Viscoelastic material behavior: Models and discretization used in process simulator DIOS

It is a known fact that melted glass, such as SiO2, shows viscoelastic beha vior But in the range of processing temperatures the mechanical properties of SiO2 vary strongly. While below 800 degrees C the material behaves like an elastic solid, at temperatures above 1000 degrees C it shows nearly pure viscous properties. In this paper, the governing equation, the so-called c onstitutive equation, describing viscoelastic behavior, and its discretizat ion are presented, The oxide viscosity depends on the local amount of shear stresses which lea ds to inhomogeneous material behavior and a nonlinear theory. This new mech anical model was implemented into the process simulator DIOS-ISE, Some obta ined simulation results are shown and discussed.