DYNAMIC CHARACTERISTICS OF SINGLE-LAYERED GRAPHENE SHEETS DUE TO ATOMIC VACANCY DEFECT USING MULTISCALE ANALYSIS TECHNIQUE INCORPORATING TERSOFF-BRENNER POTENTIAL

2015 ◽  
Vol 13 (5) ◽  
pp. 393-412
Author(s):  
Sachin O. Gajbhiye ◽  
S. P. Singh
Keyword(s):  
Dynamic Characteristics ◽  
Multiscale Analysis ◽  
Vacancy Defect ◽  
Graphene Sheets ◽  
Analysis Technique ◽  
Atomic Vacancy ◽  
Brenner Potential

Influence of Defects on Elastic Buckling Properties of Single-Layered Graphene Sheets

2014 ◽  
Vol 636 ◽  
pp. 11-14 ◽  
Author(s):  
Bao Long Li ◽  
Li Jun Zhou ◽  
Jian Gao Guo
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Vacancy Defect ◽  
Elastic Buckling ◽  
Graphene Sheets ◽  
Effect Factors ◽  
Vacancy Defects ◽  
Size Dependent ◽  
Buckling Stress ◽  
Geometrical Dimensions

Molecular structural mechanics based finite element method has been applied to study the effects of two types of Stone-Wales (SW) defects and vacancy defect on elastic buckling properties of single-layered graphene sheets (SLGSs). The defect effect factors of critical buckling stresses are calculated for the defective SLGSs with different chirality and geometrical dimensions. It is proved that defect effect factors are size-dependent and chirality-dependent. The results show that the vacancy defects will always weaken the SLGSs’ stability, and two types of SW defects have different effects on zigzag and armchair SLGSs. What’s more, the positions of defects also have remarkable influence on the critical buckling stress of SLGSs.

Multiscale Modeling of Dynamic Characteristics of Carbon Nanotube Reinforced Nanocomposites

NANO ◽  
2016 ◽  
Vol 11 (07) ◽  
pp. 1650083 ◽  
Author(s):  
Sachin O. Gajbhiye ◽  
S. P. Singh
Keyword(s):  
Carbon Nanotube ◽  
Dynamic Characteristics ◽  
Matrix Material ◽  
Three Dimensional ◽  
Vacancy Defect ◽  
Nanocomposite Material ◽  
Phase Lag ◽  
Rate Dependent ◽  
Carbon Carbon Bond ◽  
The Matrix

A unique atomic structure of carbon nanotube unveils outstanding properties. This makes it potentially highly valued reinforcing material to strengthen composite materials. The methodology is established in this research paper to investigate the static and dynamic characteristics of the nanocomposites. Repol polypropylene H110MA is used as a matrix material along with the different percentages of single-walled carbon nanotubes (SWCNTs). A concept of representative volume element (RVE) is considered to study the various properties of the nanocomposite material. The carbon–carbon bond of nanotube is modeled using Tersoff–Brenner potential and represented by space frame element. The matrix material properties are tested in the laboratory which are further used to model it and represented by three-dimensional continuum elements. The interaction between nanotube and polymer matrix is modeled using “Lennard–Jones 6-12” potential represented by nonlinear spring elements. The effect of reinforcement, chirality, % volume of SWCNT, atomic vacancy defect and Stone–Wales defect on the properties of nanocomposite are investigated. To see the effect of reinforcement, the eigenvalues of the RVE are extracted for different boundary conditions. The viscoplastic behavior of the matrix material is considered and the rate-dependent characteristics of the nanocomposite are studied. The damping property of the nanocomposite material is also investigated based on the phase lag between stress and strain field by applying harmonic strain at different frequencies.

scholarly journals Monte Carlo-Based Finite Element Method for the Study of Randomly Distributed Vacancy Defects in Graphene Sheets

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Liu Chu ◽  
Jiajia Shi ◽  
Eduardo Souza de Cursi ◽  
Xunqian Xu ◽  
Yazhou Qin ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Monte Carlo ◽  
Natural Frequencies ◽  
Vacancy Defect ◽  
Honeycomb Lattice ◽  
Graphene Sheets ◽  
Pristine Graphene ◽  
Vacancy Defects ◽  
Element Method

This paper proposed an effective stochastic finite element method for the study of randomly distributed vacancy defects in graphene sheets. The honeycomb lattice of graphene is represented by beam finite elements. The simulation results of the pristine graphene are in accordance with literatures. The randomly dispersed vacancies are propagated and performed in graphene by integrating Monte Carlo simulation (MCS) with the beam finite element model (FEM). The results present that the natural frequencies of different vibration modes decrease with the augment of the vacancy defect amount. When the vacancy defect reaches 5%, the regularity and geometrical symmetry of displacement and rotation in vibration behavior are obviously damaged. In addition, with the raise of vacancy defects, the random dispersion position of vacancy defects increases the variance in natural frequencies. The probability density distributions of natural frequencies are close to the Gaussian and Weibull distributions.

Atomic vacancy defect in 〈110〉 oriented TbDyFe alloy and its effect on the magnetostrictions

2008 ◽  
Vol 452 (2) ◽  
pp. 419-420 ◽  
Author(s):  
X.X. Gao ◽  
M.C. Zhang ◽  
H.J. Tang ◽  
J. Zhu ◽  
S.Z. Zhou
Keyword(s):  
Vacancy Defect ◽  
Atomic Vacancy

scholarly journals Atomic Vacancy Defect, Frenkel Defect and Transition Metals (Sc, V, Zr) Doping in Ti4N3 MXene Nanosheet: A First-Principles Investigation

2020 ◽  
Vol 10 (7) ◽  
pp. 2450
Author(s):  
Tingyan Zhou ◽  
Wan Zhao ◽  
Kun Yang ◽  
Qian Yao ◽  
Yangjun Li ◽  
...  
Keyword(s):  
Transition Metal ◽  
High Spin ◽  
First Principles ◽  
Density Functional ◽  
Vacancy Defect ◽  
Potential Candidate ◽  
Magnetic Exchange ◽  
Type Defect ◽  
Spin Polarizability ◽  
Atomic Vacancy

Using first-principles calculations based on the density functional theory, the effects of atomic vacancy defect, Frenkel-type defect and transition metal Z (Z = Sc, V and Zr) doping on magnetic and electric properties of the Ti4N3 MXene nanosheet were investigated comprehensively. The surface Ti and subsurface N atomic vacancies are both energetically stable based on the calculated binding energy and formation energy. In addition, the former appears easier than the latter. They can both enhance the magnetism of the Ti4N3 nanosheet. For atom-swapped disordering, the surface Ti-N swapped disordering is unstable, and then the Frenkel-type defect will happen. In the Frenkel-type defect system, the total magnetic moment decreases due to the enhancement of indirect magnetic exchange between surface Ti atoms bridged by the N atom. A relatively high spin polarizability of approximately 70% was detected. Furthermore, the doping effects of transition metal Z (Z = Sc, V and Zr) on Ti4N3 nanosheet are explored. All doped systems are structurally stable and have relatively large magnetism, which is mainly induced by the directed magnetic exchange between surface Z and Ti atoms. Especially in the doped Ti4N3-Sc system, the high spin polarizability is still reserved, suggesting that this doped system can be a potential candidate for application in spintronics.

scholarly journals Numerical Analysis Technique for Stiffness Parameters Identification of Spatial Structures by Minimizing the Difference between the Calculated (Finite Element) and Natural Dynamic Characteristics

2020 ◽  
Vol 18 (3) ◽  
pp. 64
Author(s):  
P. I. Novikov
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
Dynamic Characteristics ◽  
Parameters Identification ◽  
Spatial Structures ◽  
Digital Twins ◽  
Analysis Technique ◽  
The Difference ◽  
Natural Dynamic

В статье приводится описание разработанной математически формализованной численно-аналитиче­ской методики идентификации параметров жесткости пространственных конструкций на основе минимизации расхождений расчетных и натурных динамических характеристик. Методика позволяет решать обратные некорректные динамические задачи параметрической идентификации жесткостных характеристик пространственных конструкций на основе инструментально выявленных частот и форм собственных колебаний значимой части спектра с применением современных численных методов моделирования механических систем и процедур нелинейного программирования, реализованных в универсальных программных комплексах ANSYS Mechanical и MATLAB. Методика основана на оригинальной формулировке задачи нелинейного программирования с ограничениями в виде неравенств для расчетных частот собственных колебаний. На начальном этапе, до старта минимизации, предусмотрено выделение приоритетных компонент минимизации, что позволяет решать динамические обратные задачи в условиях «контрастного» изменения значимой части спектра и кратно увеличить вычислительную эффективность процесса минимизации. Подход применим для исследования сложных расчетных схем. Методика может применяться как составная часть информационно-аналитико-математических моделей цифровых двойников (digital twins) на этапе валидации, идентификации математических моделей реальных, структурно сложных строительных объектов в составе современных систем динамического мониторинга.

scholarly journals Dynamic characterisation of Össur Flex-Run prosthetic feet for a more informed prescription

2018 ◽  
Vol 43 (1) ◽  
pp. 62-70 ◽  
Author(s):  
Siamak Noroozi ◽  
Zhi Chao Ong ◽  
Shin Yee Khoo ◽  
Navid Aslani ◽  
Philip Sewell
Keyword(s):  
Modal Analysis ◽  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Full Range ◽  
Design Feature ◽  
Current Method ◽  
Mode Shapes ◽  
Dynamic Data ◽  
Gait Performance ◽  
Analysis Technique

Background: The current method of prescribing composite running-specific energy-storing-and-returning feet is subjective and is based only on the amputee’s static body weight/mass. Objectives: The aim was to investigate their dynamic characteristics and create a relationship between these dynamic data and the prescription of foot. Study Design: Experimental Assessment. Methods: This article presents the modal analysis results of the full range of Össur Flex-Run™ running feet that are commercially available (1LO–9LO) using experimental modal analysis technique under a constant mass at 53 kg and boundary condition. Results: It was shown that both the undamped natural frequency and stiffness increase linearly from the lowest to the highest stiffness category of foot which allows for a more informed prescription of foot when tuning to a matched natural frequency. The low damping characteristics determined experimentally that ranged between 1.5% and 2.0% indicates that the feet require less input energy to maintain the steady-state cyclic motion before take-off from the ground. An analysis of the mode shapes also showed a unique design feature of these feet that is hypothesised to enhance their performance. Conclusion: A better understanding of dynamic characteristics of the feet can help tune the feet to the user’s requirements in promoting a better gait performance. Clinical relevance The dynamic data determined from this study are needed to better inform the amputees in predicting the natural frequency of the foot prescribed. The amputees can intuitively tune the cyclic body rhythm during walking or running to match with the natural frequency. This could eventually promote a better gait performance.

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