NON-NEWTONIAN RHEOLOGY OF HOMOGENEOUS SILICATE MELTS

Several observations of non-Newtonian viscosity of silicate liquids at high stress or strain rates have been published in recent years. Howe ver, this phenomenon is not well understood yet. In this paper attenti on is drawn to the fact that steady state logarithmic values of reduce d viscosities of silicate liquids under high stress show a linear depe ndence on the squared value of the applied stress. This relationship s uggests that the elastic work done by the stress on the liquid is rela ted to the observed viscosity decreases. It is shown that the developm ent of non-Newtonian viscosity in silicate melts under high stress can be explained with the Adam and Gibbs (1965) theory, if one accepts th at this elastic work generates configurational entropy.