ASTM C1322-96a
(Practice)Standard Practice for Fractography and Characterization of Fracture Origins in Advanced Ceramics
Standard Practice for Fractography and Characterization of Fracture Origins in Advanced Ceramics
SCOPE
1.1 The objective of this practice is to provide an efficient and consistent methodology to locate and characterize fracture origins in advanced ceramics. It is applicable to advanced ceramics which are brittle; that is, the material adheres to Hooke's Law up to fracture. In such materials, fracture commences from a single location which is termed the fracture origin. The fracture origin in brittle ceramics normally consists of some irregularity or singularity in the material which acts as a stress concentrator. In the parlance of the engineer or scientist, these irregularities are termed "flaws" or "defects." The latter should not be construed to mean that the material has been prepared improperly or is somehow faulty.
1.2 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)
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Designation: C 1322 – 96a
Standard Practice for
Fractography and Characterization of Fracture Origins in
Advanced Ceramics
This standard is issued under the fixed designation C 1322; 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 (ϵ) indicates an editorial change since the last revision or reapproval.
1. Scope tion of Fracture Origins inAdvanced Structural Ceramics,
1.1 The objective of this practice is to provide an efficient
and consistent methodology to locate and characterize fracture
3. Terminology
origins in advanced ceramics. It is applicable to advanced
3.1 General—The following terms are given as a basis for
ceramics which are brittle; that is, the material adheres to
identifying fracture origins that are common to advanced
Hooke’s Law up to fracture. In such materials, fracture
ceramics. It should be recognized that origins can manifest
commences from a single location which is termed the fracture
themselves differently in various materials.The photographs in
origin.The fracture origin in brittle ceramics normally consists
Appendix X1 show examples of the origins defined in 3.8 and
of some irregularity or singularity in the material which acts as
3.17. Terms that are contained in other ASTM standards are
a stress concentrator. In the parlance of the engineer or
noted at the end of the each definition.
scientist, these irregularities are termed flaws or defects. The
3.2 advanced ceramic, n—a highly engineered, high-
latter should not be construed to mean that the material has
performance, predominately nonmetallic, inorganic, ceramic
been prepared improperly or is somehow faulty.
material having specific functional attributes. C1145
1.2 This standard does not purport to address all of the
3.3 flaw, n—a structural discontinuity in an advanced ce-
safety concerns, if any, associated with its use. It is the
ramic body that acts as a highly localized stress raiser.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
NOTE 1—The presence of such discontinuities does not necessarily
bility of regulatory limitations prior to use. imply that the ceramic has been prepared improperly or is faulty.
3.4 fracture origin, n—the source from which brittle frac-
2. Referenced Documents
ture commences. C1145
2.1 ASTM Standards:
3.5 hackle, n—as used in fractography, a line or lines on the
C 162 Terminology of Glass and Glass Products
crack surface running in the local direction of cracking,
C 242 Terminology of Ceramic Whitewares and Related
separating parallel but noncoplanar portions of the crack
Products
surface.
C 1145 Terminology of Advanced Ceramics
3.6 mirror, n—as used in fractography of brittle materials,a
C 1211 Test Method for Flexural Strength of Advanced
very smooth region in the immediate vicinity of and surround-
Ceramics at Elevated Temperatures
ing the fracture origin.
C 1239 Practice for Reporting Uniaxial Strength Data and
3.7 mist, n—as used in fractography of brittle materials,
Estimating Weibull Distribution Parameters for Advanced
markings on the surface of an accelerating crack close to its
Ceramics
effective terminal velocity, observable first as a misty appear-
C 1256 Practice for Interpreting Glass Fracture Surface
ance and with increasing velocity reveals a fibrous texture,
Features
elongated in the direction of crack propagation.
F 109 Terminology Relating to Surface Imperfections on
3.8 Inherently Volume-Distributed Origins:
Ceramics
3.9 agglomerate, n, (A(V))—as used in fractography,a
2.2 Military Standard:
cluster of grains, particles, platelets, or whiskers, or a combi-
Military Handbook 790, Fractography and Characteriza-
nation thereof, present in a larger solid mass.
NOTE 2—The codes in parentheses after each term are provided for use
in statistical analysis. A superscript V stands for inherently volume-
This practice is under the jurisdiction ofASTM Committee C-28 onAdvanced
distributed origins and a superscript S for inherently surface-distributed
Ceramics and is the direct responsibility of Subcommittee C28.05 on Processing.
Current edition approved Dec. 10, 1996. Published February 1997. Originally
published as C 1322 – 96. Last previous edition C 1322 – 96ϵ .
2 4
Annual Book of ASTM Standards, Vol 15.02. Available from Army Research Laboratory-Materials Directorate, Aberdeen
Annual Book of ASTM Standards, Vol 15.01. Proving Ground, MD 21005.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
C 1322 – 96a
origins. C1145 alternatively, the original surface of the component in the
as-firedstate.Itisrecommendedthatthetermsoriginal-surface
3.10 compositional inhomogeneity, n, (CI(V))—as used in
or as-processed surface be used if appropriate, for example,
fractography, a microstructural irregularity related to the
as-processed, surface-distributed origin.
nonuniformdistributionofanadditive,adifferentcrystallineor
glass phase or in a multiphase material, the nonuniform
4. Summary of Practice
distribution of a second phase. C1145
3.11 crack, n, (CK(V))—as used in fractography, a plane of 4.1 Whenever possible, test the specimen(s)/component(s)
to failure in a fashion that preserves the primary fracture
fracture without complete separation. C1145
3.12 inclusion, n, (I(V))—as used in fractography, a foreign surface(s) and all associated fragments for further fracto-
graphic analysis.
body from other than the normal composition of the bulk
advanced ceramic. C1145 4.2 Carefully handle and store the specimen(s)/
component(s) to minimize additional damage or contamination
3.13 large grain(s), n, (LG(V))—as used in fractography,a
single (or cluster of) grain(s) having a size significantly greater of the fracture surface(s), or both.
than that encompassed by the normal grain size distribution. 4.3 Visuallyinspectthefracturedspecimen(s)/component(s)
C1145 (1 to 103) in order to determine crack branching patterns, any
3.14 pore, n, (P(V))—as used in fractography, a discrete
evidence of abnormal failure patterns (indicative of testing
cavity or void in a solid material. C1145 misalignments), the primary fracture surfaces, the location of
3.15 porous region, n, (PR(V))—as used in fractography,a the mirror and, if possible, the fracture origin. Specimen/
3-dimensional zone of porosity or microporosity. C1145 component reconstruction may be helpful in this step.
3.16 porous seam, n, (PS(V))—as used in fractography,a
4.4 Use an optical microscope (10 to 2003) to examine
2-dimensional area of porosity or microporosity. C1145 both mating halves of the primary fracture surface in order to
3.17 Inherently Surface-Distributed Origins:
locate and, if possible, characterize the origin. If the fracture
3.18 handling damage, n, (HD(S))—as used in fractogra- origin cannot be characterized, then conduct the optical exami-
phy, scratches, chips, cracks, etc., due to the handling of the
nation with the purpose of expediting subsequent examination
specimen/component. C1145 with the scanning electron microscope (SEM).
3.19 machining damage, n, (MD(S))—as used in fractogra-
4.5 Inspect the external surfaces of the specimen(s)/
phy, surface/subsurface microcracks or chips created during component(s) near the origin for evidence of handling or
the machining process, for example, striations, scratches, and
machining damage or any interactions that may have occurred
impact cracks. between these surfaces and the environment.
4.6 Clean and prepare the specimen(s)/component(s) for
NOTE 3—Machining may result in surface or subsurface cracks, or
SEM examination, if necessary.
both.
4.7 Carry out SEM examination (10 to 20003) of both
3.20 pit, n, (PT(S))—as used in fractography, a cavity
mating halves of the primary fracture surface.
created on the specimen/component surface during the
4.8 Characterize the strength-limiting origin by its identity,
reaction/interaction between the material and the environment,
location, and size.When appropriate, use the chemical analysis
for example, corrosion or oxidation. C1145
capability of the SEM to help characterize the origin.
3.21 surface void, n, (SV(S))—as used in fractography,a
4.9 If necessary, repeat 4.5 using the SEM.
cavity created at the surface/exterior as a consequence of the
4.10 Keep appropriate records and photographs at each step
reaction/interaction between the material and the processing
in order to characterize the origin, show its location and the
environment, for example, surface reaction layer or bubble that
general features of the fractured specimen/component, as well
is trapped during processing.
as for future reference.
3.22 Miscellaneous Origins:
4.11 Compare the measured origin size to that estimated by
3.23 unidentified origin, n, (?)—as used in this practice,an
fracture mechanics. If these sizes are not in general agreement
uncertain or undetermined fracture origin.
then an explanation shall be given to account for the discrep-
3.24 Other terms or fracture origin types may be devised by
ancy.
the user if those listed in 3.8 and 3.17 are inadequate. In such
4.12 For a new material, or a new set of processing or
instances the user shall explicitly define the nature of the
exposure conditions, it is highly recommended that a represen-
fracture origin (flaw) and whether it is inherently volume- or
tative polished section of the microstructure be photographed
surface-distributed.Additional terms for surface imperfections
to show the normal microstructural features such as grain size
can be found in Terminology F 109F 109 and supplementary
and porosity.
fracture origin types for ceramics and glasses may be found in
The Ceramic Glossary and Terminologies C 162 and
5. Significance and Use
C 242C 162C 242. Examples of additional terms are hard
5.1 This practice is suitable for monolithic and some com-
agglomerate, glassy inclusion, chip, or closed chip.
posite ceramics, for example, particulate- and whisker-
3.25 The word surface may also apply to the exterior of a
reinforced and continuous-grain-boundary phase ceramics.
test specimen cut from a bulk ceramic or component, or
(Long- or continuous-fiber reinforced ceramics are excluded.)
For some materials, the location and identification of fracture
The American Ceramic Society, Westerville, OH 1984. origins may not be possible due to the specific microstructure.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
C 1322 – 96a
5.2 This practice is principally oriented towards character- practice to discuss the development of origins or their behavior
ization of fracture origins in specimens loaded in so-called fast from a fracture mechanics viewpoint.
fracture testing, but the approach can be extended to include
NOTE 5—For additional information on fracture origins and their
other modes of loading as well.
behavior from a fracture mechanics viewpoint seeAppendix X2. Fracture
5.3 The procedures described within are primarily appli-
mechanics is used in this practice as a check on the size of the feature
cable to mechanical test specimens, although the same proce- identified as an origin (see 7.2.4.4).
dures may be relevant to component failure analyses as well. It
5.9 Regardless of how origins develop they are either
is customary practice to test a number of specimens (consti-
inherently volume-distributed throughout the bulk of the ce-
tuting a sample) to permit statistical analysis of the variability
ramic material (for example, agglomerates, large grains, or
of the material’s strength. It is usually not difficult to test the
pores)orinherentlysurface-distributedontheceramicmaterial
specimens in a manner that will facilitate subsequent fracto-
(for example, handling damage, pits from oxidation, or corro-
graphic analysis. This may not be the case with component
sion). The distinction is a consequence of how the specimen or
failure analyses.
component is prepared. For example, inclusions may be
5.4 Optimumfractographicanalysisrequiresexaminationof
scattered throughout the bulk ceramic material (inherently
as many similar specimens or components as possible. This
volume-distributed), but when a particular specimen is cut
will enhance the chances of successful interpretations. Exami-
from the bulk ceramic material the strength-limiting inclusion
nation of only one or a few specimens can be misleading. Of
could be located at the specimen surface. Thus a volume-
course, in some instances the fractographer may have access to
distributedorigininaceramicmaterialcanbeinanyspecimen,
only one or a few fractured specimens or components.
volume-located, surface-located, near surface-located, or edge-
5.5 Successful and complete fractography also requires
located.
careful consideration of all ancillary information that may be
5.10 As fabricators improve materials by careful process
available, such as microstructural characteristics, material
control, thus eliminating large, abnormal microstructural fea-
fabrication, properties and service histories, component or
tures, advanced ceramics will become strength-limited by
specimen machining, or preparation techniques.
originsthatcomefromthelarge-sizedendofthedistributionof
the normal microstructural features. Such origins can be
NOTE 4—A VAMAS round robin on fractographic analysis of ceramic
origins highlights the importance of such additional information. See considered mainstream microstructural features. In other in-
,
6 7
ARL-TR-656 (or VAMAS Report No. 19) for details.
stances, regions of slightly different microstructure (locally
higher microporosity) or microcracks between grains (possibly
5.6 Fractographic inspection and analysis can be a time-
introduced by thermoelastic strains) may act as failure origins.
consuming process. Experience will in general enhance the
These origins will blend in well with the background micro-
chances of correct interpretation and characterization, but will
structure and will be extremely difficult or impossible to
not obviate the need for time and patience.
discern even with careful scanning electron microscopy. This
5.7 This practice is applicable to quality control, materials
practice can still be used to analyze such failure origins, but
research
...
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