ASTM C1322-05b(2010)
(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
SIGNIFICANCE AND USE
This practice is suitable for monolithic and some composite ceramics, for example, particulate- and whisker-reinforced and continuous-grain-boundary phase ceramics. (Long- or continuous-fiber reinforced ceramics are excluded.) For some materials, the location and identification of fracture origins may not be possible due to the specific microstructure.
This practice is principally oriented towards characterization of fracture origins in specimens loaded in so-called fast fracture testing, but the approach can be extended to include other modes of loading as well.
The procedures described within are primarily applicable to mechanical test specimens, although the same procedures may be relevant to component failure analyses as well. It is customary practice to test a number of specimens (constituting a sample) to permit statistical analysis of the variability of the material's strength. It is usually not difficult to test the specimens in a manner that will facilitate subsequent fractographic analysis. This may not be the case with component failure analyses. Component failure analysis is sometimes aided by cutting test pieces from the component and fracturing the test pieces. Fracture markings and fracture origins from the latter may aid component interpretation.
Optimum fractographic analysis requires examination of as many similar specimens or components as possible. This will enhance the chances of successful interpretations. Examination of only one or a few specimens can be misleading. Of course, in some instances the fractographer may have access to only one or a few fractured specimens or components.
Successful and complete fractography also requires careful consideration of all ancillary information that may be available, such as microstructural characteristics, material fabrication, properties and service histories, component or specimen machining, or preparation techniques.
Fractographic inspection and analysis can be a time-consuming process. ...
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 Although this practice is primarily intended for laboratory test piece analysis, the general concepts and procedures may be applied to component failure analyses as well. In many cases, component failure analysis may be aided by cutting laboratory test pieces out of the component. Information gleaned from testing the laboratory pieces (for example, flaw types, general fracture features, fracture mirror constants) may then aid interpretation of component fractures. For more information on component fracture analysis, see Ref (1).
1.3 This practice supersedes Military Handbook 790.
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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Designation: C1322 − 05b(Reapproved 2010)
Standard Practice for
Fractography and Characterization of Fracture Origins in
Advanced Ceramics
This standard is issued under the fixed designation C1322; 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.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 The objective of this practice is to provide an efficient
C162Terminology of Glass and Glass Products
and consistent methodology to locate and characterize fracture
C242Terminology of Ceramic Whitewares and Related
origins in advanced ceramics. It is applicable to advanced
Products
ceramics which are brittle; that is, the material adheres to
C1036Specification for Flat Glass
Hooke’s Law up to fracture. In such materials, fracture
C1145Terminology of Advanced Ceramics
commencesfromasinglelocationwhichistermedthefracture
C1161Test Method for Flexural Strength of Advanced
origin.Thefractureorigininbrittleceramicsnormallyconsists
Ceramics at Ambient Temperature
ofsomeirregularityorsingularityinthematerialwhichactsas
C1211Test Method for Flexural Strength of Advanced
a stress concentrator. In the parlance of the engineer or
Ceramics at Elevated Temperatures
scientist, these irregularities are termed flaws or defects. The
C1239Practice for Reporting Uniaxial Strength Data and
latter should not be construed to mean that the material has
Estimating Weibull Distribution Parameters forAdvanced
been prepared improperly or is somehow faulty.
Ceramics
1.2 Although this practice is primarily intended for labora- F109Terminology Relating to Surface Imperfections on
tory test piece analysis, the general concepts and procedures Ceramics
maybeappliedtocomponentfailureanalysesaswell.Inmany 2.2 Military Standard:
cases, component failure analysis may be aided by cutting Military Handbook 790,Fractography and Characterization
laboratory test pieces out of the component. Information of Fracture Origins in Advanced Structural Ceramics,
gleaned from testing the laboratory pieces (for example, flaw
types, general fracture features, fracture mirror constants) may
3. Terminology
then aid interpretation of component fractures. For more
3.1 Definitions:
information on component fracture analysis, see Ref (1).
3.1.1 General—Thefollowingtermsaregivenasabasisfor
1.3 This practice supersedes Military Handbook 790.
identifying fracture origins that are common to advanced
1.4 This standard does not purport to address all of the ceramics. It should be recognized that origins can manifest
safety concerns, if any, associated with its use. It is the themselvesdifferentlyinvariousmaterials.Thephotographsin
AppendixX1showexamplesoftheoriginsdefinedin3.11and
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- 3.20. Terms that are contained in other ASTM standards are
noted at the end of the each definition.
bility of regulatory limitations prior to use.
3.2 advanced ceramic, n—a highly engineered, high-
performance, predominately nonmetallic, inorganic, ceramic
material having specific functional attributes. C1145
This practice is under the jurisdiction ofASTM Committee C28 on Advanced
Ceramicsand is the direct responsibility of Subcommittee C28.01 on Mechanical
Properties and Performance. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved July 15, 2010. Published November 2010. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ε1
approved in 1996. Last previous edition approved in 2005 as C1322–05b . DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/C1322-05BR10. the ASTM website.
2 4
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof Available from Army Research Laboratory-Materials Directorate, Aberdeen
this standard. Proving Ground, MD 21005.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1322 − 05b (2010)
3.3 brittlefracture,n—fracturethattakesplacewithlittleor 3.19 porous seam, n, (PS)—as used in fractography, a
no preceding plastic deformation. volume-distributedflawthatisa2-dimensionalareaofporosity
or microporosity. C1145
3.4 flaw, n—structural discontinuity in an advanced ceramic
body that acts as a highly localized stress raiser.
3.20 Inherently Surface-Distributed Origins:
NOTE 1—The presence of such discontinuities does not necessarily 3.21 handling damage, n, (HD)—as used in fractography,
imply that the ceramic has been prepared improperly or is faulty.
surface-distributed flaws that include scratches, chips, cracks,
etc., due to the handling of the specimen/component. C1145
3.5 fractography, n—means and methods for characterizing
a fractured specimen or component. C1145
3.22 machining damage, n, (MD)—as used in fractography,
a surface-distributed flaw that is a microcrack(s), chip(s),
3.6 fracture mirror, n—as used in fractography of brittle
striation(s), or scratch(es), or a combination of these, created
materials, a relatively smooth region in the immediate vicinity
during the machining process.
of and surrounding the fracture origin.
NOTE 3—Machining may result in the formation of surface or subsur-
3.7 fracture origin, n—the source from which brittle frac-
face damage, or both.
ture commences. C1145
3.23 pit, n, (PT)—as used in fractography, a surface-
3.8 grain boundary, n (GB)—as used in fractography, a
distributed flaw that is a cavity created on the specimen/
volume-distributed flaw that is a boundary facet between two
component surface during the reaction/interaction between the
or more grains.
material and the environment, for example, corrosion or
NOTE2—Thisflawismostapttobestrengthlimitingincourse-grained
oxidation. C1145
ceramics.
3.24 surface void, n, (SV)—as used in fractography, a
3.9 hackle—as used in fractography, a line or lines on the
surface-distributed flaw that is a cavity created at the surface/
crack surface running in the local direction of cracking,
exterior as a consequence of the reaction/interaction between
separating parallel but non-coplanar portions of the crack
the material and the processing environment, for example,
surface.
surface reaction layer or bubble that is trapped during process-
3.10 mist, n—as used in fractography of brittle materials, ing.
markings on the surface of an accelerating crack close to its
3.25 Miscellaneous Origins:
effective terminal velocity, observable first as a misty appear-
3.26 unidentified origin, n, (?)—as used in this practice, an
ance and with increasing velocity reveals a fibrous texture,
uncertain or undetermined fracture origin.
elongated in the direction of crack propagation.
3.27 Othertermsorfractureorigintypesmaybedevisedby
3.11 Inherently Volume-Distributed Origins:
the user if those listed in 3.11 and 3.20 are inadequate. In such
3.12 agglomerate, n, (A)—as used in fractography, a
instances the user shall explicitly define the nature of the
volume-distributed flaw that is a cluster of grains, particles,
fracture origin (flaw) and whether it is inherently volume- or
platelets, or whiskers, or a combination thereof, present in a
surface-distributed.Additional terms for surface imperfections
larger solid mass. C1145
can be found inTerminology F109 and supplementary fracture
3.13 compositional inhomogeneity, n, (CI)—as used in
origin types for ceramics and glasses may be found in The
fractography, a volume-distributed flaw that is a microstruc-
Ceramic Glossary and Terminology C162 and Terminology
tural irregularity related to the nonuniform distribution of the
C242 and in a Specification C1036. Examples of additional
primary constituents or an additive or second phase. C1145
terms are hard agglomerate, collapsed agglomerate, poorly
bonded region, glassy inclusion, chip, or closed chip.
3.14 crack, n, (CK)—as used in fractography, a volume- or
surface-distributed flaw that is a surface of fracture without
3.28 The word “surface” may have multiple meanings. In
complete separation. C1145
the definitions above, it refers to the intrinsic spatial distribu-
3.15 inclusion, n, (I)—as used in fractography, a volume-
tionofflaws.Theword“surface”alsomayrefertotheexterior
distributed flaw that is a foreign body that has a composition of a test specimen cut from a bulk ceramic or component, or
different from the nominal composition of the bulk advanced
alternatively, the original surface of the component in the
ceramic. C1145 as-firedstate.Itisrecommendedthatthetermsoriginal-surface
or as-processed surface be used if appropriate.
3.16 large grain(s), n, (LG)—as used in fractography, a
volume- or surface-distributed flaw that is a single (or cluster
4. Summary of Practice
of) grain(s) having a size significantly greater than that
encompassed by the normal grain size distribution. C1145
4.1 Prior to testing mark the specimen or component orien-
tation and location to aid in reconstruction of the specimen/
3.17 pore, n, (P(V))—as used in fractography, a volume-
component fragments. Marker lines made with a pencil or felt
distributed flaw that is a discrete cavity or void in a solid
tip marker may suffice.
material. C1145
3.18 porous region, n, (PR)—as used in fractography, a
volume-distributed flaw that is a 3-dimensional zone of poros-
ity or microporosity. C1145 The American Ceramic Society, Westerville, OH 1984.
C1322 − 05b (2010)
4.2 Whenever possible, test the specimen(s)/component(s)
to failure in a fashion that preserves the primary fracture
surface(s) and all associated fragments for further fracto-
graphic analysis.
4.3 Carefully handle and store the specimen(s)/
component(s)tominimizeadditionaldamageorcontamination
of the fracture surface(s), or both.
4.4 Visuallyinspectthefracturedspecimen(s)/component(s)
(1 to 10×) in order to determine crack branching patterns, any
evidence of abnormal failure patterns (indicative of testing
misalignments), the primary fracture surfaces, the location of
the mirror and, if possible, the fracture origin. Specimen/
component reconstruction may be helpful in this step. Label
the pieces with a letter or numerical code and photograph the
assembly if appropriate.
4.5 Useanopticalmicroscope(10to200×)toexamineboth
matinghalvesoftheprimaryfracturesurfaceinordertolocate
and, if possible, characterize the origin. Repeat the examina-
tion of pieces as required. If the fracture origin cannot be
characterized, then conduct the optical examination with the
purpose of expediting subsequent examination with the scan-
ning electron microscope (SEM).
4.6 Inspect the external surfaces of the specimen(s)/
component(s) near the origin for evidence of handling or
machining damage or any interactions that may have occurred
between these surfaces and the environment.
4.7 Clean and prepare the specimen(s)/component(s) for
SEM examination, if necessary.
4.8 Carry out SEM examination (10 to 2000×) of both
mating halves of the primary fracture surface.
4.9 Characterize the strength-limiting origin by its identity,
location,andsize.Whenappropriate,usethechemicalanalysis
capability of the SEM to help characterize the origin.
4.10 If necessary, repeat 4.6 using the SEM.
4.11 Keep appropriate records, digital images, and photo-
graphs at each step in order to characterize the origin, show its
location and the general features of the fractured specimen/
component, as well as for future reference.
4.12 Compare the measured origin size to that estimated by
fracture mechanics. If these sizes are not in general agreement
then an explanation shall be given to account for the discrep-
ancy.
4.13 For a new material, or a new set of processing or NOTE 1—Keep appropriate records, digital images, and photographs at
each step to assist in the origin characterization and for future reference.
exposureconditions,itishighlyrecommendedthatarepresen-
FIG. 1 Simplified Schematic Diagram of the Fractographic Analy-
tative polished section of the microstructure be photographed
sis Procedure
to show the normal microstructural features such as grain size
and porosity.
5. Significance and Use 5.2 This practice is principally oriented towards character-
izationoffractureoriginsinspecimensloadedinso-calledfast
5.1 This practice is suitable for monolithic and some com-
fracture testing, but the approach can be extended to include
posite ceramics, for example, particulate- and whisker-
other modes of loading as well.
reinforced and continuous-grain-boundary phase ceramics.
(Long- or continuous-fiber reinforced ceramics are excluded.) 5.3 The procedures described within are primarily appli-
For some materials, the location and identification of fracture cable to mechanical test specimens, although the same proce-
origins may not be possible due to the specific microstructure. duresmayberelevanttocomponentfailureanalysesaswell.It
C1322 − 05b (2010)
is customary practice to test a number of specimens (consti- scattered throughout the bulk ceramic material (inherently
tuting a sample) to permit statistical analysis of the variability volume-distributed), but when a particular specimen is cut
of the material’s strength. It is usually not difficult to test the from the bulk ceramic material the strength-limiting inclusion
specimens in a manner that will facilitate subsequent fracto- could be located at the specimen surface. Thus a volume-
graphic analysis. This may not be the case with component distributedorigininaceramicmaterialcanbeinanyspecimen,
failure analyses. Component failure analysis is sometimes volume-located,surface-located,nearsurface-located,oredge-
aided by cutting test pieces from the component and fracturing located.
thetestpieces.Fracturemarkingsandfractureoriginsfromthe
5.10 As fabricators improve materials by careful process
latter may aid component interpretation.
control, thus eliminating undesirable microstructural features,
advancedceramicswillbecomestrength-limitedbyoriginsthat
5.4 Optimumfractographicanalysisrequiresexaminationof
as many similar specimens or components as possible. This comefromthelarge-sizedendofthedistributionofthenormal
microstructural features. Such origins can be considered main-
will enhance the chances of successful interpretations. Exami-
nation of only one or a few specimens can be misleading. Of stream microstructural features. In other instances, regions of
slightly different microstructure (locally
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation:C1322–05b Designation: C1322 – 05b (Reapproved 2010)
Standard Practice for
Fractography and Characterization of Fracture Origins in
Advanced Ceramics
This standard is issued under the fixed designation C1322; 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 (´) indicates an editorial change since the last revision or reapproval.
´ NOTE—Added research report footnote to Section X3.1 editorially in September 2008.
1. Scope
1.1 Theobjectiveofthispracticeistoprovideanefficientandconsistentmethodologytolocateandcharacterizefractureorigins
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 Although this practice is primarily intended for laboratory test piece analysis, the general concepts and procedures may be
applied to component failure analyses as well. In many cases, component failure analysis may be aided by cutting laboratory test
pieces out of the component. Information gleaned from testing the laboratory pieces (for example, flaw types, general fracture
features, fracture mirror constants) may then aid interpretation of component fractures. For more information on component
fracture analysis, see Ref (1).
1.3 This practice supersedes Military Handbook 790.
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.
2. Referenced Documents
2.1 ASTM Standards:
C162 Terminology of Glass and Glass Products
C242 Terminology of Ceramic Whitewares and Related Products
C1036 Specification for Flat Glass
C1145 Terminology of Advanced Ceramics
C1161 Test Method for Flexural Strength of Advanced Ceramics at Ambient Temperature
C1211 Test Method for Flexural Strength of Advanced Ceramics at Elevated Temperatures
C1239 Practice for Reporting Uniaxial Strength Data and Estimating Weibull Distribution Parameters forAdvanced Ceramics
F109 Terminology Relating to Surface Imperfections on Ceramics
2.2 Military Standard:
Military Handbook 790, Fractography and Characterization of Fracture Origins in Advanced Structural Ceramics, 1992
3. Terminology
3.1 General—The following terms are given as a basis for identifying fracture origins that are common to advanced ceramics.
It should be recognized that origins can manifest themselves differently in various materials. The photographs in Appendix X1
ThispracticeisunderthejurisdictionofASTMCommitteeC28onAdvancedCeramicsandisthedirectresponsibilityofSubcommitteeC28.01onMechanicalProperties
and Performance.
Current edition approved July 1, 2005. Published July 2005. Originally approved in 1996. Last previous edition approved in 2005 as C1322–05a. DOI:
10.1520/C1322-05BE01.
´1
Current edition approved July 15, 2010. Published November 2010. Originally approved in 1996. Last previous edition approved in 2005 as C1322 – 05b . DOI:
10.1520/C1322-05BR10.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book ofASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from Army Research Laboratory-Materials Directorate, Aberdeen Proving Ground, MD 21005.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C1322 – 05b (2010)
show examples of the origins defined in 3.11 and 3.20. Terms that are contained in otherASTM standards are noted at the end of
the each definition.
3.2 advanced ceramic, n—a highly engineered, high-performance, predominately nonmetallic, inorganic, ceramic material
having specific functional attributes. C1145
3.3 brittle fracture, n—fracture that takes place with little or no preceding plastic deformation.
3.4 flaw, n—structural discontinuity in an advanced ceramic body that acts as a highly localized stress raiser.
NOTE 1—The presence of such discontinuities does not necessarily imply that the ceramic has been prepared improperly or is faulty.
3.5 fractography, n—means and methods for characterizing a fractured specimen or component. C1145
3.6 fracture mirror, n—as used in fractography of brittle materials, a relatively smooth region in the immediate vicinity of and
surrounding the fracture origin.
3.7 fracture origin, n—the source from which brittle fracture commences. C1145
3.8 grain boundary, n (GB)—as used in fractography, a volume-distributed flaw that is a boundary facet between two or more
grains.
NOTE 2—This flaw is most apt to be strength limiting in course-grained ceramics.
3.9 hackle—as used in fractography, a line or lines on the crack surface running in the local direction of cracking, separating
parallel but non-coplanar portions of the crack surface.
3.10 mist, n—as used in fractography of brittle materials, markings on the surface of an accelerating crack close to its effective
terminal velocity, observable first as a misty appearance and with increasing velocity reveals a fibrous texture, elongated in the
direction of crack propagation.
3.11 Inherently Volume-Distributed Origins:
3.12 agglomerate, n, (A)—as used in fractography, a volume-distributed flaw that is a cluster of grains, particles, platelets, or
whiskers, or a combination thereof, present in a larger solid mass. C1145
3.13 compositional inhomogeneity, n, (CI)—as used in fractography, a volume-distributed flaw that is a microstructural
irregularity related to the nonuniform distribution of the primary constituents or an additive or second phase. C1145
3.14 crack,n,(CK)—asusedinfractography,avolume-orsurface-distributedflawthatisasurfaceoffracturewithoutcomplete
separation. C1145
3.15 inclusion, n, (I)—as used in fractography, a volume-distributed flaw that is a foreign body that has a composition different
from the nominal composition of the bulk advanced ceramic. C1145
3.16 large grain(s), n, (LG)—as used in fractography, a volume- or surface-distributed flaw that is a single (or cluster of)
grain(s) having a size significantly greater than that encompassed by the normal grain size distribution. C1145
3.17 pore, n, (P(V))—as used in fractography, a volume-distributed flaw that is a discrete cavity or void in a solid material.
C1145
3.18 porous region, n, (PR)—as used in fractography, a volume-distributed flaw that is a 3-dimensional zone of porosity or
microporosity. C1145
3.19 porous seam, n, (PS)—as used in fractography, a volume-distributed flaw that is a 2-dimensional area of porosity or
microporosity. C1145
3.20 Inherently Surface-Distributed Origins:
3.21 handling damage, n, (HD)—as used in fractography, surface-distributed flaws that include scratches, chips, cracks, etc.,
due to the handling of the specimen/component. C1145
3.22 machining damage, n, (MD)—as used in fractography, a surface-distributed flaw that is a microcrack(s), chip(s),
striation(s), or scratch(es), or a combination of these, created during the machining process.
NOTE 3—Machining may result in the formation of surface or subsurface damage, or both.
3.23 pit, n, (PT)—as used in fractography, a surface-distributed flaw that is a cavity created on the specimen/component surface
during the reaction/interaction between the material and the environment, for example, corrosion or oxidation. C1145
3.24 surface void, n, (SV)—as used in fractography, a surface-distributed flaw that is a cavity created at the surface/exterior as
aconsequenceofthereaction/interactionbetweenthematerialandtheprocessingenvironment,forexample,surfacereactionlayer
or bubble that is trapped during processing.
3.25 Miscellaneous Origins:
3.26 unidentified origin, n, (?)—as used in this practice, an uncertain or undetermined fracture origin.
3.27 Other terms or fracture origin types may be devised by the user if those listed in 3.11 and 3.20 are inadequate. In such
instances the user shall explicitly define the nature of the fracture origin (flaw) and whether it is inherently volume- or
surface-distributed. Additional terms for surface imperfections can be found in Terminology F109 and supplementary fracture
origin types for ceramics and glasses may be found in The Ceramic Glossary and Terminology C162 and Terminology C242 and
inaSpecificationC1036.Examplesofadditionaltermsarehardagglomerate,collapsedagglomerate,poorlybondedregion,glassy
inclusion, chip, or closed chip.
The American Ceramic Society, Westerville, OH 1984.
C1322 – 05b (2010)
3.28 The word “surface” may have multiple meanings. In the definitions above, it refers to the intrinsic spatial distribution of
flaws.The word “surface” also may refer to the exterior of a test specimen cut from a bulk ceramic or component, or alternatively,
theoriginalsurfaceofthecomponentintheas-firedstate.Itisrecommendedthatthetermsoriginal-surfaceoras-processedsurface
be used if appropriate.
4. Summary of Practice
4.1 Prior to testing mark the specimen or component orientation and location to aid in reconstruction of the specimen/
component fragments. Marker lines made with a pencil or felt tip marker may suffice.
4.2 Whenever possible, test the specimen(s)/component(s) to failure in a fashion that preserves the primary fracture surface(s)
and all associated fragments for further fractographic analysis.
4.3 Carefully handle and store the specimen(s)/component(s) to minimize additional damage or contamination of the fracture
surface(s), or both.
4.4 Visually inspect the fractured specimen(s)/component(s) (1 to 103) in order to determine crack branching patterns, any
evidenceofabnormalfailurepatterns(indicativeoftestingmisalignments),theprimaryfracturesurfaces,thelocationofthemirror
and, if possible, the fracture origin. Specimen/component reconstruction may be helpful in this step. Label the pieces with a letter
or numerical code and photograph the assembly if appropriate.
4.5 Use an optical microscope (10 to 2003) to examine both mating halves of the primary fracture surface in order to locate
and,ifpossible,characterizetheorigin.Repeattheexaminationofpiecesasrequired.Ifthefractureorigincannotbecharacterized,
then conduct the optical examination with the purpose of expediting subsequent examination with the scanning electron
microscope (SEM).
4.6 Inspecttheexternalsurfacesofthespecimen(s)/component(s)neartheoriginforevidenceofhandlingormachiningdamage
or any interactions that may have occurred between these surfaces and the environment.
4.7 Clean and prepare the specimen(s)/component(s) for SEM examination, if necessary.
4.8 Carry out SEM examination (10 to 20003) of both mating halves of the primary fracture surface.
4.9 Characterize the strength-limiting origin by its identity, location, and size. When appropriate, use the chemical analysis
capability of the SEM to help characterize the origin.
4.10 If necessary, repeat 4.6 using the SEM.
4.11 Keepappropriaterecords,digitalimages,andphotographsateachstepinordertocharacterizetheorigin,showitslocation
and the general features of the fractured specimen/component, as well as for future reference.
4.12 Compare the measured origin size to that estimated by fracture mechanics. If these sizes are not in general agreement then
an explanation shall be given to account for the discrepancy.
4.13 For a new material, or a new set of processing or exposure conditions, it is highly recommended that a representative
polishedsectionofthemicrostructurebephotographedtoshowthenormalmicrostructuralfeaturessuchasgrainsizeandporosity.
5. Significance and Use
5.1 This practice is suitable for monolithic and some composite ceramics, for example, particulate- and whisker-reinforced and
continuous-grain-boundary phase ceramics. (Long- or continuous-fiber reinforced ceramics are excluded.) For some materials, the
location and identification of fracture origins may not be possible due to the specific microstructure.
5.2 This practice is principally oriented towards characterization of fracture origins in specimens loaded in so-called fast
fracture testing, but the approach can be extended to include other modes of loading as well.
5.3 The procedures described within are primarily applicable to mechanical test specimens, although the same procedures may
be relevant to component failure analyses as well. It is customary practice to test a number of specimens (constituting a sample)
to permit statistical analysis of the variability of the material’s strength. It is usually not difficult to test the specimens in a manner
thatwillfacilitatesubsequentfractographicanalysis.Thismaynotbethecasewithcomponentfailureanalyses.Componentfailure
analysisissometimesaidedbycuttingtestpiecesfromthecomponentandfracturingthetestpieces.Fracturemarkingsandfracture
origins from the latter may aid component interpretation.
5.4 Optimum fractographic analysis requires examination of as many similar specimens or components as possible. This will
enhance the chances of successful interpretations. Examination of only one or a few specimens can be misleading. Of course, in
some instances the fractographer may have access to only one or a few fractured specimens or components.
5.5 Successful and complete fractography also requires careful consideration of all ancillary information that may be available,
such as microstructural characteristics, material fabrication, properties and service histories, component or specimen machining,
or preparation techniques.
5.6 Fractographic inspection and analysis can be a time-consuming process. Experience will in general enhance the chances of
correct interpretation and characterization, but will not obviate
...
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