• Steel and Composite Structures
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• 제34권2호
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• pp.261-277
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• 2020

The main objective of this research paper is to consider vibration analysis of vacancy defected graphene sheet as a nonisotropic structure via molecular dynamic and continuum approaches. The influence of structural defects on the vibration of graphene sheets is considered by applying the mechanical properties of defected graphene sheets. Molecular dynamic simulations have been performed to estimate the mechanical properties of graphene as a nonisotropic structure with single- and double- vacancy defects using open source well-known software i.e., large-scale atomic/molecular massively parallel simulator (LAMMPS). The interactions between the carbon atoms are modelled using Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential. An isogeometric analysis (IGA) based upon non-uniform rational B-spline (NURBS) is employed for approximation of single-layered graphene sheets deflection field and the governing equations are derived using nonlocal elasticity theory. The dependence of small-scale effects, chirality and different defect types on vibrational characteristic of graphene sheets is investigated in this comprehensive research work. In addition, numerical results are validated and compared with those achieved using other analysis, where an excellent agreement is found. The interesting results indicate that increasing the number of missing atoms can lead to decrease the natural frequencies of graphene sheets. It is seen that the degree of the detrimental effects differ with defect type. The Young's and shear modulus of the graphene with SV defects are much smaller than graphene with DV defects. It is also observed that Single Vacancy (SV) clusters cause more reduction in the natural frequencies of SLGS than Double Vacancy (DV) clusters. The effectiveness and the accuracy of the present IGA approach have been demonstrated and it is shown that the IGA is efficient, robust and accurate in terms of nanoplate problems.

• 대한의용생체공학회:의공학회지
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• 제21권4호
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• pp.373-384
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• 2000

본 연구의 목적은 체적 변형률 (volumetric strain)에 의한 스폰지 뼈의 밀도를 예측하는 것이다. 스폰지 뼈의 내부에서 유체의 흐름을 고려하기 위하여 각각의 normal strain의 합을 체적 변형률로 정의하였다. 체적 변형률의 경계조건에 대한 민감한 반응은 스폰지 뼈의 밀도를 예측하도록 하였다. 이러한 이론적 배경을 유한요소법 (finite element method)에 적용시켜 대퇴골 (femur)과 척구 (spine)의 스폰지 뼈에서의 밀도를 예측하였다. 예측된 뼈의 밀도는 실험적 데이터와 매우 유사하였다. (Wolff 1892, Keller et al. 1989, Codyet al. 1992). 뼈의 밀도의 함수인 뼈의 탄성계수와 강도 또한 실험적 결과와 매우 유사하였다. (Keller et al. 1989, Carter and Hayes 1977). 본 연구에서 정립된 알고리즘은 스폰지 뼈의 밀도를 예측하는데 있어서 수렴성과 민감성이 우수하였다. 따라서 본 연구의 컴퓨터 알고리즘은 스폰지 뼈의 밀도예측에 있어서 매우 유용한 방법이 될 것이다.