ASTM C978-04(2019)

Standard Test Method for Photoelastic Determination of Residual Stress in a Transparent Glass Matrix Using a Polarizing Microscope and Optical Retardation Compensation Procedures

SIGNIFICANCE AND USE
5.1 The quality and performance of an article of glassware may be affected not only by the presence of residual stresses due to heat treatment above the strain point in the ware, but also by additional residual stresses caused by differences in thermal expansion between the glass substrate, and either cord, fired-on vitreous enamel, or ACL decoration.  
5.2 The effects of those additional residual cord, enamel, or ACL stresses and the resulting performance of such items may be evaluated by performance test procedures. Such evaluations of enamel or ACL stresses may also be accomplished through the determination of appropriate physical properties of the decoration and matrix glass, or by analytical methods.  
5.3 This test method offers a direct and convenient means of determining the magnitudes and spatial distributions of residual stress systems in glass substrates. The test method is simple, convenient, and quantitatively accurate.  
5.4 This test method is useful in evaluating the degree of compatibility between the coefficient of thermal expansion of an enamel or ACL applied to a glass substrate.
SCOPE
1.1 This test method covers the determination of residual stresses in a transparent glass matrix by means of a polarizing microscope using null or retardation compensation procedures.  
1.2 Such residual stress determinations are of importance in evaluating the nature and degree of residual stresses present in glass matrixes due to cord, or the degree of fit, or suitability of a particular combination of glass matrix and enamel, or applied color label (ACL).  
1.3 The retardation compensation method of optically determining and evaluating enamel or ACL residual stress systems offers distinct advantages over methods requiring physical property measurements or ware performance tests due to its simplicity, reproducibility, and precision.  
1.4 Limitations—This test method is based on the stress-optical retardation compensation principle, and is therefore applicable only to transparent glass substrates, and not to opaque glass systems.  
1.5 Due to the possibility of additional residual stresses produced by ion exchange between glasses of different compositions, some uncertainty may be introduced in the value of the stress optical coefficient in the point of interest due to a lack of accurate knowledge of chemical composition in the areas of interest.  
1.6 This test method is quantitatively applicable to and valid only for those applications where such significant ion exchange is not a factor, and stress optical coefficients are known or determinable.  
1.7 The extent of the ion exchange process, and hence the magnitudes of the residual stresses produced due to ion exchange will depend on the exchange process parameters. The residual stress determinations made on systems in which ion exchange has occurred should be interpreted with those dependencies in mind.  
1.8 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.  
1.9 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.  
1.10 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.

General Information

• Status: Published
• Publication Date: 31-Jan-2019
• ICS: 81.040.10 - Raw materials and raw glass
• Technical Committee: C14 - Glass and Glass Products
• Drafting Committee: C14.10 - Glass Decoration

Relations

• Refers: ASTM C162-05(2015) - Standard Terminology of<brk type="line"/> Glass and Glass Products
• Effective Date: 01-Nov-2015
• Referred By: ASTM C1426-14(2020) - Standard Practices for Verification and Calibration of Polarimeters
• Effective Date: 01-Feb-2019
• Referred By: ASTM F218-13(2020) - Standard Test Method for Measuring Optical Retardation and Analyzing Stress in Glass
• Effective Date: 01-Feb-2019
• Referred By: ASTM C1048-18 - Standard Specification for Heat-Strengthened and Fully Tempered Flat Glass
• Effective Date: 01-Feb-2019
• Referred By: ASTM C1422/C1422M-20a - Standard Specification for Chemically Strengthened Flat Glass
• Effective Date: 01-Feb-2019

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: C978 − 04 (Reapproved 2019)
Standard Test Method for
Photoelastic Determination of Residual Stress in a
Transparent Glass Matrix Using a Polarizing Microscope
1
and Optical Retardation Compensation Procedures
This standard is issued under the fixed designation C978; 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 residual stress determinations made on systems in which ion
exchangehasoccurredshouldbeinterpretedwiththosedepen-
1.1 This test method covers the determination of residual
dencies in mind.
stresses in a transparent glass matrix by means of a polarizing
1.8 The values stated in SI units are to be regarded as the
microscopeusingnullorretardationcompensationprocedures.
standard. The values given in parentheses are for information
1.2 Such residual stress determinations are of importance in
only.
evaluating the nature and degree of residual stresses present in
1.9 This standard does not purport to address all of the
glass matrixes due to cord, or the degree of fit, or suitability of
safety concerns, if any, associated with its use. It is the
aparticularcombinationofglassmatrixandenamel,orapplied
responsibility of the user of this standard to establish appro-
color label (ACL).
priate safety, health, and environmental practices and deter-
1.3 The retardation compensation method of optically de-
mine the applicability of regulatory limitations prior to use.
termining and evaluating enamel or ACL residual stress sys-
1.10 This international standard was developed in accor-
tems offers distinct advantages over methods requiring physi-
dance with internationally recognized principles on standard-
calpropertymeasurementsorwareperformancetestsduetoits
ization established in the Decision on Principles for the
simplicity, reproducibility, and precision.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.4 Limitations—This test method is based on the stress-
Barriers to Trade (TBT) Committee.
optical retardation compensation principle, and is therefore
applicable only to transparent glass substrates, and not to
2. Referenced Documents
opaque glass systems.
2
2.1 ASTM Standards:
1.5 Due to the possibility of additional residual stresses
C162Terminology of Glass and Glass Products
produced by ion exchange between glasses of different
E691Practice for Conducting an Interlaboratory Study to
compositions,someuncertaintymaybeintroducedinthevalue
Determine the Precision of a Test Method
of the stress optical coefficient in the point of interest due to a
F218Test Method for Measuring Optical Retardation and
lack of accurate knowledge of chemical composition in the
Analyzing Stress in Glass
areas of interest.
3. Terminology
1.6 Thistestmethodisquantitativelyapplicabletoandvalid
3.1 Definitions:
onlyforthoseapplicationswheresuchsignificantionexchange
3.1.1 For additional definitions of terms used in this test
is not a factor, and stress optical coefficients are known or
method, refer to Terminology C162.
determinable.
3.1.2 cord—an attenuated glassy inclusion possessing opti-
1.7 The extent of the ion exchange process, and hence the
calandotherpropertiesdifferingfromthoseofthesurrounding
magnitudes of the residual stresses produced due to ion
glass.
exchangewilldependontheexchangeprocessparameters.The
3.2 Definitions of Terms Specific to This Standard:
3.2.1 analyzer—a polarizing element, typically positioned
between the specimen being evaluated and the viewer.
1
This test method is under the jurisdiction of ASTM Committee C14 on Glass
and Glass Products and is the direct responsibility of Subcommittee C14.10 on
2
Glass Decoration. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Feb. 1, 2019. Published February 2019. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1987. Last previous edition approved in 2014 as C978-04 (2014). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/C0978-04R19. the ASTM website.
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C978 − 04 (2019)
3.2.2 applied color label (ACL)—vitrifiable glass color microscope heads frequently contain a second, separate polar-
decoration or enamel applied t
...