ASTM E2899-15
(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 (6, 7, 8), Q (9, 10), stress tr...
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 −15
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.
TerminologyandSignificanceandUse.)Whenaparameterdescribingthis
1. Scope
stress state, or constraint, is used with the standard measure of crack-tip
1.1 This test method describes the method for testing
stress amplitude (K or J), the resulting two-parameter characterization
fatigue-sharpened, semi-elliptically shaped surface cracks in broadens the ability of fracture mechanics to accurately predict the
response of a crack under a wider range of loading. The two-parameter
rectangular flat panels subjected to monotonically increasing
methodology produces a more complete description of the crack-tip
tension or bending. Tests quantify the crack-tip conditions at
conditions at the initiation of crack extension.The effects of constraint on
initiationofstablecrackextensionorimmediateunstablecrack
measured fracture toughness are material dependent and are governed by
extension.
the effects of the crack-tip stress-strain state on the micromechanical
failure processes specific to the material. Surface crack tests conducted
1.2 This test method applies to the testing of metallic
with this test method can help to quantify the material sensitivity to
materials not limited by strength, thickness, or toughness.
constraint effects and to establish the degree to which the material
Materials are assumed to be essentially homogeneous and free
toughness correlates with a constraint-based fracture characterization.
of residual stress. Tests may be conducted at any appropriate
1.6 This test method provides a quantitative framework to
temperature.Theeffectsofenvironmentalfactorsandsustained
categorize test specimen conditions into one of three regimes:
or cyclic loads are not addressed in this test method.
(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
datainthecontextofatoughness-constraintlocus (2).Theuser
1.4 Tests of surface cracked, laboratory-scale specimens as
is directed to other resources for evaluation of the test
described in this test method may provide a more accurate
specimen in the field-collapse regime when extensive plastic
understanding of full-scale structural performance in the pres-
deformation in the specimen eliminates the identifiable crack-
ence of surface cracks.The provided recommendations help to
front fields of fracture mechanics.
assure test methods and data are applicable to the intended
1.7 The specimen design and test procedures described in
purpose.
thistestmethodmaybeappliedtoevaluationofsurfacecracks
1.5 This test method prescribes a consistent methodology
inwelds;however,themethodsdescribedinthistestmethodto
fortestandanalysisofsurfacecracksforresearchpurposesand
analyze test measurements may not be applicable. Weld frac-
to assist in structural assessments.The methods described here
ture tests generally have complicating features beyond the
2
utilize a constraint-based framework (1, 2) to evaluate the
scope of data analysis in this test method, including the effects
fracture behavior of surface cracks.
of residual stress, microstructural variability, and non-uniform
NOTE 1—Constraint-based framework. In the context of this test
strength. These effects will influence test results and must be
method, constraint is used as a descriptor of the three-dimensional stress
considered in the interpretation of measured quantities.
and strain fields in the near vicinity of the crack tip, where material
contractions due to the Poisson effect may be suppressed and therefore 1.8 This test method is not intended for testing surface
produce an elevated, tensile stress state (3, 4). (See further discussions in
cracks in steel in the cleavage regime. Such tests are outside
the scope of this test method.Amethodology for evaluation of
cleavage fracture toughness in ferritic steels over the ductile-
1
This te
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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 − 13 E2899 − 15
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). 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.
1.7 The specimen design and test procedures described in this test method may be applied to evaluation of surface cracks in
welds; however, the methods described in this test method to analyze test measurements may not be applicable. Weld fracture tests
generally have complicating features beyond the scope of data analysis in this test method, including the effects of residual stress,
microstructural variability, and non-un
...
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