Modeling thermally activated deformation with a variety of obstacles, and its application to creep transients

A material is modeled as an array of a variety of coupled elements of varied strength, each of which is characterized by a slip probability that is a function of local stress and temperature. A stochastic cellular automaton is used to run simulations of nominally constant structure creep where simple rules are used to ensure rough compliance with mechanical equilibrium and compatibility. Three cases are studied that incorporate distinctly different statistical and spatial strength distributions. For all three simulation conditions, a general form of creep curve is obtained. The general form, when plotted as log(strain) vs. log(time), has a slope near unity at short and long times which are connected by a region of minimum slope. The slope of the central region increases systematically with increasing temperature. These features are consistent with several experimental observations. The same simulation can also provide reasonable predictions of anelastic backflow. This analysis can be of value in interpreting experimental observations in both forward and reverse creep transients. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.