Relaxation by defect diffusion in an elastic amorphous medium

Abstract

An attempt is made to simplify the theory of relaxation through defect diffusion by regarding the excess volume in an amorphous medium as a continuously distributed species diffusing according to Fick’s law, that is, without interaction. The autocorrelation functions are estimated for the concentration of the excess volume itself — a well known result — and for the consequent shear strain components. Passage of the excess volume concentration above a given limit corresponds to the usual process of relaxation by the arrival of a point defect. Passage of the strain above a suitable limit corresponds to relaxation by the strain field of more distant defects.The first passage time problem is not so much solved as avoided by the introduction of a highly artificial relaxation process, reversal relaxation, which makes it straightforward to calculate a final relaxation function. Useful numerical tables and some sample taxation curves are shown.