1、Designation: E2714 091Standard Test Method forCreep-Fatigue Testing1This standard is issued under the fixed designation E2714; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indic
2、ates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEThe term “stress range” was moved from Definitions Specific to this Standard, 3.4 to Definitions, 3.3 in December2011.1. Scope1.1 This test method covers the determinati
3、on of mechanicalproperties pertaining to creep-fatigue deformation or crackformation in nominally homogeneous materials, or both by theuse of test specimens subjected to uniaxial forces underisothermal conditions. It concerns fatigue testing at strain ratesor with cycles involving sufficiently long
4、hold times to beresponsible for the cyclic deformation response and cycles tocrack formation to be affected by creep (and oxidation). It isintended as a test method for fatigue testing performed insupport of such activities as materials research and develop-ment, mechanical design, process and quali
5、ty control, productperformance, and failure analysis. The cyclic conditions re-sponsible for creep-fatigue deformation and cracking vary withmaterial and with temperature for a given material.1.2 The use of this test method is limited to specimens anddoes not cover testing of full-scale components,
6、structures, orconsumer products.1.3 This test method is primarily aimed at providing thematerial properties required for assessment of defect-freeengineering structures containing features that are subject tocyclic loading at temperatures that are sufficiently high to causecreep deformation.1.4 This
7、 test method is applicable to the determination ofdeformation and crack formation or nucleation properties as aconsequence of either constant-amplitude strain-controlledtests or constant-amplitude force-controlled tests. It is primar-ily concerned with the testing of round bar test specimenssubjecte
8、d to uniaxial loading in either force or strain control.The focus of the procedure is on tests in which creep andfatigue deformation and damage is generated simultaneouslywithin a given cycle. It does not cover block cycle testing inwhich creep and fatigue damage is generated sequentially. Datathat
9、may be determined from creep-fatigue tests performedunder conditions in which creep-fatigue deformation anddamage is generated simultaneously include (a) cyclic stress-strain deformation response (b) cyclic creep (or relaxation)deformation response (c) cyclic hardening, cyclic softeningresponse (d)
10、cycles to formation of a single crack or multiplecracks in test specimens.NOTE 1A crack is believed to have formed when it has nucleated andpropagated in a specimen that was initially uncracked to a specific sizethat is detectable by a stated technique. For the purpose of this standard,the formation
11、 of a crack is evidenced by a measurable increase incompliance of the specimen or by a size detectable by potential droptechnique. Specific details of how to measure cycles to crack formationare described in 9.5.1.1.5 This test method is applicable to temperatures and strainrates for which the magni
12、tudes of time-dependent inelasticstrains (creep) are on the same order or larger than time-independent inelasticNOTE 2The term inelastic is used herein to refer to all nonelasticstrains. The term plastic is used herein to refer only to time dependant(that is, non-creep) component of inelastic strain
13、. A useful engineeringestimate of time-independent strain can be obtained when the strain rateexceeds some value. For example, a strain rate of 1310-3sec-1is oftenused for this purpose. This value should increase with increasing testmeasurement.1.6 The values stated in SI units are to be regarded as
14、standard. No other units of measurement are included in thisstandard.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the
15、applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E4 Practices for Force Verification of Testing MachinesE8/E8M Test Methods for Tension Testing of MetallicMaterialsE83 Practice for Verification and Classification of Exten-someter Systems1This test meth
16、od is under the jurisdiction of ASTM Committee E08 on Fatigueand Fracture and is the direct responsibility of Subcommittee E08.05 on CyclicDeformation and Fatigue Crack Formation.Current edition approved Nov. 1, 2009. Published December 2009. DOI:10.1520/E271409E01.1Copyright ASTM International, 100
17、 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.E111 Test Method for Youngs Modulus, Tangent Modulus,and Chord ModulusE139 Test Methods for Conducting Creep, Creep-Rupture,and Stress-Rupture Tests of Metallic MaterialsE177 Practice for Use of the Terms Precision and
18、Bias inASTM Test MethodsE220 Test Method for Calibration of Thermocouples ByComparison TechniquesE230 Specification and Temperature-Electromotive Force(EMF) Tables for Standardized ThermocouplesE467 Practice for Verification of Constant Amplitude Dy-namic Forces in an Axial Fatigue Testing SystemE60
19、6 Practice for Strain-Controlled Fatigue TestingE647 Test Method for Measurement of Fatigue CrackGrowth RatesE1012 Practice for Verification of Test Frame and SpecimenAlignment Under Tensile and Compressive Axial ForceApplicationE1823 Terminology Relating to Fatigue and Fracture Test-ingE2368 Practi
20、ce for Strain Controlled ThermomechanicalFatigue Testing2.2 BSI Standards:3BS 7270: 2000 Method for Constant Amplitude StrainControlled Fatigue TestingBS 1041-4:1992 Temperature measurement Part 4: Guideto the selection and use of thermocouples2.3 CEN Standards:4EN 60584-11996 Thermocouples Referenc
21、e tables (IEC584-1)EN 60584 -2 1993 Thermocouples Tolerances (IEC584-2)PrEN 38741998 Test methods for metallic materials constant amplitude force-controlled low cycle fatiguetestingPrEN 39881998 Test methods for metallic materials constant amplitude strain-controlled low cycle fatiguetesting2.4 ISO
22、Standards:5ISO 121062003 Metallic materials Fatigue testing -Axial strain-controlled methodISO 121112005 (Draft) Strain-controlled thermo-mechanical fatigue testing methodISO 7500-12004 Metallic materials Verification of staticuniaxial testing machines Part 1. Tension/compressiontesting machines Ver
23、ification and calibration of the forcemeasuring systemISO 95131999 Metallic materials Calibration of exten-someters used in axial testingISO 57251994 Accuracy (trueness and precision) of mea-surement methods2.5 JIS Standard:6JIS Z 22791992 Method of high temperature low cyclefatigue testing for meta
24、llic materials3. Terminology3.1 The definitions in this test method that are also includedin Terminology E1823 are in accordance with TerminologyE1823.3.2 Symbols, standard definitions, and definitions specific tothis standard are in 3.2.1, 3.3, and 3.4, respectively.3.2.1 Symbols:Symbol Termd L Dia
25、meter of gage sectionof cylindrical test specimenDg, L Diameter of grip endsN, E, Eo,EN, FL-2 Elastic modulus, initial modulusof elasticity, modulus of elasticity at cycleET,ECFL-2 Tensile modulus,compressive modulusP F Forcel, loL Extensometer gage length,original extensometergage lengthL, Lo, L Le
26、ngth of parallel sectionof gage length, original lengthof parallel section of gage lengthN, NfCycle number, cycle numberto crack formationr,L Transition radius(from parallel section to grip end)min/ max,RStrain ratiosmin/ smax,RsStress ratiot TimeTu Specimen temperatureTiu Indicated specimentemperat
27、ureN versus smaxCrack formation or end-of-life criterion isexpressed as a percentage reduction inmaximum stress from the cycles,N versus smaxcurve when the stressfalls sharply (see Fig. 1), or a specific percentagedecrease in the modulus of elasticity ratiosin the tensile and compressive portionsof
28、the hysteresis diagrams, or as aspecific increase in crack size asindicated by an electricpotential drop monitoring instrumentation., max, minStrain, maximum strain in the cycle,minimum strain in the cycleea, pa, taElastic strain amplitude,plastic strain amplitude,total strain amplitudeDe, Dp, DtEla
29、stic strain range, plastic strain range,total strain range (see Fig. 2)DinInelastic strain range, (see Fig. 2) is the sum of theplastic strain range and the creep strainsduring the cycle; it is the distance on thestrain axis between points of intersectionsof the strain axis and the extrapolated line
30、arregions of the hysteresis loops duringtensile and compressive unloadings2For 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 standards Document Summary page onthe
31、ASTM website.3Available from British Standards Institute (BSI), 389 Chiswick High Rd.,London W4 4AL, U.K., http:/www.bsi-.4Available from European Committee for Standardization (CEN), 36 rue deStassart, B-1050, Brussels, Belgium, http:/www.cenorm.be.5Available from International Organization for Sta
32、ndardization (ISO), 1, ch. dela Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.6Available from Japanese Standards Organization (JSA), 4-1-24 AkasakaMinato-Ku, Tokyo, 107-8440, Japan, http:/www.jsa.or.jpE2714 0912s, smax, sminStress, maximum stress in the cycle,minimu
33、m stress in the cycleDs Stress range3.3 Definitions:3.3.1 cycleIn fatigue, one complete sequence of values offorce (strain) that is repeated under constant amplitude loading(straining)3.3.2 hold-time, thTIn fatigue testing, the amount oftime in the cycle where the controlled test variable (force,str
34、ain, displacement) remains constant with time (Fig. 3).3.3.2.1 DiscussionHold- time(s) are typically placed atpeak stress or strain in tension and/or compression, but can alsobe placed at other positions within the cycle.3.3.3 total cycle period, ttT,The time for completion ofone cycle. The paramete
35、r tt can be separated into hold andnon-hold components (tnh), where the total cycle time is thesum of the hold time and the non-hold time.3.3.4 hysteresis diagramThe stress-strain path during onecycle (see Fig. 2).3.3.5 initial modulus of elasticity, Eo, FL-2 The modulusof elasticity determined duri
36、ng the loading portion of the firstcycle.3.3.6 modulus of elasticity at cycle N, (EN, FL-2Theaverage of the modulus of elasticity determined during increas-ing load portion (see Ecin Fig. 2) and the decreasing loadportion (ETin Fig. 2) of the hysteresis diagram for the Nthcycle.3.3.7 stress range, D
37、s , FL-2The difference between themaximum and minimum stresses.3.3.7.1 DiscussionFor creep-fatigue tests, the differencebetween the maximum and minimum stresses is called the“peak stress range” and for tests conducted under straincontrol, the difference between the stresses at the points ofreversal
38、of the control parameter is called the “relaxed stressrange” (see Fig. 2b).3.4 Definitions: Defintions of Terms Specific to This Stan-dard:3.5 DCPD and ACPDDirect current and alternating cur-rent electrical potential drop crack monitoring instrumentation.3.6 homologous temperatureThe specimen temper
39、aturein K divided by the melting point of the material also in K.3.7 crack formationA crack is believed to have formedwhen it has nucleated and propagated in a specimen that wasinitially un-cracked to a size that is detectable by a statedtechnique.4. Significance and Use4.1 Creep-fatigue testing is
40、typically performed at elevatedtemperatures and involves the sequential or simultaneousapplication of the loading conditions necessary to generatecyclic deformation/damage enhanced by creep deformation/damage or vice versa. Unless such tests are performed invacuum or an inert environment, oxidation
41、can also be respon-sible for important interaction effects relating to damageaccumulation. The purpose of creep-fatigue tests can be todetermine material property data for (a) assessment input datafor the deformation and damage condition analysis of engi-neering structures operating at elevated temp
42、eratures (b) theverification of constitutive deformation and damage modeleffectiveness (c) material characterization, or (d) developmentFIG. 1 Crack Formation and End-of-Test Criterion based on Reduction of Peak Stress for (a) Hardening and (b) Softening MaterialsE2714 0913and verification of rules
43、for new construction and life assess-ment of high-temperature components subject to cyclic servicewith low frequencies or with periods of steady operation, orboth.4.2 In every case, it is advisable to have complementarycontinuous cycling fatigue data (gathered at the same strain/loading rate) and cr
44、eep data determined from test conducted asper Practice E139 for the same material and test tempera-ture(s). The procedure is primarily concerned with the testingof round bar test specimens subjected (at least remotely) touniaxial loading in either force or strain control. The focus ofthe procedure i
45、s on tests in which creep and fatigue deforma-tion and damage is generated simultaneously within a givencycle. Data which may be determined from creep-fatigue testsperformed under such conditions may characterize (a) cyclicstress-strain deformation response (b) cyclic creep (or relax-ation) deformat
46、ion response (c) cyclic hardening, cyclic soft-ening response or (d) cycles to crack formation, or both.4.3 While there are a number of testing Standards andCodes of Practice that cover the determination of low cyclefatigue deformation and cycles to crack initiation properties(See Practice E606, BS
47、7270: 2000, JIS Z 22791992, PrEN3874, 1998, PrEN 39881998, ISO 121062003,ISO 121112005, and Practice E2368-04 and (1, 2, 3)7, someof which provide guidance for testing at high temperature (forexample, Practice E606, ISO 121062003, and PracticeE2368-04, there is no single standard which specificallyp
48、rescribes a procedure for creep-fatigue testing.5. Functional Relationships5.1 Empirical relationships that have been commonly usedfor description of creep-fatigue data are given inAppendix X1.These relationships typically have limitations with respect tomaterial types such as high temperature ferri
49、tic and austeniticsteels versus nickel base alloys. Therefore, original data shouldbe reported to the greatest extent possible. Data reductionmethods should be detailed along with assumptions. Sufficientinformation should be recorded and reported to permit analy-sis, interpretation, and comparison with results for othermaterials analyzed using currently popular methods.6. Apparatus6.1 Test machines:7The boldface numbers in parentheses refer to a list of references at the
