Study of Some Binary Silicate Glasses by Means of Reflection in Infrared

Abstract

Iracture and presence ol Raws showed the rods to be quite uniform in structure w i t h the exception 01 one break which had a defect and the value for which was not used in computing tlic averages. The tests were made with center loading o n nominal spans of 6, 2, and 1 in., respectively, employing rounded hardened-steel knife edges. Breaks occurred approximately midway between the lower knife-edges. This i5 '1 necessary condition because otherwise complicating factor5 such a5 flaws or specimen misalignment would disturb tlic acciiracy..In Olscn hydraulic teqting machine of 1000-lb. capacity was used for the ti-and 2-in. spans. An Olsen mechanical tc\ting machine of 10,000-lb. capacity was used for the 1-in. \pan. 'The stress rate was 250 lb. per sq. in. per sec. on the (i-atid %in. spans, but had to be lowered t o about 100 lb. per q. in. pcr sec. on the 1-in. span to keep the load properly bnlanccd during the test with the large mechanical machine 50 that the desired accuracy could be obtained. The small difference in these loading rates is not believed to he sufficient to have h'id an important effect on the results. Modulus of rupture and stress rate were calculated by means of the simple fortnula 2.547 X load X span diameter3 'btodulus of rupturc = IV. DataThe rods were quite straight and round (0.496 inch in diamrtcr) with smooth and uniform surface. They were tested without having any finishing operations done on them. The results are given in Table I and the averages have been plotted as a curveinFig. 1.The "correction factor" is arbitrarily taken as 1.00 for each specimen broken on a 6-in. span. The other correctionfactor values are the numbers by which the average modulus of rupture calculated by the simple formula for each rod on each span is multiplied to convert it to the value for the same original rod on the 6-in. span. The correction factors for the two sets of data are considered to be in excellent agreement. V. ConclusionsThe simple cross-bending formula for cylindrical rods gives modulus of rupture results that are much too high when specimens are broken on spans that are short compared with their diameter. Although the data are meager and only one material was tested, i t is considered probable that the curve of Fig. 1 represents good corrections for short-span tests of cylindrical rods composed of ceramics or other nonductile materials. I n general, however, rectangular bars are thought to be a more desirable shape for testing. No direct comparisons between rectangular and cylindrical specimens were made in the present work, although knowledge of the strength of the same mixture in the form of rectangular bars is in general agreement with the results presented for cylindrical rods. AcknowledgmentThe cooperation of Neil N. Ault in making these tests is gratefully acknowledged. The work was carried out in the Research and DevelopmentThe reflection method provides means of studying the 10-micron infrared region that contains the fundamental vibration of the silica lattice. Structural changes pro...

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