1、Designation: G129 00 (Reapproved 2013)Standard Practice forSlow Strain Rate Testing to Evaluate the Susceptibility ofMetallic Materials to Environmentally Assisted Cracking1This standard is issued under the fixed designation G129; the number immediately following the designation indicates the year o
2、foriginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers procedures for the design,preparation
3、, and use of axially loaded, tension test specimensand fatigue pre-cracked (fracture mechanics) specimens for usein slow strain rate (SSR) tests to investigate the resistance ofmetallic materials to environmentally assisted cracking (EAC).While some investigators utilize SSR test techniques in com-b
4、ination with cyclic or fatigue loading, no attempt has beenmade to incorporate such techniques into this practice.1.2 Slow strain rate testing is applicable to the evaluation ofa wide variety of metallic materials in test environments whichsimulate aqueous, nonaqueous, and gaseous service environ-me
5、nts over a wide range of temperatures and pressures thatmay cause EAC of susceptible materials.1.3 The primary use of this practice is to furnish acceptedprocedures for the accelerated testing of the resistance ofmetallic materials to EAC under various environmental condi-tions. In many cases, the i
6、nitiation of EAC is acceleratedthrough the application of a dynamic strain in the gauge sectionor at a notch tip or crack tip, or both, of a specimen. Due to theaccelerated nature of this test, the results are not intended tonecessarily represent service performance, but rather to pro-vide a basis f
7、or screening, for detection of an environmentalinteraction with a material, and for comparative evaluation ofthe effects of metallurgical and environmental variables onsensitivity to known environmental cracking problems.1.4 Further information on SSR test methods is available inISO 7539 and in the
8、references provided with this practice(1-6).21.5 The values stated in SI units are to be regarded asstandard. The values given in parentheses are for informationonly.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of t
9、he user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Furthermore, insome cases, special facilities will be required to isolate thesetests from laboratory personnel if high pressures or toxicchemical en
10、vironments, or both, are utilized in SSR testing.2. Referenced Documents2.1 ASTM Standards:3A370 Test Methods and Definitions for Mechanical Testingof Steel ProductsB557 Test Methods for Tension Testing Wrought and CastAluminum- and Magnesium-Alloy ProductsD1193 Specification for Reagent WaterE4 Pra
11、ctices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE8 Test Methods for Tension Testing of Metallic MaterialsE399 Test Method for Linear-Elastic Plane-Strain FractureToughness KIcof Metallic MaterialsE602 Test Method for Sharp-Notch Tension Testin
12、g withCylindrical Specimens (Withdrawn 2010)4E616 Terminology Relating to Fracture Testing (Discontin-ued 1996) (Withdrawn 1996)4E647 Test Method for Measurement of Fatigue CrackGrowth RatesE1681 Test Method for Determining Threshold Stress Inten-sity Factor for Environment-Assisted Cracking of Meta
13、llicMaterialsG15 Terminology Relating to Corrosion and Corrosion Test-ing (Withdrawn 2010)4G49 Practice for Preparation and Use of Direct TensionStress-Corrosion Test SpecimensG111 Guide for Corrosion Tests in High Temperature orHigh Pressure Environment, or Both1This practice is under the jurisdict
14、ion of ASTM Committee G01 on Corrosionof Metals and is the direct responsibility of Subcommittee G01.06 on Environmen-tally Assisted Cracking.Current edition approved May 1, 2013. Published July 2013. Originally approvedin 1995. Last previous edition approved in 2006 as G129 00 (2006). DOI:10.1520/G
15、0129-00R13.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standar
16、ds Document Summary page onthe ASTM website.4The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1G142 Test Method for Determination of Susceptibility ofMet
17、als to Embrittlement in Hydrogen Containing Envi-ronments at High Pressure, High Temperature, or Both2.2 ISO Standard:5ISO 7539 Part 7, Slow Strain Rate Testing3. Terminology3.1 For purposes of this practice the following terms aredefined:3.2 control environmentan environment in which SSRspecimens a
18、re tested that has been shown not to cause EAC orexcessive corrosion of the material. The results of testsconducted in this environment may be used as a basis forcomparison with corresponding tests conducted in the testenvironment(s), usually at the same temperature as the testenvironment.3.3 enviro
19、nmentally assisted cracking (EAC) cracking ofa material caused by the combined effects of stress and thesurrounding environment, for example, stress corrosioncracking, hydrogen embrittlement cracking, sulfide stresscracking and liquid metal embrittlement.3.4 slow strain rate (SSR)a dynamic slowly in
20、creasingstrain imposed by an external means on the gauge section ornotch tip of a uniaxial tension specimen or crack tip of a fatiguepre-cracked specimen for purposes of materials evaluation.The strain rate for a plain or smooth specimen (given in unitsof extension divided by the gage length per uni
21、t time) or thestrain rate at a notch tip of a notched tension specimen or cracktip of a fatigue pre-cracked specimen is applied through theapplication of a slow constant extension rate (given in units ofextension per unit time). The slow constant extension rateproduces a gauge section strain rate, w
22、hich is usually in therange from 104to 107/s1. Rigorous analytical solutions ofthe local strain rate at a notch tip of a tension specimen or at acrack tip of a fatigue pre-cracked specimen are not available.The average or local strain rate should be slow enough to allowtime for certain corrosion pro
23、cesses to take place, but fastenough to produce failure or cracking of the specimen in areasonable period of time for evaluation purposes. In caseswhere extremely slow strain rates are being utilized (that is,107to 108/s1for smooth tension specimens), an interruptedSSR test can be employed whereby t
24、he specimen is strainedinto the plastic range at the intended strain rate followed bymore rapid straining to failure.3.5 The terminology found in Test Methods and DefinitionsA370, Test Method B557, and Test Method E602 along withthe definitions given in Terminologies E6, E616, and G15 shallapply to
25、the terms used in this practice.4. Summary of Practice4.1 This practice describes the use of tension and fatiguepre-cracked specimens for the determination of resistance toEAC of metallic materials. The procedure involves the appli-cation of very slow strain rates, which are achieved by aconstant ex
26、tension rate on the specimen while monitoring loadand extension of the specimen. The SSR test always producesfracture of the test specimen. Typically, the results from testsconducted in the test environment are compared to correspond-ing test results for the same material in a control environment.Th
27、e degree of susceptibility to EAC is generally assessedthrough observation of the differences in the behavior of thematerial in tests conducted in a test environment from thatobtained from tests conducted in the control environment. Forsmooth tension specimens, either changes in time-to-failure, ors
28、pecimen ductility, or visual indications of EAC, or often somecombination of these methods, are utilized in determiningsusceptibility to EAC. For notched tension specimens, changesin the notch tensile strength and visual indications of EAC onthe primary fracture surface are used in determining susce
29、pti-bility to EAC. For fatigue pre-cracked specimens, changes inthe threshold stress intensity factor and visual indications ofEAC on the primary fracture surface are used in determiningsusceptibility to EAC.5. Significance and Use5.1 The slow strain rate test is used for relatively rapidscreening o
30、r comparative evaluation, or both, ofenvironmental, processing or metallurgical variables, or both,that can affect the resistance of a material to EAC. Forexample, this testing technique has been used to evaluatematerials, heat treatments, chemical constituents in theenvironment, and temperature and
31、 chemical inhibitors.5.2 Where possible, the application of the SSR test and dataderived from its use should be used in combination withservice experience or long-term EAC data, or both, obtainedthrough literature sources or additional testing using othertesting techniques. In applications where the
32、re has been little orno prior experience with SSR testing or little EAC data on theparticular material/environment combination of interest, thefollowing steps are recommended:5.2.1 The SSR tests should be conducted over a range ofapplied extension rates (that is, usually at least one order ofmagnitu
33、de in applied extension rate above and below 106in/s(2.54 105mm/s) to determine the effect of strain rate or rateof increase of the stress or stress intensity factor on suscepti-bility to EAC.5.2.2 Constant load or strain EAC tests should also beconducted in simulated service environments, and servi
34、ceexperience should be obtained so that a correlation betweenSSR test results and anticipated service performance can bedeveloped.5.3 In many cases the SSR test has been found to be aconservative test for EAC. Therefore, it may produce failuresin the laboratory under conditions which do not necessar
35、ilycause EAC under service application. Additionally, in somelimited cases, EAC indications are not found in smooth tensionSSR tests even when service failures have been observed. Thiseffect usually occurs when there is a delay in the initiation oflocalized corrosion processes. Therefore, the sugges
36、tions givenin 5.2 are strongly encouraged.5Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.G129 00 (2013)25.4 In some cases, EAC will only occur in a specific rangeof strain rates. Therefore, where there is little prior in
37、formationavailable, tests should be conducted over a range of strain ratesas discussed in 5.2.6. Apparatus6.1 Testing Machines:6.1.1 Tension testing machines used for SSR testing shallconform to the requirements of Practices E4.6.1.2 The loads used in SSR testing shall be within thecalibrated load r
38、anges of the testing machine in accordancewith Practices E4.6.1.3 The testing machines used for SSR testing shall becapable of accurate application of extension rates in the rangeof interest for evaluation of EAC. These extension rates areusually between 104and 107in/s (2.54 103and 2.54 106mm/s).6.1
39、.4 An example of a SSR testing machine setup includingthe load frame, instrumentation, and local test cell is shown inFig. 1. Another example of a SSR machine setup with a metaltest cell or autoclave can be found in Test Method G142. Thetest specimen is loaded with a grip assembly and load frameinsi
40、de the autoclave. The autoclave is equipped with a tensileloading feed-through to provide transmission of loads from thetensile machine to the specimen using a pull rod in combina-tion with the feed-through. Some SSR testing machines may beable to test more than one specimen at a time in a particula
41、renvironment. However, this type of machine should only beused if it can be shown that failure of one or multiplespecimens does not influence the behavior of the other speci-mens.6.2 Gripping DevicesThe types of gripping devices thatmay be used to transmit the applied load from the testingmachine to
42、 the tension specimen conform to those described inTest Methods E8. Alignment procedures are provided in TestMethod E8.6.3 Clevices and FixturesA loading clevis that is suitablefor loading pre-cracked compact specimens should conformwith clevices described in Test Method E399. A bend testfixture for
43、 loading pre-cracked bend specimens should conformwith bend fixtures described in Test Method E399.Itisimportant that attention be given to achieving good load trainalignment through careful machining of all clevices andfixtures.6.4 Displacement GaugesAn electronic crack mouthopening displacement (C
44、MOD) gauge attached to the frontface of pre-cracked specimens and spanning the crack starternotch to detect crack growth during testing should be inaccordance with displacement gauges described in TestMethod E399. Alternatively, the displacements can be trans-ferred outside the environmental test ce
45、ll in the case of testsconducted in high temperature or severely corrosive environ-ments.An extensometer placed outside the test cell can be usedto detect the crack growth. A displacement gauge can beattached to the specimen at alternative locations to detect crackgrowth if the proper compliance-cra
46、ck length relationship hasbeen determined for the measurement location on the speci-men.6.5 Environmental Test CellsTest cells shall be con-structed in a manner to facilitate handling and monitoring ofthe test environment while allowing testing of the tensionspecimen. This will require the incorpora
47、tion of a suitablelow-friction feed-through in the vessel for application of loadto the test specimen. Additionally, the test cell shall be able tosafely contain the test environment with adequate accommo-dation for the temperature and pressure under which the SSRtests will be conducted.6.5.1 Test c
48、ells shall be effectively inert (that is, have a lowcorrosion rate and not susceptible to EAC in the test environ-ment so that they do not react with or contaminate theenvironment).6.5.2 The test cell size should be such that a solutionvolume-to-exposed specimen surface area is not less than 30mL/cm
49、2.6.6 Galvanic EffectsEliminate galvanic effects betweenthe test specimen and various metallic components of thegripping fixtures and test cell by electrically insulating orFIG. 1 An Example of a SSR Testing Machine.G129 00 (2013)3isolating these components unless it is specifically desired tosimulate galvanic interactions found in service conditions andtheir effects on EAC. Check electrical isolation with anohmmeter, if required, prior to testing. It should be noted that,in some cases, electrical insulation may be bridged by depositsof conductive or semi
