Influence of Regrinding Depth on Edge Strength of Tempered Glass

Abstract

Designers use exposed glass edges for decoration, for example within glass steps, glass beams or glass columns. This application requires a mechanical finishing to achieve a high optical quality by compensating a misalignment of the glasses, for example an edge displacement, or a supernatant of the foil resulting from the lamination process of safety glass. Regrinding of annealed glass is allowed without restrictions. In the case of tempered glass there is a risk of premature failure caused by a reduction of the compression zone. During a research project at the Institute of Building Construction, Technische Universität Dresden, the impact of the grinding depth of tempered glass on the bearing capacity of the edge is investigated. The goal is to give a strength value of reground tempered glass edges. We conducted four-point bending tests on glass beams about the strong axis in the style of EN 1288-3. The experimental investigation included 82 glass beams both made from fully tempered and heat strengthened glass in thicknesses of 6 mm with reground edges in varied grinding depths and additional reference specimens. The experimental investigation shows that an increasing grinding depth induces a decrease in edge strength. In the presented case, the result of the test series allows the definition of reduction factors for the calculation of the bending strength of glass beams with reground edges.