• Advances in nano research
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• 제9권2호
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• pp.69-82
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• 2020

In this paper, a new explicit analytical formula is derived for the critical buckling load of Double Walled Carbon Nanotubes (DWCNTs) embedded in Winkler elastic medium without taking into account the effects of the nonlocal parameter, which indicates the effects of the surrounding elastic matrix combined with the intertube Van der Waals (VdW) forces. Furthermore, we present a model which predicts that the critical axial buckling load embedded in Winkler, Pasternak or Kerr elastic medium under axial compression using the nonlocal Donnell shell theory, this model takes into account the effects of internal small length scale and the VdW interactions between the inner and outer nanotubes. The present model predicts that the critical axial buckling load of embedded DWCNTs is greater than that without medium under identical conditions and parameters. We can conclude that the embedded DWCNTs are less susceptible to axial buckling than those without medium.

• Steel and Composite Structures
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• 제13권2호
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• pp.157-169
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• 2012

Shell structures are very interesting from the design point of view and these are well recognized in the scientific literature. In this paper the analysis of the buckling loads and stability paths of a sandwich conical shell with unsymmetrical faces under combined load based on the assumptions of moderately large deflections (geometrically nonlinear theory) is considered and elastic-plastic properties of the material of the faces are taken into considerations. External load is assumed to be two-parametrical one and it is assumed that the shell deforms into the plastic range before buckling. Constitutive relations in the analysis are those of the Nadai-Hencky deformation theory of plasticity and Prandtl-Reuss plastic flow theory with the H-M-H (Huber-Mises-Hencky) yield condition. The governing stability equations are obtained by strain energy approach and Ritz method is used to solve the equations with the help of analytical-numerical methods using computer.

• Structural Engineering and Mechanics
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• 제72권2호
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• pp.203-216
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• 2019

Reliability analysis of composite structures considering random variation of involved parameters is quite important as composite materials revealed large statistical variations in their mechanical properties. The reliability analysis of such structures by the first order reliability method (FORM) and Monte Carlo Simulation (MCS) based approach involves repetitive evaluations of performance function. The response surface method (RSM) based metamodeling technique has emerged as an effective solution to such problems. In the application of metamodeling for uncertainty quantification and reliability analysis of composite structures; the finite element model is usually formulated by either classical laminate theory or first order shear deformation theory. But such theories show significant error in calculating the structural responses of composite structures. The present study attempted to apply the RSM based MCS for reliability analysis of composite shell structures where the surrogate model is constructed using higher order shear deformation theory (HSDT) of composite structures considering the uncertainties in the material properties, load, ply thickness and radius of curvature of the shell structure. The sensitivity of responses of the shell is also obtained by RSM and finite element method based direct approach to elucidate the advantages of RSM for response sensitivity analysis. The reliability results obtained by the proposed RSM based MCS and FORM are compared with the accurate reliability analysis results obtained by the direct MCS by considering two numerical examples.

• Steel and Composite Structures
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• 제38권1호
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• pp.47-66
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• 2021

This work addresses the free vibration analysis of Functionally Graded Porous (FGP) nanocomposite truncated conical shells with Graphene PLatelet (GPL) reinforcement. In this study, three different distributions for porosity and three different dispersions for graphene platelets have been considered in the direction of the shell thickness. The Halpin-Tsai equations are used to find the effective material properties of the graphene platelet reinforced materials. The equations of motion are derived based on the higher-order shear deformation theory and Sanders's theory. The Fourier Differential Quadrature (FDQ) technique is implemented to solve the governing equations of the problem and to obtain the natural frequencies of the truncated conical shell. The combination of FDQ with higher-order shear deformation theory allows a very accurate prediction of the natural frequencies. The precision and reliability of the proposed method are verified by the results of literature. Moreover, a wide parametric study concerning the effect of some influential parameters, such as the geometrical parameters, porosity distribution, circumferential wave numbers, GPLs dispersion as well as boundary restraint conditions on free vibration response of FGP-GPL truncated conical shell is also carried out and investigated in detail.

• 대한기계학회논문집
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• 제2권2호
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• pp.31-37
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• 1978

In order to specify the accuracy of the cylindrical shell theories, several cylindrical shell equations are studied. Cheng's equation is used as the exact theory for circular cylindrical shells. An error factor is defined and used for the measure of the accuracy in various cylindrical shell theories. The line load applied along generators of a thin-walled circular cylidrical shell of finite length is investigated as a numerical example. These numerical results show that Cheng's equation is used for the fundamental cylindrical shell equation and the difficulties in cumputation by a digital computer are same as the simplified equations, such as Donnell's Morley's, and Vlasov's equations.

• 대한기계학회논문집
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• 제11권5호
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• pp.789-799
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• 1987

본 연구에서는 기존연구에 비하여 해의 형태가 간단한 폐형태로 주어지는 엄 밀한 해를 구하기 위해, 직교이방성원통셸의 지배방정식을 Novozhilov 형복소미분방정 식으로 유도하였다. 수치예로서 모선전체 및 부분적으로 작용하는 선하중하에 원통 셸의 변립 및 응력상태를 해석하여 기존의 연구와 비교하였으며, 직교이방특성과 셸기 하학적 매개변수에 따르는 영향을 고찰하였다.

• Advances in concrete construction
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• 제14권5호
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• pp.309-315
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• 2022

This paper depicts the diagram of cylindrical shells as an essential idea. It centers around an outline of exploration and use of cylindrical shell in expansive current circumstance. In view of investigation of the current and prospect of model as a piece of present exploration work, a straightforward contextual analysis is examined with Love's shell theory based on Galerkin's method. The cylindrical shells are attached from one end of the cylindrical shells. The frequencies of ring support shells are investigated against the half axial wave mode. The frequencies increase on increasing the half axial wave mode. Also, the frequencies are downsized with ring supports. The software MATLAB is preferred to others because in this software computing coding is very easy to do. Just single command 'eig' furnishes shell frequencies and mode shapes by calculating eigenvalues and eigenvectors respectively. The shell vibration frequencies for cylindrical shells are compared with those results found in the open literature.

• 대한기계학회논문집A
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• 제33권1호
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• pp.1-26
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• 2009

Cylindrical shells of isotropic and composite laminated materials are being used many engineering applications. This paper reviews the literature focusing on various aspects of shell research. The aspects of research receiving interest here are the cylindrical theory being used, the stress, buckling analysis and the impact analysis. The vibration analyses and stiffening characteristics of the cylindrical shell are investigated. The design optimizations of the cylindrical shell are reviewed. The studies on the conical and spherical shell are also reviewed. This review aticles contain 236 referencees.

• 한국음향학회지
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• 제34권4호
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• pp.257-263
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• 2015

음향 공명 이론을 이용하여 단일층 원통형 껍질 속 내부 물질의 음향 식별을 연구하였다. 원통형 껍질의 이론적인 공명 피크 주파수들은 내부 물질의 밀도 변화에 의해서는 거의 영향을 받지 않으나, 음속 변화에 의해서는 두드러지게 변화를 보인다. 이와 같은 음향 의존성을 원통형 껍질 속 내부 물질을 식별하는 데 활용할 수 있다. 단일층 원통형 껍질에 대한 음향 공명 스펙트로그램을 정규화 주파수 및 내부 물질 음속의 함수로서 이론적으로 작성한다. 이 스펙트로그램에 측정한 후방 산란 음압장의 음향 공명 피크들을 중첩함으로써 내부 물질을 음향학적으로 식별할 수 있다. 이를 실험적으로 확인하기 위하여 물, 기름 또는 에틸렌글리콜을 넣은 원통형 껍질의 후방 산란 음압장을 수조 안에서 측정하였다. 단일 송수신 방식으로 중심주파수 1.05 MHz인 음파 변환기로 측정한 후방 산란 음압장의 음향 공명 피크로 내부 물질을 식별할 수 있었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.352.2-352
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• 2002

In this paper, Power Flow Analysis (PFA) method has been applied to the prediction of vibration energy density and intensity of coupled shell structures in the medium-to-high frequency ranges. To consider the wave transformation at joint between shell elements, power transmission and reflection coefficients are investigated for various joint angles, and here Donnell-Mushtari thin shell theory has been used. (omitted)