Finite-element analysis of the residual stresses in tempered glass plates with holes or cut-outs

Due to the increased mechanical strength and with respect to safety, tempered and strengthened glass plates are increasingly employed in modern buildings as architectural and structural components. However, regarding the complete fragmentation by disturbing the equilibrated residual stress state in thermally toughened glass, drillings or cut-outs must be done before quenching the glass. The present paper demonstrates 3D results of the thermal tempering simulation by the Finite Element Method in order to calculate the residual stresses in the area of the holes or cut-outs of a tempered glass plate. A viscoelastic material behavior of the glass is considered for the simulation of the tempering process. The structural relaxation is taken into account using Narayanaswamy’s model. Due to different cooling rates of the convection areas such as edge, chamfer, hole’s inner surface and far-field area, heat transfer coefficients are estimated using experimental data from the literature. It is the objective of the paper to demonstrate the simulation of the residual stresses in tempered glasses with holes or cut-outs and to quantify the amount of temper stresses based on a variation of different geometrical parameters and the local heat transfer coefficient. The residual stresses are thus calculated varying the following parameters: the hole diameter, the plate thickness, different geometries of the cut-outs and heat transfer coefficient.