The effect of disorder on the fracture nucleation process

The statistical properties of failure are studied in a fiber bundle model w ith thermal noise. We show that the macroscopic failure is produced by a th ermal activation of microcracks. Most importantly, the effective temperatur e of the system is amplified by the spatial disorder (heterogeneity) of the fiber bundle. The case of a time-dependent force and the validity of the K aiser effects are also discussed. These results can give more insight to th e recent experimental observations on thermally activated crack and can be useful to study the failure of electrical networks. (C) 2001 Elsevier Scien ce B.V. All rights reserved.