ASTM C1499-01
(Test Method)Standard Test Method for Monotonic Equibiaxial Flexural Strength of Advanced Ceramics at Ambient Temperature
Standard Test Method for Monotonic Equibiaxial Flexural Strength of Advanced Ceramics at Ambient Temperature
SCOPE
1.1 This standard test method covers the determination of the equibiaxial strength of advanced ceramics at ambient temperature via concentric 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 are considered: machined specimens and as-fired specimens exhibiting a limited degree of warpage. Strength as used in this test method refers to the maximum strength obtained under monotonic application of load. Monotonic loading refers to a test conducted at a constant rate in a continuous fashion, 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 particle-reinforced composite ceramics as well as certain discontinuous fiber-reinforced composite ceramics may also meet these macroscopic behavior assumptions. Generally, continuous fiber ceramic composites do not macroscopically exhibit isotropic, homogeneous, continuous behavior, and the application of this test method to these materials is not recommended.
1.3 Values expressed in this test method are in accordance with the International System of Units (SI) and Practice E 380.
1.4 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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Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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Designation: C 1499 – 01
Standard Test Method for
Monotonic Equibiaxial Flexural Strength of Advanced
Ceramics at Ambient Temperature
This standard is issued under the fixed designation C 1499; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope C 1239 Reporting Uniaxial Strength Data and Estimating
Weibull Distribution Parameters for Advanced Ceramics
1.1 This standard test method covers the determination of
C 1259 Test Method for Dynamic Young’s Modulus, Shear
the equibiaxial strength of advanced ceramics at ambient
Modulus and Poisson’s Ratio for Advanced Ceramics by
temperature via concentric ring configurations under mono-
Impulse Excitation of Vibration
tonic uniaxial loading. In addition, test specimen fabrication
C 1322 Practice for Fractography and Characterization of
methods, testing modes, testing rates, allowable deflection, and
Fracture Origins in Advanced Ceramics
data collection and reporting procedures are addressed. Two
E 4 Practices for Load Verification of Testing Machines
types of test specimens are considered: machined specimens
E 6 Terminology Relating to Methods of Mechanical Test-
and as-fired specimens exhibiting a limited degree of warpage.
ing
Strength as used in this test method refers to the maximum
E 83 Practice for Verification and Classification of Exten-
strength obtained under monotonic application of load. Mono-
someters
tonic loading refers to a test conducted at a constant rate in a
E 337 Test Method for Measured Humidity with Psychrom-
continuous fashion, with no reversals from test initiation to
eter (The Measurement of Wet-and Dry-Bulb Tempera-
final fracture.
tures)
1.2 This test method is intended primarily for use with
E 380 Practice for Use of International System of Units (SI)
advanced ceramics that macroscopically exhibit isotropic,
(the Modernized Metric System)
homogeneous, continuous behavior. While this test method is
F 394 Test Method for Biaxial Flexure Strength of Ceramic
intended for use on monolithic advanced ceramics, certain
Substrates
whisker- or particle-reinforced composite ceramics as well as
certain discontinuous fiber-reinforced composite ceramics may
3. Terminology
also meet these macroscopic behavior assumptions. Generally,
3.1 Definitions—The definitions of terms relating to biaxial
continuous fiber ceramic composites do not macroscopically
testing appearing in Terminology E 6 and Terminology C 1145
exhibit isotropic, homogeneous, continuous behavior, and the
may apply to the terms used in this test method. Pertinent
application of this test method to these materials is not
definitions are listed below with the appropriate source given in
recommended.
parentheses. Additional terms used in conjunction with this test
1.3 Values expressed in this test method are in accordance
method are defined in the following section.
with the International System of Units (SI) and Practice E 380.
3.1.1 advanced ceramic, n—a highly engineered, high per-
1.4 This standard does not purport to address all of the
formance predominately non- metallic, inorganic, ceramic
safety concerns, if any, associated with its use. It is the
material having specific functional attributes. C 1145
responsibility of the user of this standard to establish appro-
3.1.2 breaking load, [F], n—the load at which fracture
priate safety and health practices and determine the applica-
occurs. E6
bility of regulatory limitations prior to use.
3.1.3 equibiaxial flexural strength, [F/L ], n—the maximum
2. Referenced Documents value of stress that a material is capable of sustaining when
subjected to flexure between two concentric rings. This mode
2.1 ASTM Standards:
of flexure is a cupping of the circular plate caused by loading
C 1145 Terminology on Advanced Ceramics
at the inner load ring and outer support ring. The equibiaxial
This test method is under the jurisdiction of ASTM Committee C28 on
Advanced Ceramics and is the direct responsibility of Subcommittee C28.01 on Annual Book of ASTM Standards, Vol 03.01.
Properties and Performance. Annual Book of ASTM Standards, Vol 07.01, 11.03, 15.09.
Current edition approved June 10, 2001. Published August 2001. Annual Book of ASTM Standards, Vol 14.02.
2 6
Annual Book of ASTM Standards, Vol 15.01. Annual Book of ASTM Standards, Vol 15.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
C1499–01
flexural strength is calculated from the maximum-load of a 5.2 Fabrication of test specimens can introduce dimensional
biaxial test carried to rupture, the original dimensions of the
variations that may have pronounced effects on the measured
specimen, and Poisson’s ratio. equibiaxial mechanical properties and behavior (e.g. shape and
3.1.4 homogeneous, n—the condition of a material in which
level of the resulting stress-strain curve, equibiaxial strength,
the relevant properties (composition, structure, density, etc.)
failure location, etc.). Surface preparation can also lead to the
are uniform, so that any smaller sample taken from an original
introduction of residual stresses and final machining steps
body is representative of the whole. Practically, as long as the
might or might not negate machining damage introduced
geometrical dimensions of a sample are large with respect to
during the initial machining. Therefore, as universal or stan-
the size of the individual grains, crystals, components, pores, or
dardized methods of surface preparation do not exist, the test
microcracks, the sample can be considered homogeneous.
specimen fabrication history should be reported. In addition,
3.1.5 modulus of elasticity, [F/L ], n—the ratio of stress to
2 the nature of fabrication used for certain advanced ceramic
corresponding strain below the proportional limit. E6
components may require testing of specimens with surfaces in
3.1.6 Poisson’s ratio, n—the negative value of the ratio of
the as-fabricated condition (i.e., it may not be possible, desired
transverse strain to the corresponding axial strain resulting
or required to machine some of the test specimen surfaces
from uniformly distributed axial stress below the proportional
directly in contact with the test fixture). For very rough or
limit of the material.
wavy as-fabricated surfaces, perturbations in the stress state
due to non-symmetric cross-sections as well as variations in the
4. Significance and Use
cross-sectional dimensions may also interfere with the equibi-
4.1 This test method may be used for material development,
axial strength measurement. Finally, close geometric toler-
material comparison, quality assurance, characterization and
ances, particularly in regard to flatness of test specimen
design code or model verification.
surfaces in contact with the test fixture components are critical
4.2 Engineering applications of ceramics frequently involve
requirements for successful equibiaxial tests. In some cases it
biaxial tensile stresses. Generally, the resistance to equibiaxial
may be appropriate to use other test methods (e.g. F 394).
flexure is the measure of the least flexural strength of a
5.3 Contact and frictional stresses in equibiaxial tests can
monolithic advanced ceramic. The equibiaxial flexural strength
introduce localized failure not representative of the equibiaxial
distributions of ceramics are probabilistic and can be described
strength under ideal loading conditions. These effects may
by a weakest link failure theory, (1, 2). Therefore, a sufficient
result in either over or under estimates of the actual strength (1,
number of test specimens at each testing condition is required
3).
for statistical estimation or’ the equibiaxial strength.
5.4 Fractures that consistently initiate near or just outside
4.3 Equibiaxial strength tests provide information on the
the load-ring may be due to factors such as friction or contact
strength and deformation of materials under multiple tensile
stresses introduced by the load fixtures, or via misalignment of
stresses. Multiaxial stress states are required to effectively
the test specimen rings. Such fractures will normally constitute
evaluate failure theories applicable to component design, and
invalid tests (see Note 14). Splitting of the test specimen along
to efficiently sample surfaces that may exhibit anisotropic flaw
a diameter that expresses the characteristic size may result
distributions. Equibiaxial tests also minimize the effects of
from poor specimen preparation (e.g. severe grinding or very
specimen edge preparation as compared to uniaxial tests
poor edge preparation), excessive tangential stresses at the
because the generated stresses are lowest at the specimen
specimen edges, or a very weak material. Such fractures will
edges.
constitute invalid tests if failure occurred from the edge.
4.4 The test results of equibiaxial test specimens fabricated
to standardized dimensions from a particular material and/or
5.5 Deflections greater than one-half of the test specimen
selected portions of a component may not totally represent the
thickness can result in nonlinear behavior and stresses not
strength properties in the entire, full-size component or its
accounted for by simple plate theory.
in-service behavior in different environments.
5.6 Warpage of the test specimen can result in nonuniform
4.5 For quality control purposes, results derived from stan-
loading and contact stresses that result in incorrect estimates of
dardized equibiaxial test specimens may be considered indica-
the specimen’s actual equibiaxial strength. The test specimen
tive of the response of the bulk material from which they were
shall meet the flatness requirements (see sections 8.2 and 8.3)
taken for any given primary processing conditions and post-
or be specifically noted as warped and considered as a censored
processing heat treatments or exposures.
test.
5. Interferences
6. Apparatus
5.1 Test environment (vacuum, inert gas, ambient air, etc.)
including moisture content (e.g. relative humidity) may have 6.1 Testing Machines—Machines used for equibiaxial test-
ing shall conform to the requirements of Practice E 4. The load
an influence on the measured equibiaxial strength. Testing to
evaluate the maximum strength potential of a material can be cells used in determining equibiaxial strength shall be accurate
within 61 % at any load within the selected load range of the
conducted in inert environments and/or at sufficiently rapid
testing rates so as to minimize any environmental effects. testing machine as defined in Practice E 4. Check that the
Conversely, testing can be conducted in environments, test expected breaking load for the desired test specimen geometry
modes and test rates representative of service conditions to and test material is within the capacity of the test machine and
evaluate material performance under use conditions. load cell. Advanced ceramic equibiaxial test specimens require
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
C1499–01
greater loads to fracture than those usually encountered in 6.2.3 Load and Support Ring Materials—For machined test
uniaxial flexure of test specimens with similar cross sectional specimens (see Section 8) the load and support fixtures shall be
dimensions. made of hardened steel of HR > 40. For as-fabricated test
C
6.2 Loading Fixtures for Concentric Ring Testing—An specimens, the load/support rings shall be made of steel or
assembly drawing of a fixture and a test specimen is shown in acetyl polymer.
Fig. 1, and the geometries of the load and support rings are
6.2.4 Compliant Layer and Friction Elimination—The
given in Fig. 2. brittle nature of advanced ceramics and the sensitivity to
6.2.1 Loading Rods and Platens—Surfaces of the support
misalignment, contact stresses and friction may require a
platen shall be flat and parallel to 0.05 mm. The face of the load compliant interface between the load/support rings and the test
rod in contact with the support platen shall be flat to 0.025 mm.
specimen, especially if the specimen is not flat. Line or point
In addition, the two loading rods shall be parallel to 0.05 mm contact stresses and frictional stresses can lead to crack
per 25 mm length and concentric to 0.25 mm when installed in
initiation and fracture of the test specimen at stresses other than
the test machine. the actual equibiaxial strength.
6.2.2 Loading Fixture and Ring Geometry—Ideally, the
6.2.4.1 Machined Test Specimens—For test specimens ma-
bases of the load and support fixtures should have the same
chined according to the tolerance in Fig. 3, a compliant layer is
outer diameter as the test specimen for ease of alignment.
not necessary. However, friction needs to be eliminated. Place
Parallelism and flatness of faces as well as concentricity of the
a sheet of carbon foil (~0.13 mm thick) or Teflon tape (~0.7
load and support rings shall be as given in Fig. 2. The ratio of
mm thick) between the compressive and tensile surfaces of the
the load ring diameter, D , to that of the support ring, D , shall
test specimen and the load and support rings.
L S
be 0.2 # D /D # 0.5. For test materials exhibiting low elastic
L S
NOTE 1—Thicker layers of carbon foil or Teflon tape may be used,
modulus (E < 100 GPa) and high strength (s > 1 GPa) it is
ƒ
particularly for very strong plates. However, excessively thick layers will
recommended that the ratio of the load ring diameter to that of
redistribute the contact region and may affect results. The thicknesses
the support ring be D /D = 0.2. The sizes of the load and
L S listed above have been used successfully. Guidance regarding the use of
support rings depend on the dimensions and the properties of
thick layers cannot be given currently; some judgement may be required.
the ceramic material to be tested. The rings are sized to the
Alternatively, an appropriate lubricant (anti-seizing com-
thickness, diameter, strength, and elastic modulus of the
pound or Teflon oil) may be used to minimize friction. The
ceramic specimens (see Section 8). For test specimens made
lubricant should be placed only on the load and support rings
from typical substrates (h ’ 0.5 mm), a support ring diameter
so that ef
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