• International Journal of Aerospace System Engineering
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• v.6 no.1
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• pp.1-7
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• 2019

In the present study, structural safety and stability on the main wing and tail planes of the 1.2 ton WIG(Wing in Ground Effect) flight vehicle, which will be a high speed maritime transportation system for the next generation, was performed. The carbon-epoxy composite material was used in design of wing structure. The skin-spar with skin-stressed structural type was adopted for improvement of lightness and structural stability. As a design procedure for this study, the design load was estimated with maximum flight load. From static strength analysis results using finite element method of the commercial codes. From the stress analysis results of the main wing, it was confirmed that the upper skin structure between the second rib and the third rib was unstable for the buckling load. Therefore in order to solve this problem, three stiffeners at the buckled region were added. After design modification, even though the weight of the wing was a little bit heavier than the target weight, the structural safety and stability was satisfied for design requirements.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.10a
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• pp.16-23
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• 1993

The new p-version crack model is proposed to estimate the bending stress intensity factors of the thick cracked plate under flexure. The proposed model is based on high order theory and $C^{\circ}$-plate element including shear deformation. The displacements fields are defined by integrals of Legerdre polynomials which can be classified into three groups such as basic mode, side mode and internal mode. The computer implementation allows arbitrary variations of p-level up to a maximum value of 10. The bending stress intensity factors are computed by virtual crack extention approach. The effects of ratios of thickness to crack length(h/a), crack length to width(a/W) and boundary conditions are investigated. Very good agreement with the existing solution in the literature are shown for the uncracked plate as well as the cracked plate.

• Wind and Structures
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• v.16 no.6
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• pp.541-560
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• 2013

The aim of the paper is to use optimization and advanced numerical computation of a sail fiber-reinforced composite model to increase the performance of a yacht under wind action. Designing a composite-shell system against the wind is a very complex problem, which only in the last two decades has been approached by advanced modeling, optimization and computer fluid dynamics (CFDs) based methods. A sail is a tensile structure hoisted on the rig of a yacht, inflated by wind pressure. Our objective is the multiple criteria optimization of a sail, the engine of a yacht, in order to obtain the maximum thrust force for a given load distribution. We will compute the best possible yarn thickness orientation and distribution in order to minimize the total fiber volume with some displacement constraints and in order to leave the most uniform stress distribution over the whole structure. In this paper our attention will be focused on computer simulation, modeling and optimization of a sail-shape mathematical model in different regatta and wind conditions, with the purpose of improving maneuverability and speed made good.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.6
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• pp.876-888
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• 1986

The Study is concerned with the analysis of unconstrained axisymmetric piercing as a nonsteady forging process by the rigid-plastic finite element method. In the numerical analysis of axisymmetric piercing, the initial velocity field is generated by assuming the material as a linear viscous material to begin with in order to facilitate the input handling and to ensure better convergencey. The strain-hardening effect for nonsteady deformation and the friction of the die-material interial interface are considered in the formulation. Rigid body treatment is also incorporated in the developed program. The experiments are carried out for aluminum alloy specimens (A1204) with different specimen heights. It is shown that the experimental results are in excellent agreement with the finite element simulations is deformed configuration. For load prediction the theoretical prediction shows excellent agreement with th eexperimental laod in the initial stage of loading before fracture of the specimen is not initiated. Distribution of stresses, strains and strain rates has been found for the given cases in computation. On this basis several fracture criteria are introduced in order to check the fracture initiation. It is found that maximum shear criterion is capable of good fracture prediciton.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.4
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• pp.300-307
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• 2003

This paper presents the multi-mode noise reduction of smart panels of which passive piezoelectric shunt damping is introduced. For the piezoelectric shunt damping, a passive shunt circuit composed of inductors and a load resistor is connected to the piezoelectric patch mounted on the panel structure. An electrical impedance model is introduced for the system based on the measured electrical impedance, and the criteria for maximum energy dissipation at the shunt circuit is used to find the optimal shunt parameters. For multi-mode shunt damping, the shunt circuit is modified by the introduction of a block circuit. Also the optimal location of the piezoelectric patch is studied by finite element analysis in order to cause the maximum admittance from the patch for each mode of the structure. An acoustic test is performed for the panels and a remarkable noise reduction is obtained in multiple modes of the panel structure.

• 연구논문집
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• s.26
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• pp.33-42
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• 1996

The transmission system of a washing machine which is called by the clutch is one of the most important components to preserve the performance. The clutch housing has a role to guard and mount the transmission system on the frame of the machine. The load which is applied on the clutch housing depends on the operating conditions. Nowadays the dehydration speed is higher and higher in order to improve the efficiency. In this study, the strains on the predicted weak positions were measured using the strain gage and its measuring equipment. The relationships between the dehydration speeds and the maximum principal strains were obtained. Finite element analysis is executed to acquire the effect of the dehydration speed on the stress of the clutch housing. The distributions of the equivalent stress and the maximum stresses under the various speeds, the various loading directions and the various thickness of the clutch housing were obtained.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.05a
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• pp.207-212
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• 2001

In this paper, a method to be able to decide the possible maximum gain of P, PI control for the retarded processes under stable condition is proposed. At first, adjustable parameter set causing stability limit are obtained based on the frequency domain condition which makes the roots of transfer function locate on the $j\omega$ axis. And the cut-in frequency $\omega{_p}$ to bring the parameter set to P control from PI control is derived by an equation with 2 parameters L and $T_m$ given, then $\omega{_p}$ is used to compute the maximum gain with stable condition. For the calculation, the controlled process of first order system with time delay element is introduced and all parameters are presumed to be time invariant.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.6
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• pp.131-138
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• 2004

The objective of this paper is to decide optimal location of a pin-hole to minimize stress concentration around the hole in a rotating disc. The focus of this investigation is to evaluate the effect of pin-hole on stress distribution around the hole using optimum design technique and finite element analysis. Design variables are the radial and the angular location of pin-hole from center of the hole and objective function is the maximum stress around hole in a rotating disc. Using first order method of optimization technique, we found that the maximum equivalent stress around the hole with optimized pin-hole could be reduced by 15.1% compared to that without pin-hole.

• Advances in aircraft and spacecraft science
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• v.2 no.3
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• pp.329-343
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• 2015

This study aimed to observe the effect of a novel concept (referred to as the flap extension) implemented on the leading edge of the flap of a three element high lift device. The high lift device, consisting of a flap, main element and slat is designed around an Airbus research profile for sufficient take off and landing performance of a large commercial aircraft. The concept is realised on the profile and numerically optimised to achieve an optimum geometry. Two different optimisation approaches based on Genetic Algorithm optimisations are used: a zero order approach which makes simplifying assumptions to achieve an optimised solution: as well as a direct approach which employs an optimisation in ANSYS DesignXplorer using RANS calculations. Both methods converge to different optimised solutions due to simplifying assumptions. The solution to the zero order optimisation showed a decreased stall angle and decreased maximum lift coefficient against angle of attack due to early stall onset at the flap. The DesignXplorer optimised solution matched that of the baseline solution very closely. The concept was seen to increase lift locally at the flap for both optimisation methods.

• Journal of Ocean Engineering and Technology
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• v.33 no.3
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• pp.272-279
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• 2019

In order to perform a pressure chamber experiment with a circular cylindrical pressure vessel, the dimensions of the cylinder need to be determined in the range of the maximum externally applied pressure of the chamber to create the collapse process. In this study, the collapse load values from published chamber test results, finite element analysis and the theory of thick cylinders were thoroughly compared in a aluminum cylinder. In order to investigate the effect of collapse load according to the ovality during manufacturing, nonlinear buckling analysis was performed and the collapse load according to ovality was compared. Based on the results, the dimensions of the steel cylinder were determined for the future chamber collapse test.