1、Designation: C 1323 96 (Reapproved 2001)e1Standard Test Method forUltimate Strength of Advanced Ceramics with DiametrallyCompressed C-Ring Specimens at Ambient Temperature1This standard is issued under the fixed designation C 1323; the number immediately following the designation indicates the year
2、oforiginal adoption or, in the case of revision, 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.e1NOTEEquation X1.2 was editorially corrected in April 2007.1. Scope
3、1.1 This test method covers the determination of ultimatestrength under monotonic loading of advanced ceramics intubular form at ambient temperatures. Note that ultimatestrength as used in this test method refers to the strengthobtained under monotonic compressive loading of C-ringspecimens where mo
4、notonic refers to a continuous nonstop testrate with no reversals from test initiation to final fracture.1.2 Values expressed in this test method are in accordancewith the International System of Units (SI) and Practice E 380.1.3 This standard does not purport to address all of thesafety concerns, i
5、f 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 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 1145 Terminology on Advanced CeramicsC 1161
6、Test Method for Flexural Strength of AdvancedCeramics at Ambient TemperatureC 1239 Practice for Reporting Uniaxial Strength Data andEstimating Weibull Distribution Parameters for AdvancedCeramicsE4 Practices for Force Verification of Testing MachinesE 6 Terminology Relating to Methods of Mechanical
7、Test-ingE 337 Test Method for Measured Humidity with Psychrom-eter (Measurement of Wet- and Dry-Bulb Temperatures)E 380 Practice for Use of International System of Units (SI)(the Modernized Metric System)2.2 Military Standards:3MIL-HDBK-790 Fractography and Characterization ofFracture Origins in Adv
8、anced Structural CeramicsMIL-STD-1942(A) Flexural Strength of High PerformanceCeramics at Ambient Temperature3. Terminology3.1 Definitions:3.1.1 advanced ceramican engineered, high-performance,predominately nonmetallic, inorganic, ceramic material havingspecific functional qualities. (C 1145)3.1.2 b
9、reaking loadthe load at which fracture occurs.(E 6)3.1.3 C-ringcircular test specimen geometry with themid-section (slot) removed to allow bending displacement(compression or tension). (E 6)3.1.4 flexural strengtha measure of the ultimate strengthof a specified beam in bending.3.1.5 modulus of elast
10、icitythe ratio of stress to corre-sponding strain below the proportional limit. (E 6)3.1.6 slow crack growthsubcritical crack growth (exten-sion) which may result from, but is not restricted to, suchmechanisms as environmentally assisted stress corrosion ordiffusive crack growth.4. Significance and
11、Use4.1 This test method may be used for material development,material comparison, quality assurance, and characterization.Extreme care should be exercised when generating design data.4.2 For a C-ring under diametral compression, the maxi-mum tensile stress occurs at the outer surface. Hence, theC-ri
12、ng specimen loaded in compression will predominatelyevaluate the strength distribution and flaw population(s) on theexternal surface of a tubular component. Accordingly, thecondition of the inner surface may be of lesser consequence inspecimen preparation and testing.NOTE 1A C-ring in tension or an
13、O-ring in compression may be used1This test method is under the jurisdiction of ASTM Committee C28 onAdvanced Ceramics and is the direct responsibility of Subcommittee C28.04 onApplications.Current edition approved April 10, 2001. Published April 2001. Originallyapproved in 1996. Last previous editi
14、on approved in 2001 as C 1323 96(2001).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.3Available from Standa
15、rdization Documents Order Desk, Bldg. 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.to evaluate the internal surface.4.3 The flexure stress is computed based on
16、 simple curved-beam theory (1)4with assumptions that the material is isotropicand homogeneous, the moduli of elasticity are identical incompression or tension, and the material is linearly elastic; allhomogeneity and isotropy assumptions preclude the use of thisstandard for continuous fiber reinforc
17、ed composites. Averagegrain size(s) shall be no greater than one fiftieth (150)oftheC-ring thickness.4.4 Because advanced ceramics exhibiting brittle behaviorgenerally fracture catastrophically from a single dominant flawfor a particular tensile stress field, the surface area and volumeof material s
18、ubjected to tensile stresses is a significant factor indetermining the ultimate strength. Moreover, because of thestatistical distribution of the flaw population(s) in advancedceramics exhibiting brittle behavior, a sufficient number ofspecimens at each testing condition is required for statisticala
19、nalysis and design. This test method provides guidelines forthe number of specimens that should be tested for thesepurposes (see 8.4).4.5 Because of a multitude of factors related to materialsprocessing and component fabrication, the results of C-ringtests from a particular material or selected port
20、ions of a part, orboth, may not necessarily represent the strength and deforma-tion properties of the full-size end product or its in-servicebehavior.4.6 The ultimate strength of a ceramic material may beinfluenced by slow crack growth or corrosion, or both, and istherefore, sensitive to the testing
21、 mode, testing rate, or envi-ronmental influences, or a combination thereof. Testing atsufficiently rapid rates as outlined in this test method mayminimize the consequences of subcritical (slow) crack growthor stress corrosion.4.7 The flexural behavior and strength of an advancedmonolithic ceramic a
22、re dependent on the materials inherentresistance to fracture, the presence of flaws, or damageaccumulation processes, or a combination thereof. Analysis offracture surfaces and fractography, though beyond the scope ofthis test method, is highly recommended (further guidance maybe obtained from MIL H
23、DBK-790 and Ref (2).5. Interferences5.1 Test environment (vacuum, inert gas, ambient air, etc.)including moisture content (that is, relative humidity) mayhave an influence on the measured ultimate strength. Inparticular, the behavior of materials susceptible to slow crack-growth fracture will be str
24、ongly influenced by test environmentand testing rate.Testing to evaluate the maximum inert strength(strength potential) of a material shall therefore be conductedin inert environments or at sufficiently rapid testing rates, orboth, so as to minimize slow crack-growth effects. Conversely,testing can
25、be conducted in environments and testing modesand rates representative of service conditions to evaluatematerial performance under use conditions. When testing inuncontrolled ambient air for the purpose of evaluating maxi-mum inert strength (strength potential), relative humidity andtemperature must
26、 be monitored and reported. Testing at hu-midity levels 65 % RH is not recommended and any devia-tions from this recommendation must be reported.5.2 C-ring specimens are useful for the determination ofultimate strength of tubular components in the as-received/as-used condition without surface prepar
27、ations that may distortthe strength controlling flaw population(s). Nonetheless, ma-chining damage introduced during specimen preparation can beeither a random interfering factor in the determination of themaximum inert strength (strength potential) of pristine material(that is, increase frequency o
28、f surface or edge initiated frac-tures compared to volume initiated fractures), or an inherentpart of the strength characteristics being measured. Universalor standardized methods of surface/sample preparation do notexist. Hence, it shall be understood that final machining stepsmay or may not negate
29、 machining damage introduced duringthe initial machining. Thus, specimen fabrication history mayplay an important role in the measured strength distributionsand shall be reported.6. Apparatus6.1 LoadingSpecimens shall be loaded in any suitabletesting machine provided that uniform rates of direct loa
30、dingcan be maintained. The system used to monitor the loadingshall be free from any initial lags and will have the capacity torecord the maximum load applied to the C-ring specimenduring the test. Testing machine accuracy shall be within 1.0 %in accordance with Practices E4.6.1.1 This test method pe
31、rmits the use of either fixedloading rams or, when necessary (see 9.3), a self-adjustingfixture such as a universal joint or spherically seated platenmay be used in conjunction with the upper loading ram. Whenfixed loading rams are used, they shall be aligned so that theplaten surfaces which come in
32、to contact with the specimens areparallel to within 0.015 mm. Alignment of the testing systemmust be verified at a minimum at the beginning and at the endof a test series. An additional verification of alignment isrecommended, although not required, at the middle of the testseries.NOTE 2Atest series
33、 is interpreted to mean a discrete group of tests onindividual specimens conducted within a discrete period of time on aparticular material configuration, test specimen geometry, test conditions,or other uniquely definable qualifier (for example, a test series composedof Material A comprising ten sp
34、ecimens of Geometry B tested at a fixedrate in strain control to final fracture in ambient air).6.1.2 Materials such as foil or thin rubber sheet shall be usedbetween the loading rams and the specimen for ambienttemperature tests to reduce the effects of friction and toredistribute the load. Aluminu
35、m oxide (alumina) felt or otherhigh-temperature “cloth” with a high-temperature capabilitymay also be used. The use of a material with a high-temperature capability is recommended to ensure consistencywith elevated temperature tests (if planned), provided thehigh-temperature “cloth” is chemically co
36、mpatible with thespecimen at all testing temperatures.6.2 The fixture used during the tests shall be stiffer than thespecimen to ensure that a majority of the crosshead travel (atleast 80 %) is imposed on the C-ring specimen.4The boldface numbers in parentheses refer to a list of references at the e
37、nd ofthis test method.C 1323 96 (2001)e126.3 Data AcquisitionAt the minimum, an autographicrecord of applied load shall be obtained. Either analog chartrecorders or digital data acquisition systems can be used forthis purpose. Ideally, an analog chart recorder or plotter shallbe used in conjunction
38、with a digital data acquisition system toprovide an immediate record of the test as a supplement to thedigital record. Recording devices shall be accurate to 0.1 % offull scale and shall have a minimum data acquisition rate of 10Hz with a response of 50 Hz deemed more than sufficient.7. Hazards7.1 D
39、uring the conduct of this test, the possibility of flyingfragments of broken test material may be high. Means forcontainment and retention of these fragments for safety, laterfractographic reconstruction, and analysis is highly recom-mended.8. Specimen8.1 GeneralThe C-ring geometry is designed to ev
40、aluatethe ultimate strength of advanced monolithic materials intubular form in as-received or as-machined form. Whenpossible, the specimen shall reflect the actual size of thecomponent to minimize size scaling effects and to increase thelikelihood that the specimen will have the same microstructurea
41、nd flaw population(s) as the component. Hence, standardspecimen dimensions or overall sizes can not be recommendedwithout compromising the original purpose of the test method.Instead, specimens shall be prepared from the stock used forthe actual component when possible.8.1.1 Specimen SizeTo maintain
42、 plane stress conditions(3,4) in the specimen while avoiding undue influence from theedges (edge effects), the width of the sample shall be at leastone, but no greater than four times the thickness:1#bro2 ri#4 (1)where the dimensional terms b, ro, and riare defined in Fig.1.NOTE 3Experimental or fin
43、ite-element studies, or both, are recom-mended to verify the magnitude, distribution, and uniaxiality of thestresses in the actual C-ring used for testing.8.1.2 The slot height (L) in the C-ring specimen (Fig. 1)shall be at least equal to the width of the specimen to ensurethat the slot is significa
44、ntly greater than the maximum displace-ment at failure. When thin tubular specimens are studied, alarger slot not to exceed one fourth of the outer circumferencemay be required.8.1.3 The parallelism tolerance for the two machined sidesof the C-ring specimen is 0.015 mm.FIG. 1 C-Ring Test Geometry wi
45、th Defining Geometry and Reference Angle (u) for the Point of Fracture Initiation on the CircumferenceC 1323 96 (2001)e138.2 Specimen PreparationDepending on the intended ap-plication of the ultimate strength data, use one of the followingthree specimen preparation procedures:8.2.1 As-FabricatedThe
46、external and internal surface ofthe C-ring specimen shall simulate the surface conditions andprocessing route of an application where no machining is used.No additional machining specifications for these surfaces arerelevant. Each side section shall be machined from the tubularstock and lap finished
47、 with 15 m media to remove any largemachining defects. All edges shall then be either chamfered at45 to a distance of 0.15 6 0.05 mm or rounded to a radius of0.15 6 0.05 mm to avoid edge dominated failures (“edge-checking”).NOTE 4If the C-ring specimen has a nonuniform diameter, thetolerances stated
48、 in 8.2.1 may be relaxed; however, the edges shall still bechamfered or rounded.8.2.2 Application-Matched MachiningThe C-ring speci-men shall have the same surface preparation as that given to thecomponent. When possible, the specimen shall also retain theoriginal radii of the component provided the
49、 surface area andvolume are sufficient to sample the inherent flaws of thematerial under study. All other side finishing specificationsshall be the same as the as-fabricated specimens. Unless theprocess is proprietary, the report shall include all details aboutthe stages of material removal, wheel grits, wheel bonding, andthe material removal rates for each pass.8.2.3 Standard ProcedureIn instances where 8.2.1through 8.2.2 are not appropriate, 8.2.3 shall apply. Thisprocedure shall be viewed as a baseline; more stringentprocedures may be necessary depending
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