P2 – Atomistics of Crack-Heterogeneity Interactions

Motivation

The fracture of a brittle solid is crucially determined by material heterogeneities directly at the crack front where the stress field diverges and the usual homogenization strategies are no longer applicable. While this problem has attracted significant interest, currently no consistent theory that relates local changes in properties to the local fracture behavior and macroscopic failure criteria exists. In contrast to the long-range elastic interactions, the direct interaction of the crack front with heterogeneities cannot be described by continuum methods but requires an atomistic treatment.

Objectives

The aim of this project is to study the influence of various types of heterogeneities on the energy dissipation mechanisms in different classes of materials.

Work plan

Large-scale 3D atomistic simulations will be performed on (a) single-crystalline Si, which has clear preferred crystallographic cleavage planes (b) amorphous Si, which fractures by nucleation and coalescence of nanovoids and (c) amorphous silica as typical random network glass. The heterogeneities will take the form of voids, precipitates, or – in case of glasses – regions of reduced density.

Rough crack surfaces produced by the propagation of a crack in off-stoichiometric NiAl.