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ASTM E647-95

(Test Method)

Standard Test Method for Measurement of Fatigue Crack Growth Rates

Standard Test Method for Measurement of Fatigue Crack Growth Rates

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1.1 This test method covers the determination of fatigue crack growth rates from near-threshold to Kmax  controlled instability. Results are expressed in terms of the crack-tip stress-intensity factor range ( K), defined by the theory of linear elasticity.
1.2 Several different test procedures are provided, the optimum test procedure being primarily dependent on the magnitude of the fatigue crack growth rate to be measured.
1.3 Materials that can be tested by this test method are not limited by thickness or by strength so long as specimens are of sufficient thickness to preclude buckling and of sufficient planar size to remain predominantly elastic during testing.
1.4 A range of specimen sizes with proportional planar dimensions is provided, but size is variable to be adjusted for yield strength and applied force. Specimen thickness may be varied independent of planar size.
1.5 The details of the various specimens and test configurations are shown in Annex A1 - Annex A3. Specimen configurations other than those contained in this method may be used provided that well-established stress-intensity factor calibrations are available and that specimens are of sufficient planar size to remain predominantly elastic during testing.
1.6 Residual stress/crack closure may significantly influence the fatigue crack growth rate data, particularly at low stress-intensity factors and low stress ratios, although such variables are not incorporated into the computation of K.
1.7 Values stated in SI units are to be regarded as the standard. Values given in parentheses are for information only.
1.8 This test method is divided into two main parts. The first part gives general information concerning the recommendations and requirements for fatigue crack growth rate testing. The second part is composed of annexes that describe the special requirements for various specimen configurations, special requirements for testing in aqueous environments, and procedures for non-visual crack size determination. In addition, there are appendices that cover techniques for calculating da/dN, determining fatigue crack opening force, and guidelines for measuring the growth of small fatigue cracks. General information and requirements common to all specimen types are listed as follows:
SectionReferenced Documents2Terminology3Summary of Use4Significance and Use5Apparatus6Specimen Configuration, Size, and Preparation7Procedure8Calculations and Interpretation of Results9Report10Precision and Bias11Special Requirements for Testing in Aqueous EnvironmentsAnnex A4Guidelines for Use of Compliance to Determine Crack SizeAnnex A5Guidelines for Electric Potential Difference Determination of Crack SizeAnnex A6Recommended Data Reduction TechniquesAppendix X1Recommended Practice for Determination of Fatigue Crack Opening Force From ComplianceAppendix X2Guidelines for Measuring the Growth Rates Of Small Fatigue CracksAppendix X3
1.9 Special requirements for the various specimen configurations appear in the following order:
The Compact Tension SpecimenAnnex A1The Middle Tension SpecimenAnnex A2The Eccentrically-Loaded Single Edge Crack Tension SpecimenAnnex A3
1.10 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

Status
Historical
Publication Date
09-Dec-2000
ICS
77.040.10 - Mechanical testing of metals
Technical Committee
E08 - Fatigue and Fracture
Drafting Committee
E08.06 - Crack Growth Behavior
Current Stage
Ref Project

Relations

Replaced By
ASTM E647-99 - Standard Test Method for Measurement of Fatigue Crack Growth Rates
Effective Date
10-Dec-2000

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ASTM E647-95 - Standard Test Method for Measurement of Fatigue Crack Growth RatesASTM E647-95 - Standard Test Method for Measurement of Fatigue Crack Growth Rates
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ASTM E647-95 - Standard Test Method for Measurement of Fatigue Crack Growth Rates
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ASTM E647 95
0759530 0559533 047
Designation: E 647 - 95
4Tb
Standard Test Method for
Measurement of Fatigue Crack Growth Rates'
This standard is issued under the fixed designation E 647; 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 (e) indicates an editorial change since the last revision or reapproval.
E 337 Test Method for Measuring Humidity with a
1. Scope
Psychrometer (the Measurement of Wet- and Dry-Bulb
1. i This test method2 covers the determination of steady-
tempe rature^)^
state fatigue crack growth rates from near-threshold to K,,,
E 338 Test Method for Sharp-Notch Tension Testing of
controlled instability using either compact tension, C(T),
High-Strength Sheet Materials3
(Fig. 1) or middle-tension, M(T), (Fig. 2) specimens. Results
E 399 Test Method for Plane-Strain Fracture Toughness
are expressed in terms of the crack-tip stress-intensity factor
of Metallic Materials3
range (Am, defined by the theory of linear elasticity.
E 467 Practice for Verification of Constant Amplitude
1.2 Several different test procedures are provided, the
Dynamic Loads on Displacements in an Axial Load
optimum test procedure being primarily dependent on the
Fatigue Testing System3
magnitude of the fatigue crack growth rate to be measured.
E 56 1 Practice for R-Curve Determination3
1.3 Materials that can be tested by this test method are not
E 6 16 Terminology Relating to Fracture Testing3
limited by thicknesses or by strength so long as specimens are
E 813 Test Method for Jlo A Measure of Fracture
of sufficient thickness to preclude buckling and of sufficient
Toughness3
planar size to remain predominantly elastic during testing.
E 1 150 Definitions of Terms Relating to Fatigue3
1.4 A range of specimen sizes with proportional planar
dimensions is provided, but size is variable to be adjusted for
yield strength and applied load. Specimen thickness may be
3. Terminology
varied independent of planar size.
1.5 Specimen configurations other than those contained 3.1 The terms used in this test method are given in
in this method may be used provided that well-established Terminology E 6, Definitions E 1150, and Terminology
stress-intensity factor calibrations are available and that
E 616. Wherever these terms are not in agreement with one
specimens are of sufficient planar size to remain predomi-
another, use the definitions given in Terminology E 6 i6
nantly elastic during testing.
which are applicable to this test method.
1.6 Residual stress/crack closure may significantly influ-
3.2 Definitions:
ence the fatigue crack growth rate data, particularly at low
3.2.1 crack length, a[L], n-See crack size.
stress-intensity factors and low stress ratios, although such
3.2.2 crack size, a[L], n-a linear measure of a principal
variables are not incorporated into the computation of AK.
planar dimension of a crack. This measure is commonly
1.7 Values stated in SI units are to be regarded as the
used in the calculation of quantities descriptive of the stress
standard. Values given in parentheses are for information only.
and displacement fields and is often also termed crack length
1.8 This standard does not purport to address all of the
or depth.
safety concerns, if any, associated with its use. It is the
Discussion-In the C(T) specimen, a is measured from the
responsibility of the user of this standard to establish appro-
line connecting the bearing points of load application; in the
priate safety and health practices and determine the applica-
M(T) specimen, a is measured from the perpendicular
bility of regulatory limitations prior to use.
bisector of the central crack.
Discussion-In fatigue testing, crack length is the physical
crack size. See physical crack size in Terminology E 6 16.
2. Referenced Documents
3.2.3 cycle-in fatigue, under constant amplitude loading,
2.1 ASTM Standards:
the load variation from the minimum to the maximum and
E 4 Practices for Force Verification of Testing Machines3
then to the minimum load.
E 6 Terminology Relating to Methods of Mechanical
Discussion-In spectrum loading, the definition of cycle
Testing3
vanes with the counting method used.
E 8 Test Methods for Tension Testing of Metallic
Discussion-In this test method, the symbol N is used to
Materials3
represent the number of cycles.
3.2.4 -tätigue-crack-growth rate, da/dN, [LI-crack exten-
sion per cycle of loading.
I This test method is under the jurisdiction of ASTM Committee E-8 on
3.2.5 fatigue cycle-See cycle.
Fatigue and Fracture and is the direct responsibility of Subcommittee E08.06 on
Crack Growth Behavior.
3.2.6 load cycle-See cycle.
Current edition approved Apr. 15, 1995. Published June 1995. Originally
3.2.7 load range, A P [q-in fatigue, the algebraic
publi
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1.1 This practice covers the design, preparation, and testing of surface-crack tension (SCT) specimens. It relates specifically to testing under continuously increasing force and excludes cyclic and sustained loadings. The quantity determined is the residual strength of a specimen having a semielliptical or circular-segment fatigue crack in one surface. This value depends on the crack dimensions and the specimen thickness as well as the characteristics of the material.  
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6.2.1 Expressing CCI time, t0.2 and CCG rate, da/dt as a function of an appropriate fracture mechanics related parameter generally provides results that are independent of specimen size and planar geometry for the same stress state at the crack tip for the range of geometries and sizes presented in this document (see Annex A1). Thus, the appropriate correlation will enable exchange and comparison of data obtained from a variety of specimen configurations and loading conditions. Moreover, this feature enables creep crack growth data to be utilized in the design and evaluation of engineering structures operated at elevated temperatures where creep deformation is a concern. The concept of similitude is assumed, implying that cracks of differing sizes subjected to the same nominal C*(t), Ct, or K will advance by equal increments of crack extension per unit time, provided the conditions for the validity for the specific crack growth rate relating parameter are met. See 11.7 for details.  
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5.1 In structures containing gradients in either toughness or stress, a crack may initiate in a region of either low toughness or high stress, or both, and arrest in another region of either higher toughness or lower stress, or both. The value of the stress intensity factor during the short time interval in which a fast-running crack arrests is a measure of the ability of the material to arrest such a crack. Values of the stress intensity factor of this kind, which are determined using dynamic methods of analysis, provide a value for the crack-arrest fracture toughness which will be termed KA  in this discussion. Static methods of analysis, which are much less complex, can often be used to determine K at a short time (1 to 2 ms) after crack arrest. The estimate of the crack-arrest fracture toughness obtained in this fashion is termed K a. When macroscopic dynamic effects are relatively small, the difference between KA  and Ka  is also small (1-4). For cracks propagating under conditions of crack-front plane-strain, in situations where the dynamic effects are also known to be small, KIa  determinations using laboratory-sized specimens have been used successfully to estimate whether, and at what point, a crack will arrest in a structure (5, 6). Depending upon component design, loading compliance, and the crack jump length, a dynamic analysis of a fast-running crack propagation event may be necessary in order to predict whether crack arrest will occur and the arrest position. In such cases, values of K Ia  determined by this test method can be used to identify those values of K below which the crack speed is zero. More details on the use of dynamic analyses can be found in Ref (4).  
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5.1 Fatigue crack growth rate expressed as a function of crack-tip stress-intensity factor range, da/dN versus ΔK, characterizes a material's resistance to stable crack extension under cyclic loading. Background information on the ration-ale for employing linear elastic fracture mechanics to analyze fatigue crack growth rate data is given in Refs (3) and (4).  
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1.1 This test method2 covers the determination of fatigue crack growth rates from near-threshold (see region I in Fig. 1) to Kmax  controlled instability (see region III in Fig. 1.) Results are expressed in terms of the crack-tip stress-intensity factor range (ΔK), defined by the theory of linear elasticity.  
1.9 Special requirements for the various specimen configurations appear in the following order:
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Annex A1  
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Annex A2  
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Annex A3  
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1.1.1 The KIc test procedure is described in the main body of this test standard and is a mandatory part of the testing and results reporting procedure for this test method. The KIc test procedure is based on crack growth of up to 2 % percent of the specimen width. This can lead to a specimen size dependent rising fracture toughness resistance curve, with larger specimens producing higher fracture toughness results.  
1.1.2 The KIsi test procedure is described in Appendix X1 and is an optional part of this test method. The KIsi test procedure is based on a fixed amount of crack extension of 0.5 mm, and as a result, KIsi is less sensitive to specimen size than KIc. This less size-sensitive fracture toughness, KIsi, is called size-insensitive throughout this test method. Appendix X1 contains an optional procedure for reinterpreting the force-displacement test record recorded as part of this test method to calculate the additional fracture toughness value, KIsi.
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Standard Test Method for Measurement of Fracture Toughness

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5.1 Assuming the presence of a preexisting, sharp, fatigue crack, the material fracture toughness values identified by this test method characterize its resistance to: (1)  fracture of a stationary crack, (2) fracture after some stable tearing, (3) stable tearing onset, and (4) sustained stable tearing. This test method is particularly useful when the material response cannot be anticipated before the test. Application of procedures in Test Method E1921 is recommended for testing ferritic steels that undergo cleavage fracture in the ductile-to-brittle transition.  
5.1.1 These fracture toughness values may serve as a basis for material comparison, selection, and quality assurance. Fracture toughness can be used to rank materials within a similar yield strength range.  
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5.2 The following cautionary statements are based on some observations.  
5.2.1 Particular care must be exercised in applying to structural flaw tolerance assessment the fracture toughness value associated with fracture after some stable tearing has occurred. This response is characteristic of ferritic steel in the transition regime. This response is especially sensitive to material inhomogeneity and to constraint variations that may be induced by planar geometry, thickness differences, mode of loading, and structural details.  
5.2.2 The J-R curve from bend-type specimens recommended by this test method (SE(B), C(T), and DC(T)) has been observed to be conservative with respect to results from tensile loading configurations.  
5.2.3 The values of δc, δu, Jc, and Ju  may be affected by specimen dimensions.
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1.1 This test method covers procedures and guidelines for the determination of fracture toughness of metallic materials using the following parameters: K, J, and CTOD (δ). Toughness can be measured in the R-curve format or as a point value. The fracture toughness determined in accordance with this test method is for the opening mode (Mode I) of loading.
Note 1: Until this version, KIc could be evaluated using this test method as well as by using Test Method E399. To avoid duplication, the evaluation of KIc has been removed from this test method and the user is referred to Test Method E399.  
1.2 The recommended specimens are single-edge bend, [SE(B)], compact, [C(T)], and disk-shaped compact, [DC(T)]. All specimens contain notches that are sharpened with fatigue cracks.  
1.2.1 Specimen dimensional (size) requirements vary according to the fracture toughness analysis applied. The guidelines are established through consideration of material toughness, material flow strength, and the individual qualification requirements of the toughness value per values sought.  
Note 2: Other standard methods for the determination of fracture toughness using the parameters K, J, and CTOD are contained in Test Methods E399, E1290, and E1921. This test method was developed to provide a common method for determining all applicable toughness parameters from a single test.  
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
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4.1 Fatigue test results may be significantly influenced by the properties and history of the parent material, the operations performed during the preparation of the fatigue specimens, and the testing machine and test procedures used during the generation of the data. The presentation of fatigue test results should include citation of basic information on the material, specimens, and testing to increase the utility of the results and to reduce to a minimum the possibility of misinterpretation or improper application of those results.
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Note 1: Practice E466, although not directly referenced in the text, is considered important enough to be listed in this standard.  
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Standard Test Method for KR Curve Determination

SIGNIFICANCE AND USE
5.1 The KR curve characterizes the resistance to fracture of materials during slow, stable crack extension and results from the growth of the plastic zone ahead of the crack as it extends from a fatigue precrack or sharp notch. It provides a record of the toughness development as a crack is driven stably under increasing applied stress intensity factor K. For a given material, KR curves are dependent upon specimen thickness, temperature, and strain rate. The amount of valid KR data generated in the test depends on the specimen type, size, method of loading, and, to a lesser extent, testing machine characteristics.  
5.2 For an untested geometry, the KR curve can be matched with the applied-K curves (crack driving curves) to estimate the degree of stable crack extension and the conditions necessary to cause unstable crack propagation (2). In making this estimate, KR curves are regarded as being independent of initial crack size ao and the specimen configuration in which they are developed. For a given material, material thickness, and test temperature, KR curves appear to be a function of only the effective crack extension Δae (3).  
5.2.1 To predict crack behavior and instability in a component, a family of applied-K curves is generated by calculating  K as a function of crack size for the component using a series of force, displacement, or combined loading conditions. The KR curve may be superimposed on the family of applied-K curves as shown in Fig. 1, with the origin of the KR curve coinciding with the assumed initial crack size ao. The intersection of the applied-K curves with the KR curve shows the expected effective stable crack extension for each loading condition. The applied-K curve that develops tangency with the KR curve defines the critical loading condition that will cause the onset of unstable fracture under the loading conditions used to develop the applied-K curves.
FIG. 1 Schematic Representation of KR curve and Applied K Curves to Predict Insta...
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1.1 This test method covers the determination of the resistance to fracture of metallic materials under Mode I loading at static rates using either of the following notched and precracked specimens: the middle-cracked tension M(T) specimen or the compact tension C(T) specimen. A KR curve is a continuous record of toughness development (resistance to crack extension) in terms of KR plotted against crack extension in the specimen as a crack is driven under an increasing stress intensity factor, K. (1)2  
1.2 Materials that can be tested for KR curve development are not limited by strength, thickness, or toughness, so long as specimens are of sufficient size to remain predominantly elastic to the effective crack extension value of interest.  
1.3 Specimens of standard proportions are required, but size is variable, to be adjusted for yield strength and toughness of the materials.  
1.4 Only two of the many possible specimen types that could be used to develop KR curves are covered in this method.  
1.5 The test is applicable to conditions where a material exhibits slow, stable crack extension under increasing crack driving force, which may exist in relatively tough materials under plane stress crack tip conditions.  
1.6 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.7 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.  
1.8 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 Reco...

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ASTM
ASTM E2789-10(2021)(Guide)
Standard Guide for Fretting Fatigue Testing

SIGNIFICANCE AND USE
4.1 Fretting fatigue tests are used to determine the effects of several fretting parameters on the fatigue lives of metallic materials. Some of these parameters include differing materials, relative displacement amplitudes, normal force at the fretting contact, alternating tangential force, the contact geometry, surface integrity parameters such as finish, and the environment. Comparative tests are used to determine the effectiveness of palliatives on the fatigue life of specimens with well-controlled boundary conditions so that the mechanics of the fretting fatigue test can be modeled. Generally, it is useful to compare the fretting fatigue response to plain fatigue to obtain knockdown or reduction factors from fretting fatigue. The results may be used as a guide in selecting material combinations, design stress levels, lubricants, and coatings to alleviate or eliminate fretting fatigue concerns in new or existing designs. However, due to the synergisms of fatigue, wear, and corrosion on the fretting fatigue parameters, extreme care should be exercised in the judgment to determine if the test conditions meet the design or system conditions.  
4.2 For data to be comparable, reproducible, and correlated amongst laboratories and relevant to mimic fretting in an application, all parameters critical to the fretting fatigue life of the material in question will need to be replicated. Because alterations in environment, metallurgical properties, fretting loading (controlled forces and displacements), compliance of the test system, etc. can affect the response, no general guidelines exist to quantitatively ascertain what the effect will be on the specimen fretting fatigue life if a single parameter is varied. To assure test results can be correlated and reproduced, all material variables, testing information, physical procedures, and analytical procedures should be reported in a manner that is consistent with good current test practices.  
4.3 Because of the wear phenome...
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1.1 This guide defines terminology and covers general requirements for conducting fretting fatigue tests and reporting the results. It describes the general types of fretting fatigue tests and provides some suggestions on developing and conducting fretting fatigue test programs.  
1.2 Fretting fatigue tests are designed to determine the effects of mechanical and environmental parameters on the fretting fatigue behavior of metallic materials. This guide is not intended to establish preference of one apparatus or specimen design over others, but will establish guidelines for adherence in the design, calibration, and use of fretting fatigue apparatus and recommend the means to collect, record, and reporting of the data.  
1.3 The number of cycles to form a fretting fatigue crack is dependent on both the material of the fatigue specimen and fretting pad, the geometry of contact between the two, and the method by which the loading and displacement are imposed. Similar to wear behavior of materials, it is important to consider fretting fatigue as a system response, instead of a material response. Because of this dependency on the configuration of the system, quantifiable comparisons of various material combinations should be based on tests using similar fretting fatigue configurations and material couples.  
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.

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ASTM
ASTM E466-21(Practice)
Standard Practice for Conducting Force Controlled Constant Amplitude Axial Fatigue Tests of Metallic Materials

SIGNIFICANCE AND USE
4.1 The axial force fatigue test is used to determine the effect of variations in material, geometry, surface condition, stress, and so forth, on the fatigue resistance of metallic materials subjected to direct stress for relatively large numbers of cycles. The results may also be used as a guide for the selection of metallic materials for service under conditions of repeated direct stress.  
4.2 In order to verify that such basic fatigue data generated using this practice is comparable, reproducible, and correlated among laboratories, it may be advantageous to conduct a round-robin-type test program from a statistician's point of view. To do so would require the control or balance of what are often deemed nuisance variables; for example, hardness, cleanliness, grain size, composition, directionality, surface residual stress, surface finish, and so forth. Thus, when embarking on a program of this nature it is essential to define and maintain consistency a priori, as many variables as reasonably possible, with as much economy as prudent. All material variables, testing information, and procedures used should be reported so that correlation and reproducibility of results may be attempted in a fashion that is considered reasonably good current test practice.  
4.3 The results of the axial force fatigue test are suitable for application to design only when the specimen test conditions realistically simulate service conditions or some methodology of accounting for service conditions is available and clearly defined.
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1.1 This practice covers the procedure for the performance of axial force controlled fatigue tests to obtain the fatigue strength of metallic materials in the fatigue regime where the strains are predominately elastic, both upon initial loading and throughout the test. This practice is limited to the fatigue testing of axial unnotched and notched specimens subjected to a constant amplitude, periodic forcing function in air at room temperature.  
1.2 The use of this test method is limited to specimens and does not cover testing of full-scale components, structures, or consumer products.  
1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.4 The text of this standard references notes and footnotes that provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard.
Note 1: The following documents, although not directly referenced in the text, are considered important enough to be listed in this practice:
E739 Practice for Statistical Analysis of Linear or Linearized Stress-Life (S-N) and Strain-Life (ε-N) Fatigue Data
STP 566 Handbook of Fatigue Testing2
STP 588 Manual on Statistical Planning and Analysis for Fatigue Experiments3
STP 731 Tables for Estimating Median Fatigue Limits4  
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.

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