1、Designation: C 1499 05Standard 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 (e) 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 ambi
3、ent 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
4、specimens 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 fro
5、m 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 compo
6、site 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 th
7、ese materials is notrecommended.1.3 Values expressed in this test method are in accordancewith the International System of Units (SI) and 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 th
8、is 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 Distr
9、ibution 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 Verificati
10、on of Testing MachinesE6 Terminology Relating to Methods of Mechanical Test-ingE83 Practice for Verification and Classification of Exten-someter SystemE 337 Test Method for Measuring Humidity with a Psy-chrometer (the Measurement of Wet- and Dry-Bulb Tem-peratures)E 380 Practice for Use of Internati
11、onal System of Units (SI)(The Modernized Metric System)F 394 Test Method for Iron in Trace Quantities Using the1,10-Phenanthroline Method33. Terminology3.1 DefinitionsThe definitions of terms relating to biaxialtesting appearing in Terminology E6and Terminology C 1145may apply to the terms used in t
12、his test method. Pertinent1This test method is under the jurisdiction of ASTM Committee C28 onAdvanced Ceramics and is the direct responsibility of Subcommittee C28.01 onMechanical Properties and Performance.Current edition approved June 1, 2005. Published June 2005. Originallyapproved in 2001. Last
13、 previous edition approved in 2004 as C 1499 04.2For 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 ASTM website.3Withdrawn.1C
14、opyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.definitions are listed below with the appropriate source given inparentheses.Additional terms used in conjunction with this testmethod are defined in the following section.3.1.1 advanced
15、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 at which fracture occurs.E63.1.3 equibiaxial flexural strength, F/L2, nmaximumstress that a material is capable of susta
16、ining 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. The equibiaxial flexuralstrength is calculated from the maximum-load of a biaxial testcarried to rupture, the original d
17、imensions of the test specimen,and Poissons ratio.3.1.4 homogeneous, ncondition of a material in which therelevant properties (composition, structure, density, etc.) areuniform, so that any smaller sample taken from an originalbody is representative of the whole. Practically, as long as thegeometric
18、al 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 modulus of elasticity, F/L2, nratio of stress tocorresponding strain below the proportional limit. E63.1.6 Poissons ratio,
19、nnegative value of the ratio oftransverse strain to the corresponding axial strain resultingfrom uniformly distributed axial stress below the proportionallimit of the material.4. Significance and Use4.1 This test method may be used for material development,material comparison, quality assurance, cha
20、racterization anddesign code or model verification.4.2 Engineering applications of ceramics frequently involvebiaxial tensile stresses. Generally, the resistance to equibiaxialflexure is the measure of the least flexural strength of amonolithic advanced ceramic. The equibiaxial flexural strengthdist
21、ributions 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 requiredfor statistical estimation or the equibiaxial strength.4.3 Equibiaxial strength tests provide information on the
22、strength and deformation of materials under multiple tensilestresses. Multiaxial stress states are required to effectivelyevaluate failure theories applicable to component design, andto efficiently sample surfaces that may exhibit anisotropic flawdistributions. Equibiaxial tests also minimize the ef
23、fects 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 specimens fabricatedto standardized dimensions from a particular material and/orselected portions of a component may not to
24、tally represent thestrength properties in the entire, full-size component or itsin-service behavior in different environments.4.5 For quality control purposes, results derived from stan-dardized equibiaxial test specimens may be considered indica-tive of the response of the bulk material from which
25、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, etc.)including moisture content (for example, relative humidity)may have an influence on the measured equibiaxial strength
26、.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-mental effects. Conversely, testing can be conducted in envi-ronments, test modes and test rates representative of serviceco
27、nditions to evaluate material performance under use condi-tions.5.2 Fabrication of test specimens can introduce dimensionalvariations that may have pronounced effects on the measuredequibiaxial mechanical properties and behavior (for example,shape and level of the resulting stress-strain curve, equi
28、biaxialstrength, failure location, etc.). Surface preparation can alsolead to the introduction of residual stresses and final machiningsteps might or might not negate machining damage introducedduring the initial machining. Therefore, as universal or stan-dardized methods of surface preparation do n
29、ot exist, the testspecimen fabrication history should be reported. In addition,the nature of fabrication used for certain advanced ceramiccomponents may require testing of specimens with surfaces inthe as-fabricated condition (that is, it may not be possible,desired or required to machine some of th
30、e 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-sections as well asvariations in the cross-sectional dimensions may also interferewith the equibiaxial strength measurement. F
31、inally, closegeometric tolerances, particularly in regard to flatness of testspecimen surfaces in contact with the test fixture componentsare critical requirements for successful equibiaxial tests. Insome cases it may be appropriate to use other test methods (forexample, Test Method F 394).5.3 Conta
32、ct and frictional stresses in equibiaxial tests canintroduce localized failure not representative of the equibiaxialstrength under ideal loading conditions. These effects mayresult in either over or under estimates of the actual strength (1,3).5.4 Fractures that consistently initiate near or just ou
33、tsidethe 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 normally constituteinvalid tests (see Note 14). Splitting of the test specimen alonga diameter that expresses the character
34、istic size may resultfrom poor test specimen preparation (for example, severegrinding or very poor edge preparation), excessive tangentialstresses at the test specimen edges, or a very weak material.Such fractures will constitute invalid tests if failure occurredfrom the edge.4The boldface numbers i
35、n parentheses refer to the list of references at the end ofthis standard.C14990525.5 Deflections greater than one-quarter of the test specimenthickness can result in nonlinear behavior and stresses notaccounted for by simple plate theory.5.6 Warpage of the test specimen can result in nonuniformloadi
36、ng 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 8.3)orbespecifically noted as warped and considered as a censored test.6. Apparatus6.1 Testing MachinesMachines used for e
37、quibiaxial 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 selected loadrange of the testing machine as defined in Practice E 4. Checkthat the expected breaking load for the desired
38、 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 those usuallyencountered in uniaxial flexure of test specimens with similarcross sectional dimensions.6.2 Loading Fixtur
39、es 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 Loading Rods and PlatensSurfaces of the supportplaten shall be flat and parallel to 0.05 mm. The face of the loadrod in conta
40、ct 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 test machine.6.2.2 Loading Fixture and Ring GeometryIdeally, thebases of the load and support fixtures should have the sa
41、meouter 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 ratio ofthe load ring diameter, DL, to that of the support ring, DS, shallbe 0.2#DL/DS#0.5. For test materials exhibiti
42、ng 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 the dimensions and the properties ofthe ceramic material to be tested. The rings are sized to thethickness, diameter, s
43、trength, 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 be required. For testspecimens to be used for model verification, it is recommendedthat the test specimen support diamete
44、r 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 (see Section 8) the load and support fixtures shall bemade of hardened steel of HRC 40. For as-fabricated testspecimens,
45、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 tomisalignment, contact stresses and friction may require acompliant interface between the load/support rings and the testspecimen,
46、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 thanthe actual equibiaxial strength.6.2.4.1 Machined Test SpecimensFor test specimens ma-chined according to the toleranc
47、e 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 compressive and tensile surfaces of thetest specimen and the load and support rings.NOTE 1Thicker layers of carbon foil or T
48、eflon tape may be used,particularly for very strong plates. However, excessively thick layers willredistribute the contact region and may affect results. The thicknesseslisted above have been used successfully. Guidance regarding the use ofthick layers cannot be given currently; some judgement may b
49、e 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 with a width of DLor greater on thecompressive face of the test specimen. Do not use multiplestrips of tape, or a strip of tape with width less than DL, as thismay result in nonuniform loading.6.2.4.2 As-Fabricated Test SpecimensI
