ASTM E2368-04e1
(Practice)Standard Practice for Strain Controlled Thermomechanical Fatigue Testing
Standard Practice for Strain Controlled Thermomechanical Fatigue Testing
SIGNIFICANCE AND USE
In the utilization of structural materials in elevated temperature environments, components that are susceptible to fatigue damage may experience some form of simultaneously varying thermal and mechanical forces throughout a given cycle. These conditions are often of critical concern because they combine temperature dependent and cycle dependent (fatigue) damage mechanisms with varying severity relating to the phase relationship between cyclic temperature and cyclic mechanical strain. Such effects can be found to influence the evolution of microstructure, micromechanisms of degradation, and a variety of other phenomenological processes that ultimately affect cyclic life. The strain-controlled thermomechanical fatigue test is often used to investigate the effects of simultaneously varying thermal and mechanical loadings under idealized conditions, where cyclic theoretically uniform temperature and strain fields are externally imposed and controlled throughout the gage section of the specimen.
SCOPE
1.1 This practice covers the determination of thermomechanical fatigue (TMF) properties of materials under uniaxially loaded strain-controlled conditions. A "thermomechanical" fatigue cycle is here defined as a condition where uniform temperature and strain fields over the specimen gage section are simultaneously varied and independently controlled. This practice is intended to address TMF testing performed in support of such activities as materials research and development, mechanical design, process and quality control, product performance, and failure analysis. While this practice is specific to strain-controlled testing, many sections will provide useful information for force-controlled or stress-controlled TMF testing.
1.2 This practice allows for any maximum and minimum values of temperature and mechanical strain, and temperature-mechanical strain phasing, with the restriction being that such parameters remain cyclically constant throughout the duration of the test. No restrictions are placed on environmental factors such as pressure, humidity, environmental medium, and others, provided that they are controlled throughout the test, do not cause loss of or change in specimen dimensions in time, and are detailed in the data report.
1.3 The use of this practice is limited to specimens and does not cover testing of full-scale components, structures, or consumer products.
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Standards Content (Sample)
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Designation:E2368–04
Standard Practice for
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Strain Controlled Thermomechanical Fatigue Testing
This standard is issued under the fixed designation E2368; 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.
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´ NOTE—Editorial changes were made throughout in May 2005.
1. Scope E83 Practice for Verification and Classification of Exten-
someter Systems
1.1 This practice covers the determination of thermome-
E111 Test Method forYoung’s Modulus, Tangent Modulus,
chanicalfatigue(TMF)propertiesofmaterialsunderuniaxially
and Chord Modulus
loaded strain-controlled conditions. A “thermomechanical”
E112 Test Methods for Determining Average Grain Size
fatigue cycle is here defined as a condition where uniform
E220 Test Method for Calibration of Thermocouples By
temperature and strain fields over the specimen gage section
Comparison Techniques
are simultaneously varied and independently controlled. This
E467 Practice for Verification of Constant Amplitude Dy-
practice is intended to address TMF testing performed in
namic Forces in an Axial Fatigue Testing System
support of such activities as materials research and develop-
E606 Practice for Strain-Controlled Fatigue Testing
ment, mechanical design, process and quality control, product
E739 Practice for Statistical Analysis of Linear or Linear-
performance, and failure analysis. While this practice is spe-
ized Stress-Life ( S-N) and Strain-Life (e-N) Fatigue Data
cific to strain-controlled testing, many sections will provide
E1012 PracticeforVerificationofTestFrameandSpecimen
useful information for force-controlled or stress-controlled
Alignment Under Tensile and Compressive Axial Force
TMF testing.
Application
1.2 This practice allows for any maximum and minimum
E1823 Terminology Relating to Fatigue and Fracture Test-
values of temperature and mechanical strain, and temperature-
ing
mechanical strain phasing, with the restriction being that such
parameters remain cyclically constant throughout the duration
3. Terminology
of the test. No restrictions are placed on environmental factors
3.1 The definitions in this practice are in accordance with
such as pressure, humidity, environmental medium, and others,
definitions given in Terminology E1823 unless otherwise
provided that they are controlled throughout the test, do not
stated.
cause loss of or change in specimen dimensions in time, and
3.2 Additional definitions are as follows:
are detailed in the data report.
3.2.1 stress, s—stress is defined herein to be the engineer-
1.3 The use of this practice is limited to specimens and does
ing stress, which is the ratio of force, P, to specimen original
not cover testing of full-scale components, structures, or
cross sectional area, A:
consumer products.
s5 P/A (1)
2. Referenced Documents
The area, A, is that measured in an unloaded condition at
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2.1 ASTM Standards:
room temperature. See 7.2 for temperature state implications.
E3 Guide for Preparation of Metallographic Specimens
3.2.2 coeffıcient of thermal expansion, a—the fractional
E4 Practices for Force Verification of Testing Machines
change in free expansion strain for a unit change in tempera-
ture, as measured on the test specimen.
1 3.2.3 total strain, ´—the strain component measured on the
t
This practice is under the jurisdiction ofASTM Committee E08 on Fatigue and
Fracture and is the direct responsibility of Subcommittee E08.05 on Cyclic test specimen, and is the sum of the thermal strain and the
Deformation and Fatigue Crack Formation.
mechanical strain.
Current edition approved May 1, 2004. Published June 2004. DOI: 10.1520/
3.2.4 thermal strain, ´ —the strain component resulting
th
E2368-04E01.
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from a change in temperature under free expansion conditions
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
(as measured on the test specimen).
Standards volume information, refer to the standard’s Document Summary page on
´ 5s · DT (2)
th
the ASTM website.
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E2368–04
NOTE 1—For some materials, s may be nonlinear over the temperature
(test frame and associated fixtures) shall be in compliance with
range of interest.
the bending strain criteria specified in Practices E606, E1012,
and E467. The test system shall be able to independently
3.2.5 mechanical strain, ´ —thestraincomponentresulting
m
control both temperature and total strain. In addition it sh
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