The Effect of Disorder on Crackling Noise in Fracture Phenomena

We study the effect of disorder on crackling noise accompanying the fracture of heterogeneous materials. Two different types of system are considered: we analyze the three-point bending of a bar shaped specimen where the boundary and loading conditions ensure that crackling occurs during the propagation of a single crack; then we study a bundle of fibers where noise emerges as a consequence of spatially uncorrelated stick-slip rearrangements. We show that bursts characterizing the jerky propagation of a crack have a power law size distribution with an exponent which does not depend on the amount of disorder. Our calculations revealed that varying the amount of disorder in a stick-slip system, a phase-transition occurs: at high disorder stick-slip rearrangements occur in small bursts, while at low disorder macroscopic avalanches snap the system. Our investigations demonstrate that the relevance of disorder on crackling noise is strongly influenced by the presence or absence of stress concentrations in the system.