Molecular Dynamics Simulations Correlating Mechanical Property Changes of Alumina with Atomic Voids under Triaxial Tension Loading

Abstract

The functionalization of nanoporous ceramics for applications in healthcare and defence necessitates the study of the effects of geometric structures on their fundamental mechanical properties. However, there is a lack of research on their stiffness and fracture strength along diverse directions under multi-axial loading conditions, particularly with the existence of typical voids in the models. In this study, accurate atomic models and corresponding properties were meticulously selected and validated for further investigation. Comparisons were made between typical material geometric and elastic properties with measured results to ensure the reliability of the selected models. The mechanical behavior of nanoporous alumina under multiaxial stretching was explored through molecular dynamics simulations. The results indicated that the stiffness of nanoporous alumina ceramics under uniaxial tension was greater, while the fracture strength was lower compared to that under multiaxial loading. The fracture of nanoporous ceramics under multi-axial stretching, was mainly dominated by void and crack extension, atomic bond fracture, and cracking with different orientations. Furthermore, the effects of increasing strain rates on the void volume fraction were found to be similar across different initial radii. It was also found that the increasing tension loading rates had greater effects on decreasing the fracture strain. These findings provide additional insight into the fracture mechanisms of nanoporous ceramics under complex loading states, which can also contribute to the development of higher-scale models in the future.

Temperature-Dependent Elastic Properties of B4C from First-Principles Calculations and Phonon Modeling

“…By comparing the DFTcalculated elastic properties with data available in the literature and from experimental measurements, a comprehensive assessment of the accuracy and reliability of the DFT results can be achieved. Understanding elastic properties, including Young's modulus (E), shear modulus (G), bulk modulus (B), and Poisson's ratio (ν), is crucial for unraveling the behavior of materials, guiding predictions of failure mechanisms [33,75], understanding dynamic loading in ceramics [21,37], and recognizing temperature dependency [26,34] under extreme conditions.…”

“…Traditional methods for predicting the elastic properties of materials rely on empirical relationships, such as Hooke's law, which are based on experimental data and generally provide reasonable estimates for well-established materials [17]. However, these methods can be limited when applied to extreme conditions (e.g., very low or high temperatures [18], high pressure [19], and corrosive environments [20]), as well as for complex materials (e.g., advanced ceramics [21,22] and composites [23,24]). The elastic properties reported for boron carbide typically originate from room-temperature experimental setups.…”

“…Traditional methods often overlook factors like microstructural effects [23], anisotropy [33], and temperature dependence [34]. To address these challenges, advanced computational techniques, including first-principles methods [28,35,36], molecular dynamics simulations [21,37], and machine learning approaches [14,38], have been developed. These methods not only enable more accurate predictions of elastic properties, but also, when appropriately validated, can overcome the limitations of traditional approaches based solely on empirical relationships and experimental data [17,39].…”