ASTM G129-00(2013)
(Practice)Standard Practice for Slow Strain Rate Testing to Evaluate the Susceptibility of Metallic Materials to Environmentally Assisted Cracking
Standard Practice for Slow Strain Rate Testing to Evaluate the Susceptibility of Metallic Materials to Environmentally Assisted Cracking
SIGNIFICANCE AND USE
5.1 The slow strain rate test is used for relatively rapid screening or comparative evaluation, or both, of environmental, processing or metallurgical variables, or both, that can affect the resistance of a material to EAC. For example, this testing technique has been used to evaluate materials, heat treatments, chemical constituents in the environment, and temperature and chemical inhibitors.
5.2 Where possible, the application of the SSR test and data derived from its use should be used in combination with service experience or long-term EAC data, or both, obtained through literature sources or additional testing using other testing techniques. In applications where there has been little or no prior experience with SSR testing or little EAC data on the particular material/environment combination of interest, the following steps are recommended:
5.2.1 The SSR tests should be conducted over a range of applied extension rates (that is, usually at least one order of magnitude in applied extension rate above and below 10−6 in/s (2.54 × 10–5 mm/s) to determine the effect of strain rate or rate of increase of the stress or stress intensity factor on susceptibility to EAC.
5.2.2 Constant load or strain EAC tests should also be conducted in simulated service environments, and service experience should be obtained so that a correlation between SSR test results and anticipated service performance can be developed.
5.3 In many cases the SSR test has been found to be a conservative test for EAC. Therefore, it may produce failures in the laboratory under conditions which do not necessarily cause EAC under service application. Additionally, in some limited cases, EAC indications are not found in smooth tension SSR tests even when service failures have been observed. This effect usually occurs when there is a delay in the initiation of localized corrosion processes. Therefore, the suggestions given in 5.2 are strongly encouraged.
5.4 In some cases, EAC will only ...
SCOPE
1.1 This practice covers procedures for the design, preparation, and use of axially loaded, tension test specimens and fatigue pre-cracked (fracture mechanics) specimens for use in slow strain rate (SSR) tests to investigate the resistance of metallic materials to environmentally assisted cracking (EAC). While some investigators utilize SSR test techniques in combination with cyclic or fatigue loading, no attempt has been made to incorporate such techniques into this practice.
1.2 Slow strain rate testing is applicable to the evaluation of a wide variety of metallic materials in test environments which simulate aqueous, nonaqueous, and gaseous service environments over a wide range of temperatures and pressures that may cause EAC of susceptible materials.
1.3 The primary use of this practice is to furnish accepted procedures for the accelerated testing of the resistance of metallic materials to EAC under various environmental conditions. In many cases, the initiation of EAC is accelerated through the application of a dynamic strain in the gauge section or at a notch tip or crack tip, or both, of a specimen. Due to the accelerated nature of this test, the results are not intended to necessarily represent service performance, but rather to provide a basis for screening, for detection of an environmental interaction with a material, and for comparative evaluation of the effects of metallurgical and environmental variables on sensitivity to known environmental cracking problems.
1.4 Further information on SSR test methods is available in ISO 7539 and in the references provided with this practice (1-6).2
1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.6 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 s...
General Information
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: G129 − 00 (Reapproved 2013)
Standard Practice for
Slow Strain Rate Testing to Evaluate the Susceptibility of
Metallic Materials to Environmentally Assisted Cracking
This standard is issued under the fixed designation G129; 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 1.6 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This practice covers procedures for the design,
responsibility of the user of this standard to establish appro-
preparation, and use of axially loaded, tension test specimens
priate safety and health practices and determine the applica-
andfatiguepre-cracked(fracturemechanics)specimensforuse
bility of regulatory limitations prior to use. Furthermore, in
in slow strain rate (SSR) tests to investigate the resistance of
some cases, special facilities will be required to isolate these
metallicmaterialstoenvironmentallyassistedcracking(EAC).
tests from laboratory personnel if high pressures or toxic
While some investigators utilize SSR test techniques in com-
chemical environments, or both, are utilized in SSR testing.
bination with cyclic or fatigue loading, no attempt has been
made to incorporate such techniques into this practice.
2. Referenced Documents
1.2 Slowstrainratetestingisapplicabletotheevaluationof 3
2.1 ASTM Standards:
awidevarietyofmetallicmaterialsintestenvironmentswhich
A370Test Methods and Definitions for Mechanical Testing
simulate aqueous, nonaqueous, and gaseous service environ-
of Steel Products
ments over a wide range of temperatures and pressures that
B557Test Methods for Tension Testing Wrought and Cast
may cause EAC of susceptible materials.
Aluminum- and Magnesium-Alloy Products
D1193Specification for Reagent Water
1.3 The primary use of this practice is to furnish accepted
procedures for the accelerated testing of the resistance of E4Practices for Force Verification of Testing Machines
E6Terminology Relating to Methods of Mechanical Testing
metallic materials to EAC under various environmental condi-
tions. In many cases, the initiation of EAC is accelerated E8Test Methods for Tension Testing of Metallic Materials
E399Test Method for Linear-Elastic Plane-Strain Fracture
throughtheapplicationofadynamicstraininthegaugesection
oratanotchtiporcracktip,orboth,ofaspecimen.Duetothe Toughness K of Metallic Materials
Ic
E602Test Method for Sharp-Notch Tension Testing with
accelerated nature of this test, the results are not intended to
necessarily represent service performance, but rather to pro- Cylindrical Specimens (Withdrawn 2010)
E616Terminology Relating to Fracture Testing (Discontin-
vide a basis for screening, for detection of an environmental
interaction with a material, and for comparative evaluation of ued 1996) (Withdrawn 1996)
E647 Test Method for Measurement of Fatigue Crack
the effects of metallurgical and environmental variables on
sensitivity to known environmental cracking problems. Growth Rates
E1681Test Method for DeterminingThreshold Stress Inten-
1.4 Further information on SSR test methods is available in
sityFactorforEnvironment-AssistedCrackingofMetallic
ISO 7539 and in the references provided with this practice
Materials
(1-6).
G15TerminologyRelatingtoCorrosionandCorrosionTest-
1.5 The values stated in SI units are to be regarded as
ing (Withdrawn 2010)
standard. The values given in parentheses are for information
G49Practice for Preparation and Use of Direct Tension
only.
Stress-Corrosion Test Specimens
G111Guide for Corrosion Tests in High Temperature or
High Pressure Environment, or Both
This practice is under the jurisdiction ofASTM Committee G01 on Corrosion
of Metals and is the direct responsibility of Subcommittee G01.06 on Environmen-
tally Assisted Cracking. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
CurrenteditionapprovedMay1,2013.PublishedJuly2013.Originallyapproved contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
in 1995. Last previous edition approved in 2006 as G129–00 (2006). DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/G0129-00R13. the ASTM website.
2 4
The boldface numbers in parentheses refer to a list of references at the end of The last approved version of this historical standard is referenced on
this standard. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G129 − 00 (2013)
G142Test Method for Determination of Susceptibility of constant extension rate on the specimen while monitoring load
Metals to Embrittlement in Hydrogen Containing Envi- and extension of the specimen. The SSR test always produces
ronments at High Pressure, High Temperature, or Both
fracture of the test specimen. Typically, the results from tests
conductedinthetestenvironmentarecomparedtocorrespond-
2.2 ISO Standard:
ISO 7539Part 7, Slow Strain Rate Testing ing test results for the same material in a control environment.
The degree of susceptibility to EAC is generally assessed
3. Terminology
through observation of the differences in the behavior of the
material in tests conducted in a test environment from that
3.1 For purposes of this practice the following terms are
defined: obtained from tests conducted in the control environment. For
smoothtensionspecimens,eitherchangesintime-to-failure,or
3.2 control environment—an environment in which SSR
specimenductility,orvisualindicationsofEAC,oroftensome
specimens are tested that has been shown not to cause EAC or
combination of these methods, are utilized in determining
excessive corrosion of the material. The results of tests
susceptibilitytoEAC.Fornotchedtensionspecimens,changes
conducted in this environment may be used as a basis for
in the notch tensile strength and visual indications of EAC on
comparison with corresponding tests conducted in the test
the primary fracture surface are used in determining suscepti-
environment(s), usually at the same temperature as the test
bility to EAC. For fatigue pre-cracked specimens, changes in
environment.
the threshold stress intensity factor and visual indications of
3.3 environmentally assisted cracking (EAC)— cracking of
EAC on the primary fracture surface are used in determining
a material caused by the combined effects of stress and the
susceptibility to EAC.
surrounding environment, for example, stress corrosion
cracking, hydrogen embrittlement cracking, sulfide stress
5. Significance and Use
cracking and liquid metal embrittlement.
5.1 The slow strain rate test is used for relatively rapid
3.4 slow strain rate (SSR)—a dynamic slowly increasing
screening or comparative evaluation, or both, of
strain imposed by an external means on the gauge section or
environmental, processing or metallurgical variables, or both,
notchtipofauniaxialtensionspecimenorcracktipofafatigue
pre-cracked specimen for purposes of materials evaluation. that can affect the resistance of a material to EAC. For
The strain rate for a plain or smooth specimen (given in units example, this testing technique has been used to evaluate
of extension divided by the gage length per unit time) or the materials, heat treatments, chemical constituents in the
strainrateatanotchtipofanotchedtensionspecimenorcrack
environment, and temperature and chemical inhibitors.
tip of a fatigue pre-cracked specimen is applied through the
5.2 Wherepossible,theapplicationoftheSSRtestanddata
application of a slow constant extension rate (given in units of
derived from its use should be used in combination with
extension per unit time). The slow constant extension rate
service experience or long-term EAC data, or both, obtained
produces a gauge section strain rate, which is usually in the
through literature sources or additional testing using other
−4 −7 −1
range from 10 to 10 /s . Rigorous analytical solutions of
testingtechniques.Inapplicationswheretherehasbeenlittleor
the local strain rate at a notch tip of a tension specimen or at a
no prior experience with SSR testing or little EAC data on the
crack tip of a fatigue pre-cracked specimen are not available.
particular material/environment combination of interest, the
Theaverageorlocalstrainrateshouldbeslowenoughtoallow
following steps are recommended:
time for certain corrosion processes to take place, but fast
5.2.1 The SSR tests should be conducted over a range of
enough to produce failure or cracking of the specimen in a
applied extension rates (that is, usually at least one order of
reasonable period of time for evaluation purposes. In cases
−6
magnitude in applied extension rate above and below 10 in/s
where extremely slow strain rates are being utilized (that is,
−7 −8 −1 –5
(2.54 × 10 mm/s) to determine the effect of strain rate or rate
10 to10 /s forsmoothtensionspecimens),aninterrupted
of increase of the stress or stress intensity factor on suscepti-
SSR test can be employed whereby the specimen is strained
bility to EAC.
into the plastic range at the intended strain rate followed by
more rapid straining to failure.
5.2.2 Constant load or strain EAC tests should also be
conducted in simulated service environments, and service
3.5 The terminology found inTest Methods and Definitions
experience should be obtained so that a correlation between
A370, Test Method B557, and Test Method E602 along with
SSR test results and anticipated service performance can be
thedefinitionsgiveninTerminologiesE6,E616,andG15shall
developed.
apply to the terms used in this practice.
5.3 In many cases the SSR test has been found to be a
4. Summary of Practice
conservative test for EAC. Therefore, it may produce failures
4.1 This practice describes the use of tension and fatigue
in the laboratory under conditions which do not necessarily
pre-cracked specimens for the determination of resistance to
cause EAC under service application. Additionally, in some
EAC of metallic materials. The procedure involves the appli-
limitedcases,EACindicationsarenotfoundinsmoothtension
cation of very slow strain rates, which are achieved by a
SSR tests even when service failures have been observed.This
effect usually occurs when there is a delay in the initiation of
5 localizedcorrosionprocesses.Therefore,thesuggestionsgiven
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. in 5.2 are strongly encouraged.
G129 − 00 (2013)
5.4 In some cases, EAC will only occur in a specific range
ofstrainrates.Therefore,wherethereislittlepriorinformation
available,testsshouldbeconductedoverarangeofstrainrates
as discussed in 5.2.
6. Apparatus
6.1 Testing Machines:
6.1.1 Tension testing machines used for SSR testing shall
conform to the requirements of Practices E4.
6.1.2 The loads used in SSR testing shall be within the
calibrated load ranges of the testing machine in accordance
with Practices E4.
6.1.3 The testing machines used for SSR testing shall be
capable of accurate application of extension rates in the range
of interest for evaluation of EAC. These extension rates are
−4 −7 –3
usually between 10 and 10 in/s (2.54 × 10 and 2.54 ×
–6
10 mm/s).
6.1.4 An example of a SSR testing machine setup including
the load frame, instrumentation, and local test cell is shown in
Fig. 1.Another example of a SSR machine setup with a metal
test cell or autoclave can be found in Test Method G142. The
test specimen is loaded with a grip assembly and load frame
inside the autoclave. The autoclave is equipped with a tensile
loadingfeed-throughtoprovidetransmissionofloadsfromthe
tensile machine to the specimen using a pull rod in combina-
tionwiththefeed-through.SomeSSRtestingmachinesmaybe
able to test more than one specimen at a time in a particular
environment. However, this type of machine should only be
used if it can be shown that failure of one or multiple
specimens does not influence the behavior of the other speci-
mens.
6.2 Gripping Devices—The types of gripping devices that
may be used to transmit the applied load from the testing
machinetothetensionspecimenconformtothosedescribedin
Test Methods E8. Alignment procedures are provided in Test
Method E8.
6.3 Clevices and Fixtures—Aloading clevis that is suitable
FIG. 1 An Example of a SSR Testing Machine.
for loading pre-cracked compact specimens should conform
with clevices described in Test Method E399. A bend test
fixtureforloadingpre-crackedbendspecimensshouldconform 6.5 Environmental Test Cells—Test cells shall be con-
with bend fixtures described in Test Method E399.Itis structed in a manner to facilitate handling and monitoring of
important that attention be given to achieving good load train the test environment while allowing testing of the tension
alignment through careful machining of all clevices and specimen. This will require the incorporation of a suitable
low-friction feed-through in the vessel for application of load
fixtures.
to the test specimen.Additionally, the test cell shall be able to
6.4 Displacement Gauges—An electronic crack mouth
safely contain the test environment with adequate accommo-
opening displacement (CMOD) gauge attached to the front
dation for the temperature and pressure under which the SSR
face of pre-cracked specimens and spanning the crack starter
tests will be conducted.
notch to detect crack growth during testing should be in
6.5.1 Test cells shall be effectively inert (that is, have a low
accordance with displacement gauges described in Test
corrosion rate and not susceptible to EAC in the test environ-
Method E399. Alternatively, the displacements can be trans-
ment so that they do not react with or contaminate the
ferred outside the environmental test cell in the case of tests
environment).
conducted in high temperature or severely corrosive environ-
6.5.2 The test cell size should be such that a solution
ments.Anextensometerplacedoutsidethetestcellcanbeused
volume-to-exposed specimen surface area is not less than 30
to detect the crack growth. A displacement gauge can be
mL/cm .
attachedtothespecimenatalternativelocationstodetectcrack
growth if the proper compliance-crack length relationship has 6.6 Galvanic Effects—Eliminate galvanic effects between
been determined for the measurement location on the speci- the test specimen and various metallic components of the
men. gripping fixtures and test cell by electrically insulating or
...
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