Optimising The Cooling Parameters For Annealing Of Glass Bottles By Stress Simulation According To The Viscoelastic Theory

The annealing process of glass bottles was calculated by means of the stress simulation according to Narayanaswamy, a finite element method coded in ANSYS. The glass characteristics were described according to the viscoelastic theory. The change of glass properties was computed with the help of the fictive temperature, which is described by the relaxation function of the glass structure. For a successful annealing process, the heating of the entire glass bottle to the annealing temperature is fundamental. Heat-up time depends strongly on the initial temperature & wall thickness of the bottles. Maximum cooling stresses are located at the bend between bottle wall & bottom. Residual stress depends particularly on the cooling rate in the critical cooling zone. Maximum residual stress in the bottle was fitted as an exponential function of cooling time.