• Steel and Composite Structures
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• 제43권5호
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• pp.533-552
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• 2022

The current article deals with the dynamic stability, and structural improvement of vibrating electrically curved screen on the viscoelastic substrate. By considering optimum value for radius curvature of the electrically curved screen, the structure improvement of the system occurs. For modeling the electrically system, the Maxwell's' equation is developed. Hertz contact model in employed to obtain contact forces between impactor and structure. Moreover, variational methods and nonlinear von Kármán model are used to derive boundary conditions (BCs) and nonlinear governing equations of the vibrating electrically curved screen. Galerkin and Multiple scales solution approach are coupled to solve the nonlinear set of governing equations of the vibrating electrically curved screen. Along with the analytical solution, 3D finite element simulation via ABAQUS package is provided with the aid of a FE package for simulating the current system's response. The results are categorized in 3 different sections. First, effects of geometrical and material parameters on the vibrational performance and stability of the curves panel. Second, physical properties of the impactor are taken in to account and their effect on the absorbed energy and velocity profile of the impactor are presented. Finally, effect of the radius and initial velocity on the mode shapes of the current structure is demonstrated.

• Advances in nano research
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• 제15권2호
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• pp.113-128
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• 2023

The advancement of theoretical research has numerous challenges, particularly with regard to the modeling of structures, in contrast to experimental investigation of the mechanical behavior of complex systems. The main objective of this investigation is to provide an analytical analysis of the static problem of a new generation of composite structure, namely, functionally graded FG graphene reinforced composite GRC coated plates/shells. A complex power law function is used to define the material's graduation. Investigations are conducted on Hardcore and Softcore coated FG plates/shells. The virtual work approach is used to perform the equilibrium equations, which are then solved using the Galerkin technique to account for various boundary conditions. With reliable published articles, the presented solution is validated. The effects of hardcore and softcore distributions, gradation indexes, and boundary conditions on the buckling, bending deflection and stresses of FG GRC-coated shells are presented in detail. Obtained results and the developed procedure are supportive for design and manufacturing of FG-GRC coated plates/shells in several fields and industries e.g., aerospace, automotive, marine, and biomedical implants.

• Geomechanics and Engineering
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• 제21권5호
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• pp.471-487
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• 2020

In this work, the buckling analysis of material sandwich plates based on a two-parameter elastic foundation under various boundary conditions is investigated on the basis of a new theory of refined trigonometric shear deformation. This theory includes indeterminate integral variables and contains only four unknowns in which any shear correction factor not used, with even less than the conventional theory of first shear strain (FSDT). Applying the principle of virtual displacements, the governing equations and boundary conditions are obtained. To solve the buckling problem for different boundary conditions, Galerkin's approach is utilized for symmetric EGM sandwich plates with six different boundary conditions. A detailed numerical study is carried out to examine the influence of plate aspect ratio, elastic foundation coefficients, ratio, side-to-thickness ratio and boundary conditions on the buckling response of FGM sandwich plates. A good agreement between the results obtained and the available solutions of existing shear deformation theories that have a greater number of unknowns proves to demonstrate the precision of the proposed theory.

• 대한기계학회논문집A
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• 제26권5호
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• pp.939-951
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• 2002

We propose a new multiscale Galerkin method based on interpolation wavelets for two-dimensional Poisson's and plane elasticity problems. The major contributions of the present work are: 1) full multiresolution numerical analysis is carried out, 2) general boundaries are handled by a fictitious domain method without using a penalty term or the Lagrange multiplier, 3) no special integration rule is necessary unlike in the (bi-)orthogonal wavelet-based methods, and 4) an efficient adaptive scheme is easy to incorporate. Several benchmark-type problems are considered to show the effectiveness and the potentials of the present approach. is 1-2m/s and impact deformation of the electrode depends on the strain rate at that velocity, the dynamic behavior of the sinter-forged Cu-Cr is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain rate is obtained from the split Hopkinson pressure bar test using disc-type specimens. Experimental results from both quasi-static and dynamic compressive tests are Interpolated to construct the Johnson-Cook model as the constitutive relation that should be applied to simulation of the dynamic behavior of the electrodes. The impact characteristics of a vacuum interrupter are investigated with computer simulations by changing the value of five parameters such as the initial velocity of a movable electrode, the added mass of a movable electrode, the wipe spring constant, initial offset of a wipe spring and the virtual fixed spring constant.

• Structural Engineering and Mechanics
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• 제72권1호
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• pp.71-81
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• 2019

The objective of this paper is to develop a size-dependent nonlinear model of beams for fluid-conveying nanotubes with an initial deflection. The nonlinear frequency response of the nanotube is analysed via an Euler-Bernoulli model. Size influences on the behaviour of the nanosystem are described utilising the nonlocal strain gradient theory (NSGT). Relative motions at the inner wall of the nanotube is taken into consideration via Beskok-Karniadakis model. Formulating kinetic and elastic energies and then employing Hamilton's approach, the nonlinear motion equations are derived. Furthermore, Galerkin's approach is employed for discretisation, and then a continuation scheme is developed for obtaining numerical results. It is observed that an initial deflection significantly alters the frequency response of NSGT nanotubes conveying fluid. For small initial deflections, a hardening nonlinearity is found whereas a softening-hardening nonlinearity is observed for large initial deflections.

• Structural Engineering and Mechanics
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• 제87권5호
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• pp.461-473
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• 2023

This study aims to solve for nonlinear cylindrical shell systems with a semi-analytical and numerical approach implementing the P-T method. The procedures and conditions for such a study are presented in practically solving and analyzing the cylindrical shell systems. An analytical model for a nonlinear thick cylindrical shell (TCS) is established on the basis of the stress function and Reddy's higher-order shear deformation theory (HSDT). According to Reddy's HSDT, Hooke's law in three dimensions, and the von-Kármán equation, the stress-strain relations are developed for the thick cylindrical shell systems, and the three coupled nonlinear governing equations are thus established and discretized as per the Galerkin method, for implementing the P-T method. The solution generated with the approach is continuous everywhere in the entire time domain considered. The approach proposed can also be used to numerically solve and analyze the nonlinear shell systems. The procedures and recurrence relations for numerical solutions of shell systems are presented. To demonstrate the application of the approach in numerically solving for nonlinear cylindrical shell systems, a specific nonlinear cylindrical shell system subjected to an external excitation is solved numerically. In numerically solving for the system, the present approach shows higher efficiency, accuracy, and reliability in comparison with that of the Runge-Kutta method. The approach with the P-T method presented is practically sound especially when continuous and high-quality numerical solutions for the shell systems are considered.

• 한국전산유체공학회지
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• 제1권1호
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• pp.88-97
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• 1996

This paper treats an adaptive finite-element method for the viscous compressible flow governed by Navier-Stokes equations in two dimensions. The numerical algorithm is the two-step Taylor-Galerkin mettled using unstructured triangular grids. To increase accuracy and stability, combined moving node method and grid refinement method have been used for grid adaption. Validation of the present algorithm has been made by comparing the present computational results with the existing experimental data and other numerical solutions. Four benchmark problems are solved for demonstration of the present numerical approach. They include a subsonic flow over a flat plate, the Carter flat plate problem, a laminar shock-boundary layer interaction. and finally a laminar flow around NACA0012 airfoil at zero angle of attack and free stream Mach number of 0.85. The results indicates that the present adaptive triangular grid method is accurate and useful for laminar viscous flow calculations.

• Advances in aircraft and spacecraft science
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• 제3권2호
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• pp.149-170
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• 2016

Multi-Disciplinary Optimization (MDO) is widely used to handle the advanced design in several engineering applications. Such applications are commonly simulation-based, in order to capture the physics of the phenomena under study. This framework demands fast optimization algorithms as well as trustworthy numerical analyses, and a synergic integration between the two is required to obtain an efficient design process. In order to meet these needs, an adaptive Computational Fluid Dynamics (CFD) solver and a fast optimization algorithm have been developed and combined by the authors. The CFD solver is based on a high-order discontinuous Galerkin discretization while the optimization algorithm is a high-performance version of the Artificial Bee Colony method. In this work, they are used to address a typical aero-mechanical problem encountered in turbomachinery design. Interesting achievements in the considered test case are illustrated, highlighting the potential applicability of the proposed approach to other engineering problems.

• Structural Engineering and Mechanics
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• 제41권5호
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• pp.617-632
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• 2012

An isogeometric approach is presented for static analysis of thin plate problems of various geometries. Non-Uniform Rational B-Splines (NURBS) basis function is applied for approximation of the thin plate deflection, as for description of the geometry. The governing equation based on Kirchhoff plate theory, is discretized using the standard Galerkin method. The essential boundary conditions are enforced by the Lagrange multiplier method. Several typical examples of thin plate and thin plate on elastic foundation are solved and compared with the theoretical solutions and other numerical methods. The numerical results show the robustness and efficiency of the proposed approach.

• 조명전기설비학회논문지
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• 제27권1호
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• pp.46-52
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• 2013

The current distribution passing through grounding electrode is required for calculating an impedance of grounding electrode using the electromagnetic field model. In this paper the numerical calculation for currents passing through a grounding electrode as a function of frequency was given. The proposed approach is based on the wire antenna model(AM) in the frequency domain. The Pocklington's equation driven from the wire antenna theory was numerically calculated by the Galerkin's method. The triangle function was applied to both the basis function and the weighting function. The current distribution of a horizontal ground electrode was simulated in MATLAB. Also these results were compared with the data obtained from the CDEGS HIFREQ calculation.