ASTM C1678-21

Standard Practice for Fractographic Analysis of Fracture Mirror Sizes in Ceramics and Glasses

SIGNIFICANCE AND USE
5.1 Fracture mirror size analysis is a powerful tool for analyzing glass and ceramic fractures. Fracture mirrors are tell-tale fractographic markings in brittle materials that surround a fracture origin as discussed in Practices C1256 and C1322. Fig. 1 shows a schematic with key features identified. Fig. 2 shows an example in glass. The fracture mirror region is very smooth and highly reflective in glasses, hence the name “fracture mirror.” In fact, high magnification microscopy reveals that, even within the mirror region in glasses, there are very fine features and escalating roughness as the crack advances away from the origin. These are submicrometer in size and hence are not discernable with an optical microscope. Early investigators interpreted fracture mirrors as having discrete boundaries including a “mirror-mist” boundary and also a “mist-hackle” boundary in glasses. These were also termed “inner mirror” or “outer mirror” boundaries, respectively. It is now known that there are no discrete boundaries corresponding to specific changes in the fractographic features. Surface roughness increases gradually from well within the fracture mirror to beyond the apparent boundaries. The boundaries were a matter of interpretation, the resolving power of the microscope, and the mode of viewing. In very weak specimens, the mirror may be larger than the specimen or component and the boundaries will not be present. Eq 1 is hereafter referred to as the “empirical stress – fracture mirror size relationship,” or “stress-mirror size relationship” for short. A review of the history of Eq 1, and fracture mirror analysis in general, may be found in Refs (1)3 and (2).  
5.5 A, the “fracture mirror constant” (sometimes also known as the “mirror constant”) has units of stress intensity (MPa√m or ksi√in.) and is considered by many to be a material property. As shown in Figs. 1 and 2, it is possible to discern separate mist and hackle regions and the apparent boundaries between them i...
SCOPE
1.1 This practice pertains to the analysis and interpretation of fracture mirror sizes in brittle materials. Fracture mirrors (Fig. 1) are telltale fractographic markings that surround a fracture origin in brittle materials. The fracture mirror size may be used with known fracture mirror constants to estimate the stress in a fractured component. Alternatively, the fracture mirror size may be used in conjunction with known stresses in test specimens to calculate fracture mirror constants. The practice is applicable to glasses and polycrystalline ceramic laboratory test specimens as well as fractured components. The analysis and interpretation procedures for glasses and ceramics are similar, but they are not identical. Different optical microscopy examination techniques are listed and described, including observation angles, illumination methods, appropriate magnification, and measurement protocols. Guidance is given for calculating a fracture mirror constant and for interpreting the fracture mirror size and shape for both circular and noncircular mirrors including stress gradients, geometrical effects, residual stresses, or combinations thereof. The practice provides figures and micrographs illustrating the different types of features commonly observed in and measurement techniques used for the fracture mirrors of glasses and polycrystalline ceramics.
FIG. 1 Schematic of a Fracture Mirror Centered on a Surface Flaw of Initial Size (a)
Note 1: The initial flaw may grow stably to size ac prior to unstable fracture when the stress intensity reaches KIc. The mirror-mist radius is Ri, the mist-hackle radius is Ro, and the branching distance is Rb. These transitions correspond to the mirror constants, Ai, Ao, and Ab, respectively.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 This standard does not purport to address all of the safet...

General Information

• Status: Published
• Publication Date: 30-Jun-2021
• ICS: 81.060.20 - Ceramic products
• Technical Committee: C28 - Advanced Ceramics
• Drafting Committee: C28.03 - Physical Properties and Non-Destructive Evaluation

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C1678 − 21
Standard Practice for
Fractographic Analysis of Fracture Mirror Sizes in Ceramics
1
and Glasses
This standard is issued under the fixed designation C1678; 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.
1. Scope Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.1 This practice pertains to the analysis and interpretation
Barriers to Trade (TBT) Committee.
of fracture mirror sizes in brittle materials. Fracture mirrors
(Fig. 1) are telltale fractographic markings that surround a
2. Referenced Documents
fractureorigininbrittlematerials.Thefracturemirrorsizemay
2
2.1 ASTM Standards:
be used with known fracture mirror constants to estimate the
C1145 Terminology of Advanced Ceramics
stress in a fractured component. Alternatively, the fracture
C1256 Practice for Interpreting Glass Fracture Surface Fea-
mirror size may be used in conjunction with known stresses in
tures
test specimens to calculate fracture mirror constants. The
C1322 Practice for Fractography and Characterization of
practice is applicable to glasses and polycrystalline ceramic
Fracture Origins in Advanced Ceramics
laboratorytestspecimensaswellasfracturedcomponents.The
analysis and interpretation procedures for glasses and ceramics
3. Terminology
are similar, but they are not identical. Different optical micros-
copy examination techniques are listed and described, includ-
3.1 Definitions: (See Fig. 1)
ing observation angles, illumination methods, appropriate 3.1.1 fracture mirror, n—as used in fractography of brittle
magnification, and measurement protocols. Guidance is given
materials, a relatively smooth region in the immediate vicinity
for calculating a fracture mirror constant and for interpreting of and surrounding the fracture origin. C1145, C1322
the fracture mirror size and shape for both circular and
3.1.2 fracture origin, n—the source from which brittle
noncircular mirrors including stress gradients, geometrical
fracture commences. C1145, C1322
effects, residual stresses, or combinations thereof. The practice
3.1.3 hackle, n—as used in fractography of brittle materials,
providesfiguresandmicrographsillustratingthedifferenttypes
alineorlinesonthecracksurfacerunninginthelocaldirection
of features commonly observed in and measurement tech-
of cracking, separating parallel but noncoplanar portions of the
niques used for the fracture mirrors of glasses and polycrys-
crack surface. C1145, C1322
talline ceramics.
3.1.4 mist, n—as used in fractography of brittle materials,
1.2 The values stated in SI units are to be regarded as
markings on the surface of an accelerating crack close to its
standard. No other units of measurement are included in this
effective terminal velocity, observable first as a misty appear-
standard.
ance and with increasing velocity reveals a fibrous texture,
1.3 This standard does not purport to address all of the
elongated in the direction of crack propagation. C1145, C1322
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
(See Fig. 1)
priate safety, health, and environmental practices and deter-
3.2.1 mirror-mist boundary in glasses, n—the periphery
mine the applicability of regulatory limitations prior to use.
where one can discern the onset of mist around a glass fracture
1.4 This international standard was developed in accor-
mirror. This boundary corresponds to A, the inner mirror
i
dance with internationally recognized principles on standard-
constant.
ization established in the Decision on Principles for the
3.2.2 mist-hackle boundary in glasses, n—the periphery
where one can discern the onset of systematic hackle around a
1
This practice is under the jurisdiction of ASTM Committee C28 on Advanced
Ceramics and is the direct responsibility of Subcommittee C28.03 on Physical
2
Properties and Non-Destructive Evaluation. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved July 1, 2021. Published July 2021. Originally approved contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
in 2007. Last previous edition approved in 2015 as C1678 – 10 (2015). DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/C1678-21. the ASTM website.
Copyright © ASTM
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM 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.
Designation: C1678 − 10 (Reapproved 2015) C1678 − 21
Standard Practice for
Fractographic Analysis of Fracture Mirror Sizes in Ceramics
1
and Glasses
This standard is issued under the fixed designation C1678; 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.
1. Scope
1.1 This practice pertains to the analysis and interpretation of fracture mirror sizes in brittle materials. Fracture mirrors (Fig. 1)
are telltale fractographic markings that surround a fracture origin in brittle materials. The fracture mirror size may be used with
known fracture mirror constants to estimate the stress in a fractured component. Alternatively, the fracture mirror size may be used
in conjunction with known stresses in test specimens to calculate fracture mirror constants. The practice is applicable to glasses
and polycrystalline ceramic laboratory test specimens as well as fractured components. The analysis and interpretation procedures
for glasses and ceramics are similar, but they are not identical. Different optical microscopy examination techniques are listed and
described, including observation angles, illumination methods, appropriate magnification, and measurement protocols. Guidance
is given for calculating a fracture mirror constant and for interpreting the fracture mirror size and shape for both circular and
noncircular mirrors including stress gradients, geometrical effects, and/or residual stresses. residual stresses, or combinations
thereof. The practice provides figures and micrographs illustrating the different types of features commonly observed in and
measurement techniques used for the fracture mirrors of glasses and polycrystalline ceramics.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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.
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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2
2.1 ASTM Standards:
C1145 Terminology of Advanced Ceramics
C1256 Practice for Interpreting Glass Fracture Surface Features
1
This practice is under the jurisdiction of ASTM Committee C28 on Advanced Ceramics and is the direct responsibility of Subcommittee C28.03 on Physical Properties
and Non-Destructive Evaluation.
Current edition approved July 1, 2015July 1, 2021. Published September 2015July 2021. Originally approved in 2007. Last previous edition approved in 20102015 as
C1678 – 10.C1678 – 10 (2015). DOI: 10.1520/C1678-10R15.10.1520/C1678-21.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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C1678 − 21
NOTE 1—The initial flaw may grow stably to size a prior to unstable fracture when the stress intensity reaches K . The mirror-mist radius is R , the
c Ic i
mist-hackle radius is R , and the branching distance is R . These transitions correspond to the mirror constants, A , A , and A , respectively.
o b i o b
FIG. 1 Schematic of a Fracture Mirror Centered on a Surface Flaw of Initial Size (a)
C1322 Practice for Fractography and Characterization of Fracture Origins in Advanced Ceramics
3. Terminology
3.1 Definitions: (See Fig. 1)
3.1.1 fracture mirror, n—as used in fractography of brittle
...