• 한국해양공학회지
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• 제10권1호
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• pp.92-99
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• 1996

Longline type aquaculture facilities are being used for scallpop culture in 30 m of water 2.5 km off the coast of Joomoonjin, Kangwon-do. In this paper, the facilities are modeled by the cabele-buoy-weight system, subject to the nonlinear behaviors of the mooring lines and the effects of current. Its static configuration is shown as a solution of 3-D nonlinear static equation and Runge-Kutta $4^{th}$ method is employed.

• 전자공학회논문지C
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• 제35C권3호
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• pp.90-96
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• 1998

The self-excited oscillation is the phenomenon which can be observed in the systems composed of nonlinear elements. The phenomenon is of fundamental importance in nonlinear systems and, as far as the design of a nonlinear system is concerned, it should be considered along with the stability analysis. In this paper, the oscillation of a system controlled by a static nonlinear fuzzy controller is theoretically addressed. First, the describing functionof a static fuzzy controller is derived and then, based on the derived describing function, self-excited oscillation of the system controlled by a static fuzzy controller is predicted. To obtain the describing function of the static fuzzy controller, a simple struture is assumed for the fuzzy controller. Finally, computer simulation is included to show an example where the describing function given in the paper is used to predict the self-excited oscillation of a fuzzy-control system.

• Steel and Composite Structures
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• 제43권2호
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• pp.241-256
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• 2022

In this article, an analytical procedure is presented for static analysis of composite cylinders with the geometrically nonlinear behavior, and non-uniform thickness profiles under different loading conditions by considering moderately large deformation. The composite cylinder includes two inner and outer isotropic layers and one honeycomb core layer with adjustable Poisson's ratio. The Mirsky-Herman theory in conjunction with the von-Karman nonlinear theory is employed to extract the governing equations which are a system of nonlinear differential equations with variable coefficients. The governing equations are solved analytically using the matched asymptotic expansion (MAE) method of the perturbation technique and the effects of moderately large deformations are studied. The presented method obtains the results with fast convergence and high accuracy even in the regions near the boundaries. Highlights: • An analytical procedure based on the matched asymptotic expansion method is proposed for the static nonlinear analysis of composite cylindrical shells with a honeycomb core layer and non-uniform thickness. • The effect of moderately large deformation has been considered in the kinematic relations by assuming the nonlinear von Karman theory. • By conducting a parametric study, the effect of the honeycomb structure on the results is studied. • By adjusting the Poisson ratio, the effect of auxetic behavior on the nonlinear results is investigated.

• Advances in aircraft and spacecraft science
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• 제11권1호
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• pp.55-81
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• 2024

This paper presents the exact solutions and closed forms for of nonlinear stability and vibration behaviors of straight and curved beams with nonlinear viscoelastic boundary conditions, for the first time. The mathematical formulations of the beam are expressed based on Euler-Bernoulli beam theory with the von Karman nonlinearity to include the mid-plane stretching. The classical boundary conditions are replaced by nonlinear viscoelastic boundary conditions on both sides, that are presented by three elements (i.e., linear spring, nonlinear spring, and nonlinear damper). The nonlinear integro-differential equation of buckling problem subjected to nonlinear nonhomogeneous boundary conditions is derived and exactly solved to compute nonlinear static response and critical buckling load. The vibration problem is converted to nonlinear eigenvalue problem and solved analytically to calculate the natural frequencies and to predict the corresponding mode shapes. Parametric studies are carried out to depict the effects of nonlinear boundary conditions and amplitude of initial curvature on nonlinear static response and vibration behaviors of curved beam. Numerical results show that the nonlinear boundary conditions have significant effects on the critical buckling load, nonlinear buckling response and natural frequencies of the curved beam. The proposed model can be exploited in analysis of macrosystem (airfoil, flappers and wings) and microsystem (MEMS, nanosensor and nanoactuators).

• Structural Engineering and Mechanics
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• 제72권4호
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• pp.433-441
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• 2019

In this paper, geometrically nonlinear static analysis of laminated composite beams is investigated under hygrothermal effect. In the solution of problem, the finite element method is used within the first shear beam theory. Total Lagrangian approach is used nonlinear kinematic model. The geometrically nonlinear formulations are developed for the laminated beams with hygro-thermal effects. In the nonlinear solution of the problem, the Newton-Raphson method is used with incremental displacement. In order to verify of obtained formulations, a comparison study is performed. The effects of the fiber orientation angles, the stacking sequence of laminates, temperature rising and moisture changes on the nonlinear static displacements and configurations of the composite laminated beam are investigated in the numerical results.

• 제어로봇시스템학회논문지
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• 제10권12호
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• pp.1280-1286
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• 2004

A lot of industrial chemical processes contain certain input nonlinearities even though they are controlled by several linear controllers. Here we investigate a sequential loop closing identification method for MIMO Hammerstein nonlinear processes with diagonal nonlinearities. The proposed method separates the identification of the nonlinear static function from that of the linear subsystem by using a relay feedback test and a triangular type signal test. From 2 n activations for n n MIMO nonlinear processes, we sequentially identify the whole range of the nonlinear static function as well as the transfer function matrix of the linear subsystem.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1960-1965
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• 2005

This paper presents theory for stability analysis and design of a servo system for a MIMO Wiener system with nonlinear uncertainty. The Wiener system consists of a linear time-invariant system(LTI) in cascade with a static nonlinear part ${\psi}$(y) at the output. We assume that the uncertain static nonlinear part is sector bounded and decoupled. In this research, we treat the static nonlinear part as multiplicative uncertainty by dividing the nonlinear part ${\psi}$(y) into ${\phi}$(y) := ${\psi}$(y)-y and y, and then we reduce this stabilizing problem to a Lur'e problem. As a result, we show that the servo system with no steady state error for step references can be constructed for the Wiener system.

• Advances in aircraft and spacecraft science
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• 제11권2호
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• pp.129-152
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• 2024

The applicability of a novel incremental-iterative technique with 2D differential/integral quadrature method (DIQM) in analyzing the nonlinear behavior of Bi-directional functionally graded (BDFG) porous plate based on neutral surface is verified in the present works. A formulation of four variables high shear deformation theory is used to describe the kinematic relations with respect to neutral surface rather than mid-plane. Bi-directional material distributions are presented by power functions through both thickness and axial directions. Porosities and voids are distributed by different cosine functions. The large deformations are included within the sense of nonlinear von Kármán strains. The integro-differential equilibrium equations with associated modified boundary conditions are solved numerically and iteratively by using 2D DIQM. Model validations and parametric analysis are depicted to present the influence of neutral axis, nonlinear strains, gradation indices, elastic foundations, and modified boundary conditions on the static deflection in addition to normal and shear stresses. The proposed model is effective in analyzing the static behavior of many real applications in nuclear reactors, marine and aerospace structures with large deformations.

• Architectural research
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• 제18권1호
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• pp.39-47
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• 2016

A finite element analysis technology applicable to the prediction of the static nonlinear response of cable roof structure is presented. The unified kinematic description is employed to formulate the present cable element and different strain definitions such as Green-Lagrange strain, Biot strain and Hencky strain can be adopted. The Newton-Raphson method is used to trace the nonlinear load-displacement path. In the iteration process, the compressive stress of a cable element is not allowed. For the verification of the present cable element, four numerical examples are tackled. Finally, numerical results obtained by using the present cable element are provided as new benchmark test results for cable structures under static loads.

• International Journal of Aeronautical and Space Sciences
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• 제7권1호
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• pp.99-105
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• 2006

In this study, nonlinear static and dynamic aeroelastic analyses for a high-aspect-ratio wing have been performed. To achieve these aims, the transonic small disturbance (TSD) theory for the aerodynamic analysis and the large deflection beam theory considering a geometrical nonlinearity for the structural analysis are applied, respectively. For the coupling between fluid and structure, the transformation of a displacement from the structural mesh to the aerodynamic grid is performed by a shape function which is used for the finite element and the inverse transformation of force by work equivalent load method. To validate the current method, the present analysis results of a high-aspect-ratio wing are compared with the experimental results. Static deformations in the vertical and torsional directions caused by an angle of attack and gravity loading are compared with experimental results. Also, static and dynamic aeroelastic characteristics are investigated. The comparisons of the flutter speed and frequency between a linear and nonlinear analysis are presented.