1、Designation: C 1273 05Standard Test Method forTensile Strength of Monolithic Advanced Ceramics atAmbient Temperatures1This standard is issued under the fixed designation C 1273; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the y
2、ear 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 cer
3、am-ics at ambient 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, disp
4、lacement rate, or strainrate), allowable bending, and data collection and reportingprocedures are addressed. Note that tensile strength as used inthis test method refers to the tensile strength obtained underuniaxial loading.1.2 This test method applies primarily to advanced ceramicsthat macroscopic
5、ally exhibit isotropic, homogeneous, continu-ous 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 a
6、ssumptions. Generally, continuous fiberceramic composites (CFCCs) do not macroscopically exhibitisotropic, homogeneous, continuous behavior and applicationof this practice to these materials is not recommended.1.3 Values expressed in this test method are in accordancewith the International System of
7、 Units (SI) and SI10-02IEEE/ASTM SI 10.1.4 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 l
8、imitations prior to use. Specific precau-tionary statements are given in Section 7.2. 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
9、 andEstimating Weibull Distribution Parameters 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 MaterialsE4 Practices for Force Verification of T
10、esting MachinesE6 Terminology Relating to Methods of Mechanical Test-ingE83 Practice for Verification and Classification of Exten-someters SystemE 337 Test Method for Measuring Humidity with a Psy-chrometer (the Measurement of Wet- and Dry-Bulb Tem-peratures)E 1012 Practice for Verification of Speci
11、men AlignmentUnder Tensile LoadingSI10-02 IEEE/ASTM SI 10 American National Standardfor Use of the International System of Units (SI): TheModern Metric System3. Terminology3.1 DefinitionsThe definitions of terms relating to tensiletesting appearing in Terminology E6apply to the terms used inthis tes
12、t method on tensile testing. The definitions of termsrelating to advanced ceramics testing appearing in Terminol-ogy C 1145 apply to the terms used in this test method.1This test method is under the jurisdiction of ASTM Committee C28 onAdvanced Ceramics and is the direct responsibility of Subcommitt
13、ee C28.01 onMechanical Properties and Performance.Current edition approved June 1, 2005. Published July 2005. Originally approvedin 1994. Last previous edition approved in 2000 as C 1273 95a (2000).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service
14、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.Pertinent definitions as listed in Practice C 12
15、39, PracticeE 1012, Terminology C 1145, and Terminology E6are shownin the following with the appropriate source given in paren-theses. Additional terms used in conjunction with this testmethod are defined in the following:3.1.1 advanced ceramica highly engineered, high perfor-mance predominately non
16、metallic, inorganic, ceramic materialhaving specific functional attributes. C 11453.1.2 axial strainthe average of longitudinal strains mea-sured at the surface on opposite sides of the longitudinal axisof symmetry of the specimen by two strain-sensing deviceslocated at the mid length of the reduced
17、 section. E 10123.1.3 bending strainthe difference between the strain atthe surface and the axial strain. In general, the bending strainvaries from point to point around and along the reduced sectionof the specimen. E 10123.1.4 breaking forcethe force at which fracture occurs.E63.1.5 fractographymea
18、ns and methods for characterizinga fractured specimen or component. C 11453.1.6 fracture originthe source from which brittle fracturecommences. C 11453.1.7 percent bendingthe bending strain times 100 di-vided by the axial strain. E 10123.1.8 slow crack growth (SCG)subcritical crack growth(extension)
19、 which may result from, but is not restricted to, suchmechanisms as environmentally-assisted stress corrosion ordiffusive crack growth. C 11453.1.9 tensile strength,Suthe maximum tensile stresswhich a material is capable of sustaining. Tensile strength iscalculated from the maximum force during a te
20、nsion testcarried to rupture and the original cross-sectional area of thespecimen. E64. Significance and Use4.1 This test method may be used for material development,material comparison, quality assurance, characterization, anddesign data generation.4.2 High strength, monolithic advanced ceramic mat
21、erialsgenerally characterized by small grain sizes (65 % relative humidity (RH) is not recommended and anydeviations from this recommendation must be reported.5.2 Surface preparation of test specimens can introducefabrication flaws that may have pronounced effects on tensilestrength. Machining damag
22、e introduced during test specimenpreparation can be either a random interfering factor in thedetermination of ultimate strength of pristine material (that is,increase frequency of surface initiated fractures compared tovolume initiated fractures), or an inherent part of the strengthC1273052character
23、istics to be measured. Surface preparation can alsolead to the introduction of residual stresses. Universal orstandardized test methods of surface preparation do not exist. Itshould be understood that final machining steps may or maynot negate machining damage introduced during the earlycoarse or in
24、termediate machining. Thus, test specimen fabri-cation history may play an important role in the measuredstrength distributions and should be reported.5.3 Bending in uniaxial tensile tests can cause or promotenon-uniform stress distributions with maximum stresses occur-ring at the test specimen surf
25、ace leading to non-representativefractures originating at surfaces or near geometrical transitions.In addition, if strains or deformations are measured at surfaceswhere maximum or minimum stresses occur, bending mayintroduce over or under measurement of strains. Similarly,fracture from surface flaws
26、 may be accentuated or muted by thepresence of the non-uniform stresses caused by bending.6. Apparatus6.1 Testing MachinesMachines used for tensile testingshall conform to the requirements of Practices E4. The forcesused in determining tensile strength shall be accurate within61 % at any force withi
27、n the selected force range of the testingmachine as defined in Practices E4. A schematic showingpertinent features of the tensile testing apparatus is shown inFig. 1.6.2 Gripping Devices:6.2.1 GeneralVarious types of gripping devices may beused to transmit the measured force applied by the testingma
28、chine to the test specimens. The brittle nature of advancedceramics requires a uniform interface between the grip com-ponents and the gripped section of the test specimen. Line orpoint contacts and non-uniform pressure can produce Hertizan-type stresses leading to crack initiation and fracture of th
29、e testspecimen in the gripped section. Gripping devices can beclassed generally as those employing active and those employ-ing passive grip interfaces as discussed in the followingsections.6.2.2 Active Grip InterfacesActive grip interfaces requirea continuous application of a mechanical, hydraulic,
30、or pneu-matic force to transmit the force applied by the test machine tothe test specimen. Generally, these types of grip interfacescause a force to be applied normal to the surface of the grippedsection of the test specimen. Transmission of the uniaxial forceapplied by the test machine is then acco
31、mplished by frictionbetween the test specimen and the grip faces. Thus, importantaspects of active grip interfaces are uniform contact betweenthe gripped section of the test specimen and the grip faces andconstant coefficient of friction over the grip/specimen inter-face.6.2.2.1 For cylindrical test
32、 specimens, a one-piece split-collet arrangement acts as the grip interface (1, 2)3as illus-trated in Fig. 2. Generally, close tolerances are required forconcentricity of both the grip and test specimen diameters. Inaddition, the diameter of the gripped section of the testspecimen and the unclamped,
33、 open diameter of the grip facesmust be within similarly close tolerances to promote uniformcontact at the test specimen/grip interface. Tolerances will varydepending on the exact configuration as shown in the appro-priate test specimen drawings.6.2.2.2 For flat test specimens, flat-face, wedge-grip
34、 facesact as the grip interface as illustrated in Fig. 3. Generally, closetolerances are required for the flatness and parallelism as wellas wedge angle of the grip faces. In addition, the thickness,flatness, and parallelism of the gripped section of the test3The boldface numbers given in parenthese
35、s refer to a list of references at theend of the text.FIG. 1 Schematic Diagram of One Possible Apparatus forConducting a Uniaxially-Loaded Tensile TestFIG. 2 Example of a Smooth, Split Collet Active Gripping Systemfor Cylindrical Test SpecimensC1273053specimen must be within similarly close toleranc
36、es to promoteuniform contact at the test specimen/grip interface. Toleranceswill vary depending on the exact configuration as shown in theappropriate test specimen drawings.6.2.3 Passive Grip InterfacesPassive grip interfacestransmit the force applied by the test machine to the testspecimen through
37、a direct 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 is uniformcontact be
38、tween the gripped section of the test specimen andthe grip faces.6.2.3.1 For cylindrical test specimens, a multi-piece splitcollet arrangement acts as the grip interface at button-headfillets of the test specimen (3) as illustrated in Fig. 4. Becauseof the limited contact area at the test specimen/g
39、rip interface,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 (3).Moderately close tolerances are requir
40、ed for 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 dr
41、awings.6.2.3.2 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 (4, 5, 6). Closetolerances are required of shoulder radii and grip interfaces topromote uniform contact along the entire test s
42、pecimen/gripinterface 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) m
43、ay be used to attach the active or passive grip interfaceassemblies to the testing machine. The load train couplers inconjunction with the type of gripping device play major rolesin the alignment of the load train and thus subsequent bendingimposed in the test specimen. Load train couplers can becla
44、ssified as fixed and nonfixed as discussed in the followingsections. Note that use of well-aligned fixed or self-aligningnon fixed couplers does not automatically guarantee lowbending in the gage section of the tensile test specimen.Well-aligned fixed or self-aligning non fixed couplers providefor w
45、ell aligned load trains, but the type and operation of gripinterfaces as well as the as-fabricated dimensions of the tensiletest specimen can add significantly to the final bendingimposed in the gage section of the test specimen.6.3.1.1 Regardless of which type of coupler is used, align-ment of the
46、testing system must be verified as a minimum at thebeginning and end of a test series.An additional verification ofalignment is recommended, although not required, at themiddle of the test series. Either a dummy or actual testspecimen and the alignment verification procedures detailed inFIG. 3 Examp
47、le of a Smooth, Wedge Active Gripping System forFlat Test SpecimensFIG. 4 Examples of Straight- and Tapered-Collet Passive Gripping Systems for Cylindrical Test Specimens (3)C1273054the appendix must be used. Allowable bending requirementsare discussed in 6.4. Tensile test specimens used for alignme
48、ntverification should be equipped with a recommended eightseparate longitudinal strain gages to determine bending contri-butions from both eccentric and angular misalignment of thegrip heads. (Although it is possible to use a minimum of sixseparate longitudinal strain gages for test specimens withci
49、rcular cross sections, eight strain gages are recommendedhere for simplicity and consistency in describing the techniquefor both circular and rectangular cross sections). If dummy testspecimens are used for alignment verification, they shouldhave the same geometry and dimensions of the actual testspecimens as well as the same mechanical properties (that is,elastic modulus, hardness, etc.) as the test material to ensuresimilar axial and bending stiffness characteristics as the actualtest specimen and material.6.3.2 Fixed Load Train CouplersFixed couplers mayincorpor
