ASTM E2760-19e2

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.
´2
Designation: E2760 − 19
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. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1
ε NOTE—Section 3.2.18.4 was editorially corrected in July 2020.
2
ε NOTE—Sections 3.2.3 and 3.2.14 were editorially corrected in April 2024.
1. Scope have rupture ductility of 10 % or higher, creep strains dominate
and creep-fatigue crack growth is accompanied by substantial
1.1 This test method covers the determination of creep-
time-dependent creep strains near the crack tip. In creep-brittle
fatigue crack growth properties of nominally homogeneous
materials, creep-fatigue crack growth occurs at low creep
materials by use of pre-cracked compact type, C(T), test
ductility. Consequently, the time-dependent creep strains are
specimens subjected to uniaxial cyclic forces. It concerns
comparable to or less than the accompanying elastic strains
fatigue cycling with sufficiently long loading/unloading rates
near the crack tip.
or hold-times, or both, to cause creep deformation at the crack
1.3.1 In creep-brittle materials, creep-fatigue crack growth
tip and the creep deformation be responsible for enhanced
rates per cycle or da/dN, are expressed in terms of the
crack growth per loading cycle. It is intended as a guide for
magnitude of the cyclic stress intensity parameter, ∆K. These
creep-fatigue testing performed in support of such activities as
crack growth rates depend on the loading/unloading rates and
materials research and development, mechanical design, pro-
hold-time at maximum load, the force ratio, R, and the test
cess and quality control, product performance, and failure
temperature (see Annex A1 for additional details).
analysis. Therefore, this method requires testing of at least two
1.3.2 In creep-ductile materials, the average time rates of
specimens that yield overlapping crack growth rate data. The
crack growth during a loading cycle, (da/dt) , are expressed
avg
cyclic conditions responsible for creep-fatigue deformation and
as a function of the average magnitude of the C parameter,
enhanced crack growth vary with material and with tempera- t
(C ) (2).
t avg
ture for a given material. The effects of environment such as
time-dependent oxidation in enhancing the crack growth rates
NOTE 1—The correlations between (da/dt) and (C ) have been
avg t avg
are assumed to be included in the test results; it is thus essential shown to be independent of hold-times (2, 3) for highly creep-ductile
materials that have rupture ductility of 10 percent or higher.
to conduct testing in an environment that is representative of
the intended application.
1.4 The crack growth rates derived in this manner and
expressed as a function of the relevant crack tip parameter(s)
1.2 Two types of crack growth mechanisms are observed
are identified as a material property which can be used in
during creep/fatigue tests: (1) time-dependent intergranular
integrity assessment of structural components subjected to
creep and (2) cycle dependent transgranular fatigue. The
similar loading conditions during service and life assessment
interaction between the two cracking mechanisms is complex
methods.
and depends on the material, frequency of applied force cycles
and the shape of the force cycle. When tests are planned, the
1.5 The use of this practice is limited to specimens and does
loading frequency and waveform that simulate or replicate
not cover testing of full-scale components, structures, or
service loading must be selected.
consumer products.
1.3 Two types of creep behavior are generally observed in
1.6 This practice is primarily aimed at providing the mate-
materials during creep-fatigue crack growth tests: creep-ductile
rial properties required for assessment of crack-like defects in
2
and creep-brittle (1) . For highly creep-ductile materials that
engineering structures operated at elevated temperatures where
creep deformation and damage is a design concern and are
subjected to cyclic loading involving slow loading/unloading
1
This test method is under the jurisdiction of ASTM Committee E08 on Fatigue
rates or hold-times, or both, at maximum loads.
and Fracture and is the direct responsibility of Subcommittee E08.06 on Crack
1.7 This practice is applicable to the determination of crack
Growth Behavior.
Current edition approved Nov. 1, 2019. Published January 2020. Origin
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