ASTM C978-04

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
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.
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.
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.
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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-May-2004
• ICS: 81.040.10 - Raw materials and raw glass
• Technical Committee: C14 - Glass and Glass Products
• Drafting Committee: C14.10 - Glass Decoration

Relations

• Replaces: ASTM C978-02 - Standard Test Method for Photoelastic Determination of Residual Stress in a Transparent Glass Matrix Using a Polarizing Microscope and Optical Retardation Compensation Procedures
• Effective Date: 01-Jun-2004
• Replaced By: ASTM C978-04(2009) - Standard Test Method for Photoelastic Determination of Residual Stress in a Transparent Glass Matrix Using a Polarizing Microscope and Optical Retardation Compensation Procedures
• Effective Date: 01-May-2009
• Referred By: ASTM F218-13(2020) - Standard Test Method for Measuring Optical Retardation and Analyzing Stress in Glass
• Effective Date: 01-Jun-2004
• Referred By: ASTM C1426-14(2020) - Standard Practices for Verification and Calibration of Polarimeters
• Effective Date: 01-Jun-2004
• Referred By: ASTM C1422/C1422M-20a - Standard Specification for Chemically Strengthened Flat Glass
• Effective Date: 01-Jun-2004
• Referred By: ASTM C1048-18 - Standard Specification for Heat-Strengthened and Fully Tempered Flat Glass
• Effective Date: 01-Jun-2004

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:C978–04
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 C 978; 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 1.8 The values stated in SI units are to be regarded as the
standard. The values given in parentheses are for information
1.1 This test method covers the determination of residual
only.
stresses in a transparent glass matrix by means of a polarizing
1.9 This standard does not purport to address all of the
microscope using null or retardation compensation procedures.
safety concerns, if any, associated with its use. It is the
1.2 Such residual stress determinations are of importance in
responsibility of the user of this standard to establish appro-
evaluating the nature and degree of residual stresses present in
priate safety and health practices and determine the applica-
glass matrixes due to cord, or the degree of fit, or suitability of
bility of regulatory limitations prior to use.
aparticularcombinationofglassmatrixandenamel,orapplied
color label (ACL).
2. Referenced Documents
1.3 The retardation compensation method of optically de-
2
2.1 ASTM Standards:
termining and evaluating enamel or ACL residual stress sys-
C 162 Terminology of Glass and Glass Products
tems offers distinct advantages over methods requiring physi-
C 770 Test Method for Measurement of Glass Stress-
cal property measurements or ware performance tests due to its
Optical Coefficient
simplicity, reproducibility, and precision.
E 691 Practice for Conducting an Interlaboratory Study to
1.4 Limitations—This test method is based on the stress-
Determine the Precision of a Test Method
optical retardation compensation principle, and is therefore
F 218 Test Method for Analyzing Stress in Glass
applicable only to transparent glass substrates, and not to
opaque glass systems.
3. Terminology
1.5 Due to the possibility of additional residual stresses
3.1 Definitions—For additional definitions of terms used in
produced by ion exchange between glasses of different com-
this test method, refer to Terminology C 162.
positions, some uncertainty may be introduced in the value of
3.1.1 cord—an attenuated glassy inclusion possessing opti-
thestressopticalcoefficientinthepointofinterestduetoalack
cal and other properties differing from those of the surrounding
of accurate knowledge of chemical composition in the areas of
glass. C 162
interest.
3.2 Definitions of Terms Specific to This Standard:
1.6 Thistestmethodisquantitativelyapplicabletoandvalid
3.2.1 analyzer—a polarizing element, typically positioned
onlyforthoseapplicationswheresuchsignificantionexchange
between the specimen being evaluated and the viewer.
is not a factor, and stress optical coefficients are known or
3.2.2 applied color label (ACL)—vitrifiable glass color
determinable.
decoration or enamel applied to and fused on a glass surface.
1.7 The extent of the ion exchange process, and hence the
3.2.3 polarizer—an optical assembly that transmits light
magnitudes of the residual stresses produced due to ion
vibrating in a single planar direction, typically positioned
exchangewilldependontheexchangeprocessparameters.The
between a light source and the specimen being evaluated.
residual stress determinations made on systems in which ion
exchange has occurred should be interpreted with those depen-
dencies in mind.
1
This test method is under the jurisdiction of ASTM Committee C14 on Glass
2
and Glass Products and is the direct responsibility of Subcommittee C14.10 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Glass Decoration. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Current edition approved June 1, 2004. Published June 2004. Originally Standards volume information, refer to the standard’s Document Summary page on
approved in 1987. Last previous edition approved in 2002 as C 978 - 02. the ASTM website.
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C978–04
3.2.4 residual stress—permanent stress that is resident in a methods, the polarizing microscope must be equipped with a
glassy matrix. Such residual stress may result either from heat rotatable analyzer element, having a scale graduated in degrees
treatment above the strain point of the glass, or from differ- of rotation, capable of being rea
...