1、Designation: C1499 09 (Reapproved 2013)C1499 15Standard Test Method forMonotonic Equibiaxial Flexural Strength of AdvancedCeramics at Ambient Temperature1This standard is issued under the fixed designation C1499; the number immediately following the designation indicates the year oforiginal adoption
2、 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 of the equibiaxial strength of adv
3、anced ceramics at ambient temperature viaconcentric ring configurations under monotonic uniaxial loading. In addition, test specimen fabrication methods, testing modes,testing rates, allowable deflection, and data collection and reporting procedures are addressed. Two types of test specimens arecons
4、idered: machined test specimens and as-fired test specimens exhibiting a limited degree of warpage. Strength as used in thistest method refers to the maximum strength obtained under monotonic application of load. Monotonic loading refers to a testconducted at a constant rate in a continuous fashion,
5、 with no reversals from test initiation to final fracture.1.2 This test method is intended primarily for use with advanced ceramics that macroscopically exhibit isotropic, homogeneous,continuous behavior. While this test method is intended for use on monolithic advanced ceramics, certain whisker- or
6、particle-reinforced composite ceramics as well as certain discontinuous fiber-reinforced composite ceramics may also meet thesemacroscopic behavior assumptions. Generally, continuous fiber ceramic composites do not macroscopically exhibit isotropic,homogeneous, continuous behavior, and the applicati
7、on of this test method to these materials is not recommended.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is
8、the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C1145 Terminology of Advanced CeramicsC1239 Practice for Reporting Uniaxial Strength Da
9、ta and Estimating Weibull Distribution Parameters for Advanced CeramicsC1259 Test Method for Dynamic Youngs Modulus, Shear Modulus, and Poissons Ratio for Advanced Ceramics by ImpulseExcitation of VibrationC1322 Practice for Fractography and Characterization of Fracture Origins in Advanced CeramicsE
10、4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE83 Practice for Verification and Classification of Extensometer SystemsE337 Test Method for Measuring Humidity with a Psychrometer (the Measurement of Wet- and Dry-Bulb Temperatures)F394 Te
11、st Method for Biaxial Flexure Strength (Modulus of Rupture) of Ceramic Substrates (Discontinued 2001) (Withdrawn2001)3IEEE/ASTM SI 10 Standard for Use of the International System of Units (SI): The Modern Metric System3. Terminology3.1 Definitions:1 This test method is under the jurisdiction of ASTM
12、 Committee C28 on Advanced Ceramics and is the direct responsibility of Subcommittee C28.01 on MechanicalProperties and Performance.Current edition approved Aug. 1, 2013July 1, 2015. Published September 2013October 2013. Originally approved in 2001. Last previous edition approved in 20092013as C1499
13、 09.C1499 09 (2013). DOI: 10.1520/C1499-09R13.10.1520/C1499-15.2 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 websit
14、e.3 The last 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 t
15、o adequately 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 Con
16、shohocken, PA 19428-2959. United States13.1.1 The definitions of terms relating to biaxial testing appearing in Terminology E6 and Terminology C1145 may apply to theterms used in this test method. Pertinent definitions are listed below with the appropriate source given in parentheses. Additionalterm
17、s used in conjunction with this test method are defined in the following section.3.1.2 advanced ceramic, nhighly engineered, high performance predominately non- metallic, inorganic, ceramic materialhaving specific functional attributes. C11453.1.3 breaking load, F, nload at which fracture occurs. E6
18、3.1.4 equibiaxial flexural strength, F/L2, nmaximum stress that a material is capable of sustaining when subjected to flexurebetween two concentric rings. This mode of flexure is a cupping of the circular plate caused by loading at the inner load ring andouter support ring. The equibiaxial flexural
19、strength is calculated from the maximum-load of a biaxial test carried to rupture, theoriginal dimensions of the test specimen, and Poissons ratio.3.1.5 homogeneous, ncondition of a material in which the relevant properties (composition, structure, density, etc.) areuniform, so that any smaller samp
20、le taken from an original body is representative of the whole. Practically, as long as thegeometrical dimensions of a sample are large with respect to the size of the individual grains, crystals, components, pores, ormicrocracks, the sample can be considered homogeneous.3.1.6 modulus of elasticity,
21、F/L2, nratio of stress to corresponding strain below the proportional limit. E63.1.7 Poissons ratio, nnegative value of the ratio of transverse strain to the corresponding axial strain resulting fromuniformly distributed axial stress below the proportional limit of the material.4. Significance and U
22、se4.1 This test method may be used for material development, material comparison, quality assurance, characterization and designcode or model verification.4.2 Engineering applications of ceramics frequently involve biaxial tensile stresses. Generally, the resistance to equibiaxialflexure is the meas
23、ure of the least flexural strength of a monolithic advanced ceramic.The equibiaxial flexural strength distributionsof ceramics are probabilistic and can be described by a weakest link failure theory, (1, 2)4. Therefore, a sufficient number of testspecimens at each testing condition is required for s
24、tatistical estimation or the equibiaxial strength.4.3 Equibiaxial strength tests provide information on the strength and deformation of materials under multiple tensile stresses.Multiaxial stress states are required to effectively evaluate failure theories applicable to component design, and to effi
25、cientlysample surfaces that may exhibit anisotropic flaw distributions. Equibiaxial tests also minimize the effects of test specimen edgepreparation as compared to uniaxial tests because the generated stresses are lowest at the test specimen edges.4.4 The test results of equibiaxial test specimens f
26、abricated to standardized dimensions from a particular material and/orselected portions of a component may not totally represent the strength properties in the entire, full-size component or its in-servicebehavior in different environments.4.5 For quality control purposes, results derived from stand
27、ardized equibiaxial test specimens may be considered indicative ofthe response of the bulk material from which they were taken for any given primary processing conditions and post-processingheat treatments or exposures.5. Interferences5.1 Test environment (vacuum, inert gas, ambient air, etc.) inclu
28、ding moisture content (for example, relative humidity) mayhave an influence on the measured equibiaxial strength. Testing to evaluate the maximum strength potential of a material can beconducted in inert environments and/or at sufficiently rapid testing rates so as to minimize any environmental effe
29、cts. Conversely,testing can be conducted in environments, test modes and test rates representative of service conditions to evaluate materialperformance under use conditions.5.2 Fabrication of test specimens can introduce dimensional variations that may have pronounced effects on the measuredequibia
30、xial mechanical properties and behavior (for example, shape and level of the resulting stress-strain curve, equibiaxialstrength, failure location, etc.). Surface preparation can also lead to the introduction of residual stresses and final machining stepsmight or might not negate machining damage int
31、roduced during the initial machining. Therefore, as universal or standardizedmethods of surface preparation do not exist, the test specimen fabrication history should be reported. In addition, the nature offabrication used for certain advanced ceramic components may require testing of specimens with
32、 surfaces in the as-fabricatedcondition (that is, it may not be possible, desired or required to machine some of the test specimen surfaces directly in contact withthe test fixture). For very rough or wavy as-fabricated surfaces, perturbations in the stress state due to non-symmetric cross-sectionsa
33、s well as variations in the cross-sectional dimensions may also interfere with the equibiaxial strength measurement. Finally, closegeometric tolerances, particularly in regard to flatness of test specimen surfaces in contact with the test fixture components arecritical requirements for successful eq
34、uibiaxial tests. In some cases it may be appropriate to use other test methods (for example,Test Method F394).4 The boldface numbers in parentheses refer to the list of references at the end of this standard.C1499 1525.3 Contact and frictional stresses in equibiaxial tests can introduce localized fa
35、ilure not representative of the equibiaxialstrength under ideal loading conditions. These effects may result in either over or under estimates of the actual strength (1, 3).5.4 Fractures that consistently initiate near or just outside the load-ring may be due to factors such as friction or contact s
36、tressesintroduced by the load fixtures, or via misalignment of the test specimen rings. Such fractures will normally constitute invalid tests(see Note 14). Splitting of the test specimen along a diameter that expresses the characteristic size may result from poor testspecimen preparation (for exampl
37、e, severe grinding or very poor edge preparation), excessive tangential stresses at the testspecimen edges, or a very weak material. Such fractures will constitute invalid tests if failure occurred from the edge.5.5 Deflections greater than one-quarter of the test specimen thickness can result in no
38、nlinear behavior and stresses notaccounted for by simple plate theory.5.6 Warpage of the test specimen can result in nonuniform loading and contact stresses that result in incorrect estimates of thetest specimens actual equibiaxial strength. The test specimen shall meet the flatness requirements (se
39、e 8.2 and 8.3) or bespecifically noted as warped and considered as a censored test.6. Apparatus6.1 Testing MachinesMachines used for equibiaxial testing shall conform to the requirements of Practices E4. The load cellsused in determining equibiaxial strength shall be accurate within 61 % at any load
40、 within the selected load range of the testingmachine as defined in Practice E4. Check that the expected breaking load for the desired test specimen geometry and test materialis within the capacity of the test machine and load cell. Advanced ceramic equibiaxial test specimens require greater loads t
41、ofracture than those usually encountered in uniaxial flexure of test specimens with similar cross sectional dimensions.6.2 Loading Fixtures for Concentric Ring TestingAn assembly drawing of a fixture and a test specimen is shown in Fig. 1,and the geometries of the load and support rings are given in
42、 Fig. 2.6.2.1 Loading Rods and PlatensSurfaces of the support platen shall be flat and parallel to 0.05 mm. The face of the load rodin contact with the support platen shall be flat to 0.025 mm. In addition, the two loading rods shall be parallel to 0.05 mm per 25mm length and concentric to 0.25 mm w
43、hen installed in the test machine.6.2.2 Loading Fixture and Ring GeometryIdeally, the bases of the load and support fixtures should have the same outerdiameter as the test specimen for ease of alignment. Parallelism and flatness of faces as well as concentricity of the load and supportrings shall be
44、 as given in Fig. 2. The ratio of the load ring diameter, DL, to that of the support ring, DS, shall be 0.2 DL/DS 0.5. For test materials exhibiting low elastic modulus (E 1 GPa) it is recommended that theratio of the load ring diameter to that of the support ring be DL/DS = 0.2. The sizes of the lo
45、ad and support rings depend on thedimensions and the properties of the ceramic material to be tested. The rings are sized to the thickness, diameter, strength, andelastic modulus of the ceramic test specimens (see Section 8). For test specimens made from typical substrates (h 0.5 mm), asupport ring
46、diameter as small as 12 mm may be required. For test specimens to be used for model verification, it is recommendedthat the test specimen support diameter be at least 35 mm. The tip radius, r, of the cross sections of the load and support ringsshould be h/2 r 3h/2.FIG. 1 Section View and Perspective
47、 View of Basic Fixturing and Test Specimen for Equibiaxial TestingC1499 1536.2.3 Load and Support Ring MaterialsFor machined test specimens (see Section 8) the load and support fixtures shall bemade of hardened steel of HRC 40. For as-fabricated test specimens, the load/support rings shall be made o
48、f steel or acetylpolymer.6.2.4 Compliant Layer and Friction EliminationThe brittle nature of advanced ceramics and the sensitivity to misalignment,contact stresses and friction may require a compliant interface between the load/support rings and the test specimen, especially ifthe test specimen is n
49、ot flat. Line or point contact stresses and frictional stresses can lead to crack initiation and fracture of thetest specimen at stresses other than the actual equibiaxial strength.6.2.4.1 Machined Test SpecimensFor test specimens machined according to the tolerance in Fig. 3, a compliant layer is notnecessary. However, friction needs to be eliminated. Place a sheet of carbon foil (0.13 mm thick) or Teflon tape (0.07 mm thick)between the compressive and tensile surfaces of the test specimen and the load and support rings.NOTE 1Thicker layer
