arXiv subjects

Aarosh Dahal

Publications and source records attributed to Aarosh Dahal.

4 recordsLinked to original sources

arXiv2026

Adaptive Mesh Coarsening for Efficient Phase-Field Fracture Simulations

Phase-field models provide a versatile framework for simulating fracture nucleation and propagation without explicit crack tracking. Their principal computational challenge is the need to resolve a small regularization length with a sufficiently fine finite element mesh. This requirement can render uniform-mesh simulations prohibitively expensive, particularly for three-dimensional problems, problems involving distributed crack nucleation, and soft nearly incompressible materials. Adaptive mesh refinement offers a natural means of reducing this cost, but existing approaches often rely on heuristic refinement indicators, are primarily designed for problems containing pre-existing cracks, and retain increasingly large refined regions as cracks grow in size. This work presents an adaptive mesh coarsening framework along with adaptive mesh refinement for phase-field fracture. The coarsening strategy replaces the fractured region in the crack wake with a coarse crack band that preserves the essential mechanical behavior of a crack, making it necessary to have a refined mesh only in a small region near the tip of the growing crack. The method introduces a physics-based refinement indicator derived from the violation of the material strength surface, which is a necessary condition for fracture evolution. The indicator therefore robustly identifies regions where crack nucleation or propagation is imminent and can be applied across arbitrary materials, geometries, and loading conditions. The framework is implemented in parallel within FEniCSx; the supporting finite element codes are made available. Its generality and substantial computational benefit are demonstrated through benchmark problems involving crack propagation and nucleation under quasi-static and dynamic loading, for soft and hard materials, and for thermomechanical fracture.

cond-mat.mtrl-sci↗

arXiv2026

Dynamic phase-field model for brittle fracture in grounded glaciers

Fracture and calving of glaciers are key contributors to ice-mass loss and sea-level rise, yet predictive modeling remains challenging. Fracture in grounded glaciers is driven by gravitational forces and is typically studied within the framework of quasi-static linear elastic fracture mechanics. In this work, we show that purely quasistatic brittle fracture simulations within the phase field fracture framework under fixed self-weight can become strongly overdriven after crevasse initiation, producing unphysical thickening of the diffusive crack band and diffuse damage patterns. This pathology arises because gravity drives a growing region ahead of the crack tip beyond the strength surface. To resolve this, we show that the post-nucleation propagation is fundamentally a dynamic instability rather than a quasistatic process and propose the use of dynamic formulations of fracture. We demonstrate that accounting for inertia results in sharp, localized cracks that propagate through the ice thickness. As a second objective, this paper introduces a new dynamic formulation of the phase-field fracture model of Kumar et al. (J. Mech. Phys. Solids 2018) in which elastic, inertial, and gravitational contributions are degraded consistently in fractured regions.

cond-mat.mtrl-sci↗

arXiv2025

On failure mechanisms and load-parallel cracking in confined elastomeric layers

Thin layers of elastomers bonded to two rigid plates demonstrate unusual failure response. Historically, it has been believed that strongly-bonded layers fail by two distinct mechanisms: (i) internal/external penny-shaped crack nucleation and propagation, and (ii) cavitation, that is, cavity growth leading to fibrillation and then failure. However, recent work has demonstrated that cavitation itself is predominantly a fracture process. While the equations describing cavitation from a macroscopic or top-down view are now known and validated with experiments, several aspects of the cavitation crack growth need to be better understood. Notably, cavitation often involves through-thickness crack growth parallel to the loading direction, raising questions about when it initiates instead of the more typical penny-shaped cracks perpendicular to the load. Understanding and controlling the two vertical and horizontal crack growth is key to developing tougher soft films and adhesives. The purpose of this Letter is to provide an explanation for the load-parallel crack growth through a comprehensive numerical analysis and highlight the role of various material and geometrical parameters.

cond-mat.soft↗

arXiv2025

A comparison of phase field models of brittle fracture incorporating strength: I -- Mixed-mode loading

The classical variational phase-field model for brittle fracture effectively predicts the growth of large pre-existing cracks. However, the modeling of crack nucleation continues to be a significant challenge. Crack nucleation under uniform stress depends on the material's strength surface whose description is fundamentally incompatible with the energy-based Griffith propagation criterion. To address this, three main phase-field approaches have emerged, each attempting to reconcile material strength and toughness. The first, known as the classical variational approach, preserves the variational structure but fails to accurately incorporate the strength surface. In contrast, the other two approaches -- the complete nucleation and hybrid cohesive zone models -- sacrifice variational consistency. Among these, only the complete nucleation approach precisely accounts for the strength surface. All three approaches, especially the second one, deviate from the sharp variational theory of brittle fracture, raising concerns about their reliability in predicting the growth of cracks under non-mode-I loading. This paper evaluates precisely this issue. It is the first in a series of studies comparing the three approaches, systematically investigating crack growth under mode II, mode III, and mixed-mode loadings. The results confirm that the complete nucleation approach effectively predicts crack growth across all investigated problems, and its predictions agree well with those from other two approaches for tension-dominated cases. Additionally, the findings highlight that inaccurate accounting of the strength surface in the classical variational approach can influence crack path predictions. Lastly, they reveal that modifying the crack driving force to incorporate the strength surface in the hybrid cohesive zone approach causes crack propagation at an incorrect fracture toughness.

cond-mat.mtrl-sci↗