Origins of phase-field crack widening in dynamic fragmentation explained

TL;DR

This paper explores the origins of phase-field crack widening during dynamic fragmentation, identifying unphysical wave trapping as a key factor, and proposes mass erosion to improve damage modeling accuracy.

Contribution

It reveals how wave interactions cause damage zone widening and introduces mass erosion to reduce spurious damage diffusion in phase-field fracture simulations.

Findings

Damage zones do not accurately represent free boundaries.

Wave interactions induce additional damage.

Mass erosion reduces damage diffusion and improves convergence.

Abstract

We investigate dynamic crack propagation and fragmentation with the phase-field fracture approach. The method was chosen for its ability to yield crack paths that are independent of the underlying mesh, thanks to the damage regularization zone. In dynamics, we observe a progressive widening of this regularization zone and attribute it to an unphysical trapping of elastic waves. We show that the damage zones do not represent free boundaries accurately and that wave interactions induce additional damage. We reveal how mass erosion, by conserving the elastic wave speed in the damaged regions, can be used to efficiently reduce the spurious diffusion of damage. Furthermore, we provide numerical evidence that dynamically propagating cracks in the phase-field formulation, both with and without mass erosion, converge to the predictions of linear elastic fracture mechanics. For vanishing regularization length, the crack speed and energy release rate become independent of the phase-field regularization length, provided that this length scale is small enough and the mesh fine enough to resolve the process zone.