ASTM C1279 – Standard Test Method for Non-Destructive Photoelastic Measurement of Edge and Surface Stresses in Annealed, Heat-Strengthened, and Fully Tempered Flat Glass
Description:
Significance and Use
5.1 The strength and performance of heat-strengthened and fully-tempered glass is greatly affected by the surface and edge stress induced during the heat-treating process.
5.2 The edge and surface stress levels are specified in Specification C1048, in the Engineering Standards Manual3 of GANA Tempering Division and in foreign specifications.
5.3 This test method offers a direct and convenient way to non-destructively determine the residual state of stress on the surface and at the edge of annealed and heat-treated glass.
Scope
1.1 This test method covers the determination of edge stresses and surface stresses in annealed, heat-strengthened, and fully tempered flat glass products.
1.2 This test method is non-destructive.
1.3 This test method uses transmitted light and is, therefore, applicable to light-transmitting glasses.
1.4 The 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 Surface-stress measuring instruments are designed for a specific range of surface index of refraction.
1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
ASTM C1275