ASTM G129-00
(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
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 gage 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).
1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are provided 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 safety and health practices and determine the applicability of regulatory limitations prior to use. Furthermore, in some cases, special facilities will be required to isolate these tests from laboratory personnel if high pressures or toxic chemical environments, or both, are utilized in SSR testing.
General Information
Relations
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
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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope bility of regulatory limitations prior to use. Furthermore, in
some cases, special facilities will be required to isolate these
1.1 This practice covers procedures for the design, prepara-
tests from laboratory personnel if high pressures or toxic
tion, and use of axially loaded, tension test specimens and
chemical environments, or both, are utilized in SSR testing.
fatigue pre-cracked (fracture mechanics) specimens for use in
slow strain rate (SSR) tests to investigate the resistance of
2. Referenced Documents
metallicmaterialstoenvironmentallyassistedcracking(EAC).
2.1 ASTM Standards:
While some investigators utilize SSR test techniques in com-
A370 TestMethodsandDefinitionsforMechanicalTesting
bination with cyclic or fatigue loading, no attempt has been
of Steel Products
made to incorporate such techniques into this practice.
B557 Test Methods for Tension Testing of Wrought and
1.2 Slowstrainratetestingisapplicabletotheevaluationof
Cast Aluminum and Magnesium-Alloy Products
awidevarietyofmetallicmaterialsintestenvironmentswhich
D1193 Specification for Reagent Water
simulate aqueous, nonaqueous, and gaseous service environ-
E4 Practices for Load Verification of Testing Machines
ments over a wide range of temperatures and pressures that
E6 Terminology Relating to Methods of Mechanical Test-
may cause EAC of susceptible materials.
ing
1.3 The primary use of this practice is to furnish accepted
E8 TestMethodsforTensionTestingofMetallicMaterials
procedures for the accelerated testing of the resistance of
E399 Test Method for Plane-Strain Fracture Toughness of
metallic materials to EAC under various environmental condi-
Metallic Materials
tions. In many cases, the initiation of EAC is accelerated
E602 Test Method for Sharp-Notch Tension Testing with
through the application of a dynamic strain in the gage section
Cylindrical Specimens
oratanotchtiporcracktip,orboth,ofaspecimen.Duetothe
E616 Terminology Relating to Fracture Testing
accelerated nature of this test, the results are not intended to
E647 Test Method for Measurement of Fatigue Crack
necessarily represent service performance, but rather to pro-
Growth Rates
vide a basis for screening, for detection of an environmental
E1681 Test Method for Determining a Threshold Stress
interaction with a material, and for comparative evaluation of
Intensity Factor for Environmentally-Assisted Cracking of
the effects of metallurgical and environmental variables on
Metallic Materials
sensitivity to known environmental cracking problems.
G15 Terminology Relating to Corrosion and Corrosion
1.4 Further information on SSR test methods is available in
Testing
ISO 7539 and in the references provided with this practice
2 G49 Practice for Preparation and Use of Direct Tension
(1-6).
Stress Corrosion Test Specimens
1.5 The values stated in SI units are to be regarded as the
G111 Guide for Corrosion Tests in High Temperature or
standard. The values given in parentheses are provided for
High Pressure Environment, or Both
information only.
G142 Test Method for Determination of Susceptibility of
1.6 This standard does not purport to address all of the
MetalstoEmbrittlementinHydrogenContainingEnviron-
safety concerns, if any, associated with its use. It is the
ments at High Pressure, High Temperature, or Both
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
This practice is under the jurisdiction ofASTM Committee G01 on Corrosion
of Metals and is the direct responsibility of Subcommittee G01.06 on Stress Annual Book of ASTM Standards, Vol 01.03.
Corrosion Cracking and Corrosion Fatigue. Annual Book of ASTM Standards, Vol 02.02.
Current edition approved Nov. 10, 2000. Published November 2000. Originally Annual Book of ASTM Standards, Vol 11.01.
published as G129–95. Last previous edition G129–95. Annual Book of ASTM Standards, Vol 03.01.
2 7
Boldface numbers refer to the list of references at the end of this standard. Annual Book of ASTM Standards, Vol 03.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G129
2.2 ISO Standard: ing test results for the same material in a control environment.
7539, Part 7, Slow Strain Rate Testing The degree of susceptibility to EAC is generally assessed
through observation of the differences in the behavior of the
3. Terminology
material in tests conducted in a test environment from that
obtained from tests conducted in the control environment. For
3.1 For purposes of this practice the following terms are
defined: smoothtensionspecimens,eitherchangesintime-to-failure,or
specimenductility,orvisualindicationsofEAC,oroftensome
3.2 control environment—an environment in which SSR
specimens are tested that has been shown not to cause EAC or combination of these methods, are utilized in determining
susceptibilitytoEAC.Fornotchedtensionspecimens,changes
excessive corrosion of the material. The results of tests
conducted in this environment may be used as a basis for in the notch tensile strength and visual indications of EAC on
the primary fracture surface are used in determining suscepti-
comparison with corresponding tests conducted in the test
environment(s), usually at the same temperature as the test bility to EAC. For fatigue pre-cracked specimens, changes in
the threshold stress intensity factor and visual indications of
environment.
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 crack-
5. Significance and Use
ing, hydrogen embrittlement cracking, sulfide stress cracking
5.1 The slow strain rate test is used for relatively rapid
and liquid metal embrittlement.
screening or comparative evaluation, or both, of environmen-
3.4 slow strain rate (SSR)—a dynamic slowly increasing
tal, processing or metallurgical variables, or both, that can
strain imposed by an external means on the gage section or
affect the resistance of a material to EAC. For example, this
notchtipofauniaxialtensionspecimenorcracktipofafatigue
testing technique has been used to evaluate materials, heat
pre-cracked specimen for purposes of materials evaluation.
treatments, chemical constituents in the environment, and
The strain rate for a plain or smooth specimen (given in units
temperature and chemical inhibitors.
of extension divided by the gage length per unit time) or the
5.2 Wherepossible,theapplicationoftheSSRtestanddata
strainrateatanotchtipofanotchedtensionspecimenorcrack
derived from its use should be used in combination with
tip of a fatigue pre-cracked specimen is applied through the
service experience or long-term EAC data, or both, obtained
application of a slow constant extension rate (given in units of
through literature sources or additional testing using other
extension per unit time). The slow constant extension rate
testingtechniques.Inapplicationswheretherehasbeenlittleor
produces a gage section strain rate, which is usually in the
−4 −7 −1
no prior experience with SSR testing or little EAC data on the
range from 10 to 10 /s . Rigorous analytical solutions of
particular material/environment combination of interest, the
the local strain rate at a notch tip of a tension specimen or at a
following steps are recommended:
crack tip of a fatigue pre-cracked specimen are not available.
5.2.1 The SSR tests should be conducted over a range of
Theaverageorlocalstrainrateshouldbeslowenoughtoallow
applied extension rates (that is, usually at least one order of
time for certain corrosion processes to take place, but fast
−6
magnitude in applied extension rate above and below 10 in/s
enough to produce failure or cracking of the specimen in a
–5
(2.54 310 mm/s)todeterminetheeffectofstrainrateorrate
reasonable period of time for evaluation purposes. In cases
of increase of the stress or stress intensity factor on suscepti-
where extremely slow strain rates are being utilized (that is,
−7 −8 −1
bility to EAC.
10 to10 /s forsmoothtensionspecimens),aninterrupted
5.2.2 Constant load or strain EAC tests should also be
SSR test can be employed whereby the specimen is strained
conducted in simulated service environments, and service
into the plastic range at the intended strain rate followed by
experience should be obtained so that a correlation between
more rapid straining to failure.
SSR test results and anticipated service performance can be
3.5 The terminology found inTest Methods and Definitions
developed.
A370, Test Method B557, and Test Method E602 along with
5.3 In many cases the SSR test has been found to be a
the definitions given in Terminologies E6, E616, and G15
conservative test for EAC. Therefore, it may produce failures
shall apply to the terms used in this practice.
in the laboratory under conditions which do not necessarily
4. Summary of Practice
cause EAC under service application. Additionally, in some
limitedcases,EACindicationsarenotfoundinsmoothtension
4.1 This practice describes the use of tension and fatigue
SSR tests even when service failures have been observed.This
pre-cracked specimens for the determination of resistance to
effect usually occurs when there is a delay in the initiation of
EAC of metallic materials. The procedure involves the appli-
localizedcorrosionprocesses.Therefore,thesuggestionsgiven
cation of very slow strain rates, which are achieved by a
in 5.2 are strongly encouraged.
constant extension rate on the specimen while monitoring load
5.4 In some cases, EAC will only occur in a specific range
and extension of the specimen. The SSR test always produces
ofstrainrates.Therefore,wherethereislittlepriorinformation
fracture of the test specimen. Typically, the results from tests
available,testsshouldbeconductedoverarangeofstrainrates
conductedinthetestenvironmentarecomparedtocorrespond-
as discussed in 5.2.
6. Apparatus
Available from American National Standards Institute, 11 W. 42nd St., 13th
Floor, New York, NY 10036. 6.1 Testing Machines:
G129
6.1.1 Tension testing machines used for SSR testing shall environment. However, this type of machine should only be
conform to the requirements of Practices E4. used if it can be shown that failure of one or multiple
6.1.2 The loads used in SSR testing shall be within the
specimens does not influence the behavior of the other speci-
calibrated load ranges of the testing machine in accordance mens.
with Practices E4.
6.2 Gripping Devices—The types of gripping devices that
6.1.3 The testing machines used for SSR testing shall be
may be used to transmit the applied load from the testing
capable of accurate application of extension rates in the range
machinetothetensionspecimenconformtothosedescribedin
of interest for evaluation of EAC. These extension rates are
Test Methods E8. Alignment procedures are provided in Test
−4 −7 –3
usually between 10 and 10 in/s (2.54 3 10 and 2.54 3
Method E8.
–6
10 mm/s).
6.3 Clevices and Fixtures—Aloading clevis that is suitable
6.1.4 An example of a SSR testing machine setup including
for loading pre-cracked compact specimens should conform
the load frame, instrumentation, and local test cell is shown in
with clevices described in Test Method E399. A bend test
Fig. 1.Another example of a SSR machine setup with a metal
fixtureforloadingpre-crackedbendspecimensshouldconform
test cell or autoclave can be found in Test Method G142. The
with bend fixtures described in Test Method E399. It is
test specimen is loaded with a grip assembly and load frame
important that attention be given to achieving good load train
inside the autoclave. The autoclave is equipped with a tensile
alignment through careful machining of all clevices and
loadingfeed-throughtoprovidetransmissionofloadsfromthe
fixtures.
tensile machine to the specimen using a pull rod in combina-
6.4 Displacement Gages—Anelectroniccrackmouthopen-
tionwiththefeed-through.SomeSSRtestingmachinesmaybe
ing displacement (CMOD) gage attached to the front face of
able to test more than one specimen at a time in a particular
pre-cracked specimens and spanning the crack starter notch to
detect crack growth during testing should be in accordance
with displacement gages described in Test Method E399.
Alternatively, the displacements can be transferred outside the
environmental test cell in the case of tests conducted in high
temperatureorseverelycorrosiveenvironments.Anextensom-
eter placed outside the test cell can be used to detect the crack
growth. A displacement gage can be attached to the specimen
at alternative locations to detect crack growth if the proper
compliance-crack length relationship has been determined for
the measurement location on the specimen.
6.5 Environmental Test Cells—Test cells shall be con-
structed in a manner to facilitate handling and monitoring of
the test environment while allowing testing of the tension
specimen. This will require the incorporation of a suitable
low-friction feed-through in the vessel for application of load
to the test specimen.Additionally, the test cell shall be able to
safely contain the test environment with adequate accommo-
dation for the temperature and pressure under which the SSR
tests will be conducted.
6.5.1 Test cells shall be effectively inert (that is, have a low
corrosion rate and not susceptible to EAC in the test environ-
ment so that they do not react with or contaminate the
environment).
6.5.2 The test cell size should be such that a solution
volume-to-exposed specimen surface area is not less than 30
mL/cm .
6.6 Galvanic Effects—Eliminate galvanic effects between
the test specimen and various metallic components of the
gripping fixtures and test cell by electrically insulating or
isolating these components unless it is specifically desired to
simulate galvanic interactions found in service conditions and
their effects on EAC. Check electrical isolation with an
ohmmeter, if required, prior to testing. It should be noted that,
in some cases, electrical insulation may be bridged by deposits
of conductive
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.