1、Designation: C 1424 04Standard Test Method forMonotonic Compressive Strength of Advanced Ceramics atAmbient Temperature1This standard is issued under the fixed designation C 1424; 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 compres-sive strength including stress-strain behavior, under m
3、onotonicuniaxial loading of advanced ceramics at ambient temperature.This test method is restricted to specific test specimen geom-etries. In addition, test specimen fabrication methods, testingmodes (load or displacement), testing rates (load rate, stressrate, displacement rate, or strain rate), al
4、lowable bending, anddata collection and reporting procedures are addressed. Com-pressive strength as used in this test method refers to thecompressive strength obtained under monotonic uniaxial load-ing. Monotonic loading refers to a test conducted at a constantrate in a continuous fashion, with no
5、reversals from testinitiation to final fracture.1.2 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 reg
6、ulatory limitations prior to use.1.3 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 composi
7、te ceramics as well ascertain discontinuous fiber-reinforced composite ceramics mayalso meet these macroscopic behavior assumptions. Generally,continuous fiber ceramic composites (CFCCs) do not macro-scopically exhibit isotropic, homogeneous, continuous behav-ior and, application of this test method
8、 to these materials is notrecommended.1.4 Values expressed in this test method are in accordancewith the International System of Units (SI) and IEEE/ASTM SI10.2. Referenced Documents2.1 ASTM Standards:2C 773 Test Method for Compressive (Crushing) Strength ofFired Whiteware MaterialsC 1145 Terminolog
9、y on Advanced CeramicsD 695 Test Method for Compressive Properties of RigidPlasticsE 4 Practices for Force Verification of Testing MachinesE 6 Terminology Relating to Methods of Mechanical Test-ingE 83 Practice for Verification and Classification of Exten-sometersE 337 Test Method for Measured Humid
10、ity with Psychrom-eter (the Measurement of Wet-and Dry-Bulb Temperatures)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 System3. Terminology3.1 DefinitionsThe definitions of terms
11、 relating to com-pressive testing appearing in Terminology E 6, Test MethodD 695, and Terminology C 1145 may apply to the terms used inthis test method. Pertinent definitions as listed in PracticeE 1012, Terminology C 1145, and Terminology E 6 are shownin the following with the appropriate source gi
12、ven in paren-theses. Additional terms used in conjunction with this testmethod are defined in the following.3.1.1 advanced ceramic, na highly engineered, high-performance predominately nonmetallic, inorganic, ceramicmaterial having specific functional attributes. (C 1145)3.1.2 axial strain, n L/Lthe
13、 average longitudinal strainsmeasured at the surface on opposite sides of the longitudinalaxis of symmetry of the specimen by two strain-sensing1This test method is under the jurisdiction of ASTM Committee C28 onAdvanced Ceramics and is the direct responsibility of Subcommittee C28.01 onProperties a
14、nd Performance.Current edition approved May 1, 2004. Published June 2004. Originallypublished in 1999. Last previous edition approved in 1999 as C1424-99.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMS
15、tandards 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.devices located at the mid length of the reduced section.(E 1012)3.1.3 bending strain, n L/L
16、the difference between thestrain at the surface and the axial strain. In general, the bendingstrain varies from point to point around and along the reducedsection of the test specimen. (E 1012)3.1.4 breaking load, n Fthe load at which fractureoccurs. (E 6)3.1.5 compressive strength, n F/L2the maximu
17、m com-pressive stress which a material is capable of sustaining.Compressive strength is calculated from the maximum loadduring a compression test carried to rupture and the originalcross-sectional area of the specimen. (E 6)3.1.6 gage length, n Lthe original length of that portionof the specimen ove
18、r which strain or change of length isdetermined. (E 6)3.1.7 modulus of elasticity, n F/L2the ratio of stress tocorresponding strain below the proportional limit. (E 6)3.1.8 percent bending, nthe bending strain times 100divided by the axial strain. (E 1012)4. Significance and Use4.1 This test method
19、may be used for material development,material comparison, quality assurance, characterization, anddesign data generation.4.2 Generally, resistance to compression is the measure ofthe greatest strength of a monolithic advanced ceramic. Ideally,ceramics should be compressively stressed in use, althoug
20、hengineering applications may frequently introduce tensilestresses in the component. Nonetheless, compressive behavioris an important aspect of mechanical properties and perfor-mance. Although tensile strength distributions of ceramics areprobabilistic and can be described by a weakest link failuret
21、heory, such descriptions have been shown to be inapplicable tocompressive strength distributions in at least one study (1).3However, the need to test a statistically significant number ofcompressive test specimens is not obviated. Therefore, asufficient number of test specimens at each testing condi
22、tion isrequired for statistical analysis and design.4.3 Compression tests provide information on the strengthand deformation of materials under uniaxial compressivestresses. Uniform stress states are required to effectivelyevaluate any nonlinear stress-strain behavior which may de-velop as the resul
23、t of cumulative damage processes (forexample, microcracking) which may be influenced by testingmode, testing rate, processing or compositional effects, micro-structure, or environmental influences.4.4 The results of compression tests of test specimensfabricated to standardized dimensions from a part
24、icular mate-rial or selected portions of a part, or both, may not totallyrepresent the strength and deformation properties in the entire,full-size product or its in-service behavior in different environ-ments.4.5 For quality control purposes, results derived from stan-dardized compressive test speci
25、mens may be considered in-dicative of the response of the material from which they weretaken for given primary processing conditions and post-processing heat treatments.5. Interferences5.1 Test environment (vacuum, inert gas, ambient air, and soforth) including moisture content (for example, relativ
26、e humid-ity) may have an influence on the measured compressivestrength. Testing to evaluate the maximum strength potential ofa material can be conducted in inert environments or atsufficiently rapid testing rates, or both, so as to minimize anyenvironmental effects. Conversely, testing can be conduc
27、ted inenvironments, test modes, and test rates representative ofservice conditions to evaluate material performance under useconditions. When testing is conducted in uncontrolled ambientair with the intent of evaluating maximum strength potential,relative humidity and temperature must be monitored a
28、ndreported.5.2 Fabrication of test specimens can introduce dimensionalvariations which may have pronounced effects on compressivemechanical properties and behavior (for example, shape andlevel of the resulting stress-strain curve, compressive strength,induced bending, and so forth). Machining effect
29、s introducedduring test specimen preparation can be an interfering factor inthe determination of ultimate strength of pristine material (thatis, increased frequency of loading block related fractures (seeFig. 1) compared to volume-initiated fractures). Surface prepa-ration can also lead to the intro
30、duction of residual stresses.Universal or standardized test methods of surface preparationdo not exist. It should be understood that final machining stepsmay or may not negate machining damage introduced duringthe initial machining. Note that final compressive fracture ofadvanced ceramics can be att
31、ributed to the interaction of largenumbers of microcracks that are generated in the volume of thematerial and ultimately lead to loss of structural integrity. (1,2).Therefore, although surface roughness in the gage section ofthe test specimen is not as critical for determining maximumstrength potent
32、ial as it is for flexure or tension tests ofadvanced ceramics, test specimen fabrication history may play3The boldface numbers in parenthesis refer to the list of references at the end ofthis test methodFIG. 1 Schematic Diagram of One Possible Apparatus forConducting a Uniaxially Loaded Compression
33、TestC1424042an important role in the measured compressive strength distri-butions and should be reported. In addition, the nature offabrication used for certain advanced ceramics (for example,pressureless sintering, hot pressing) may require the testing oftest specimens with gage sections in the as-
34、processed condition(that is, it may not be possible or desired/required to machinesome test specimen surfaces not directly in contact with testfixture components). For very rough or wavy as-processedsurfaces eccentricities in the stress state due to nonsymmetriccross sections as well as variation in
35、 the cross-sectionaldimensions may also interfere with the compressive strengthmeasurement. Finally, close geometric tolerances, particularlyin regard to flatness, concentricity, and cylindricity of testspecimen surfaces or geometric entities in contact with the testfixture components) are critical
36、requirements for successfulcompression tests.5.3 Bending in uniaxial compression tests can introduceeccentricity leading to geometric instability of the test speci-men and buckling failure before valid compressive strength isattained. In addition, if deformations or strains are measured atsurfaces w
37、here maximum or minimum stresses occur, bendingmay introduce over or under measurement of strains dependingon the location of the strain-measuring device on the testspecimen.5.4 Fractures that initiate outside the uniformly stressedgage section or splitting of the test specimen along itslongitudinal
38、 centerline may be due to factors such as stressconcentrations or geometrical transitions, extraneous stressesintroduced by the load fixtures, misalignment of the testspecimen/loading blocks, nonflat loading blocks or nonflat testspecimen ends, or both, or strength-limiting features in themicrostruc
39、ture of the test specimen. Such non-gage sectionfractures will normally constitute invalid tests.6. Apparatus6.1 Testing MachinesMachines used for compression test-ing shall conform to the requirements of Practices E 4. Theforces used in determining compressive strength shall beaccurate within 61 %
40、at any force within the selected forcerange of the testing machine as defined in Practices E 4. Aschematic showing pertinent features of one possible compres-sive testing apparatus is shown in Fig. 1. Check that theexpected breaking force for the desired test specimen geometryand test material is wi
41、thin the capacity of the test machine andforce transducer. Advanced ceramic compression test speci-mens require much greater forces to fracture than those usuallyencountered in tension or flexure test specimens of the samematerial.6.2 Loading Fixtures:6.2.1 GeneralCompression loading fixtures are ge
42、nerallycomposed of two parts: (1) basic steel compression fixtures (forexample, platens) attached to the test machine and (2) loadingblocks which are non-fixed and act as the interface between thecompression platens and the test specimen. An assemblydrawing of such a fixture and a test specimen is s
43、hown in Fig.2. The brittle nature of advanced ceramics requires a uniforminterface between the loading fixtures and the test specimen.Line or point contact stresses lead to crack initiation andfracture of the test specimen at stresses less than the actualcompressive strength (that is, where actual s
44、trength is theintrinsic strength of the material not influenced by the test ortest conditions). In addition, large mismatches of Poissonsratios or elastic moduli between the loading fixture and testspecimen, or both, can introduce lateral tensile forces leadingto splitting of the compression test sp
45、ecimen. Similarly, plasticdeformation of the load fixture can induce lateral tensile forceswith the same effect.6.2.1.1 Hardened (48 HRc) steel compression platens shallbe greater in diameter ($25.4 mm) than the loading blocks andshall be at least 25.4 mm in thickness. The loading surfaces ofthe com
46、pression platens shall be flat to 0.005 mm. In addition,the two loading surfaces (loading face used to contact theloading blocks and bolted face used to attach the platen to thetest machine) shall be parallel to 0.005 mm. When installed inthe test machine, the loading surfaces of the upper and lower
47、compression platens shall be parallel to each other within 0.01mm and perpendicular to the load line of the test machine towithin 0.01 mm (2). The upper and lower compression platensshall be concentric within 0.005 mm of each other and the loadline of the test machine. Angular and concentricity alig
48、nmentshave been achieved with commercial alignment devices or byusing available hole tolerances in commercial compressionplatens in conjunction with shims (2).6.2.1.2 Loading blocks as shown in Fig. 3 shall have thesame diameter as the test specimen ends at their interface.Parallelism and flatness o
49、f faces as well as concentricity of theloading blocks shall be as given in Fig. 3. The material for theFIG. 2 Example of Basic Fixturing and Test Specimen forCompression TestingC1424043loading blocks shall be chosen to meet the following require-ments. Generally, cobalt-sintered tungsten carbide (Co-WC)has worked satisfactorily for this purpose in compression testsof a variety of advanced ceramics (2). However, for somehigh-performance advanced ceramics, other loading blockmaterials may be required to meet the requirements of 6.2.1.2.1and 6.2.1.2.2.6.2.1.2.1 Lat
