ASTM E647-23b
(Test Method)Standard Test Method for Measurement of Fatigue Crack Growth Rates
Standard Test Method for Measurement of Fatigue Crack Growth Rates
SIGNIFICANCE AND USE
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).
5.1.1 In innocuous (inert) environments fatigue crack growth rates are primarily a function of ΔK and force ratio, R, or Kmax and R (Note 1). Temperature and aggressive environments can significantly affect da/dN versus ΔK, and in many cases accentuate R-effects and introduce effects of other loading variables such as cycle frequency and waveform. Attention needs to be given to the proper selection and control of these variables in research studies and in the generation of design data.
Note 1: ΔK, Kmax, and R are not independent of each other. Specification of any two of these variables is sufficient to define the loading condition. It is customary to specify one of the stress-intensity parameters (ΔK or Kmax) along with the force ratio, R.
5.1.2 Expressing da/dN as a function of ΔK provides results that are independent of planar geometry, thus enabling exchange and comparison of data obtained from a variety of specimen configurations and loading conditions. Moreover, this feature enables da/dN versus ΔK data to be utilized in the design and evaluation of engineering structures. The concept of similitude is assumed, which implies that cracks of differing lengths subjected to the same nominal ΔK will advance by equal increments of crack extension per cycle.
5.1.3 Fatigue crack growth rate data are not always geometry-independent in the strict sense since thickness effects sometimes occur. However, data on the influence of thickness on fatigue crack growth rate are mixed. Fatigue crack growth rates over a wide range of ΔK have been reported to either increase, decrease, or remain unaffected as specimen...
SCOPE
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:
The Compact Specimen
Annex A1
The Middle Tension Specimen
Annex A2
The Eccentrically-Loaded Single Edge Crack Tension Specimen
Annex 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.11 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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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: E647 − 23b
Standard Test Method for
1
Measurement of Fatigue Crack Growth Rates
This standard is issued under the fixed designation E647; 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 1.8 This test method is divided into two main parts. The first
2 part gives general information concerning the recommenda-
1.1 This test method covers the determination of fatigue
tions and requirements for fatigue crack growth rate testing.
crack growth rates from near-threshold (see region I in Fig. 1)
The second part is composed of annexes that describe the
to K controlled instability (see region III in Fig. 1.) Results
max
special requirements for various specimen configurations, spe-
are expressed in terms of the crack-tip stress-intensity factor
cial requirements for testing in aqueous environments, and
range (ΔK), defined by the theory of linear elasticity.
procedures for non-visual crack size determination. In addition,
1.2 Several different test procedures are provided, the opti-
there are appendices that cover techniques for calculating
mum test procedure being primarily dependent on the magni-
da/dN, determining fatigue crack opening force, and guidelines
tude of the fatigue crack growth rate to be measured.
for measuring the growth of small fatigue cracks. General
1.3 Materials that can be tested by this test method are not information and requirements common to all specimen types
are listed as follows:
limited by thickness or by strength so long as specimens are of
sufficient thickness to preclude buckling and of sufficient
Section
Referenced Documents 2
planar size to remain predominantly elastic during testing.
Terminology 3
1.4 A range of specimen sizes with proportional planar Summary of Use 4
Significance and Use 5
dimensions is provided, but size is variable to be adjusted for
Apparatus 6
yield strength and applied force. Specimen thickness may be
Specimen Configuration, Size, and Preparation 7
varied independent of planar size. Procedure 8
Calculations and Interpretation of Results 9
1.5 The details of the various specimens and test configu-
Report 10
Precision and Bias 11
rations are shown in Annex A1 – Annex A3. Specimen
Special Requirements for Testing in Aqueous Environments Annex A4
configurations other than those contained in this method may
Guidelines for Use of Compliance to Determine Crack Size Annex A5
be used provided that well-established stress-intensity factor
Guidelines for Electric Potential Difference Determination of Annex A6
Crack Size
calibrations are available and that specimens are of sufficient
Recommended Data Reduction Techniques Appendix X1
planar size to remain predominantly elastic during testing.
Recommended Practice for Determination of Fatigue Crack Appendix X2
Opening Force from Compliance
1.6 Residual stress as well as a variety of shielding effects
Guidelines for Measuring the Growth Rates of Small Fatigue Appendix X3
such as crack closure may significantly influence the interpre-
Cracks
tation of fatigue crack growth rate data, particularly at low Recommended Practice for Determination of ACR-Based Appendix X4
3
Stress-Intensity Factor Range
stress-intensity factors and low force ratios (1, 2). None of
1.9 Special requirements for the various specimen configu-
these variables are incorporated into the classical computation
of applied ΔK. rations appear in the following order:
The Compact Specimen Annex A1
1.7 Values stated in SI units are to be regarded as the
The Middle Tension Specimen Annex A2
standard. Values given in parentheses are for information only.
The Eccentrically-Loaded Single Edge Crack Tension Annex A3
Specimen
1
This test method is under the jurisdiction of ASTM Committee E08 on Fatigue 1.10 This standard does not purport to address all of the
and Fracture and is the direct responsibility of Subcommittee E08.06 on Crack
safety concerns, if any, associated with its use. It is the
Growth Behavior.
responsibility of the user of this standard to establish appro-
Current edition approved Nov. 15, 2023. Published April 2024. Originally
priate safety, health, and environmental practices and deter-
approved in 1978. Last previous approved in 2023 as E647 – 23a. DOI: 10.1520/
E0647-23B.
mine the applicability of regulatory limitations prior to use.
2
For additional information on this test method see RR: E24 – 1001. Available
1.11 This international standard was developed in accor-
from A
...
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: E647 − 23a E647 − 23b
Standard Test Method for
1
Measurement of Fatigue Crack Growth Rates
This standard is issued under the fixed designation E647; 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
2
1.1 This test method covers the determination of fatigue crack growth rates from near-threshold (see region I in Fig. 1) to K
max
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.
1.2 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 as well as a variety of shielding effects such as crack closure may significantly influence the interpretation of
3
fatigue crack growth rate data, particularly at low stress-intensity factors and low force ratios (1, 2). None of these variables are
incorporated into the classical computation of applied ΔK.
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:
1
This test method is under the jurisdiction of ASTM Committee E08 on Fatigue and Fracture and is the direct responsibility of Subcommittee E08.06 on Crack Growth
Behavior.
Current edition approved June 1, 2023Nov. 15, 2023. Published June 2023April 2024. Originally approved in 1978. Last previous approved in 2023 as
E647 – 23.E647 – 23a. DOI: 10.1520/E0647-23A.10.1520/E0647-23B.
2 For additional information on this test method see RR: E24 – 1001. Available from ASTM Headquarters, 100 Barr Harbor Drive, West Conshohocken, PA 19428.
3
The boldface numbers in parentheses refer to the list of references at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
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E647 − 23b
FIG. 1 Defined Regions of a Typical Fatigue Crack Growth Rate Curve
Section
Referenced Documents 2
Terminology 3
Summary of Use 4
Significance and Use 5
Apparatus 6
Specimen Configuration, Size, and Preparation 7
Procedure 8
Calculations and Interpretation of Results 9
Report 10
Precision and Bias 11
Special Requirements for Testing in Aqueous Environments Annex A4
Guidelines for Use of Compliance to Determine Crack Size Annex A5
Guidelines for Electric Potential Difference Determination of Annex A6
Crack Size
Recommended Data Reduction Techniques Appendix X1
Recommended Practice for Determination of Fatigue Crack Appendix X2
Opening Force from Compliance
Guidelines for Measuring the Growth Rates of Small Fatigue Appendix X3
Cracks
Recommended Practice for Determination of ACR-Based Appendix X4
Stress-Intensity Factor Range
1.9 S
...
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