arXiv subjects

Abdelrahman Hussein

Publications and source records attributed to Abdelrahman Hussein.

4 recordsLinked to original sources

arXiv2026

A coupled fully kinetic hydrogen transport and ductile phase-field fracture framework for modeling hydrogen embrittlement

Modeling hydrogen embrittlement (HE) is a long-standing engineering challenge, which has experienced significant developments in recent years. Yet, there is a gap in modeling the effect of the kinetics of hydrogen segregation at dislocations and the resulting interaction between ductile tearing and hydrogen-induced brittle fracture. In this work, a comprehensive chemo-mechanical framework is developed by coupling the fully kinetic hydrogen transport model with the geometric phase-field fracture method. A novel driving force is proposed that utilizes a hyperbolic tangent function of stress triaxiality to ensure that plastic dissipation contributes to fracture only under tensile conditions, phenomenologically representing void-driven ductile damage. The model successfully predicts the hydrogen-dependent shift in damage initiation from the specimen core to the surface. More importantly, hydrogen segregation at dislocations was shown to be crucial for modeling the multiple surface cracking experimentally observed at the necking region. Furthermore, the framework captures the competition between loading rates and diffusion kinetics, resolving the transition from multiple circumferential surface cracking at high strain rates to center-initiated single crack at lower rates. Finally, the model reproduced the experimental J-resistance curves for compact tension specimens, showing the transition from ductile tearing to embrittled crack.

cond-mat.mtrl-sci↗

arXiv2025

Finite Element Theory for PHIMATS

This document summarizes the main concepts of the finite element (FE) theory and constitutive relations as implemented in the open-source code phase-field multiphysics materials simulator PHIMATS https://github.com/ahcomat/PHIMATS. PHIMATS is written in C++ and uses Python for pre- and post-processing. It provides tools for discretizing the weak form of partial differential equations (PDE), interfacing with PETSc data structures (Vec/Mat) and solvers (KSP/SNES). The framework supports both single-physics and coupled multiphysics problems primarily using staggered coupling schemes. Hands-on examples can be found in the CaseStudies directory on GitHub repository. Rather than detailing the derivations of specific models, this document focuses on the key mathematical formulations and numerical strategies used within the implementation. For in-depth theoretical discussions, the reader is encouraged to consult the references. For citing this document, please use: [Abdelrahman Hussein. Finite Element Theory for PHIMATS. 2025. doi: 10.48550/ARXIV.2502.16283].

math.NA↗

arXiv2024

The effect of grain boundary misorientation on hydrogen flux using a phase-field based diffusion and trapping model

Understanding hydrogen-grain boundary (GB) interactions is critical to the analysis of hydrogen embrittlement in metals. This work presents a mesoscale fully kinetic model to investigate the effect of GB misorientation on hydrogen diffusion and trapping using phase-field based representative volume elements (RVEs). The flux equation consists of three terms: a diffusive term and two terms for high and low angle grain boundary (H/LAGB) trapping. Uptake simulations showed that decreasing the grain size resulted in higher hydrogen content due to increasing the GB density. Permeation simulations showed that GBs are high flux paths due to their higher enrichment with hydrogen. Since HAGBs have higher enrichment than LAGBs, due to their higher trap-binding energy, they generally have the highest hydrogen flux. Nevertheless, the flux shows a convoluted behavior as it depends on the local concentration, alignment of GB with external concentration gradient as well as the GB network connectivity. Finally, decreasing the grain size resulted in a larger break-through time and a larger steady-state exit flux.

cond-mat.mtrl-sci↗

arXiv2024

Modeling the effect of grain boundary diffusivity and trapping on hydrogen transport using a phase-field compatible formulation

Hydrogen grain boundary (GB) trapping is widely accepted as the main cause for hydrogen induced intergranular failure. Several studies were conducted to unveil the role of GBs on hydrogen transport; however, a clear understanding is yet to be attained. This is due to the limitations of the state-of-the-art experimental procedures for such highly kinetic processes. In this study, we aim at providing a deeper understanding of hydrogen-GB interactions using full-field representative volume element (RVE). The phase-field method is chosen for generating RVEs, since it is the an appropriate numerical tool to represent GBs. A novel fully-kinetic formulation for hydrogen diffusion and GB trapping is presented, which is compatible with the phase-field based RVEs. GB diffusivity ($D_\mathrm{gb}$) and trap-binding energy ($E_\mathrm{gb}$) were used as parameters to understand the interactions between diffusion and GB trapping. Uptake and permeation simulations were performed with constant and gradient occupancy boundary conditions respectively. In both cases, increasing $E_\mathrm{gb}$, increased the hydrogen GB occupancy. The permeation simulations showed that the hydrogen flux along the GBs increased with increasing both, $D_\mathrm{gb}$ and, surprisingly, $E_\mathrm{gb}$. Since trapping increases the hydrogen occupancy along GBs, it also increases the occupancy gradients, resulting in a higher flux. This led to the conclusion that, in the case of an external occupancy gradient, GB trapping and diffusion cooperate, rather than compete, to increase the hydrogen flux. On the other hand, the decisive factor for the retention of hydrogen at the GBs in permeation simulations was $D_\mathrm{gb}$ rather than $E_\mathrm{gb}$.

cond-mat.mtrl-sci↗