Description of cyclic deformation processes with a stochastic model for inelastic behaviour of metals

Abstract The well-known phenomena connected with cyclic loading of metallic materials, such as Bauschinger effect, cyclic hardening or softening, or the occurence of saturated states, are caused by several mechanisms on the microscale, which depend on various influences, for example, type of material composition, temperature range in which the experiment is performed, or previous plastic deformations. Based on a stochastic model, which was developed by the authors and their coworkers in the last years, four typical mechanisms, which are responsible for these macroscopic effects, have been examined, and the resulting macroscopic constitutive model has been compared with results of experiments. The Bauschinger effect, which is connected with stored energy built up during loading in one direction and then supporting plastic deformations at load reversal, decreases the yield stress at opposite loading in the high and in the low temperature ranges. A similar effect, which is, however, strongly time-dependent, results in the high temperature range from recovery processes during unloading time intervals. In the examined cstochastic model, which results in Markov chains, the mentioned mechanismscan be included by transition probabilities for the stochastic process. Their interaction can be examined by numerical simulations of cyclic processes and compared with experimental results.