Complexity in dislocation dynamics: experiments

We present a statistical analysis of the acoustic emissions induced by disl ocation motion during the creep of ice single crystals. The recorded acoust ic waves provide an indirect measure of the inelastic energy dissipated dur ing dislocation motion. Compression and torsion creep experiments indicate that viscoplastic deformation, even in the steady-state (secondary creep), is a complex and inhomogeneous process characterized by avalanches in the m otion of dislocations. The distribution of avalanche sizes, identified with the acoustic wave amplitude (or the acoustic wave energy), is found to fol low a power law with a cutoff at large amplitudes which depends on the cree p stage (primary, secondary, tertiary). These results suggest that viscopla stic deformation in ice and possibly in other materials could be described in the framework of non-equilibrium critical phenomena. (C) 2001 Elsevier S cience B.V. All rights reserved.