ASTM C1323-96(2001)e1
(Test Method)Standard Test Method for Ultimate Strength of Advanced Ceramics with Diametrally Compressed C-Ring Specimens at Ambient Temperature
Standard Test Method for Ultimate Strength of Advanced Ceramics with Diametrally Compressed C-Ring Specimens at Ambient Temperature
SCOPE
1.1 This test method covers the determination of ultimate strength under monotonic loading of advanced ceramics in tubular form at ambient temperatures. Note that ultimate strength as used in this test method refers to the strength obtained under monotonic compressive loading of C-ring specimens where monotonic refers to a continuous nonstop test rate with no reversals from test initiation to final fracture.
1.2 Values expressed in this test method are in accordance with the International System of Units (SI) and Practice E 380.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: C1323 – 96 (Reapproved 2001)
Standard Test Method for
Ultimate Strength of Advanced Ceramics with Diametrally
Compressed C-Ring Specimens at Ambient Temperature
This standard is issued under the fixed designation C1323; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
´ NOTE—Equation X1.2 was editorially corrected in April 2007.
1. Scope 2.2 Military Standards:
MIL-HDBK-790 Fractography and Characterization of
1.1 This test method covers the determination of ultimate
Fracture Origins in Advanced Structural Ceramics
strength under monotonic loading of advanced ceramics in
MIL-STD-1942(A) Flexural Strength of High Performance
tubular form at ambient temperatures. Note that ultimate
Ceramics at Ambient Temperature
strength as used in this test method refers to the strength
obtained under monotonic compressive loading of C-ring
3. Terminology
specimenswheremonotonicreferstoacontinuousnonstoptest
3.1 Definitions:
rate with no reversals from test initiation to final fracture.
3.1.1 advancedceramic—anengineered,high-performance,
1.2 Values expressed in this test method are in accordance
predominatelynonmetallic,inorganic,ceramicmaterialhaving
with the International System of Units (SI) and Practice E380.
specific functional qualities. (C1145)
1.3 This standard does not purport to address all of the
3.1.2 breaking load—the load at which fracture occurs.
safety concerns, if any, associated with its use. It is the
(E6)
responsibility of the user of this standard to establish appro-
3.1.3 C-ring—circular test specimen geometry with the
priate safety and health practices and determine the applica-
mid-section (slot) removed to allow bending displacement
bility of regulatory limitations prior to use.
(compression or tension). (E6)
2. Referenced Documents 3.1.4 flexural strength—a measure of the ultimate strength
of a specified beam in bending.
2.1 ASTM Standards:
3.1.5 modulus of elasticity—the ratio of stress to corre-
C1145 Terminology of Advanced Ceramics
sponding strain below the proportional limit. (E6)
C1161 Test Method for Flexural Strength of Advanced
3.1.6 slow crack growth—subcritical crack growth (exten-
Ceramics at Ambient Temperature
sion) which may result from, but is not restricted to, such
C1239 Practice for Reporting Uniaxial Strength Data and
mechanisms as environmentally assisted stress corrosion or
Estimating Weibull Distribution Parameters for Advanced
diffusive crack growth.
Ceramics
E4 Practices for Force Verification of Testing Machines
4. Significance and Use
E6 TerminologyRelatingtoMethodsofMechanicalTesting
4.1 Thistestmethodmaybeusedformaterialdevelopment,
E337 Test Method for Measuring Humidity with a Psy-
material comparison, quality assurance, and characterization.
chrometer (the Measurement of Wet- and Dry-Bulb Tem-
Extremecareshouldbeexercisedwhengeneratingdesigndata.
peratures)
4.2 For a C-ring under diametral compression, the maxi-
E380 Practice for Use of International System of Units (SI)
mum tensile stress occurs at the outer surface. Hence, the
(the Modernized Metric System)
C-ring specimen loaded in compression will predominately
evaluate the strength distribution and flaw population(s) on the
external surface of a tubular component. Accordingly, the
This test method is under the jurisdiction of ASTM Committee C28 on
condition of the inner surface may be of lesser consequence in
Advanced Ceramics and is the direct responsibility of Subcommittee C28.04 on
specimen preparation and testing.
Applications.
Current edition approved April 10, 2001. Published April 2001. Originally
NOTE 1—AC-ring in tension or an O-ring in compression may be used
approved in 1996. Last previous edition approved in 2001 as C1323–96(2001).
to evaluate the internal surface.
DOI: 10.1520/C1323-96R01E01.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on AvailablefromStandardizationDocumentsOrderDesk,Bldg.4SectionD,700
the ASTM website. Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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C1323 – 96 (2001)
4.3 The flexure stress is computed based on simple curved- temperature must be monitored and reported. Testing at hu-
beamtheory(1) withassumptionsthatthematerialisisotropic midity levels >65% RH is not recommended and any devia-
and homogeneous, the moduli of elasticity are identical in tions from this recommendation must be reported.
compression or tension, and the material is linearly elastic; all 5.2 C-ring specimens are useful for the determination of
homogeneityandisotropyassumptionsprecludetheuseofthis
ultimate strength of tubular components in the as-received/as-
standard for continuous fiber reinforced composites. Average used condition without surface preparations that may distort
grain size(s) shall be no greater than one fiftieth ( ⁄50)ofthe
the strength controlling flaw population(s). Nonetheless, ma-
C-ring thickness. chiningdamageintroducedduringspecimenpreparationcanbe
4.4 Because advanced ceramics exhibiting brittle behavior
either a random interfering factor in the determination of the
generallyfracturecatastrophicallyfromasingledominantflaw maximuminertstrength(strengthpotential)ofpristinematerial
for a particular tensile stress field, the surface area and volume
(that is, increase frequency of surface or edge initiated frac-
ofmaterialsubjectedtotensilestressesisasignificantfactorin tures compared to volume initiated fractures), or an inherent
determining the ultimate strength. Moreover, because of the
part of the strength characteristics being measured. Universal
statistical distribution of the flaw population(s) in advanced or standardized methods of surface/sample preparation do not
ceramics exhibiting brittle behavior, a sufficient number of
exist. Hence, it shall be understood that final machining steps
specimens at each testing condition is required for statistical
may or may not negate machining damage introduced during
analysis and design. This test method provides guidelines for
the initial machining. Thus, specimen fabrication history may
the number of specimens that should be tested for these
play an important role in the measured strength distributions
purposes (see 8.4). and shall be reported.
4.5 Because of a multitude of factors related to materials
processing and component fabrication, the results of C-ring
6. Apparatus
testsfromaparticularmaterialorselectedportionsofapart,or
6.1 Loading—Specimens shall be loaded in any suitable
both, may not necessarily represent the strength and deforma-
testing machine provided that uniform rates of direct loading
tion properties of the full-size end product or its in-service
can be maintained. The system used to monitor the loading
behavior.
shall be free from any initial lags and will have the capacity to
4.6 The ultimate strength of a ceramic material may be
record the maximum load applied to the C-ring specimen
influenced by slow crack growth or corrosion, or both, and is
duringthetest.Testingmachineaccuracyshallbewithin1.0%
therefore, sensitive to the testing mode, testing rate, or envi-
in accordance with Practices E4.
ronmental influences, or a combination thereof. Testing at
6.1.1 This test method permits the use of either fixed
sufficiently rapid rates as outlined in this test method may
loading rams or, when necessary (see 9.3), a self-adjusting
minimize the consequences of subcritical (slow) crack growth
fixture such as a universal joint or spherically seated platen
or stress corrosion.
may be used in conjunction with the upper loading ram.When
4.7 The flexural behavior and strength of an advanced
fixed loading rams are used, they shall be aligned so that the
monolithic ceramic are dependent on the material’s inherent
platensurfaceswhichcomeintocontactwiththespecimensare
resistance to fracture, the presence of flaws, or damage
parallel to within 0.015 mm. Alignment of the testing system
accumulation processes, or a combination thereof.Analysis of
must be verified at a minimum at the beginning and at the end
fracturesurfacesandfractography,thoughbeyondthescopeof
of a test series. An additional verification of alignment is
thistestmethod,ishighlyrecommended(furtherguidancemay
recommended, although not required, at the middle of the test
be obtained from MIL HDBK-790 and Ref (2)).
series.
5. Interferences
NOTE 2—Atestseriesisinterpretedtomeanadiscretegroupoftestson
individual specimens conducted within a discrete period of time on a
5.1 Test environment (vacuum, inert gas, ambient air, etc.)
particular material configuration, test specimen geometry, test conditions,
including moisture content (that is, relative humidity) may
or other uniquely definable qualifier (for example, a test series composed
have an influence on the measured ultimate strength. In
of Material A comprising ten specimens of Geometry B tested at a fixed
particular, the behavior of materials susceptible to slow crack-
rate in strain control to final fracture in ambient air).
growthfracturewillbestronglyinfluencedbytestenvironment
6.1.2 Materialssuchasfoilorthinrubbersheetshallbeused
andtestingrate.Testingtoevaluatethemaximuminertstrength
between the loading rams and the specimen for ambient
(strength potential) of a material shall therefore be conducted
temperature tests to reduce the effects of friction and to
in inert environments or at sufficiently rapid testing rates, or
redistribute the load. Aluminum oxide (alumina) felt or other
both, so as to minimize slow crack-growth effects. Conversely,
high-temperature “cloth” with a high-temperature capability
testing can be conducted in environments and testing modes
may also be used. The use of a material with a high-
and rates representative of service conditions to evaluate
temperature capability is recommended to ensure consistency
material performance under use conditions. When testing in
with elevated temperature tests (if planned), provided the
uncontrolled ambient air for the purpose of evaluating maxi-
high-temperature “cloth” is chemically compatible with the
mum inert strength (strength potential), relative humidity and
specimen at all testing temperatures.
6.2 The fixture used during the tests shall be stiffer than the
specimen to ensure that a majority of the crosshead travel (at
The boldface numbers in parentheses refer to a list of references at the end of
this test method. least 80%) is imposed on the C-ring specimen.
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C1323 – 96 (2001)
6.3 Data Acquisition—At the minimum, an autographic specimendimensionsoroverallsizescannotberecommended
record of applied load shall be obtained. Either analog chart without compromising the original purpose of the test method.
recorders or digital data acquisition systems can be used for Instead, specimens shall be prepared from the stock used for
this purpose. Ideally, an analog chart recorder or plotter shall the actual component when possible.
beusedinconjunctionwithadigitaldataacquisitionsystemto
8.1.1 Specimen Size—To maintain plane stress conditions
provide an immediate record of the test as a supplement to the
(3,4) in the specimen while avoiding undue influence from the
digital record. Recording devices shall be accurate to 0.1% of
edges (edge effects), the width of the sample shall be at least
full scale and shall have a minimum data acquisition rate of 10
one, but no greater than four times the thickness:
Hz with a response of 50 Hz deemed more than sufficient.
b
1# #4 (1)
r 2 r
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7. Hazards
7.1 During the conduct of this test, the possibility of flying where the dimensional terms b, r , and r are defined in Fig.
o i
1.
fragments of broken test material may be high. Means for
containment and retention of these fragments for safety, later
NOTE 3—Experimental or finite-element studies, or both, are recom-
fractographic reconstruction, and analysis is highly recom-
mended to verify the magnitude, distribution, and uniaxiality of the
mended.
stresses in the actual C-ring used for testing.
8. Specimen
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 ensure
8.1 General—The C-ring geometry is designed to evaluate
thattheslotissignificantlygreaterthanthemaximumdisplace-
the ultimate strength of advanced monolithic materials in
ment at failure. When thin tubular specimens are studied, a
tubular form in as-received or as-machined form. When
larger slot not to exceed one fourth of the outer circumference
possible, the specimen shall reflect the actual size of the
may be required.
component to minimize size scaling effects and to increase the
likelihood that the specimen will have the same microstructure 8.1.3 The parallelism tolerance for the two machined sides
and flaw population(s) as the component. Hence, standard of the C-ring specimen is 0.015 mm.
FIG. 1 C-Ring Test Geometry with Defining Geometry and Reference Angle (u) for the Point of Fracture Initiation on the Circumference
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C1323 – 96 (2001)
8.2 Specimen Preparation—Depending on the intended ap- attention shall be given to pre-test storage of specimens in
plicationoftheultimatestrengthdata,useoneofthefollowing controlled environments or desiccators to avoid unquantifiable
three specimen preparation procedures: environmental degradation of specimens prior to testing.
8.2.1 As-Fabricated—The external and internal surface of 8.4 Number of Specimens—A minimum of ten tests is
the C-ring specimen shall simulate the surface conditions and recommended for the purpose of estimating a mean. A mini-
processingrouteofanapplicationwherenomachiningisused. mum of 30 tests may be necessary if estimates regarding the
No additional machining specifications for these surfaces are formofthestrengthdistributionandWeibull(5)parametersare
relevant. Each side section shall be machined from the tubular desired within the confidence bounds established by Practice
stock and lap finished with 15 µm media to remove any large C1239.
machining defects.All edges shall then be either chamfered at
45° to a distance of 0.15 6 0.05 mm or rounded to a radius of 9. Procedure
0.15 6 0.05 mm to avoid edge dominated failures (“edge-
9.1 Specimen Dimensions—After machining the C-ring and
checking”).
slot, measure th
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