1、Designation: C1291 16C1291 18Standard Test Method forElevated Temperature Tensile Creep Strain, Creep StrainRate, and Creep Time-to-Failure Time to Failure forMonolithic Advanced Ceramics1This standard is issued under the fixed designation C1291; the number immediately following the designation indi
2、cates the year oforiginal 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 test method covers the determination
3、of tensile creep strain, creep strain rate, and creep time-to-failure time to failurefor advanced monolithic ceramics at elevated temperatures, typically between 1073 and 2073 K. A variety of test specimengeometries are included. The creep strain at a fixed temperature is evaluated from direct measu
4、rements of the gage length extensionover the time of the test. The minimum creep strain rate, which may be invariant with time, is evaluated as a function oftemperature and applied stress. Creep time-to-failure time to failure is also included in this test method.1.2 This test method is for use with
5、 advanced ceramics that behave as macroscopically isotropic, homogeneous, continuousmaterials. While this test method is intended for use on monolithic ceramics, whisker- or particle-reinforced composite ceramicsas well as low-volume-fraction discontinuous fiber-reinforced composite ceramics may als
6、o meet these macroscopic behaviorassumptions. Continuous fiber-reinforced ceramic composites (CFCCs) do not behave as macroscopically isotropic, homogeneous,continuous materials, and application of this test method to these materials is not recommended.1.3 The values in SI units are to be regarded a
7、s the standard (see IEEE/ASTM SI 10). The values given in parentheses aremathematical conversions to inch-pound units that are provided for information only and are not considered standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It i
8、s the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized princip
9、les on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2C1145 Terminology of Advanced Cerami
10、csC1273 Test Method for Tensile Strength of Monolithic Advanced Ceramics at Ambient TemperaturesE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE83 Practice for Verification and Classification of Extensometer SystemsE139 Test Methods for
11、 Conducting Creep, Creep-Rupture, and Stress-Rupture Tests of Metallic MaterialsE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE220 Test Method for Calibration of Thermocouples By Comparison TechniquesE230 Specification and Temperature-Electromotive Force (EMF) Tables for
12、Standardized ThermocouplesE639 Test Method for Measuring Total-Radiance Temperature of Heated Surfaces Using a Radiation Pyrometer (Withdrawn2011)3E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method1 This test method is under the jurisdiction of ASTM Com
13、mittee C28 on Advanced Ceramics and is the direct responsibility of Subcommittee C28.01 on MechanicalProperties and Performance.Current edition approved Sept. 1, 2016Jan. 1, 2018. Published October 2016January 2018. Originally approved in 1995. Last previous edition approved in 20102016 asC1291 00a
14、(2010). 16. DOI: 10.1520/C1291-16.10.1520/C1291-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 The last
15、 approved version of this historical standard is referenced on www.astm.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately
16、 depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, P
17、A 19428-2959. United States1E1012 Practice for Verification of Testing Frame and Specimen Alignment Under Tensile and Compressive Axial ForceApplicationIEEE/ASTM SI 10 American National Standard for Use of the International System of Units (SI): The Modern Metric System3. Terminology3.1 DefinitionsT
18、he definitions of terms relating to creep testing,testing which appear in Section E of Terminology E6 shallapply to the terms used in this test method. For the purpose of this test method only, some of the more general terms are used withthe restricted meanings given as follows.3.2 Definitions of Te
19、rms Specific to This Standard:3.2.1 axial strain, a, L/L, naverage of the strain measured on diametrically opposed sides and equally distant from the testspecimen axis.3.2.2 bending strain, b L/L, ndifference between the strain at the surface and the axial strain.3.2.2.1 DiscussionIn general, it var
20、ies from point to point around and along the gage length of the test specimen. (E1012)3.2.3 creep-rupture creep rupture test, ntest in which progressive test specimen deformation and the time-to-failure time tofailure are measured. In general, deformation is greater than that developed during a cree
21、p test.3.2.4 creep strain, , L/L, ntime dependent time-dependent strain that occurs after the application of force which isthereafter maintained constant. Also known as engineering creep strain.3.2.5 creep test, ntest that has as its objective the measurement of creep and creep rates occurring at st
22、resses usually wellbelow those that would result in fast fracture.3.2.5.1 DiscussionSince the maximum deformation is only a few percent, a sensitive extensometer is required.3.2.6 creep time-to-failure, time to failure, tf, T, ntime required for a test specimen to fracture under constant force as a
23、resultof creep.3.2.6.1 DiscussionThis is also known as creep rupture time.3.2.7 gage length, l, L, noriginal distance between fiducial markers on or attached to the test specimen for determiningelongation.3.2.8 maximum bending strain, bmax, L/L, nlargest value of bending strain along the gage length
24、. It can be calculated frommeasurements of strain at three circumferential positions at each of two different longitudinal positions.3.2.9 minimum creep strain rate, min, T1, nminimum value of the strain rate prior to test specimen failure as measuredfrom the strain-time curve. The minimum creep str
25、ain rate may not necessarily correspond to the steady-state creep strain rate.3.2.10 slow crack growth, , L/T, (SCG), nsubcritical crack growth (extension) which may result from, but is not restrictedto, such mechanisms as environmentally assisted stress corrosion, diffusive crack growth, or other m
26、echanisms. (C1145)3.2.11 steady-state creep, ss, L/L, nstage of creep wherein the creep rate is constant with time.3.2.11.1 DiscussionAlso known as secondary creep.3.2.12 stress corrosion, nenvironmentally induced degradation that initiates from the exposed surface.3.2.12.1 DiscussionSuch environmen
27、tal effects commonly include the action of moisture, as well as other corrosive species, often with a strongtemperature dependence.3.2.13 tensile creep strain, t, L/L, ncreep strain that occurs as a result of a uniaxial tensile-applied stress.C1291 1824. Significance and Use4.1 Creep tests measure t
28、he time-dependent deformation under force at a given temperature, and, by implication, theforce-carrying capability of the material for limited deformations. Creep-rupture Creep rupture tests, properly interpreted, providea measure of the force-carrying capability of the material as a function of ti
29、me and temperature. The two tests complement eachother in defining the force-carrying capability of a material for a given period of time. In selecting materials and designing partsfor service at elevated temperatures, the type of test data used will depend on the criteria for force-carrying capabil
30、ity that bestdefines the service usefulness of the material.4.2 This test method may be used for material development, quality assurance, characterization, and design data generation.4.3 High-strength, monolithic ceramic materials, generally characterized by small grain sizes (2K.2 K. It is preferab
31、le to use fully sheathed thermocouples in order tominimize degradation.6.5.3 Pyrometers:6.5.3.1 CalibrationThe pyrometer(s) shall be calibrated in accordance with Test Method E639.5 Thermocouples shall be periodically checked since calibration may drift with usage or contamination.6 Resolutions shal
32、l not be confused with accuracy. Beware of instruments that readout to 1C1 C (resolution), but have an accuracy of only 10 K or 12 % of full scale(12 % of 1200 K is 6 K).7 Temperature measuring instruments typically approximate the temperature-EMF tables, but with a few degrees of error.C1291 1856.5
33、.3.2 AccuracyThe measurement of temperature shall be accurate to within 5 K. This shall include the error inherent to thepyrometer and any error in the measuring instruments.6,76.6 Extensometers:6.6.1 The strain measuring equipment shall be capable of being used at elevated temperatures. The sensiti
34、vity and accuracy ofthe strain-measuring strain measuring equipment shall be suitable to define the creep characteristics with the precision required forthe application of the data.6.6.2 CalibrationExtensometers shall be calibrated in accordance with Practice E83.6.6.3 AccuracyExtensometers with acc
35、uracies equivalent to the B-1 classification of extensometer systems specified inPractice E83 are suitable for use in high-temperature testing of ceramics. Results of analytical and empirical evaluations at elevatedtemperatures show that mechanical extensometers (16) can meet these requirements. Opt
36、ical extensometers using flags have gagelength uncertainties that will generally prevent them from achieving class B-1 accuracy (17). Empirical evaluations at elevatedtemperature (18) show that these extensometers can yield highly repeatable creep data, however.6.7 Timing ApparatusFor creep rupture
37、tests, a timing apparatus capable of measuring the elapsed time between completeapplication of the force and the time at which fracture of the test specimen occurs to within 1 % of the elapsed time shall beemployed.7. Test Specimens and Sample7.1 Test Specimen Size:7.1.1 DescriptionThe size and shap
38、e of test specimens shall be based on the requirements necessary to obtain representativesamples of the material being investigated as discussed in Test Method C1273. The test specimen geometry shall be such that thereis no more than a 5 % elastic stress concentration at the ends of the gage section
39、. Typical shapes include square or rectangularcross-section dogbones and cylindrical button-head geometries, and are shown in Appendix X1. It is recommended, in accordancewith Test Methods E139 and in the absence of additional information to the contrary, that the grip section be at least four times
40、larger than the larger dimension of either width or thickness of the gage section.7.1.2 DimensionsSuggested dimensions for tensile creep test specimens that have been successfully used in previousinvestigations are given in Appendix X1. Cross-sectional tolerances are 0.05 mm. Parallelism tolerances
41、on the faces of the testspecimen are 0.03 mm. Various radii of curvature may be used to adjust the gage section or change the mounting configuration.Although these radii are expected to be larger, resulting in a smaller stress concentration, wherever possible, resort shall be madeto a finite element
42、 analysis to determine the locations and intensities of stress concentrations in the new geometry.7.2 Test Specimen PreparationDepending on the intended application of the data, use one of the following test specimenpreparation procedures:7.2.1 Application-matchedApplication-Matched MachiningThe tes
43、t specimen shall have the same surface preparation as thatspecified for a component. Unless the process is proprietary, the report shall be specified about the stages of material removal,wheel grits, wheel bonding, and the amount of material removed per pass.7.2.2 Customary ProcedureIn instances whe
44、re a customary machining procedure has been developed that is completelysatisfactory for a class of materials (that is, it induces no unwanted surface damage or residual stresses), then this procedure shallbe used. It shall be fully specified in the report.7.2.3 Standard ProcedureIn instances where
45、7.2.1 or 7.2.2 are not appropriate, then 7.2.3 will apply. This procedure will serveas the minimum requirements, but a more stringent procedure may be necessary.7.2.3.1 Grinding ProcessAll grinding using diamond-grit diamond grit wheels shall be done with an ample supply ofappropriate filtered coola
46、nt to keep workpiece and wheel constantly flooded and particles flushed. Grinding shall be done in at leasttwo stages, ranging from coarse to fine rates of material removal. All machining shall be done in the surface grinding mode, andbe parallel to the test specimen long axis (several test specimen
47、s are shown in the appendix). Do not use Blanchard or rotarygrinding.7.2.3.2 Material Removal RateThe material removal rate shall not exceed 0.03 mm (0.001 in.) per pass to the last 0.06 mm0.06 mm (0.002 in.) per face. Final and intermediate finishing shall be performed with a resinoid-bonded diamon
48、d grit wheel thatis between 320 and 600 grit. No less than 0.06 mm per face shall be removed during the final finishing phase, and at a rate of notmore than 0.002 mm (0.0001 in.) per pass. Remove approximately equal stock from opposite faces.7.2.3.3 PrecautionMaterials with low fracture toughness an
49、d a high susceptibility to grinding damage may require finergrinding wheels at very low removal rates.7.2.3.4 ChamfersChamfers on the edges of the gage section are preferred in order to minimize premature failures due to stressconcentrations or slow crack growth. The use of chamfers and their geometry shall be clearly indicated in the test report (see10.1.1).7.2.4 Button-Head Test Specimen-Specific ProcedureBecause of the axial symmetry of the button-head tensile test specimen,fabrication of the test specimens i
