Crackling noise in three-point bending of heterogeneous materials

TL;DR

This study investigates crackling noise during crack propagation in heterogeneous materials under three-point bending, revealing power-law distributions and the formation of a process zone ahead of the crack tip.

Contribution

It introduces a discrete element model to simulate crackling noise and analyzes the statistical properties and spatial structure of damage in quasi-brittle materials.

Findings

Fracture occurs in bursts with power-law size and waiting time distributions.

A scaling form for crackling noise characteristics is identified.

A process zone forms ahead of the crack tip with specific damage statistics.

Abstract

We study the crackling noise emerging during single crack propagation in a specimen under three-point bending conditions. Computer simulations are carried out in the framework of a discrete element model where the specimen is discretized in terms of convex polygons and cohesive elements are represented by beams. Computer simulations revealed that fracture proceeds in bursts whose size and waiting time distributions have a power law functional form with an exponential cutoff. Controlling the degree of brittleness of the sample by the amount of disorder, we obtain a scaling form for the characteristic quantities of crackling noise of quasi-brittle materials. Analyzing the spatial structure of damage we show that ahead of the crack tip a process zone is formed as a random sequence of broken and intact mesoscopic elements. We characterize the statistics of the shrinking and expanding steps of the process zone and determine the damage profile in the vicinity of the crack tip.