• Steel and Composite Structures
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• 제45권4호
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• pp.483-499
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• 2022

In present work, bending and free vibration studies are carried out on different kinds of sandwich FGM beams using recently proposed (Chakrabarty et al. 2011) C-0 finite element (FE) based higher-order zigzag theory (HOZT). The material gradation is assumed along the thickness direction of the beam. Power-law, exponential-law, and sigmoidal laws (Garg et al 2021c) are used during the present study. Virtual work principle is used for bending solutions and Hamilton's principle is applied for carrying out free vibration analysis as done by Chalak et al. 2014. Stress distribution across the thickness of the beam is also studied in detail. It is observed that the behavior of an unsymmetric beam is different from what is exhibited by a symmetric one. Several new results are also reported which will be useful in future studies.

• Structural Engineering and Mechanics
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• 제63권5호
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• pp.683-689
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• 2017

In this paper, a hyperbolic shear deformation theory is presented for bending analysis of functionally graded beams. This theory used in displacement field in terms of thickness co-ordinate to represent the shear deformation effects and does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. The governing equations are derived by employing the virtual work principle and the physical neutral surface concept. A simply supported functionally graded beam subjected to uniformly distributed loads and sinusoidal loads are consider for detail numerical study. The accuracy of the present solutions is verified by comparing the obtained results with available published ones.

• 한국재난정보학회:학술대회논문집
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• 한국재난정보학회 2015년 정기학술대회
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• pp.294-297
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• 2015

Decommissioning of nuclear facilities should be accomplished by assuring the safety of workers because decommissioning activities of nuclear facilities are under high radioactivity and work difficulty. It is necessary that before decommissioning, the radiation exposure dose of workers has to be evaluated and assessed under the principle of ALARA (as low as reasonably achievable). Furthermore, to improve the proficiency of decommissioning environments, method and system need to be developed. The legacy methods of exposure dose measurement and assessment had the limitations to modify and simulate the exposure dose to workers prior to practical activities because those should be accomplished without changes of working routes under predetermined scenarios. To simulate a lot of decommissioning scenarios, decommissioning environments were designed in virtual reality. To simulate and assess the exposure dose to workers, human model also was designed in virtual environments. These virtual decommissioning environments made it possible to real-time simulate and assess the exposure dose to workers. It can be concluded that this system is able to protect from accidents and enable workers to improve his familiarization about working environments. It is expected that this system can reduce human errors because workers are able to improve the proficiency of hazardous working environments due to virtual training like real decommissioning situations. In the end, the safety during decommissioning of nuclear facilities will be guaranteed under the principle of ALARA.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2009년도 정기 학술대회
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• pp.488-491
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• 2009

본 논문에서는 응력함수와 Kantorovich method를 이용하여 기저판(substrate)에 인장과 굽힘이 작용할 때 복합재 패치의 3차원 응력을 해석하였다. 면내 방향과 면외 방향의 두 응력함수에 가상 공액일의 법칙(Complementary virtual work principle)을 적용하였으며 복합재 패치의 자유 경계조건과 바닥의 기저판으로부터 전달되는 전단 수직 응력 조건을 부여하였다. 이를 통해서 패치 구조물의 지배방정식을 연립 미분 방정식 형태의 고유치 문제로 변환하여 응력함수를 구하였다. 위 방법의 타당성과 효용성을 검증하기 위한 수치 예제로 cross-ply, angle-ply, quasi-isotropic의 패치 적층 배열을 고려하였으며, 층간 응력함수 값이 자유 경계에서 최고치를 나타내고 패치 중심부로 갈수록 급격히 감소하는 모습을 확인하였다. 제안된 기법은 기저판에 인장하중이 작용하는 경우뿐만 아니라 굽힘 하중이 작용하는 경우에도 정확한 예측이 가능하여, 패치 구조물의 층간 응력을 포함한 3차원 응력을 해석하는데 있어서 효율적인 해석 도구로서 사용할 수 있을 것이라 사료된다.

• Structural Engineering and Mechanics
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• 제85권5호
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• pp.593-605
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• 2023

This work presents a comparison between analytical and finite element analysis for bending of porous sandwich functionally graded material (FGM) plates. The plate is rectangular and simply supported under static sinusoidal loading. Material properties of FGM are assumed to vary continuously across the face sheets thickness according to a power-law function in terms of the volume fractions of the constituents while the core is homogeneous. Four types of porosity are considered. A refined higher-order shear with normal deformation theory is used. The number of unknowns in this theory is five, as against six or more in other shear and normal deformation theories. This theory assumes the nonlinear variation of transverse shear stresses and satisfies its nullity in the top and bottom surfaces of the plate without the use of a shear correction factor. The governing equations of equilibrium are derived from the virtual work principle. The Navier approach is used to solve equilibrium equations. The constitutive law of the porous FGM sandwich plate is implemented for a 3D finite element through a subroutine in FORTRAN (UMAT) in Abaqus software. Results show good agreement between the finite element model and the analytical method for some results, but the analytical method keeps giving symmetric results even with the thickness stretching effect and load applied to the top surface of the sandwich.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.156-159
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• 2003

The analytic solution of displacements of thin cylindrical pressure vessel made by carbon fiber T700/Epoxy was obtained using equilibrium equations of orthogonal curvilinear coordinate system. Equilibrium equations with the assumed displacement field were derived from a reasonable description of the behavior of thin elastic shells using principle of virtual work. Some analyses of the theoretical solution are presented and compared with the results of hydraulic tests of the pressure vessel.

• Wind and Structures
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• 제32권1호
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• pp.19-30
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• 2021

This study presents buckling analysis of a simply supported sandwich plate with functionally graded porous layers. In the kinematic relation of the plate, a hyperbolic shear displacement model is used. The governing equations of the problem are derived by using the principle of virtual work. In the solution of the governing equations, the Navier procedure is implemented. In the porosity effect, four different porosity types are used for functionally graded sandwich layers. In the numerical examples, the effects of the porosity parameters, porosity types and geometry parameters on the critical buckling of the functionally graded sandwich plates are investigated.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 추계학술대회 논문집
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• pp.220-225
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• 2001

High rigidity of structure is required to obtain its accuracy and performance in a coordinates measuring machine(CMM). Modeling of bridge column of a CMM is introduced and the unit-load method by the principle of virtual work is suggested to analyze deflections of bridge column which is designed for high rigidity. Also design of porous air bearings of each moving axis is introduced to satisfy the loading conditions.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.254-259
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• 1992

In this paper, we propose an optimal method for the tracking a trajectory of the end-effector of flexible robot arms with multiple joints. The proposed method finds joint trajectories and joint torques necessary to produce the desired end-effector motion of flexible manipulator. In inverse kinematics, optimized joint trajectories are computed from elastic equations. In inverse dynamics, joint torques are obtained from the joint equations by using the optimized joint trajectories. The equations of motion using finite element method and virtual work principle are employed. Optimal control is applied to optimize joint trajectories which are computed in inverse kinematics. The simulation of flexible planner manipulator is presented.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1993년도 봄 학술발표회논문집
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• pp.207-212
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• 1993

In the construction of underground structures, it is critical to accurately predict the ground deformations during excavation. In this paper, a finite element procedure for the computation of solid displacement and fluid pore pressure during incremental excavation is presented based on Biot's theory. The numerical formulation is done using the virtual work principle. The proposed procedure is applied to some example problems with different excavation rates and permeabilities.