Key parameters for the non-destructive quality control of thermally toughened safety glass

Currently, destructive tests are mandated in the factory production control of thermally toughened safety glass in accordance with EN 12150–1 to guarantee compliance with the specifications concerning the fracture pattern and bending tensile strength. Such tests are time-consuming and result in material losses. This study, therefore, investigates the potential of photoelastic measurements as a non-destructive, digital approach to evaluate toughening quality. European standards currently lack minimum values for photoelastic measurements. Therefore, this paper presents statistical analyses of experimental investigations of thermally toughened glass panes (360 mm x 1100 mm) in thicknesses of 6 mm, 8 mm, 10 mm and 12 mm. The experimental investigations combine photoelastic measurements of edge and surface stress with fracture and strength tests. Minimum values for photoelastic stresses are proposed based on quantile regression models to fulfil the requirements of EN 12150–1. These results provide a basis for incorporating non-destructive methods into routine quality assurance, thus contributing to more efficient and sustainable glass production processes. • Detecting positive Pearson correlations between photoelastic and destructive tests. • Establishing limit values of photoelastic tests via quantile regression models. • Quantifying the confidence intervals in dependence of the glass thickness. • Proposing reliable photoelastic limit values fulfilling the criteria of EN 12150-1.