The dynamics of crack front waves in 3D material failure

TL;DR

This paper investigates the behavior of crack front waves in 3D materials using a phase-field model, revealing their dynamics, interactions, and the effects of out-of-plane perturbations on their propagation.

Contribution

It introduces a 3D phase-field framework to study crack front wave dynamics, including nonlinear effects and out-of-plane interactions, with quantitative reproduction of high-speed oscillatory instability.

Findings

In-plane FWs show weak time dependence and solitonic interactions.

Nonlinear in-plane FWs propagate slower than linear predictions.

Out-of-plane FWs are excited by symmetry-breaking perturbations and can be persistent with anti-plane loading.

Abstract

Crack front waves (FWs) are dynamic objects that propagate along moving crack fronts in 3D materials. We study FW dynamics in the framework of a 3D phase-field framework that features a rate-dependent fracture energy $\Gamma(v)$ ($v$ is the crack propagation velocity) and intrinsic lengthscales, and quantitatively reproduces the high-speed oscillatory instability in the quasi-2D limit. We show that in-plane FWs feature a rather weak time dependence, with decay rate that increases with $d\Gamma(v)/dv\!>\!0$, and largely retain their properties upon FW-FW interactions, similarly to a related experimentally-observed solitonic behavior. Driving in-plane FWs into the nonlinear regime, we find that they propagate slower than predicted by a linear perturbation theory. Finally, by introducing small out-of-plane symmetry-breaking perturbations, coupled in- and out-of-plane FWs are excited, but the out-of-plane component decays under pure tensile loading. Yet, including a small anti-plane loading component gives rise to persistent coupled in- and out-of-plane FWs.