ASTM E2760-10e2

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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´2
Designation: E2760 − 10
Standard Test Method for
1
Creep-Fatigue Crack Growth Testing
This standard is issued under the fixed designation E2760; 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
ε NOTE—3.2.19 was editorially revised in December 2011.
2
ε NOTE—Sections 3.2.20 and 3.3.3 were editorially revised in March 2013.
1. Scope substantial time-dependent creep strains near the crack tip. In
creep-brittle materials, creep-fatigue crack growth occurs at
1.1 This test method covers the determination of creep-
low creep ductility. Consequently, the time-dependent creep
fatigue crack growth properties of nominally homogeneous
strainsarecomparabletoorlessthantheaccompanyingelastic
materials by use of pre-cracked compact type, C(T), test
strains near the crack tip.
specimens subjected to uniaxial cyclic forces. It concerns
1.3.1 In creep-brittle materials, creep-fatigue crack growth
fatigue cycling with sufficiently long loading/unloading rates
rates per cycle or da/dN, are expressed in terms of the
or hold-times, or both, to cause creep deformation at the crack
magnitude of the cyclic stress intensity parameter, ∆K. These
tip and the creep deformation be responsible for enhanced
crack growth rates depend on the loading/unloading rates and
crack growth per loading cycle. It is intended as a guide for
hold-time at maximum load, the force ratio, R, and the test
creep-fatigue testing performed in support of such activities as
temperature (see Annex A1 for additional details).
materials research and development, mechanical design, pro-
1.3.2 In creep-ductile materials, the average time rates of
cess and quality control, product performance, and failure
crack growth during a loading cycle, (da/dt) , are expressed
avg
analysis.Therefore, this method requires testing of at least two
as a function of the average magnitude of the C parameter,
t
specimens that yield overlapping crack growth rate data. The
(C) (2).
t avg
cyclicconditionsresponsibleforcreep-fatiguedeformationand
enhanced crack growth vary with material and with tempera-
NOTE 1—The correlations between (da/dt) and (C) have been
avg t avg
ture for a given material. The effects of environment such as shown to be independent of hold-times (2, 3).
time-dependent oxidation in enhancing the crack growth rates
1.4 The crack growth rates derived in this manner and
areassumedtobeincludedinthetestresults;itisthusessential
expressed as a function of the relevant crack tip parameter(s)
to conduct testing in an environment that is representative of
are identified as a material property which can be used in
the intended application.
integrity assessment of structural components subjected to
similar loading conditions during service and life assessment
1.2 Two types of crack growth mechanisms are observed
during creep/fatigue tests: (1) time-dependent intergranular methods.
creep and (2) cycle dependent transgranular fatigue. The
1.5 Theuseofthispracticeislimitedtospecimensanddoes
interaction between the two cracking mechanisms is complex
not cover testing of full-scale components, structures, or
and depends on the material, frequency of applied force cycles
consumer products.
and the shape of the force cycle. When tests are planned, the
1.6 This practice is primarily aimed at providing the mate-
loading frequency and waveform that simulate or replicate
rial properties required for assessment of crack-like defects in
service loading must be selected.
engineeringstructuresoperatedatelevatedtemperatureswhere
1.3 Two types of creep behavior are generally observed in
creep deformation and damage is a design concern and are
materialsduringcreep-fatiguecrackgrowthtests:creep-ductile
subjected to cyclic loading involving slow loading/unloading
2
and creep-brittle (1). In creep-ductile materials, creep strains
rates or hold-times, or both, at maximum loads.
dominate and creep-fatigue crack growth is accompanied by
1.7 This practice is applicable to the determination of crack
growth rate properties as a consequence of constant-amplitude
load-controlledtestswithcontrolledloading/unloadingratesor
1
This test method is under the jurisdiction ofASTM Committee E08 on Fatigue
hold-times at the maximum load, or both. It is primarily
and Fracture and is the direct responsibility of Subcommittee E08.06 on Crack
Growth Behavior.
concerned with the testing of C(T) specimens subjected to
Current edition approved May 1, 2010. Published July 2010. DOI: 10.1520/
uniaxial loading in load control mode. The focus of the
E2760-10E02.
2
procedure is on tests in which creep and fatigue defor
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