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FRACTURE AT THIN GLASS EDGES
Professor John C. Lambropoulos Department of Mechanical Engineering Materials Science Program Laboratory for Laser Energetics
Friday, October 25, 2013
The problem of fracture at thin glass edges is important for optical components made of brittle materials, such as glasses and ceramics. Broken smart phone or tablet screens are obvious examples, as are chipped teeth. I will describe some recent exciting research work done by a group of undergraduate and graduate students during the past year at the University of Rochester. I will start with an introductory description of fracture in brittle materials, and how models can be used to assess manufacturing features such as surface microroughness and subsurface damage, and why surfaces are different from edges. I will extend these concepts to the case of thin edges, and argue that, based on our recent results, one may identify two regions of grinding-induced flaws or chips along edges: For deeper flaws (leading to reduced strength and greater fracture probability) the flaws are controlled by the manufacturing conditions, such as abrasive size. For shallower flaws (i.e. statistically stronger edges), the flaw size may be seen to be controlled by the glass material properties, in that different manufacturing conditions lead to similar edge strength. I will also describe some recent work indicating that, contrary to our usual perception of glass as a brittle material, glass is actually very ductile at the nm-scale, leading to the identification of manufacturing conditions and parameters that may entirely avoid brittle fracture.