Dynamics Simulations Of Mechanical Properties Research Articles

Molecular dynamics simulation of mechanical properties of decagonal quasicrystal approximate phase Al2Fe

By using the molecular dynamics method, the tensile and elastic mechanical properties of Al2Fe (tI6 and oF24) alloys for decagonal quasicrystals approximation are simulated. Structural models for tI6 and oF24 are first established and then the appropriate embedded atom method (EAM) potential function is selected to analyze the effects of temperature and strain rate on the stress-strain relation, atomic structure and deformation mechanism. Furthermore, all the elastic constants Cij of tI6 and oF24 are calculated by the molecular dynamics explicit deformation method, and the crystal structure and stability of tI6 and oF24 are also judged. Besides, the elastic mechanical properties of tI6 and oF24 including bulk modulus, shear modulus, elastic modulus, and Poisson's ratio, are derived by means of both the general formula and the independent crystal system formula. The results show that the elastic modulus and tensile strength of tI6 and oF24 almost decrease linearly with increasing temperature. An increase of strain rate has little effect on the elastic modulus of tI6 and oF24, but it can result in an obvious increase of the tensile strength and ultimate strain. By calculating, tI6 possesses a stable tetragonal crystal structure and oF24 has a stable orthorhombic crystal structure, which are consistent with the previous results derived by the first-principle. The Young's modulus, shear modulus and Poisson's ratio display high anisotropy except for the bulk modulus. The anisotropic of oF24 is higher than that of tI6, while the stiffness and hardness of tI6 are greater than those of oF24. The present work can provide a theoretical reference for analyzing the mechanical properties of the approximate phase of decagonal quasicrystal as well as a novel numerical calculation method for determining the mechanical properties of related materials.

Molecular dynamics simulation of mechanical properties of carbon nanotube reinforced cellulose.

Cellulose, hemicellulose, and lignin are the major chemical components in wood paper. Various types of wet and dry strength additives are used to enhance the optical and mechanical properties of recycled paper. One of the possible materials is the carbon nanotube. In order to explore the probability of the use of carbon nanotubes as reinforcing materials and to understand how carbon nanotubes affect the mechanical properties of paper, a single-walled carbon nanotube is inserted into a [Formula: see text] cellulose nanocrystal, and its mechanical properties are studied by using energy minimization and molecular dynamics (MD) simulations. During simulations, the crystals are stretched in the axial direction at a constant speed, and stress and strain are computed and recorded at the atomic level. Our results indicate that carbon nanotube can significantly enhance the mechanical properties of paper.

Atomistic modeling of the mechanical properties: the rise of machine learning interatomic potentials.

Since the birth of the concept of machine learning interatomic potentials (MLIPs) in 2007, a growing interest has been developed in the replacement of empirical interatomic potentials (EIPs) with MLIPs, in order to conduct more accurate and reliable molecular dynamics calculations. As an exciting novel progress, in the last couple of years the applications of MLIPs have been extended towards the analysis of mechanical and failure responses, providing novel opportunities not heretofore efficiently achievable, neither by EIPs nor by density functional theory (DFT) calculations. In this minireview, we first briefly discuss the basic concepts of MLIPs and outline popular strategies for developing a MLIP. Next, by considering several examples of recent studies, the robustness of MLIPs in the analysis of the mechanical properties will be highlighted, and their advantages over EIP and DFT methods will be emphasized. MLIPs furthermore offer astonishing capabilities to combine the robustness of the DFT method with continuum mechanics, enabling the first-principles multiscale modeling of mechanical properties of nanostructures at the continuum level. Last but not least, the common challenges of MLIP-based molecular dynamics simulations of mechanical properties are outlined and suggestions for future investigations are proposed.

Molecular dynamics simulation of mechanical properties of graphene reinforced natural rubber composites

Molecular dynamics simulation has been performed to compare the properties of graphene (GE) sheet reinforced natural rubber (NR) nanocomposites with pristine natural rubber. Three different molecular level models have been prepared, one for pristine natural rubber and the other two for 3.6% and 7.8% volume fraction of graphene in rubber nanocomposite. The Constant strain minimization approach is used to predict the mechanical properties of the developed molecular models. It has been observed that there is a significant increment of up to 83.37% in Young’s modulus, 40.06% in bulk modulus, and 23.24% in shear modulus by the addition of 7.8% volume fraction of graphene in NR nanocomposite, respectively.

Molecular dynamics simulations of mechanical properties of epoxy-amine: Cross-linker type and degree of conversion effects

Molecular dynamics (MD) simulations are conducted to study the thermo-mechanical properties of a family of thermosetting epoxy-amines. The crosslinked epoxy resin EPON862 with a series of cross-linkers is built and simulated under the polymer consistent force field (PCFF). Three types of curing agents (rigidity1,3-phenylenediamine (1,3-P), 4,4-diaminodiphenylmethane (DDM), and phenol-formaldehyde-ethylenediamine (PFE)) with different numbers of active sites are selected in the simulations. We focus on the effects of the cross-linkers on thermo-mechanical properties such as density, glass transition temperature (T g), elastic constants, and strength. Our simulations show a significant increase in the T g, Young’s modulus and yield stress with the increase in the degree of conversion. The simulation results reveal that the mechanical properties of thermosetting polymers are strongly dependent on the molecular structures of the cross-linker and network topological properties, such as end-to-end distance, crosslinking density and degree of conversion.

Molecular dynamics simulation of mechanical properties of nitrile rubber composites reinforced by carbon nanotube with different chirality and diameter

Molecular dynamics simulation of mechanical properties of nitrile rubber composites reinforced by carbon nanotube with different chirality and diameter

Molecular dynamics simulation of mechanical properties of intercalated GO/C-S-H nanocomposites

Graphene oxide (GO) cementitious composites have recently attracted considerable interest due to their improved mechanical properties and durability. However, most research is focused on the macroscale performance of these composites with very little experimental and modelling research on the characterization of their nanoscale behavior. This makes the design of these new GO-cementitious composites challenging. In this paper, we present a novel molecular dynamics (MD) model for GO-cementitious nanocomposites to understand their behavior and predict their mechanical and fracture properties. In this model, different numbers of GO nanoplatelets were inserted into the C-S-H structure and a number of nanoscale mechanical parameters and crack bridging mechanism were obtained. The MD simulation results revealed that the addition of GO sheets increased the tensile and compressive strength of C-S-H by roughly 50% and 100%. The MD simulation results also identified a double-peak phenomenon which is an indication of additional plasticity when the intercalated GO/C-S-H structures are subjected to compressive stress. The fracture simulation results showed that the failure mode of the intercalated GO/C-S-H composites was marked by high energy release. The results of fracture simulations with different notch lengths also indicated that the addition of GO could improve the fracture performance due to a good interfacial connection between the GO and the C-S-H gel.

Molecular dynamics simulations of mechanical properties of swollen nitrile rubber composites by incorporating carbon nanotubes

AbstractMolecular models of pure and 10% and 20% swollen nitrile rubber matrices were developed. Different amounts of carbon nanotubes (CNTs) were incorporated into the swollen nitrile rubber matrices. The effects of the swelling behaviors and introduced CNTs on the mechanical properties of the nitrile rubber matrices were investigated using molecular dynamics simulations. The simulation results show that compared to the pure nitrile‐butadiene rubber (NBR) models, the elastic moduli and tensile strengths of the nitrile rubber matrices were reduced by ~31.72% and 20.10% (at a swelling ratio of 10%) and 68.28% and 36.82% (at a swelling ratio of 20%), respectively. Compared to those of the swollen NBR models without CNTs, after the introduction of one CNT, the elastic modulus and tensile strength improved by ~67.02% and 4.17% (at a swelling ratio of 10%) and 215.27% and 7.00% (at a swelling ratio of 20%), respectively. The mechanical properties of the nitrile rubber matrix improved when the content of CNTs increased. The radial distribution functions of the rubber materials, interfacial energies of the reinforced regions, and mean square displacements and diffusion coefficients of the solutions were analyzed. The introduced CNTs blocked the diffusion of the solute in the nitrile rubber matrix. This study elucidates the swelling behaviors of rubber materials from an atomic perspective and mechanical properties of carbon‐nanotube‐reinforced swollen rubber matrices.

Molecular dynamics simulation of mechanical properties of polystyrene nanoparticles under uniaxial compression test

Chemical mechanical planarization (CMP) is an important step in the semiconductor technology. The surface of the wafer after CMP must be defect-free with low roughness. Polymer particles are one of the potential candidates for using as abrasive in CMP. Hence, studying mechanical properties of these abrasives is of great importance. In the current study, the size-dependence elastic modulus and hardness of polystyrene (PS) nanoparticles is investigated via molecular dynamics (MD) simulations. The effect of strain on elastic modulus and hardness is examined and also the impact of strain rate on the mechanical response of PS nanoparticles during compression is studied. Additionally, the pop-in event during loading is precisely examined using volumetric analysis and shear strain distribution inside the nanoparticles is investigated. The results show that the elastic modulus increases linearly by decreasing the particle size while the hardness has a non-linear behavior. The predictions are compared with empirical measurements and good agreement is accomplished.

Mechanical Properties of Soot Particles: The Impact of Crosslinked Polycyclic Aromatic Hydrocarbons

ABSTRACT In this paper, we estimate the degree of crosslinking within soot particles making use of reactive molecular dynamics simulations of mechanical properties of crosslinked polycyclic aromatic hydrocarbons (PAH). Representative systems of PAH (pyrene, coronene, ovalene and circumpyrene) with a density similar to soot and with varying degrees of crosslinking were built. Uniaxial tensile test simulations were carried out on the systems and the yield stress of each sample was calculated. The hardness was estimated from the yield stress using an empirical conversion constant and the obtained values were compared with nanoindentation experiments of soot particles. The results show that mature ethylene and diesel soot particles are expected to present a degree of crosslinking between 2.1–3.0 and 3.0–3.5, respectively, to have a value comparable to the hardness found experimentally. Finally, an MD simulation of nanoindentation of a particle of crosslinked coronene molecules provided an alternative means to compute the empirical constant used to convert the yield stress in hardness. These results reveal the importance of crosslinking reactions during soot maturation that give rise to a structure in which the majority of aromatics are aliphatically linked in a 3D network.

Molecular dynamics simulation of mechanical properties of nanocrystalline platinum: Grain-size and temperature effects

A series of molecular dynamics simulations has been carried out to study the mechanical properties of nanocrystalline platinum. The effects of average grain size and temperature on mechanical behaviors are discussed. The simulated uniaxial tensile results indicate the presence of a critical average grain size about 14.1 nm, for which there is an inversion of the conventional Hall-Petch relation at temperature of 300 K. The transition can be explained by a change of dominant deformation mechanism from dislocation motion for average grain size above 14.1 nm to grain boundary sliding for smaller grain size. The Young's modulus shows a linear relationship with the reciprocal of grain size, and the modulus of the grain boundary is about 42% of that of the grain core at 300 K. The parameters of mechanical properties, including Young's modulus, ultimate strength, yield stress and flow stress, decrease with the increase of temperature. It is noteworthy that the critical average grain size for the inversion of the Hall-Petch relation is sensitive to temperature and the Young's modulus has an approximate linear relation with the temperature. The results will accelerate its functional applications of nanocrystalline materials.

Molecular Dynamics Simulations of Mechanical Properties of C-S-H Structures with Varying Calcium-to-Silicon Ratios

Molecular Dynamics Simulations of Mechanical Properties of C-S-H Structures with Varying Calcium-to-Silicon Ratios

Molecular dynamics simulations of mechanical properties of monolayer MoS2

Based on the benchmark created by the first principle calculations, the effectiveness of different empirical potential functions, including CVFF1, CVFF2, SW and REBO potentials, on describing the mechanical behavior of single layer MoS2 (SLMoS2) are evaluated. The mechanical properties including the elastic modulus E, Poisson’s ratio ν, nonlinear elastic modulus D, failure stress and ultimate strain are considered. It is found that under a small deformation, the REBO and CVFF2 potentials can provide an effective description of the elastic behavior of SLMoS2; whereas under a large deformation, the SW potential gives a more accurate stress value and the CVFF2 potential can only predict the right value under biaxial tension. After modifying the cut-off distances in the REBO potential, the failure strain can be reasonably predicted by the REBO potential; whereas the failure stress will be overestimated by about 20–40% for biaxial and uniaxial tension. The present study can provide help on accurately understanding the mechanical behavior of SLMoS2.

Molecular Dynamics Simulation of Mechanical Properties for Poly(vinyl pyrrolidone)/Poly(vinyl alcohol) Hydrogel

Molecular Dynamics Simulation of Mechanical Properties for Poly(vinyl pyrrolidone)/Poly(vinyl alcohol) Hydrogel

Molecular dynamics simulations of mechanical properties for Cu(0 0 1)/Ni(0 0 1) twist boundaries

Molecular dynamics simulations were carried out to study the mechanical properties of Cu(001)/Ni(001) interface boundaries with different twist angles subjected to uniaxial loading. The results obtained revealed that square misfit dislocations networks can be observed when the twist angle was lower than 15.124°, and the density of misfit dislocations increased with increasing twist angle. Face defects were formed when the twist angle was higher than 15.124°. It has been found that the interface configuration had a significant effect on the interface strength of the Cu/Ni system. The yield stress was found to decrease first with increasing twist angle and it reached its lowest value at 5.906° twist angle. Subsequently, it increased with increasing twist angle till it reached its highest value at 15.124° of the latter; it then decreased again and finally became almost constant when the twist angle was larger than approximately 20°.

Molecular dynamics simulation of mechanical properties of TATB/fluorine-polymer PBXs along different surfaces

The mechanical properties of PBXs composed of the well-known insensitive explosive TATB (1,3,5-Triamino-2,4,6-trinitrobenzene) crystal and four kinds of typical fluorine-polymers, i.e. poly (vinylidene difluoride) (PVDF), polychlorotrifluoroethylene (PCTFE), fluorine rubber (F 2311 ) and fluorine resin (F2314) individually, have been simulated by molecular dynamics (MD) method. The results show that the mechanical properties of TATB can be effectively improved by blending with a small amount of fluorine-polymers. Different mechanical properties of PBXs are obtained by putting fluorine-polymer binders parallel to different crystalline surfaces. The whole effect of im-proving mechanical properties is found to be (010)≈(100)>(001).