arXiv subjects

Gergely Molnár

Publications and source records attributed to Gergely Molnár.

4 recordsLinked to original sources

arXiv2026

How glass breaks -- Damage explains the difference between surface and fracture energies in amorphous silica

The difference between free surface energy and fracture toughness in amorphous silica is studied via multi-scale simulations. We combine the homogenization of a molecular dynamics fracture model with a phase-field approach to track and quantify the various energy contributions. We clearly separate free surface energy localized as potential energy on the surface and damage diffusion over a 16-23 A range around the crack path. The plastic contribution is negligible. These findings, which clarify brittle fracture mechanisms in amorphous materials, align with toughness measurements in silica.

cond-mat.mtrl-sci↗

arXiv2026

Fracture initiation in silicate glasses via a universal shear localization mechanism

Shear bands lie at the root of fracture initiation in bulk metallic glasses and amorphous polymers. For silicate glasses, in contrast, studies have largely emphasized permanent volumetric strain, commonly referred to as densification. Here we systematically investigate indentation-induced fracture in two distinct families of aluminoborosilicate glasses. The results demonstrate that plastic shear flow plays a decisive role in governing fracture initiation. In addition, molecular dynamics simulations reveal a pronounced composition dependence of softening associated with plastic shear flow, closely mirroring the experimentally observed propensity for strain localization. We conclude that silicate glasses conform to a universal pattern of rupture initiation governed by localization of shear-deformation, aligning with a broad range of amorphous materials, including bulk metallic glasses and glassy polymers.

cond-mat.soft↗

arXiv2025

Origins of phase-field crack widening in dynamic fragmentation explained

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.

physics.comp-ph↗

arXiv2024

Thermomechanical Dissipative behaviour of CuZr metallic glasses

We performed molecular dynamics simulations of Zr$_{50}$Cu$_{50}$ metallic glass samples submitted to mechanical deformation at different strain rates. The simultaneous measurements of the stress-strain curve, and of the temperature evolution during the cyclic mechanical load, are used to determine the thermo-mechanical constitutive laws at the continuum scale. It is shown that plastic deformation acts as a heat source, but strong finite size effects affect the unfolding of shear bands and its related dissipation rate. Finally, a thermo-mechanical constitutive law is proposed to reproduce quantitavely self-heating processes at different scales.

cond-mat.mtrl-sci↗