ASTM E647-08
(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
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 (1) and (2).
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.
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.
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 thickness is increased. ...
SCOPE
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 (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/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 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 ...
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Designation: E647 – 08
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.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope proceduresfornon-visualcracksizedetermination.Inaddition,
2 there are appendices that cover techniques for calculating
1.1 This test method covers the determination of fatigue
da/dN,determiningfatiguecrackopeningforce,andguidelines
crack growth rates from near-threshold to K controlled
max
for measuring the growth of small fatigue cracks. General
instability. Results are expressed in terms of the crack-tip
information and requirements common to all specimen types
stress-intensity factor range (DK), defined by the theory of
are listed as follows:
linear elasticity.
Section
1.2 Several different test procedures are provided, the opti-
Referenced Documents 2
mum test procedure being primarily dependent on the magni-
Terminology 3
tude of the fatigue crack growth rate to be measured.
Summary of Use 4
Significance and Use 5
1.3 Materials that can be tested by this test method are not
Apparatus 6
limited by thickness or by strength so long as specimens are of
Specimen Configuration, Size, and Preparation 7
sufficient thickness to preclude buckling and of sufficient
Procedure 8
Calculations and Interpretation of Results 9
planar size to remain predominantly elastic during testing.
Report 10
1.4 A range of specimen sizes with proportional planar
Precision and Bias 11
dimensions is provided, but size is variable to be adjusted for Special Requirements for Testing in Aqueous Environments Annex A4
Guidelines for Use of Compliance to Determine Crack Size Annex A5
yield strength and applied force. Specimen thickness may be
Guidelines for Electric Potential Difference Determination of Annex A6
varied independent of planar size.
Crack Size
1.5 The details of the various specimens and test configu- Recommended Data Reduction Techniques Appendix X1
Recommended Practice for Determination of Fatigue Crack Appendix X2
rations are shown inAnnexA1-AnnexA3. Specimen configu-
Opening Force From Compliance
rations other than those contained in this method may be used
Guidelines for Measuring the Growth Rates Of Small Fatigue Appendix X3
Cracks
provided that well-established stress-intensity factor calibra-
tions are available and that specimens are of sufficient planar
1.9 Special requirements for the various specimen configu-
size to remain predominantly elastic during testing.
rations appear in the following order:
1.6 Residualstress/crackclosuremaysignificantlyinfluence
The Compact Specimen Annex A1
the fatigue crack growth rate data, particularly at low stress-
The Middle Tension Specimen Annex A2
The Eccentrically-Loaded Single Edge Crack Tension Speci- Annex A3
intensity factors and low stress ratios, although such variables
men
are not incorporated into the computation of DK.
1.7 Values stated in SI units are to be regarded as the 1.10 This standard does not purport to address all of the
standard.Values given in parentheses are for information only.
safety concerns, if any, associated with its use. It is the
1.8 Thistestmethodisdividedintotwomainparts.Thefirst responsibility of the user of this standard to establish appro-
part gives general information concerning the recommenda-
priate safety and health practices and determine the applica-
tions and requirements for fatigue crack growth rate testing. bility of regulatory limitations prior to use.
The second part is composed of annexes that describe the
2. Referenced Documents
special requirements for various specimen configurations, spe-
3
cial requirements for testing in aqueous environments, and 2.1 ASTM Standards:
E4 Practices for Force Verification of Testing Machines
1
This test method is under the jurisdiction ofASTM Committee E08 on Fatigue
and Fracture and is the direct responsibility of Subcommittee E08.06 on Crack
Growth Behavior.
Current edition approved April 1, 2008. Published May 2008. Originally
3
approved in 1978. Last previous approved in 2005 as E647–05. DOI: 10.1520/ For referenced ASTM standards, visit the ASTM website, www.astm.org, or
E0647-08. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
2
For additional information on this test method see RR: E24–1001. Available Standards volume information, refer to the standard’s Document Summary page on
fromASTM Headquarters, 100 Barr Harbor Drive,West Conshohocken, PA19428. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 1942
...
This document is not anASTM standard and is intended only to provide the user of anASTM 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:E647–05 Designation: E 647 – 08
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.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) 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 to K controlled instability.
max
Results are expressed in terms of the crack-tip stress-intensity factor range (D 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 DK.
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:
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
1.9 Special requirements for the various specimen configurations appear in the following order:
The Compact Tension Specimen Annex A1
The Compact Specimen Annex A1
1
This test method is under the jurisdiction ofASTM Committee E08 on Fatigue and Fracture and is the direct responsibility of Subcommittee E08.06 on Crack Growth
Behavior.
Current edition approved June 15, 2005. Published July 2005. Originally approved in 1978. Last previous approved in 2000 as E647–00.
Current edition approved April 1, 2008. Published May 2008. Originally approved in 1978. Last previous approved in 2005 as E647–05.
2
For additional information on this test method see RR: E24–1001. Available from ASTM Headquarters, 100 Barr Harbor Drive, West Conshohocken, PA 19428.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
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E647–08
The Middle Tension Specimen Annex A2
The Eccentrically-Loaded Single Edge Crack Tension Speci- Annex A3
men
1.10 This standard does not purport to address all of the safety concerns, if any,
...
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