Special Seminar | Eran Bouchbinder

Topological defects and multi-plane crack interactions in materials failure
Crack propagation is the main dynamical process that mediates materials failure. Even under the simplest conditions involving slow, initially planar, crack propagation in nominally homogeneous three-dimensional materials (i.e., materials featuring no mesoscopic structures) under applied tensile (opening) loading, the emerging fracture surfaces reveal complex out-of-plane patterns. A generic pattern is a symmetry-breaking topological defect, corresponding to two crack fronts simultaneously propagating at different fracture planes and separated by a step. The origin of these crack front topological defects and their characteristic lengthscale are far from understood. We show that these defects/steps emerge from an interplay between finite-amplitude quenched disorder and anti-plane shear loading fluctuations, and grow out of surface roughness ridges. We then show that the step size is determined by an intrinsic lengthscale associated with the intense deformation near crack fronts. The implications of these results for understanding materials failure, as well as open questions, are briefly discussed.