Optimizing the cooling parameters for annealing of glass bottles by stress simulation according to the viscoelastic theory

Abstract

The anneahng 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 anneahng process, the heating of the entire glass bottle to the annealing temperature is fundamental. The heating-up time depends strongly on the initial temperature and the wall thickness of the bottles. The maximum cooling stresses in the bottle are located at the bend between bottle wall and bottom. The residual stress depends particularly on the cooling rate in the critical cooling zone and for the smaller part on the cooling rate in the cooling-down zone. The maximum residual stress in the bottle was fitted as an exponendal function of the cooling time.