1、Designation: C 1366 04Standard Test Method forTensile Strength of Monolithic Advanced Ceramics atElevated Temperatures1This standard is issued under the fixed designation C 1366; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of tensilestrength under uniaxial loading of monolithic advanced ce
3、ram-ics at elevated temperatures. This test method addresses, but isnot restricted to, various suggested test specimen geometries aslisted in the appendix. In addition, test specimen fabricationmethods, testing modes (force, displacement, or strain control),testing rates (force rate, stress rate, di
4、splacement rate, or strainrate), allowable bending, and data collection and reportingprocedures are addressed. Tensile strength as used in this testmethod refers to the tensile strength obtained under uniaxialloading.1.2 This test method applies primarily to advanced ceramicswhich macroscopically ex
5、hibit isotropic, homogeneous, con-tinuous behavior. While this test method applies primarily tomonolithic advanced ceramics, certain whisker, or particle-reinforced composite ceramics as well as certain discontinuousfiber-reinforced composite ceramics may also meet thesemacroscopic behavior assumpti
6、ons. Generally, continuous fiberceramic composites (CFCCs) do not macroscopically exhibitisotropic, homogeneous, continuous behavior and applicationof this test method to these materials is not recommended.1.3 The values stated in SI units are to be regarded as thestandard and are in accordance with
7、 Practice E 380.1.4 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 applica-bility of regulatory limitations prior to use
8、. Refer to Section 7for specific precautions.2. Referenced Documents2.1 ASTM Standards:2C 1145 Terminology of Advanced CeramicsC 1161 Test Method for Flexural Strength of AdvancedCeramics at Ambient TemperatureC 1239 Practice for Reporting Uniaxial Strength Data andEstimating Weibull Distribution Pa
9、rameters for AdvancedCeramicsC 1322 Practice for Fractography and Characterization ofFracture Origins in Advanced CeramicsD 3379 Test Method for Tensile Strength and YoungsModulus for High-Modulus Single-Filament MaterialsE 4 Practices for Force Verification of Testing MachinesE 6 Terminology Relati
10、ng to Methods of Mechanical Test-ingE 21 Practice for Elevated Temperature Tension Tests ofMetallic MaterialsE 83 Practice for Verification and Classification of Exten-sometersE 220 Method for Calibration of Thermocouples by Com-parison TechniquesE 337 Test Method for Measure Humidity with a Psychro
11、m-eter (The Measurement of Wet- and Dry-Bulb Tempera-tures)E 1012 Practice for Verification of Specimen AlignmentUnder Tensile LoadingIEEE/ASTM SI 10 Standard for Use of the InternationalSystem of Units (SI) (The Modern Metric System)3. Terminology3.1 Definitions:3.1.1 Definitions of terms relating
12、to tensile testing andadvanced ceramics as they appear in Terminology E 6 andTerminology C 1145, respectively, apply to the terms used inthis test method. Pertinent definitions are shown in the follow-ing with the appropriate source given in parenthesis. Additionalterms used in conjunction with this
13、 test method are defined inthe following.3.1.2 advanced ceramic, na highly engineered, high per-formance predominately non-metallic, inorganic, ceramic ma-terial having specific functional attributes. (See TerminologyC 1145.)1This test method is under the jurisdiction of ASTM Committee C28 onAdvance
14、d Ceramics and is the direct responsibility of Subcommittee C28.01 onProperties and Performance.Current edition approved May 1, 2004. Published June 2004. Originallyapproved in 1997. Last previous edition approved in 1997 as C 136697.2For referenced ASTM standards, visit the ASTM website, www.astm.o
15、rg, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.3 axial
16、strain LL1, nthe average longitudinalstrains measured at the surface on opposite sides of thelongitudinal axis of symmetry of the specimen by two strain-sensing devices located at the mid length of the reducedsection. (See Practice E 1012.)3.1.4 bending strain LL1, nthe difference between thestrain
17、at the surface and the axial strain. In general, the bendingstrain varies from point to point around and along the reducedsection of the specimen. (See Practice E 1012.)3.1.5 breaking load F, nthe load at which fractureoccurs. (See Terminology E 6.)3.1.6 fractography, nthe means and methods for char
18、ac-terizing a fractured specimen or component. (See TerminologyC 1145.)3.1.7 fracture origin, nthe source from which brittlefracture commences. (See Terminology C 1145).3.1.8 percent binding, nthe bending strain times 100divided by the axial strain. (See Practice E 1012.)3.1.9 slow crack growth, nsu
19、b critical crack growth(extension) that may result from, but is not restricted to, suchmechanisms as environmentally-assisted stress corrosion ordiffusive crack growth.3.1.10 tensile strength, SuFL2, nthe maximum tensilestress which a material is capable of sustaining. Tensilestrength is calculated
20、from the maximum load during a tensiontest carried to rupture and the original cross-sectional area ofthe specimen. (See Terminology E 6.)4. Significance and Use4.1 This test method may be used for material development,material comparison, quality assurance, characterization, reli-ability assessment
21、, and design data generation.4.2 High strength, monolithic advanced ceramic materialsare generally characterized by small grain sizes ( 65 %relative humidity (RH) is not recommended.5.2 Surface preparation of test specimens can introducefabrication flaws that may have pronounced effects on tensilest
22、rength. Machining damage introduced during test specimenpreparation can be either a random interfering factor in thedetermination of ultimate strength of pristine material (that isincrease frequency of surface initiated fractures compared tovolume initiated fractures), or an inherent part of the str
23、engthcharacteristics. Surface preparation can also lead to the intro-duction of residual stresses. Universal or standardized testmethods of surface preparation do not exist. Final machiningsteps may, or may not negate machining damage introducedduring the early coarse or intermediate machining. Thus
24、, reporttest specimen fabrication history since it may play an importantrole in the measured strength distributions.5.3 Bending in uniaxial tensile tests can cause or promotenon uniform stress distributions with maximum stresses occur-ring at the test specimen surface leading to non representativefr
25、actures originating at surfaces or near geometrical transitions.Bending may be introduced from several sources includingC 1366 042misaligned load trains, eccentric or mis-shaped test specimens,and non-uniformly heated test specimens or grips. In addition,if strains or deformations are measured at su
26、rfaces wheremaximum or minimum stresses occur, bending may introduceover or under measurement of strains. Similarly, fracture fromsurface flaws may be accentuated or muted by the presence ofthe non uniform stresses caused by bending.6. Apparatus6.1 Testing MachinesMachines used for tensile testingsh
27、all conform to the requirements of Practice E 4. The forcesused in determining tensile strength shall be accurate within 61 % at any force within the selected force range of the testingmachine as defined in Practice E 4. A schematic showingpertinent features of a possible tensile testing apparatus i
28、sshown in Fig. 16.2 Gripping Devices:6.2.1 GeneralVarious types of gripping devices may beused to transmit the measured load applied by the testingmachine to the test specimen. The brittle nature of advancedceramics requires a uniform interface between the grip com-ponents and the gripped section of
29、 the test specimen. Line orpoint contacts and non uniform pressure can produce Hertzian-type stress leading to crack initiation and fracture of the testspecimen in the gripped section. Gripping devices can beclassed generally as those employing active and those employ-ing passive grip interfaces as
30、discussed in the followingsections. Uncooled grips located inside the heated zone aretermed “hot grips” and generally produce almost no thermalgradient in the test specimen but at the relative expense of gripmaterials of at least the same temperature capability as the testmaterial and increased degr
31、adation of the grips due to exposureto the elevated-temperature oxidizing environment. Grips lo-cated outside the heated zone surrounding the test specimenmay or may not employ cooling. Uncooled grips locatedoutside the heated zone are termed“ warm grips” and generallyinduce a mild thermal gradient
32、in the test specimen but at therelative expense of elevated-temperature alloys in the grips andincreased degradation of the grips due to exposure to theelevated-temperature oxidizing environment. Cooled grips lo-cated outside the heated zone are termed“ cold grips” andgenerally induce a steep therma
33、l gradient in the test specimenat a greater relative expense because of grip cooling equipmentand allowances, although with the advantage of consistentalignment and little degradation from exposure to elevatedtemperatures.NOTE 1The expense of the cooling system for cold grips is balancedagainst main
34、taining alignment which remains consistent from test to test(stable grip temperature) and decreased degradation of the grips due toexposure to the elevated-temperature oxidizing environment. When gripcooling is employed, means should be provided to control the coolingmedium to maximum fluctuations o
35、f 5 K (less than 1 K preferred) abouta setpoint temperature (1)3over the course of the test to minimizethermally-induced strain changes in the test specimen. In addition,opposing grip temperatures should be maintained at uniform and consis-tent temperatures within6 5 K (less than 6 1 K preferred) (1
36、) so as toavoid introducing unequal thermal gradients and subsequent non uniaxialstresses in the test specimen. Generally, the need for control of griptemperature fluctuations or differences may be indicated if test specimengage-section temperatures cannot be maintained within the limits requiredin
37、9.3.26.2.1.1 Active Grip InterfacesActive grip interfaces re-quire a continuous application of a mechanical, hydraulic, orpneumatic force to transmit the load applied by the testmachine to the test specimen. Generally, these types of gripinterfaces cause a force to be applied normal to the surface o
38、fthe gripped section of the test specimen. Transmission of theuniaxial force applied by the test machine is then accomplishedby friction between the test specimen and the grip faces. Thus,important aspects of active grip interfaces are uniform contactbetween the gripped section of the test specimen
39、and the gripfaces and constant coefficient of friction over the grip/testspecimen interface.(a) For cylindrical test specimens, a one-piece split-colletarrangement acts as the grip interface (2, 3) as illustrated byFig. 2. Close tolerances are required for concentricity of boththe grip and test spec
40、imen diameters. In addition, the diameterof the gripped section of the test specimen and the unclamped,open diameter of the grip faces must be within similarly closetolerances to promote uniform contact at the test specimen/gripinterface. Tolerances will vary depending on the exact configu-ration as
41、 shown in the appropriate specimen drawings.(b) For, flat test specimens, flat-face, wedge-grip faces act asthe grip interface as illustrated in Fig. 3. Close tolerances arerequired for the flatness and parallelism as well as wedge angleof the grip faces. In addition, the thickness, flatness, andpar
42、allelism of the gripped section of the test specimen must be3The boldface numbers given in parentheses refer to a list of references at theend of the text.FIG. 1 Schematic Diagram of One Possible Apparatus forConducting a Uniaxially-Loaded Tensile TestC 1366 043within similarly close tolerances to p
43、romote uniform contact atthe test specimen/grip interface. Tolerances will vary depend-ing on the exact configuration as shown in the appropriate testspecimen drawings.6.2.1.2 Passive Grip InterfacesPassive grip interfacestransmit the force applied by the test machine to the testspecimen through a d
44、irect mechanical link. Generally, thesemechanical links transmit the test forces to the test specimenvia geometrical features of the test specimens such as button-head fillets, shank shoulders, or holes in the gripped head.Thus, the important aspect of passive grip interfaces in uniformcontact betwe
45、en the gripped section of the test specimen andthe grip faces.(a) For cyclindrical test specimens, a multi-piece split colletarrangement acts as the grip interface at button-head fillets ofthe test specimen (4) as illustrated in Fig. 4. Because of thelimited contact area at the test specimen/grip in
46、terface, soft,deformable collet materials may be used to conform to theexact geometry of the test specimen. In some cases taperedcollets may be used to transfer the axial force into the shank ofthe test specimen rather than into the button-head radius (4).Moderately close tolerances are required for
47、 concentricity ofboth the grip and test specimen diameters. In addition, toler-ances on the collet height must be maintained to promoteuniform axial-loading at the test specimen/grip interface.Tolerances will vary depending on the exact configuration asshown in the appropriate test specimen drawings
48、.(b) For flat test specimens, pins or pivots act as gripinterfaces at either the shoulders of the test specimen shank orat holes in the gripped test specimen head (5,6,7). Closetolerances are required of shoulder radii and grip interfaces topromote uniform contact along the entire test specimen/grip
49、interface as well as to provide for non eccentric loading asshown in Fig. 5. Moderately close tolerances are required forlongitudinal coincidence of the pin and hole centerlines asillustrated in Fig. 6.6.3 Load Train Couplers:6.3.1 GeneralVarious types of devices (load-train cou-plers) may be used to attach the active or passive grip interfaceassemblies to the testing machine (for example, Fig. 7). Theload-train couplers in conjunction with the type of grippingdevice play major roles in the alignment of the load train andthus subsequent bending imposed in t
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