics.
to assist in structural assessments.The methods described here
NOTE2—TASC.ThecomputerprogramTASCisavailableatnocharge
2
utilize a constraint-based framework (1, 2) to evaluate the
either at https://software.nasa.gov/software/MFS-33082-1 or at https://
fracture behavior of surface cracks.
sourceforge.net/projects/tascnasa/. The use of TASC relieves the user of
theburdenofperforminguniqueelastic-plasticfiniteelementanalysesfor
NOTE 1—Constraint-based framework. In the context of this test
each test performed in the elastic-plastic regime. For the purposes of this
method, constraint is used as a descriptor of the three-dimensional stress
standard, TASC calculations are equivalent to finite element analysis
and strain fields in the near vicinity of the crack tip, where material
results. Users ofTASC should follow the methodologies in AnnexA6 for
contractions due to the Poisson effect may be suppressed and therefore
establishing analysis material property inputs. Documentation on the
development, verification and validati
...
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.
Designation: E2899 − 15 E2899 − 19
Standard Test Method for
Measurement of Initiation Toughness in Surface Cracks
1
Under Tension and Bending
This standard is issued under the fixed designation E2899; 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
1.1 This test method describes the method for testing fatigue-sharpened, semi-elliptically shaped surface cracks in rectangular
flat panels subjected to monotonically increasing tension or bending. Tests quantify the crack-tip conditions at initiation of stable
crack extension or immediate unstable crack extension.
1.2 This test method applies to the testing of metallic materials not limited by strength, thickness, or toughness. Materials are
assumed to be essentially homogeneous and free of residual stress. Tests may be conducted at any appropriate temperature. The
effects of environmental factors and sustained or cyclic loads are not addressed in this test method.
1.3 This test method describes all necessary details for the user to test for the initiation of crack extension in surface crack test
specimens. Specific requirements and recommendations are provided for test equipment, instrumentation, test specimen design,
and test procedures.
1.4 Tests of surface cracked, laboratory-scale specimens as described in this test method may provide a more accurate
understanding of full-scale structural performance in the presence of surface cracks. The provided recommendations help to assure
test methods and data are applicable to the intended purpose.
1.5 This test method prescribes a consistent methodology for test and analysis of surface cracks for research purposes and to
2
assist in structural assessments. The methods described here utilize a constraint-based framework (1, 2) to evaluate the fracture
behavior of surface cracks.
NOTE 1—Constraint-based framework. In the context of this test method, constraint is used as a descriptor of the three-dimensional stress and strain
fields in the near vicinity of the crack tip, where material contractions due to the Poisson effect may be suppressed and therefore produce an elevated,
tensile stress state (3, 4). (See further discussions in Terminology and Significance and Use.) When a parameter describing this stress state, or constraint,
is used with the standard measure of crack-tip stress amplitude (K or J), the resulting two-parameter characterization broadens the ability of fracture
mechanics to accurately predict the response of a crack under a wider range of loading. The two-parameter methodology produces a more complete
description of the crack-tip conditions at the initiation of crack extension. The effects of constraint on measured fracture toughness are material dependent
and are governed by the effects of the crack-tip stress-strain state on the micromechanical failure processes specific to the material. Surface crack tests
conducted with this test method can help to quantify the material sensitivity to constraint effects and to establish the degree to which the material
toughness correlates with a constraint-based fracture characterization.
1.6 This test method provides a quantitative framework to categorize test specimen conditions into one of three regimes: (I) a
linear-elastic regime, (II) an elastic-plastic regime, or (III) a field-collapse regime. Based on this categorization, analysis techniques
and guidelines are provided to determine an applicable crack-tip parameter for the linear-elastic regime (K or J) or the
elastic-plastic regime (J), and an associated constraint parameter. Recommendations are provided to assess the test data in the
context of a toughness-constraint locus (2). For tension loading, a computer program referred to as TASC V1.0.2 (Tool for Analysis
of Surface Cracks) may be used to perform the analytical assessments in Section 9, Analysis of Results. The user is directed to
other resources for evaluation of the test specimen in the field-collapse regime when extensive plastic deformation in the specimen
eliminates the identifiable crack-front fields of fracture mechanics.
NOTE 2—TASC. The computer program TASC is available at no charge either at https://software.nasa.gov/software/MFS-33082-1 or at https://
sourceforge.net/projects/tascnasa/. The use of TASC relieves the user of the burden of performing un
...
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