Proceedings PaperScratch Diamond Test
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During its use, a spectacle lens is subjected to numerous different abrasive conditions (e.g. cleaning ; wipping) which make two types of surface scratches : Viscoelastic and brittle scratches. We present here a scratch testing machine (rayoscope) and a scratch diamond test which allows to reproduce these two kinds of scratches and to caracterize the material by : - The "scratch rupture resistance" which is equal to the load, called critical load Cc, applied on a known penetrator, at which begins the chips formation. - The "scratchability curve" which expresses the whole behaviour of the material until the critical load value Cc and which is obtained by recording the scratch width as a function of the load. The scratch resistance R then equals Cc/∝B where ∝= slope of the asymptote of the curve B = ordinate at the origin of the asymptote Cc= critical load The scratch resistance values are in good correlation with the wearing test results.