ASTM C1377-97(2003)e1
(Test Method)Standard Test Method for Calibration of Surface/Stress Measuring Devices
Standard Test Method for Calibration of Surface/Stress Measuring Devices
SCOPE
1.1 This test method covers calibration or verification of calibration or both, of surface-stress measuring devices used to measure stress in annealed and heat-strengthened or tempered glass, using polariscopic or refractometry based principles.
1.2 This test method is nondestructive.
1.3 This test method uses transmitted light, and therefore, is applicable to light-transmitting glasses.
1.4 This test method is not applicable to chemically tempered glass.
1.5 Using the procedure described, surface stresses can be measured only on the "tin" side of float glass.
1.6 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:C1377–97 (Reapproved 2003)
Standard Test Method for
Calibration of Surface/Stress Measuring Devices
This standard is issued under the fixed designation C 1377; 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.
e NOTE—Figure 1 was editorially corrected in February 2005.
1. Scope 4. Summary of Test Method
1.1 This test method covers calibration or verification of 4.1 In this test method, a test bar is subjected to bending
calibration,orboth,ofsurface-stressmeasuringdevicesusedto using deadweights or calibrated load-cells to introduce surface
measure stress in annealed and heat-strengthened or tempered stressesthatcanbecalculatedfromthespecimengeometryand
glass using polariscopic or refractometry based principles. forces applied. At a point in which the stresses are calculated,
1.2 This test method is nondestructive. those same stresses also are measured using the instrument to
1.3 This test method uses transmitted light, and therefore, is be calibrated or verified. Since both the specimen dimension
applicable to light-transmitting glasses. and the applied forces can be established accurately using
1.4 This test method is not applicable to chemically tem- traceable (primary) standards, the method permits a fully
pered glass. traceable calibration of the stress-measuring instrument.
1.5 Using the procedure described, surface stresses can be
5. Significance and Use
measured only on the “tin” side of float glass.
1.6 This standard does not purport to address all of the 5.1 The strength and performance of heat-strengthened and
fully tempered glass is greatly affected by the surface and edge
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- stress induced during the heat-treating process.
5.2 The edge and surface stress levels are specified in
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. Specification C 1048, in the Engineering Standards Manual of
GANA , and in foreign specifications.
2. Referenced Documents
5.3 Surfacestressescanbemeasurednondestructivelyusing
2.1 ASTM Standards: methods, such as Test Method C 1279. The calibration of
C 158 Test Methods for Strength of Glass by Flexure surface measuring devices used in those procedures and
(Determination of Modulus of Rupture) periodicverificationofcalibrationareneeded.Thistestmethod
C 162 Terminology of Glass and Glass Products offers a convenient way to accomplish this task.
C 770 Test Method for Measurements of Glass Stress—
6. Principle of Operation
Optical Coefficient
C 1048 Specification for Heat-Treated Flat Glass—Kind 6.1 The instrument to be calibrated is placed on the surface
of the calibration specimen. Stresses at a point where the
HS, Kind FT Coated and Uncoated Glass
instrument is placed are calculated using expressions shown in
C 1279 Test Method for Nondestructive Photoelastic Mea-
surement of Edge and Surface Stresses in Annealed, Section 9. To increase the precision of measurement, several
levels of stress are produced by applying forces incrementally.
Heat-Strengthened, and Fully Tempered Flat Glass
Measurement of stress using the instrument to be calibrated is
3. Terminology
repeated for each stress level and these measurements are used
3.1 Definitions—For terminology used in this test method, to calibrate the instrument.
refer to Terminology C 162.
7. Test Specimens and Loading Schemes
1 Two loading geometries can be practiced: cantilever and
This test method is under the jurisdiction of ASTM Committee C14 on Glass
four-point bending.
and Glass Products and is the direct responsibility of Subcommittee C14.08 on Flat
Glass.
Current edition approved Oct. 1, 2003. Published October 2003. Originally
approved in 1997. Last previous edition approved in 1997 as C 1377 – 97.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contactASTM Customer Service at service@astm.org. ForAnnual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on GANA, Glass Association of North America, 3310 SW Harrison St., Topeka,
the ASTM website. KS 66611–2279.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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C1377–97 (2003)
7.1 Cantilever-Beam Specimen (Fig. 1)—the dimensions of clampingsurfaces,withroundededges,asshowninFig.3.The
the specimen used for cantilever loading should be selected forces can be applied using a calibrated testing machine or
within limits shown below: dead weights, by means of knife edges, to insure exact
positioning of the line-of-loading B-B. The pad used for load
Thickness (t): 6 mm (0.22 in.) minimum
Width (w): 8t# w# 12t
application can be secured from slipping using high-friction
Length (L): 6w minimum
materials. To eliminate possible twisting action, the knife edge
Distance to the point of measurement (L ): 4w
o
should be narrow, or a steel ball used to center the point of
Clamped length: 1.5w
application of force.
7.1.1 A heat-strengthened or tempered specimen, with pol-
7.3.2 Four-Point Bending Specimen—In the case of four-
ished edges is preferred, but annealed specimens can be used if
point bending, the force must be applied equally at two points,
the range of stress is less than 24.13 MPa (3500 psi).
and two articulated knives or roller supports are required to
7.2 Four-Point Bending Specimen (Fig. 2)—The four-point
ascertainaccuratelythelength L and L .Particularprecautions
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