Thermal strain and viscous flow of glass films

Abstract

The effect of viscous flow on thermal strain in fluids is especially significant for materials such as glass. Thermally strained glass flows to accommodate the volume change caused by expansion or contraction. Viscous flow is responsible for the observed phenomenon of stress relaxation which occurs during annealing of glass. In this paper we present a mathematical solution to the problem of viscous flow in thermally strained compressible fluids. This result is used to study thermal stress in glass films undergoing heating and cooling. The effect of viscous flow on thermal stress is demonstrated numerically and is used to explain experimental observations of stress relaxation in glass films which were reported elsewhere. This paper includes a general formulation of the mechanics of slow viscous flow of compressible Newtonian fluids in the presence of a thermal strain.