ASTM C1377-97
(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: C 1377 – 97
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
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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.
1. Scope forces applied. At a point in which the stresses are calculated,
those same stresses also are measured using the instrument to
1.1 This test method covers calibration or verification of
be calibrated or verified. Since both the specimen dimension
calibration or both, of surface-stress measuring devices used to
and the applied forces can be established accurately using
measure stress in annealed and heat-strengthened or tempered
traceable (primary) standards, the method permits a fully
glass, using polariscopic or refractometry based principles.
traceable calibration of the stress-measuring instrument.
1.2 This test method is nondestructive.
1.3 This test method uses transmitted light, and therefore, is
5. Significance and Use
applicable to light-transmitting glasses.
5.1 The strength and performance of heat-strengthened and
1.4 This test method is not applicable to chemically tem-
fully tempered glass is greatly affected by the surface and edge
pered glass.
stress induced during the heat-treating process.
1.5 Using the procedure described, surface stresses can be
5.2 The edge and surface stress levels are specified in
measured only on the “tin” side of float glass.
Specification C 1048, in the Engineering Standards Manual of
1.6 This standard does not purport to address all of the
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GANA , and in foreign specifications.
safety concerns, if any, associated with its use. It is the
5.3 Surface stresses can be measured nondestructively using
responsibility of the user of this standard to establish appro-
methods, such as Test Method C 1279. The calibration of
priate safety and health practices and determine the applica-
surface measuring devices used in those procedures and
bility of regulatory limitations prior to use.
periodic verification of calibration are needed. This test method
offers a convenient way to accomplish this task.
2. Referenced Documents
6. Principle of Operation
2.1 ASTM Standards:
C 158 Test Methods for Strength of Glass by Flexurermi-
6.1 The instrument to be calibrated is placed on the surface
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nation of Modulus of Rupture
of the calibration specimen. Stresses at a point where the
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C 162 Terminology of Glass and Glass Products
instrument is placed are calculated using expressions shown in
C 770 Test Method for Measurements of Glass Stress—
Section 9. To increase the precision of measurement, several
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Optical Coefficient
levels of stress are produced by applying forces incrementally.
C 1048 Specification for Heat-Treated Flat Glass—Kind
Measurement of stress using the instrument to be calibrated is
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HS, Kind FT Coated and Uncoated Glass
repeated for each stress level and these measurements are used
C 1279 Test Method for Nondestructive Photoelastic Mea-
to calibrate the instrument.
surement of Edge and Surface Stresses in Annealed,
2 7. Test Specimens and Loading Schemes
Heat-Strengthened, and Fully Tempered Flat Glass
Two loading geometries can be practiced: cantilever and
3. Terminology
four-point bending.
7.1 Cantilever-Beam Specimen (Fig. 1)—the dimensions of
3.1 Definitions—For terminology used in this test method,
the specimen used for cantilever loading should be selected
refer to Terminology C 162.
within limits shown below:
4. Summary of Test Method
Thickness (t): 6 mm (0.22 in.) minimum
Width (w): 8t # w # 12t
4.1 In this test method, a test bar is subjected to bending
Length (L): 6w minimum
using deadweights or calibrated load-cells to introduce surface Distance to the point of measurement (L ): 4w
o
Clamped length: 1.5w
stresses that can be calculated from the specimen geometry and
7.1.1 A heat-strengthened or tempered specimen, with pol-
ished edges is preferred, but annealed specimens can be used if
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This test method is under the jurisdiction of ASTM Committee C-14 on Glass
the range of stress is less than 24.13 MPa (3500 psi).
and Glass Products and is the direct responsibility of Subcommittee C14.08 on Flat
Glass.
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Current edition approved Oct. 10, 1997. Published February 1998. GANA, Glass Association of North America, 3310 SW Harrison St., Topeka,
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Annual Book of ASTM Standards, Vol 15.02. KS 66611–2279.
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