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THE SCRATCH‐RESISTING POWER OF GLASS AND ITS MEASUREMENT *
Author(s) -
Bailey James
Publication year - 1937
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1937.tb19856.x
Subject(s) - scratch , materials science , hardness , composite material , ball (mathematics) , vickers hardness test , microstructure , mathematics , geometry
A bstract Methods used by previous investigators yield valuable data but do not give the order of hardness of different glasses, nor do the results agree in many instances with usual conceptions of relative hardness. A study of the problem had indicated that the scratch resistance of a glass surface depends upon factors other than the mechanical strength of the body of the glass. An examination of used glass articles showed that the scratches could be divided roughly into two classes: surface abrasions and scratches produced by crushing the surface. The ability of one material to scratch another depends upon the velocity of motion and upon the refractoriness of the material forming the point. Preliminary work has shown that a test for the scratch‐resisting power of a glass surface should test the surface as it exists upon the article. The conditions causing the initial rupture of the surface should be used as a measure of the scratch‐resisting power of the particular surface. The method adopted for testing the surface consisted of rolling a 1/8‐inch diameter steel ball over the surface in such a manner that the pressure increased as the ball rolled along. The pressure at which the first conchoidal breaks occurred was used as a measure of the hardness. Natural surfaces such as those of drawn window glass vary in hardness. Fused silica glass has a value of 10 to 12 pounds, common window glass has values of about 25 pounds, while some glass with a high alumina content has much higher values. Ground and polished surfaces are softer than fire‐polished surfaces on the same glass, and strained glass has a harder surface than the same glass in the annealed state. Illustrations of various types of new scratches, weathering effects along scratches, weathering effects in cracks and fractures, and a series of the ball tracks left in a glass surface by the tests are shown.