Study of Helium Bubble Induced Hardening in BCC-Fe by Molecular Dynamics Simulation

2019 ◽  
Vol 944 ◽  
pp. 378-386
Author(s):  
Li Xia Jia ◽  
Xin Fu He ◽  
Shi Wu ◽  
Dong Jie Wang ◽  
Han Cao ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Edge Dislocation ◽  
Reasonable Agreement ◽  
Md Simulation ◽  
Md Simulations ◽  
Defect Size ◽  
Dynamics Simulation ◽  
Helium Bubble ◽  
Increasing Temperature ◽  
Critical Resolved Shear Stress

The interaction between an moving edge dislocation and helium bubble was studied in BCC-Fe using Molecular dynamics（MD）simulation. Edge dislocation passed the bubble via cut mechanism. A step with a length of b is left on both sides of the bubble after dislocation left away. The influence of simulation temperature, defect size and He/V ratio in bubble on critical resolved shear stress (CRSS) for dislocation to shear bubble were investigated. The CRSS increases with increasing defect sizes, and decreases with increasing temperature. When He/V ratio is at the range of 0-1, CRSS depends weakly on the He/V ratio. The estimated obstacle strength of helium bubble based on MD simulations is acceptable and reasonable agreement with one deduced from the dispersion barrier-hardening model applied to experimental results.

STUDY OF AFFINITIES BETWEEN SINGLE-WALLED NANOTUBE AND EPOXY RESIN USING MOLECULAR DYNAMICS SIMULATION

2006 ◽  
Vol 05 (01) ◽  
pp. 131-144 ◽  
Author(s):  
JIHUA GOU ◽  
BIN FAN ◽  
GANGBING SONG ◽  
AURANGZEB KHAN
Keyword(s):  
Molecular Dynamics ◽  
Epoxy Resin ◽  
Md Simulation ◽  
Average Distance ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Repulsive Interaction ◽  
Curing Agent ◽  
Single Walled Nanotubes ◽  
Simulation Results

In the processing of carbon nanotube/polymer composites, the interactions between the nanotube and polymer matrix will occur at the molecular level. Understanding their interactions before curing is crucial for nanocomposites processing. In this study, molecular dynamics (MD) simulations were employed to reveal molecular interactions between (10, 10) single-walled nanotube and two kinds of epoxy resin systems. The two kinds of resin systems were EPON 862/EPI-CURE W curing agent (DETDA) and DGEBA (diglycidylether of bisphenol A)diethylenetriamine (DETA) curing agent. The MD simulation results show that the EPON 862, DETDA and DGEBA molecules had strong attractive interactions with single-walled nanotubes and their molecules changed their conformation to align their aromatic rings parallel to the nanotube surface due to π-stacking effect, whereas the DETA molecule had a repulsive interaction with the single-walled nanotubes. The interaction energies of the molecular systems were also calculated. Furthermore, an affinity index (AI) of the average distance between the atoms of the resin molecule and nanotube surface was defined to quantify the affinities between the nanotubes and resin molecules. The MD simulation results show that the EPON 862/EPI-CURE W curing agent system has good affinities with single-walled nanotubes.

Establishing a data-based scattering kernel model for gas–solid interaction by molecular dynamics simulation

2021 ◽  
Vol 928 ◽  
Author(s):  
Zijing Wang ◽  
Chengqian Song ◽  
Fenghua Qin ◽  
Xisheng Luo
Keyword(s):  
Machine Learning ◽  
Molecular Dynamics ◽  
Md Simulation ◽  
Rarefied Gas ◽  
Interaction Model ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Rarefied Gas Flows ◽  
Accommodation Coefficients ◽  
Scattering Kernel

Scattering kernel models for gas–solid interaction are crucial for rarefied gas flows and microscale flows. However, most existing models depend on certain accommodation coefficients (ACs). We propose here to construct a data-based model using molecular dynamics (MD) simulation and machine learning. The gas–solid interaction is first modelled by 100 000 MD simulations of a single gas molecule reflecting on the wall surface, which is fulfilled by GPU parallel technology. The results showed a correlation of the reflection velocity with the incidence velocity in the same direction, and also revealed correlations that may exist in different directions, which are neglected by the traditional gas–solid interaction model. Inspired by the sophisticated Cercignani–Lampis–Lord (CLL) model, two improved scattering kernels were constructed to better reproduce the probability density of velocity determined from MD simulation. The first one adopts variable ACs which depend on the incidence velocity and the second one combines three CLL-like kernels. All the parameters in the improved kernels are automatically chosen by the machine learning method. Compared with the numerical experiments of a molecular beam, the reconstructed scattering kernels are basically consistent with the MD results.

Molecular Dynamics Simulation of Interaction between Screw Dislocation and Copper Precipitate in Iron

2008 ◽  
Vol 33-37 ◽  
pp. 895-900 ◽  
Author(s):  
Akiyuki Takahashi ◽  
Yuji Aoki ◽  
Masanori Kikuchi
Keyword(s):  
Molecular Dynamics ◽  
Shear Stress ◽  
Molecular Dynamics Simulation ◽  
Screw Dislocation ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Peierls Stress ◽  
Attractive Interaction ◽  
Good Prediction ◽  
Critical Resolved Shear Stress

This paper provides the results of the MD simulations of the interaction between a screw dislocation and a copper precipitate in iron. From the results, the screw dislocation has an attractive interaction with the copper precipitate. Also, the dependence of the Critical Resolved Shear Stress (CRSS) for the screw dislocation to break away from the copper precipitate on the size of the precipitate and temperature is studied. Finally, the CRSS obtained by the MD simulations is modeled statistically using a Russel-Brown model. Then we found that an addition of the Peierls stress, which is calculated by the MD simulations, to the Russel-Brown model gives a good prediction of the CRSS.

Molecular Dynamics Simulation on Effect of Nanoparticle Aggregation on Transport Properties of a Nanofluid1

2012 ◽  
Vol 3 (2) ◽  
Author(s):  
Hongbo Kang ◽  
Yuwen Zhang ◽  
Mo Yang ◽  
Ling Li
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Transport Properties ◽  
Periodic Boundary Condition ◽  
Md Simulation ◽  
Periodic Boundary ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Nanoparticle Aggregation ◽  
Nanoparticle Cluster

Effect of nanoparticle aggregation on the transport properties that include thermal conductivity and viscosity of nanofluids is studied by molecular dynamics (MD) simulation. Unlike many other MD simulations on nanofluids which have only one nanoparticle in the simulation box with periodic boundary condition, in this work, multiple nanoparticles are placed in the simulation box which makes it possible to simulate the aggregation of the nanoparticles. Thermal conductivity and viscosity of the nanofluid are calculated using Green–Kubo method and results show that the nanoparticle aggregation induces a significant enhancement of thermal conductivity in nanofluid, while the increase of viscosity is moderate. The results also indicate that different configurations of the nanoparticle cluster result in different enhancements of thermal conductivity and increase of viscosity in the nanofluid.

THE MOBILITY OF THE EDGE DISLOCATION IN METAL: A MOLECULAR DYNAMICS SIMULATION

2011 ◽  
Vol 25 (25) ◽  
pp. 3315-3324
Author(s):  
XIYUAN YANG
Keyword(s):  
Molecular Dynamics ◽  
Relaxation Time ◽  
Edge Dislocation ◽  
Initial Period ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Embedded Atom ◽  
Partial Dislocations ◽  
Dislocation Movement ◽  
Straight Lines

In this paper, we use molecular dynamics (MD) simulations and a modified analytic embedded-atom method to investigate the edge dislocation movement without imposed strain at 0 K. The obtained results indicate that the straight lines of the partial dislocations always preserve their original shapes and are parallel to each other during the simulation process. According to the energy of each atom, the positions of both partial dislocation cores are determined. Then the velocities in the period of the relaxation process are investigated in detail. The MD simulations reveal that the MD relaxation time dependence of the edge dislocation mobility is divided into two parts. First, during the initial period ranging from 0 to 6 ps, the relative velocity of the dislocation movement lineally increases with the incremental relaxation time. Second, in the latter period from 6 ps to the end of the simulated process the velocity decreases exponentially as the MD simulation time evolves.

Synthesis and molecular dynamics simulation of hyperbranched poly(amine-ester)/neodymium nanocomposites

2016 ◽  
Vol 23 (1) ◽  
pp. 53-60
Author(s):  
Zunli Mo ◽  
Xiaobo Zhu ◽  
Yanzhi Liu ◽  
Ruibin Guo
Keyword(s):  
Molecular Dynamics ◽  
Hyperbranched Polymer ◽  
Md Simulation ◽  
Md Simulations ◽  
Canonical System ◽  
Dynamics Simulation ◽  
Static And Dynamic Characteristics ◽  
Transmission Electron ◽  
Hyperbranched Poly ◽  
The Stability

AbstractFully atomistic molecular dynamics (MD) simulations were employed to examine the static and dynamic characteristics of hyperbranched poly(amine-ester) (HPAE). In this work, use of G2, G3, and G4 HPAE as a template and stabilizer to prepare HPAE/neodymium (Nd) nanocomposites was studied. The results of transmission electron microscopy showed that Nd particles were deposited on the surface of HPAE within nanoscales, the size of nanoparticles was uniform, and there was better dispersion with high generation of hyperbranched polymer. Virtual Materiale software was applied to research the MD simulation of HPAE/Nd nanocomposites. The stability of the system and mechanism was studied from the perspective of molecular structure and energy change in canonical system (constant NVT). G4 HPAE is more suitable for use as template and stabilizer in MD simulation, which is consistent with experimental results.

scholarly journals Molecular dynamics simulation of sI methane hydrate under compression and tension

2020 ◽  
Vol 18 (1) ◽  
pp. 69-76
Author(s):  
Qiang Wang ◽  
Qizhong Tang ◽  
Sen Tian
Keyword(s):  
Molecular Dynamics ◽  
Methane Hydrate ◽  
Fracture Process ◽  
Md Simulation ◽  
Maximum Stress ◽  
Dynamics Simulation ◽  
Tensile Fracture ◽  
Maximum Compressive Stress ◽  
Motion State ◽  
Stress States

AbstractMolecular dynamics (MD) analysis of methane hydrate is important for the application of methane hydrate technology. This study investigated the microstructure changes of sI methane hydrate and the laws of stress–strain evolution under the condition of compression and tension by using MD simulation. This study further explored the mechanical property and stability of sI methane hydrate under different stress states. Results showed that tensile and compressive failures produced an obvious size effect under a certain condition. At low temperature and high pressure, most of the clathrate hydrate maintained a stable structure in the tensile fracture process, during which only a small amount of unstable methane broke the structure, thereby, presenting a free-motion state. The methane hydrate cracked when the system reached the maximum stress in the loading process, in which the maximum compressive stress is larger than the tensile stress under the same experimental condition. This study provides a basis for understanding the microscopic stress characteristics of methane hydrate.

scholarly journals Understanding Covalent Grafting of Nanotubes onto Polymer Nanocomposites: Molecular Dynamics Simulation Study

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2621
Author(s):  
Seunghwa Yang
Keyword(s):  
Molecular Dynamics ◽  
Load Transfer ◽  
Cell Model ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Covalent Grafting ◽  
Modelling Strategies ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes ◽  
External Loads

Here, we systematically interrogate the effects of grafting single-walled (SWNT) and multi-walled carbon nanotubes (MWNT) to polymer matrices by using molecular dynamics (MD) simulations. We specifically investigate key material properties that include interfacial load transfer, alteration of nanotube properties, and dispersion of nanotubes in the polymer matrix. Simulations are conducted on a periodic unit cell model of the nanocomposite with a straight carbon nanotube and an amorphous polyethylene terephthalate (PET) matrix. For each type of nanotube, either 0%, 1.55%, or 3.1% of the carbon atoms in the outermost nanotubes are covalently grafted onto the carbon atoms of the PET matrix. Stress-strain curves and the elastic moduli of nanotubes and nanocomposites are determined based on the density of covalent grafting. Covalent grafting promotes two rivalling effects with respect to altering nanotube properties, and improvements in interfacial load transfer in the nanocomposites are clearly observed. The enhanced interface enables external loads applied to the nanocomposites to be efficiently transferred to the grafted nanotubes. Covalent functionalization of the nanotube surface with PET molecules can alter the solubility of nanotubes and improve dispersibility. Finally, we discuss the current limitations and challenges in using molecular modelling strategies to accurately predict properties on the nanotube and polymers systems studied here.

scholarly journals Fully Atomistic Molecular Dynamics Computation of Physico-Mechanical Properties of PB, PS, and SBS

Nanomaterials ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 1088 ◽  
Author(s):  
Yang Kang ◽  
Dunhong Zhou ◽  
Qiang Wu ◽  
Fuyan Duan ◽  
Rufang Yao ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Strain Rate ◽  
Strain Hardening ◽  
Md Simulation ◽  
Md Simulations ◽  
Strain Rates ◽  
Young’S Moduli ◽  
Plastic Modulus ◽  
Styrene Butadiene ◽  
Butadiene Styrene

The physical properties—including density, glass transition temperature (Tg), and tensile properties—of polybutadiene (PB), polystyrene (PS) and poly (styrene-butadiene-styrene: SBS) block copolymer were predicted by using atomistic molecular dynamics (MD) simulation. At 100 K, for PB and SBS under uniaxial tension with strain rate ε ˙ = 1010 s−1 and 109 s−1, their stress–strain curves had four features, i.e., elastic, yield, softening, and strain hardening. At 300 K, the tensile curves of the three polymers with strain rates between 108 s−1 and 1010 s−1 exhibited strain hardening following elastic regime. The values of Young’s moduli of the copolymers were independent of strain rate. The plastic modulus of PS was independent of strain rate, but the Young’s moduli of PB and SBS depended on strain rate under the same conditions. After extrapolating the Young’s moduli of PB and SBS at strain rates of 0.01–1 s−1 by the linearized Eyring-like model, the predicted results by MD simulations were in accordance well with experimental results, which demonstrate that MD results are feasible for design of new materials.

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