1、Designation: C 1499 09Standard Test Method forMonotonic Equibiaxial Flexural Strength of AdvancedCeramics at Ambient Temperature1This standard is issued under the fixed designation C 1499; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revi
2、sion, 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 of the equibi-axial strength of advanced ceramics at ambie
3、nt temperature viaconcentric ring configurations under monotonic uniaxial load-ing. In addition, test specimen fabrication methods, testingmodes, testing rates, allowable deflection, and data collectionand reporting procedures are addressed. Two types of testspecimens are considered: machined test s
4、pecimens and as-fired test specimens exhibiting a limited degree of warpage.Strength as used in this test method refers to the maximumstrength obtained under monotonic application of load. Mono-tonic loading refers to a test conducted at a constant rate in acontinuous fashion, with no reversals from
5、 test initiation tofinal fracture.1.2 This test method is intended primarily for use withadvanced ceramics that macroscopically exhibit isotropic,homogeneous, continuous behavior. While this test method isintended for use on monolithic advanced ceramics, certainwhisker- or particle-reinforced compos
6、ite ceramics as well ascertain discontinuous fiber-reinforced composite ceramics mayalso meet these macroscopic behavior assumptions. Generally,continuous fiber ceramic composites do not macroscopicallyexhibit isotropic, homogeneous, continuous behavior, and theapplication of this test method to the
7、se materials is notrecommended.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.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
8、this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 1145 Terminology of Advanced CeramicsC 1239 Practice for Reporting Uniaxial Strength Data andEstimating Weibull Dis
9、tribution Parameters for AdvancedCeramicsC 1259 Test Method for Dynamic Youngs Modulus, ShearModulus, and Poissons Ratio for Advanced Ceramics byImpulse Excitation of VibrationC 1322 Practice for Fractography and Characterization ofFracture Origins in Advanced CeramicsE4 Practices for Force Verifica
10、tion of Testing MachinesE6 Terminology Relating to Methods of Mechanical Test-ingE83 Practice for Verification and Classification of Exten-someter SystemsE 337 Test Method for Measuring Humidity with a Psy-chrometer (the Measurement of Wet- and Dry-Bulb Tem-peratures)F 394 Test Method for Biaxial Fl
11、exure Strength (Modulusof Rupture) of Ceramic Substrates (Discontinued 2001)3IEEE/ASTM SI 10 Standard for Use of the InternationalSystem of Units (SI): The Modern Metric System3. Terminology3.1 DefinitionsThe definitions of terms relating to biaxialtesting appearing in Terminology E6and Terminology
12、C 1145may apply to the terms used in this test method. Pertinentdefinitions are listed below with the appropriate source given inparentheses.Additional terms used in conjunction with this testmethod are defined in the following section.1This test method is under the jurisdiction of ASTM Committee C2
13、8 onAdvanced Ceramics and is the direct responsibility of Subcommittee C28.01 onMechanical Properties and Performance.Current edition approved May 1, 2009. Published June 2009. Originallyapproved in 2001. Last previous edition approved in 2008 as C 1499 08.2For referenced ASTM standards, visit the A
14、STM 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 ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.1Copyrigh
15、t ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.1 advanced ceramic, nhighly engineered, high perfor-mance predominately non- metallic, inorganic, ceramic mate-rial having specific functional attributes. C 11453.1.2 breaking load, F, nload
16、 at which fracture occurs.E63.1.3 equibiaxial flexural strength, F/L2, nmaximumstress that a material is capable of sustaining when subjected toflexure between two concentric rings. This mode of flexure isa cupping of the circular plate caused by loading at the innerload ring and outer support ring.
17、 The equibiaxial flexuralstrength is calculated from the maximum-load of a biaxial testcarried to rupture, the original dimensions of the test specimen,and Poissons ratio.3.1.4 homogeneous, ncondition of a material in which therelevant properties (composition, structure, density, etc.) areuniform, s
18、o that any smaller sample taken from an originalbody is representative of the whole. Practically, as long as thegeometrical dimensions of a sample are large with respect tothe size of the individual grains, crystals, components, pores, ormicrocracks, the sample can be considered homogeneous.3.1.5 mo
19、dulus of elasticity, F/L2, nratio of stress tocorresponding strain below the proportional limit. E63.1.6 Poissons ratio, nnegative value of the ratio oftransverse strain to the corresponding axial strain resultingfrom uniformly distributed axial stress below the proportionallimit of the material.4.
20、Significance and Use4.1 This test method may be used for material development,material comparison, quality assurance, characterization anddesign code or model verification.4.2 Engineering applications of ceramics frequently involvebiaxial tensile stresses. Generally, the resistance to equibiaxialfle
21、xure is the measure of the least flexural strength of amonolithic advanced ceramic. The equibiaxial flexural strengthdistributions of ceramics are probabilistic and can be describedby a weakest link failure theory, (1, 2)4. Therefore, a sufficientnumber of test specimens at each testing condition is
22、 requiredfor statistical estimation or the equibiaxial strength.4.3 Equibiaxial strength tests provide information on thestrength and deformation of materials under multiple tensilestresses. Multiaxial stress states are required to effectivelyevaluate failure theories applicable to component design,
23、 andto efficiently sample surfaces that may exhibit anisotropic flawdistributions. Equibiaxial tests also minimize the effects of testspecimen edge preparation as compared to uniaxial testsbecause the generated stresses are lowest at the test specimenedges.4.4 The test results of equibiaxial test sp
24、ecimens fabricatedto standardized dimensions from a particular material and/orselected portions of a component may not totally represent thestrength properties in the entire, full-size component or itsin-service behavior in different environments.4.5 For quality control purposes, results derived fro
25、m stan-dardized equibiaxial test specimens may be considered indica-tive of the response of the bulk material from which they weretaken for any given primary processing conditions and post-processing heat treatments or exposures.5. Interferences5.1 Test environment (vacuum, inert gas, ambient air, e
26、tc.)including moisture content (for example, relative humidity)may have an influence on the measured equibiaxial strength.Testing to evaluate the maximum strength potential of amaterial can be conducted in inert environments and/or atsufficiently rapid testing rates so as to minimize any environ-men
27、tal effects. Conversely, testing can be conducted in envi-ronments, test modes and test rates representative of serviceconditions to evaluate material performance under use condi-tions.5.2 Fabrication of test specimens can introduce dimensionalvariations that may have pronounced effects on the measu
28、redequibiaxial mechanical properties and behavior (for example,shape and level of the resulting stress-strain curve, equibiaxialstrength, failure location, etc.). Surface preparation can alsolead to the introduction of residual stresses and final machiningsteps might or might not negate machining da
29、mage introducedduring the initial machining. Therefore, as universal or stan-dardized methods of surface preparation do not exist, the testspecimen fabrication history should be reported. In addition,the nature of fabrication used for certain advanced ceramiccomponents may require testing of specime
30、ns with surfaces inthe as-fabricated condition (that is, it may not be possible,desired or required to machine some of the test specimensurfaces directly in contact with the test fixture). For veryrough or wavy as-fabricated surfaces, perturbations in thestress state due to non-symmetric cross-secti
31、ons as well asvariations in the cross-sectional dimensions may also interferewith the equibiaxial strength measurement. Finally, closegeometric tolerances, particularly in regard to flatness of testspecimen surfaces in contact with the test fixture componentsare critical requirements for successful
32、equibiaxial tests. Insome cases it may be appropriate to use other test methods (forexample, Test Method F 394).5.3 Contact and frictional stresses in equibiaxial tests canintroduce localized failure not representative of the equibiaxialstrength under ideal loading conditions. These effects mayresul
33、t in either over or under estimates of the actual strength (1,3).5.4 Fractures that consistently initiate near or just outsidethe load-ring may be due to factors such as friction or contactstresses introduced by the load fixtures, or via misalignment ofthe test specimen rings. Such fractures will no
34、rmally constituteinvalid tests (see Note 14). Splitting of the test specimen alonga diameter that expresses the characteristic size may resultfrom poor test specimen preparation (for example, severegrinding or very poor edge preparation), excessive tangentialstresses at the test specimen edges, or a
35、 very weak material.Such fractures will constitute invalid tests if failure occurredfrom the edge.5.5 Deflections greater than one-quarter of the test specimenthickness can result in nonlinear behavior and stresses notaccounted for by simple plate theory.4The boldface numbers in parentheses refer to
36、 the list of references at the end ofthis standard.C14990925.6 Warpage of the test specimen can result in nonuniformloading and contact stresses that result in incorrect estimates ofthe test specimens actual equibiaxial strength. The test speci-men shall meet the flatness requirements (see 8.2 and 8
37、.3)orbespecifically noted as warped and considered as a censored test.6. Apparatus6.1 Testing MachinesMachines used for equibiaxial test-ing shall conform to the requirements of Practices E4. Theload cells used in determining equibiaxial strength shall beaccurate within 61 % at any load within the s
38、elected loadrange of the testing machine as defined in Practice E4. Checkthat the expected breaking load for the desired test specimengeometry and test material is within the capacity of the testmachine and load cell. Advanced ceramic equibiaxial testspecimens require greater loads to fracture than
39、those usuallyencountered in uniaxial flexure of test specimens with similarcross sectional dimensions.6.2 Loading Fixtures for Concentric Ring TestingAnassembly drawing of a fixture and a test specimen is shown inFig. 1, and the geometries of the load and support rings aregiven in Fig. 2.6.2.1 Loadi
40、ng Rods and PlatensSurfaces of the supportplaten shall be flat and parallel to 0.05 mm. The face of the loadrod in contact with the support platen shall be flat to 0.025 mm.In addition, the two loading rods shall be parallel to 0.05 mmper 25 mm length and concentric to 0.25 mm when installed inthe t
41、est machine.6.2.2 Loading Fixture and Ring GeometryIdeally, thebases of the load and support fixtures should have the sameouter diameter as the test specimen for ease of alignment.Parallelism and flatness of faces as well as concentricity of theload and support rings shall be as given in Fig. 2. The
42、 ratio ofthe load ring diameter, DL, to that of the support ring, DS, shallbe 0.2#DL/DS#0.5. For test materials exhibiting low elasticmodulus (E 1 GPa) it isrecommended that the ratio of the load ring diameter to that ofthe support ring be DL/DS= 0.2. The sizes of the load andsupport rings depend on
43、 the dimensions and the properties ofthe ceramic material to be tested. The rings are sized to thethickness, diameter, strength, and elastic modulus of theceramic test specimens (see Section 8). For test specimensmade from typical substrates (h 0.5 mm), a support ringdiameter as small as 12 mm may b
44、e required. For testspecimens to be used for model verification, it is recommendedthat the test specimen support diameter be at least 35 mm. Thetip radius, r, of the cross sections of the load and support ringsshould be h/2 # r # 3h/2.6.2.3 Load and Support Ring MaterialsFor machined testspecimens (
45、see Section 8) the load and support fixtures shall bemade of hardened steel of HRC 40. For as-fabricated testspecimens, the load/support rings shall be made of steel oracetyl polymer.6.2.4 Compliant Layer and Friction EliminationThebrittle nature of advanced ceramics and the sensitivity tomisalignme
46、nt, contact stresses and friction may require acompliant interface between the load/support rings and the testspecimen, especially if the test specimen is not flat. Line orpoint contact stresses and frictional stresses can lead to crackinitiation and fracture of the test specimen at stresses other t
47、hanthe actual equibiaxial strength.6.2.4.1 Machined Test SpecimensFor test specimens ma-chined according to the tolerance in Fig. 3, a compliant layer isnot necessary. However, friction needs to be eliminated. Placea sheet of carbon foil (0.13 mm thick) or Teflon tape (0.07mm thick) between the comp
48、ressive and tensile surfaces of thetest specimen and the load and support rings.NOTE 1Thicker layers of carbon foil or Teflon tape may be used,particularly for very strong plates. However, excessively thick layers willredistribute the contact region and may affect results. The thicknessesFIG. 1 Sect
49、ion View and Perspective View of Basic Fixturing and Test Specimen for Equibiaxial TestingC1499093listed above have been used successfully. Guidance regarding the use ofthick layers cannot be given currently; some judgement may be required.Alternatively, an appropriate lubricant (anti-seizing com-pound or Teflon oil) may be used to minimize friction. Thelubricant should be placed only on the load and support ringsso that effects of the test environment are not significantlyaltered. To aid fractographic examination, place a single stripof adhesive tape
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