A Study of the Stresses in Flashed Glasses

JSGT_1933_V17_T273_T286

The paper gives the results of a mathematical investigation into the stress distribution present in a system consisting of two or more glasses fused together. The stress distribution is first worked out for the case of a doublet system where the coefficients of expansion of the two glasses are slightly dissimilar. The two cases are distinguished, first, where the strip is free to bend, and secondly, where it is rigidly held at the ends, as this approximates to the conditions for the manufacture of such articles as globes. The effect of varying the thickness of the portions of the sheet is discussed, and curves arc drawn for the stress distribution, showing close agreement with actual photographs taken by means of a Babinet compensator. By a modification of the equations a method is indicated whereby an estimate of the difference in coefficient of expansion of two glasses can be obtained from a measurement of the curvature of two rods which are drawn together. In the second portion of the paper, the distribution is worked out for the case of three glasses fused together; and subsequently the practical case where the two outer glasses are of one composition, and the inner glass of another, is worked out in detail. Again, typical instances are computed and the results compared with actual photographs.

W. M. Hampton