• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.166-173
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• 2007

Fatigue fracture behavior of a hybrid bolted joint was evaluated in comparison to the case of static fracture. Two kinds of specimens were fabricated for the mechanical tests; a hybrid bolted joint specimen for the shear test and a hybrid joint part specimen applied in the real tilting car body for the bending test. Characteristic fracture behaviors of those specimens under cyclic toads were obviously different from the case under static loads. For the hybrid bolted joint specimen, static shear loading caused the fracture of the bolt body itself in a pure shear mode, whereas cyclic shear loading brought about the fracture at the site of local tensile stress concentration. For the hybrid joint part specimen, static bend loading caused the shear deformation and fracture in the honeycomb core region, while cyclic bend loading did the delamination along the interface between composite skin and honeycomb core layers as well as the fracture of welded joint part. Experimental results obtained by static and fatigue tests were reflected in modifications of design parameters of the hybrid joint structure in the real tilting car body.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.5
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• pp.960-968
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• 2002

In this research, the effects of fiber stacking sequence on damage behaviors of FML(Fiber Metal Laminates) subject to indentation loading. SOP (Singly Oriented Ply) FML and angle ply FML were fabricated to study fiber orientation effects and angle ply effects. FML were fabricated by using 1050 aluminum laminate and carbon/epoxy prepreg. To increase adhesive bonding strength, Al laminate was etched using FPL methods. The static indentation test were conducted by using UTM under the 2side clamped conditions. During the tests, load and displacement curve and crack initiation and propagation behaviors were investigated. As fiber orientation angle increases, the crack initiation load of SOP FML increases because the stiffness induced by fiber orientation is increased. The penetration load of SOP FML is influenced by the deformation tendency and boundary conditions. However, the macro-crack of angle ply FML was initiated by fiber breakage of lower ply because angle plies in Angle ply FML prevents the crack growth and consolidation. The Angle ply FML has a critical cross-angle which prevent crack growth and consolidation. Damage behavior of Angle ply FML is changed around the critical cross-angle.

• Journal of KIISE:Software and Applications
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• v.31 no.8
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• pp.1073-1082
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• 2004

This paper presents a technique for an agent to adaptively behave to unforeseen and dynamic circumstances. Since the traditional methods utilized the information about an environment to control intelligent agents, they were robust but could not behave adaptively in a complex and dynamic world. A behavior-based method is suitable for generating adaptive behaviors within environments, but it is necessary to devise a hybrid control architecture that incorporates the capabilities of inference, learning and planning for high-level abstract behaviors. This Paper proposes a 2-level control architecture for generating adaptive behaviors to perceive and avoid dynamic moving obstacles as well as static obstacles. The first level is behavior-network for generating reflexive and autonomous behaviors, and the second level is to infer dynamic situation of agents. Through simulation, it has been confirmed that the agent reaches a goal point while avoiding static and moving obstacles with the proposed method.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.4
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• pp.35-43
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• 2011

This study examined the structural behaviors of foam insulated concrete sandwich panels subjected to uniform pressure. Finite element models were used to simulate the detailed shear resistance of connectors and the nonlinear behaviors of concrete, foam and rebar components. The models were then validated using data from static tests performed at the University of Missouri. Both composite and non-composite action had a significant effect on the response of the foam insulated concrete sandwich panels, indicating that the simulated shear tie resistance should indeed be incorporated in numerical analyses. The modeling approach used here conveniently simulated the structural behaviors during all loading stages (elastic, yielding, ultimate and post-failure) and was compatible with the American Concrete Institute (ACI) Code and existing design practices. The results of this study will therefore provide useful guidelines for the analysis and design of foam insulated sandwich panels under both static and dynamic loadings.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.2
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• pp.268-275
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• 2003

Generally, structural optimization is carried out based on external static loads. All forces have dynamic characteristics in the real world. Mathematical optimization with dynamic loads is extremely difficult in a large-scale problem due to the behaviors in the time domain. The dynamic loads are often transformed into static loads by dynamic factors, design codes, and etc. Therefore, the optimization results can give inaccurate solutions. Recently, a systematic transformation has been proposed as an engineering algorithm. Equivalent static loads are made to generate the same displacement field as the one from dynamic loads at each time step of dynamic analysis. Thus, many load cases are used as the multiple leading conditions which are not costly to include in modern structural optimization. In this research, it is mathematically proved that the solution of the algorithm satisfies the Karush-Kuhn-Tucker necessary condition. At first, the solution of the new algorithm is mathematically obtained. Using the termination criteria, it is proved that the solution satisfies the Karush-Kuhn-Tucker necessary condition of the original dynamic response optimization problem. The application of the algorithm is discussed.

• KIEE International Transactions on Power Engineering
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• v.5A no.3
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• pp.244-251
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• 2005

Power transfer capability has been recently highlighted as a key issue in many utilities. It is determined by the thermal stability, dynamic stability and voltage stability limits of generation and transmission systems. In particular, voltage stability affects power transfer capability to a great extent in many power systems. This paper presents a tool for determining total transfer capability from a static voltage stability viewpoint using IPLAN, which is a high level language used with the PSS/E program. The tool was developed so as to analyze static voltage stability and to determine the total transfer capability between different areas from a static voltage stability viewpoint by tracing stationary behaviors of power systems. A unified power flow controller (UPFC) is applied for enhancing total transfer capability between different areas from the viewpoint of static voltage stability. Evaluation of the total transfer capability of a practical KEPCO power system is performed from the point of view of static voltage stability, and the effect of enhancing the total transfer capability by UPFC is analyzed.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.294-299
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• 2005

A machining center is a complex dynamic system whose behavior influences the machining stability and machined surface quality. This paper focused on establishment of a measurement system and experimental study on static, dynamic, and modal analysis of a machining center. The dynamic stiffness result by the analysis showed the weak part of the machining center. The results provided structure modification data for getting better dynamic behaviors.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.262-267
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• 2016

In this paper, to design Human Powered Aircraft(HPAC) with high aspect ratio wing which behave with large displacement under lift distribution causing a failure itself, then steel wire has been designed to prevent its failure. unit load method is used to calculate reaction force on wire and Optimal Triangle(OPT) membrane is employed to analyze its main wing spar with large displacement. EDISON CSD solver, linear static analysis and co-rotational nonlinear static anaysis both using OPT membrane produce behaviors of beam for each case of wire location about main wing spar, and aerodynamic coefficient also, by using aerodynamic analysis tool.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.97-98
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• 2006

High current behaviors of the grounded gate extended drain N-type metal-oxide-semiconductor field effects transistor (GG_EDNMOS) electro-static discharge (ESD) protection devices are analyzed. Simulation based contour analyses reveal that combination of BJT operation and deep electron channeling induced by high electron injection gives rise to the 2-nd on-state. Thus, the deep electron channel formation needs to be prevented in order to realize stable and robust ESD protection performance. Based on our analyses, general methodology to avoid the double snapback and to realize stable ESD protection is to be discussed.

• Structural Engineering and Mechanics
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• v.71 no.1
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• pp.89-98
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• 2019

In this study, the mechanical bending behaviors of functionally graded porous nanobeams are investigated. Four types of porosity which are, the classical power porosity function, the symmetric with mid-plane cosine function, bottom surface distribution and top surface distribution are proposed in analysis of nanobeam for the first time. A comparison between four types of porosity are illustrated. The effect of nano-scale is described by the differential nonlocal continuum theory of Eringen by adding the length scale into the constitutive equations as a material parameter comprising information about nanoscopic forces and its interactions. The graded material is designated by a power function through the thickness of nanobeam. The beam is simply-supported and is assumed to be thin, and hence, the kinematic assumptions of Euler-Bernoulli beam theory are held. The mathematical model is solved numerically using the finite element method. Numerical results show effects of porosity type, material graduation, and nanoscale parameters on the static deflection of nanobeam.