The effect of edge processing in thin glass for cold bending applications

Cold bent glass is nowadays of primary importance both for industrial and civil applications. In fact, thin glass with a maximum thickness of 1.5 mm is often part of a wide range of technological devices and architectural surfaces (e.g. touchscreens, displays, mirrors, optical instruments, claddings and building interiors). The manufacturing process of cold bent glass is generally considered faster and less demanding in terms of necessary equipment with respect to hot bending or casting techniques. On the contrary, both the design of the manufacturing procedure and of the products are still a challenge and they are mainly based on a trial and error approach. Generalized defects and imperfections are always present on the surface of the raw glass product, while another significant source of flaws is usually localized at the edges and it is associated with the specific cutting technique and edges processing. The aim of this work is to experimental investigate the influence of the edge processing on the failure strength of 1.5 mm glass plates by means of four point bending tests. Two edge conditions are taken into account: manual diamond cut and ground by hand-operated tool which introduces randomly diffused small-size flaws. Test results are then statistically assessed and compared with the stresses that arise during the cold bending process due to the imposed curvature. In the end, grinding somehow increases the level of damage as it increases the number of flaws. On the contrary, the improved uniformity of the damage leads to less scattered resistance values. These allows to achieve smaller curvature radii or, for a given design radius, it reduces accidental failures during the cold bending process.