1、Designation: C1424 15Standard Test Method forMonotonic Compressive Strength of Advanced Ceramics atAmbient Temperature1This standard is issued under the fixed designation C1424; 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 () 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 mono
3、tonicuniaxial 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 (force or displacement), testing rates (force rate, stressrate, displacement rate, or strain rate), all
4、owable 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 r
5、eversals from testinitiation to final 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-rein
6、forced composite 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 th
7、is test method to these materials is notrecommended.1.3 Values expressed in this test method are in accordancewith the International System of Units (SI) and IEEE/ASTM SI10.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibili
8、ty of the user of 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:2C773 Test Method for Compressive (Crushing) Strength ofFired Whiteware MaterialsC1145 Terminology o
9、f Advanced CeramicsD695 Test Method for Compressive Properties of RigidPlasticsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE83 Practice for Verification and Classification of Exten-someter SystemsE337 Test Method for Measuring Humidi
10、ty with a Psy-chrometer (the Measurement of Wet- and Dry-Bulb Tem-peratures)E1012 Practice for Verification of Testing Frame and Speci-men Alignment Under Tensile and Compressive AxialForce ApplicationIEEE/ASTM SI 10 Standard for Use of the InternationalSystem of Units (SI) (The Modern Metric System
11、3. Terminology3.1 Definitions:3.1.1 The definitions of terms relating to compressive test-ing appearing in Terminology E6, Test Method D695, andTerminology C1145 may apply to the terms used in this testmethod. Pertinent definitions as listed in Practice E1012,Terminology C1145, and Terminology E6 ar
12、e shown in thefollowing with the appropriate source given in parentheses.Additional terms used in conjunction with this test method aredefined in the following.3.1.2 advanced ceramic, na highly engineered, high-performance predominately nonmetallic, inorganic, ceramicmaterial having specific functio
13、nal attributes. (C1145)3.1.3 axial strain, n L/Lthe average longitudinal strainsmeasured at the surface on opposite sides of the longitudinalaxis of symmetry of the specimen by two strain-sensingdevices located at the mid length of the reduced section.(E1012)1This test method is under the jurisdicti
14、on of ASTM Committee C28 onAdvanced Ceramics and is the direct responsibility of Subcommittee C28.01 onMechanical Properties and Performance.Current edition approved July 1, 2015. Published October 2015. Originallypublished in 1999. Last previous edition approved in 2015 as C1424 10 (2015).DOI: 10.1
15、520/C1424-15.2For 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.Copyright ASTM International, 100 Barr Harbor Dr
16、ive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.4 bending strain, n L/Lthe 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. (E1012)3.1.5 breaking
17、load, n Fthe load at which fractureoccurs. (E6)3.1.6 compressive strength, n F/L2the maximum 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
18、specimen. (E6)3.1.7 gage length, n Lthe original length of that portionof the specimen over which strain or change of length isdetermined. (E6)3.1.8 modulus of elasticity, n F/L2the ratio of stress tocorresponding strain below the proportional limit. (E6)3.1.9 percent bending, nthe bending strain ti
19、mes 100divided by the axial strain. (E1012)4. Significance and Use4.1 This test method 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 monolit
20、hic advanced ceramic. Ideally,ceramics should be compressively stressed in use, althoughengineering applications may frequently introduce tensilestresses in the component. Nonetheless, compressive behavioris an important aspect of mechanical properties and perfor-mance. Although tensile strength dis
21、tributions of ceramics areprobabilistic and can be described by a weakest link failuretheory, 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
22、 is not obviated. Therefore, asufficient number of test specimens at each testing condition 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 e
23、ffectivelyevaluate any nonlinear stress-strain behavior which may de-velop as the result of cumulative damage processes (forexample, microcracking) which may be influenced by testingmode, testing rate, processing or compositional effects,microstructure, or environmental influences.4.4 The results of
24、 compression tests of test specimensfabricated to standardized dimensions from a particular 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 Fo
25、r quality control purposes, results derived from stan-dardized compressive test specimens 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,
26、inert gas, ambient air, and soforth) including moisture content (for example, relative 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, o
27、r both, so as to minimize anyenvironmental effects. Conversely, testing can be conducted 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 evalua
28、ting maximum strength potential,relative humidity and temperature must be monitored andreported.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 stres
29、s-strain curve, compressive strength,induced bending, and so forth). Machining effects 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) com
30、pared to volume-initiated fractures). Surface prepa-ration can also lead to the introduction 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 i
31、nitial machining. Note that final compressive fracture ofadvanced ceramics can be attributed 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
32、section ofthe test specimen is not as critical for determining maximumstrength potential as it is for flexure or tension tests of3The boldface numbers in parenthesis refer to the list of references at the end ofthis test methodFIG. 1 Schematic Diagram of One Possible Apparatus for Con-ducting a Unia
33、xially Loaded Compression TestC1424 152advanced ceramics, test specimen fabrication history may playan 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 sinteri
34、ng, hot pressing) may require the testing oftest specimens with gage sections in the as-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 ecce
35、ntricities in the stress state due to nonsymmetriccross sections as well as variation in the cross-sectionaldimensions may also interfere with the compressive strengthmeasurement. Finally, close geometric tolerances, particularlyin regard to flatness, concentricity, and cylindricity of testspecimen
36、surfaces or geometric entities in contact with the testfixture components) are critical 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 compressiv
37、e strength isattained. In addition, if deformations or strains are measured atsurfaces where 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 th
38、e uniformly stressedgage section or splitting of the test specimen along itslongitudinal 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 bloc
39、ks or nonflat testspecimen ends, or both, or strength-limiting features in themicrostructure 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 Practic
40、es E4. Theforces used in determining compressive strength shall beaccurate within 61 % at any force within the selected forcerange of the testing machine as defined in Practices E4.Aschematic showing pertinent features of one possible compres-sive testing apparatus is shown in Fig. 1. Check that the
41、expected breaking force for the desired test specimen geometryand test material is within 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 t
42、he samematerial.6.2 Loading Fixtures:6.2.1 GeneralCompression loading fixtures are generallycomposed 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
43、 and the test specimen. An assemblydrawing of such a fixture and a test specimen is shown 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 s
44、pecimen at stresses less than the actualcompressive strength (that is, where actual strength 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
45、, can introduce lateral tensile forces leadingto splitting of the compression test specimen. 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 load
46、ing blocks andshall be at least 25.4 mm in thickness. The loading surfaces ofthe compression 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 0.00
47、5 mm. When installed inthe test machine, the loading surfaces of the upper and lowercompression 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 m
48、m of each other and the loadline of the test machine. Angular and concentricity alignmentshave been achieved with commercial alignment devices or byusing available hole tolerances in commercial compressionplatens in conjunction with shims (2).FIG. 2 Example of Basic Fixturing and Test Specimen for C
49、om-pression TestingC1424 1536.2.1.2 Loading blocks as shown in Fig. 3 shall have thesame diameter as the test specimen ends at their interface.Parallelism and flatness of faces as well as concentricity of theloading blocks shall be as given in Fig. 3. The material for theloading 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 blo
