Sara Adibi - Academia.edu (original) (raw)
Papers by Sara Adibi
The MEAM potential for the Fe, Mn, Si, and C system is developed by employing a hierarchical mult... more The MEAM potential for the Fe, Mn, Si, and C system is developed by employing a hierarchical multiscale modeling paradigm to simulate low-alloy steels. Experimental information alongside first-principles calculations based on Density Functional Theory served as calibration data to develop and upscale the potential. The cohesive energy, lattice parameters, elastic constants, and vacancy and interstitial formation energies are used as target data for calibrating the single element potentials. The heat of formation and elastic constants of binary compounds and substitutional and interstitial formation energies serve as binary potential calibration data, while substitutional and interstitial pair binding energies aid in developing the ternary potential. Molecular dynamics simulations employing this model predict the thermal expansion coefficient, heat capacity, self-diffusion coefficients, and stacking fault energy for steel alloys comparable to those reported in the literature. NOTE: T...
Bulletin of the American Physical Society, 2017
Metallic glasses exhibit high strength and high hardness, but severe lack of tensile ductility. I... more Metallic glasses exhibit high strength and high hardness, but severe lack of tensile ductility. In order to improve the plasticity a new type of metallic glass architecture referred to as nanoglass has been recently proposed. In this work, we use molecular dynamics simulations to investigate the mechanical behavior of 2D Cu64Zr36 films nanoglass over a range of particle sizes. The architectures are generated using Voronoi tessellation in a procedure that qualitatively mimics the real synthesis approach. Results show that films with nanoglass architectures experience a transition from a localized deformation in the form of a single dominant shear band to a near homogeneous plastic deformation with decreasing particle size. This occurs because the interfacial regions act as preferred channels for plasticity, causing the generation of an interconnected motif of shear bands that depends on the microstructure particle size. These results highlight the intriguing effects of nanoglass arch...
We develop an Fe-C-H interatomic potential based on the modified embedded-atom method (MEAM) form... more We develop an Fe-C-H interatomic potential based on the modified embedded-atom method (MEAM) formalism based on density functional theory to enable large-scale modular dynamics simulations of carbon steel and hydrogen.
Extreme Mechanics Letters
Journal of Applied Physics
Here, we use molecular dynamics simulations as a tool to investigate vacancy clustering in pure a... more Here, we use molecular dynamics simulations as a tool to investigate vacancy clustering in pure aluminum single crystals. A 1% superconcentration of single vacancies are randomly introduced into an otherwise perfect lattice, and the system is allowed to evolve for 500 ns at an elevated temperature of 728 K. Under these conditions, the individual vacancies rapidly agglomerate into larger clusters to reduce their overall energy. The systems are then subject to mechanical deformation to failure. The results of a total of 35 molecular dynamics simulations are reported. The mechanical behavior of these systems is found to be highly sensitive to the vacancy cluster microstructure, with the largest cluster size being most closely correlated with the cavitation strength. Since the largest cluster size evolves, an interesting time–structure–property coupling governs the behavior of these supersaturated metals. Despite the idealizations of the microstructure and loading conditions, we find a remarkably favorable agreement with laser-driven spall experiments.
Scientific reports, Jan 27, 2015
In order to improve the properties of metallic glasses (MG) a new type of MG structure, composed ... more In order to improve the properties of metallic glasses (MG) a new type of MG structure, composed of nanoscale grains, referred to as nanoglass (NG), has been recently proposed. Here, we use large-scale molecular dynamics (MD) simulations of tensile loading to investigate the deformation and failure mechanisms of Cu64Zr36 NG nanopillars with large, experimentally accessible, 50 nm diameter. Our results reveal NG ductility and failure by necking below the average glassy grain size of 20 nm, in contrast to brittle failure by shear band propagation in MG nanopillars. Moreover, the results predict substantially larger ductility in NG nanopillars compared with previous predictions of MD simulations of bulk NG models with columnar grains. The results, in excellent agreement with experimental data, highlight the substantial enhancement of plasticity induced in experimentally relevant MG samples by the use of nanoglass architectures and point out to exciting novel applications of these mater...
RSC Adv., 2016
Large-scale molecular-dynamics simulations are used to investigate the mechanical properties of 5... more Large-scale molecular-dynamics simulations are used to investigate the mechanical properties of 50 nm diameter Cu64Zr36 nanolaminate nanopillars constructed from 5 nm thick layers of metallic glass (MG) or MG and 5 nm grain sized nanoglass.
Extreme Mechanics Letters, 2015
Experiments show an intriguing brittle-to-ductile transition on size reduction on nanoscale metal... more Experiments show an intriguing brittle-to-ductile transition on size reduction on nanoscale metallic glasses (MGs). Here we demonstrate that such phenomena is linked to a fundamental characteristic size effect in the failure mode under tensile loading. Large-scale molecular dynamics simulations reveal that nanoscaled MGs with atomistically smooth surface exhibit catastrophic failure via sharp, localized shear band propagation. In contrast, nanosized specimens with surface imperfections exhibit a clear transition from shear banding to necking instability above a critical roughness ratio of ~ 1/20, defined as the ratio between the average surface imperfection size and sample diameter. The observed brittle-to-ductile transition that emerges in nanosized MGs deformed at room temperature can be strongly attributed to this roughness argument. In addition, the results suggest that the suppression of brittle failure may be scale-free and be realizable on length scales much beyond those considered here, provided the threshold roughness ratio is exceeded. The fundamental critical roughness ratio demonstrated sheds light on the complex mechanical behavior of amorphous metals and has implications for the application of MGs in nano-and micro-devices.
A refined sandwich beam model is proposed in the present work. The facing layers respect Euler-Be... more A refined sandwich beam model is proposed in the present work. The facing layers respect Euler-Bernoulli assumptions and the core is modeled with the third-order shear deformation theory (TSDT). In the Von Karman sense, the geometrically nonlinear relations between displacement fields and strains are developed. In what follows, a theoretical variational formulation of the problem is presented and then used to develop the electromechanically coupled finite element model of multilayer sandwich beam with considering mechanical DoFs as well as the electric ones. Finally, the nonlinear system of equations is linearized. It is shown that natural frequencies can change considerably for higher applied voltage to extensional piezoelectric layers. Introduction With respect to widely use of smart structures with piezoelectric actuators and sensors, modeling of these structures is a major concern for many engineers. Many papers report on various models for piezoelectric actuators which are norm...
Journal of Applied Physics, 2014
Applied Physics Letters, 2015
A refined sandwich beam model is proposed in the present work. The facing layers respect Euler-Be... more A refined sandwich beam model is proposed in the present work. The facing layers respect Euler-Bernoulli assumptions and the core is modeled with the thirdorder shear deformation theory (TSDT). In the Von Karman sense, the geometrically nonlinear relations between displacement fields and strains are developed. In what follows, a theoretical variational formulation of the problem is presented and then used to develop the electromechanically coupled finite element model of multilayer sandwich beam with considering mechanical DoFs as well as the electric ones. Finally, the nonlinear system of equations is linearized. It is shown that natural frequencies can change considerably for higher applied voltage to extensional piezoelectric layers.
The MEAM potential for the Fe, Mn, Si, and C system is developed by employing a hierarchical mult... more The MEAM potential for the Fe, Mn, Si, and C system is developed by employing a hierarchical multiscale modeling paradigm to simulate low-alloy steels. Experimental information alongside first-principles calculations based on Density Functional Theory served as calibration data to develop and upscale the potential. The cohesive energy, lattice parameters, elastic constants, and vacancy and interstitial formation energies are used as target data for calibrating the single element potentials. The heat of formation and elastic constants of binary compounds and substitutional and interstitial formation energies serve as binary potential calibration data, while substitutional and interstitial pair binding energies aid in developing the ternary potential. Molecular dynamics simulations employing this model predict the thermal expansion coefficient, heat capacity, self-diffusion coefficients, and stacking fault energy for steel alloys comparable to those reported in the literature. NOTE: T...
Bulletin of the American Physical Society, 2017
Metallic glasses exhibit high strength and high hardness, but severe lack of tensile ductility. I... more Metallic glasses exhibit high strength and high hardness, but severe lack of tensile ductility. In order to improve the plasticity a new type of metallic glass architecture referred to as nanoglass has been recently proposed. In this work, we use molecular dynamics simulations to investigate the mechanical behavior of 2D Cu64Zr36 films nanoglass over a range of particle sizes. The architectures are generated using Voronoi tessellation in a procedure that qualitatively mimics the real synthesis approach. Results show that films with nanoglass architectures experience a transition from a localized deformation in the form of a single dominant shear band to a near homogeneous plastic deformation with decreasing particle size. This occurs because the interfacial regions act as preferred channels for plasticity, causing the generation of an interconnected motif of shear bands that depends on the microstructure particle size. These results highlight the intriguing effects of nanoglass arch...
We develop an Fe-C-H interatomic potential based on the modified embedded-atom method (MEAM) form... more We develop an Fe-C-H interatomic potential based on the modified embedded-atom method (MEAM) formalism based on density functional theory to enable large-scale modular dynamics simulations of carbon steel and hydrogen.
Extreme Mechanics Letters
Journal of Applied Physics
Here, we use molecular dynamics simulations as a tool to investigate vacancy clustering in pure a... more Here, we use molecular dynamics simulations as a tool to investigate vacancy clustering in pure aluminum single crystals. A 1% superconcentration of single vacancies are randomly introduced into an otherwise perfect lattice, and the system is allowed to evolve for 500 ns at an elevated temperature of 728 K. Under these conditions, the individual vacancies rapidly agglomerate into larger clusters to reduce their overall energy. The systems are then subject to mechanical deformation to failure. The results of a total of 35 molecular dynamics simulations are reported. The mechanical behavior of these systems is found to be highly sensitive to the vacancy cluster microstructure, with the largest cluster size being most closely correlated with the cavitation strength. Since the largest cluster size evolves, an interesting time–structure–property coupling governs the behavior of these supersaturated metals. Despite the idealizations of the microstructure and loading conditions, we find a remarkably favorable agreement with laser-driven spall experiments.
Scientific reports, Jan 27, 2015
In order to improve the properties of metallic glasses (MG) a new type of MG structure, composed ... more In order to improve the properties of metallic glasses (MG) a new type of MG structure, composed of nanoscale grains, referred to as nanoglass (NG), has been recently proposed. Here, we use large-scale molecular dynamics (MD) simulations of tensile loading to investigate the deformation and failure mechanisms of Cu64Zr36 NG nanopillars with large, experimentally accessible, 50 nm diameter. Our results reveal NG ductility and failure by necking below the average glassy grain size of 20 nm, in contrast to brittle failure by shear band propagation in MG nanopillars. Moreover, the results predict substantially larger ductility in NG nanopillars compared with previous predictions of MD simulations of bulk NG models with columnar grains. The results, in excellent agreement with experimental data, highlight the substantial enhancement of plasticity induced in experimentally relevant MG samples by the use of nanoglass architectures and point out to exciting novel applications of these mater...
RSC Adv., 2016
Large-scale molecular-dynamics simulations are used to investigate the mechanical properties of 5... more Large-scale molecular-dynamics simulations are used to investigate the mechanical properties of 50 nm diameter Cu64Zr36 nanolaminate nanopillars constructed from 5 nm thick layers of metallic glass (MG) or MG and 5 nm grain sized nanoglass.
Extreme Mechanics Letters, 2015
Experiments show an intriguing brittle-to-ductile transition on size reduction on nanoscale metal... more Experiments show an intriguing brittle-to-ductile transition on size reduction on nanoscale metallic glasses (MGs). Here we demonstrate that such phenomena is linked to a fundamental characteristic size effect in the failure mode under tensile loading. Large-scale molecular dynamics simulations reveal that nanoscaled MGs with atomistically smooth surface exhibit catastrophic failure via sharp, localized shear band propagation. In contrast, nanosized specimens with surface imperfections exhibit a clear transition from shear banding to necking instability above a critical roughness ratio of ~ 1/20, defined as the ratio between the average surface imperfection size and sample diameter. The observed brittle-to-ductile transition that emerges in nanosized MGs deformed at room temperature can be strongly attributed to this roughness argument. In addition, the results suggest that the suppression of brittle failure may be scale-free and be realizable on length scales much beyond those considered here, provided the threshold roughness ratio is exceeded. The fundamental critical roughness ratio demonstrated sheds light on the complex mechanical behavior of amorphous metals and has implications for the application of MGs in nano-and micro-devices.
A refined sandwich beam model is proposed in the present work. The facing layers respect Euler-Be... more A refined sandwich beam model is proposed in the present work. The facing layers respect Euler-Bernoulli assumptions and the core is modeled with the third-order shear deformation theory (TSDT). In the Von Karman sense, the geometrically nonlinear relations between displacement fields and strains are developed. In what follows, a theoretical variational formulation of the problem is presented and then used to develop the electromechanically coupled finite element model of multilayer sandwich beam with considering mechanical DoFs as well as the electric ones. Finally, the nonlinear system of equations is linearized. It is shown that natural frequencies can change considerably for higher applied voltage to extensional piezoelectric layers. Introduction With respect to widely use of smart structures with piezoelectric actuators and sensors, modeling of these structures is a major concern for many engineers. Many papers report on various models for piezoelectric actuators which are norm...
Journal of Applied Physics, 2014
Applied Physics Letters, 2015
A refined sandwich beam model is proposed in the present work. The facing layers respect Euler-Be... more A refined sandwich beam model is proposed in the present work. The facing layers respect Euler-Bernoulli assumptions and the core is modeled with the thirdorder shear deformation theory (TSDT). In the Von Karman sense, the geometrically nonlinear relations between displacement fields and strains are developed. In what follows, a theoretical variational formulation of the problem is presented and then used to develop the electromechanically coupled finite element model of multilayer sandwich beam with considering mechanical DoFs as well as the electric ones. Finally, the nonlinear system of equations is linearized. It is shown that natural frequencies can change considerably for higher applied voltage to extensional piezoelectric layers.