• Proceedings of the KSR Conference
• /
• 2002.10a
• /
• pp.54-59
• /
• 2002

In general, the aluminum extrusions are used to the light construction of the high speed rail vehicle structures. However, the research works ok the crashworthy design of the high speed rail vehicle structures are not published sufficiently because the crash test of high speed rail vehicle structures costs high and is complicated. So, a method that can predict crash characteristics of a large size structure like a high speed tail vehicle should be suggested. In this study, the scale model studies are performed to predict the impact energy absorption characteristics of full scale model. In the first place, we verified the theory of scale law using FE-simulation from the crashworthiness point of view. Secondly, we performed the crush test using scale model, made of aluminum sub structure. As a result, we could predict the crash characteristics using scale model by 10∼20% error.

• Journal of Ocean Engineering and Technology
• /
• v.18 no.6 s.61
• /
• pp.70-78
• /
• 2004

In order to increase the load carrying capacity of tubular structures, the joints of tubular members are usually reinforced with various reinforcement system. A stiffening method with internal ring stiffeners is effectively used for the steel tubular joint with a large diameter. In this study, the behavior of internally ring-stiffened tubular T-joints subjected to axial loading is assessed. For the parametric study, nonlinear finite element analyses are used to compute the static strength on non-stiffened and ring-stiffened T-joints. Based on the numerical results, an internal ring stiffener is found to be efficient in improving the static strength. The influence of geometric parameters has been determined, and the reinforcement effect are evaluated. Based on the FE results, regression analises are performed considering the practical size of ring stiffener. Finally strength estimation formulas for ring-stiffened tubular T-joints are proposed.

• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.929-931
• /
• 2004

Recently, there are growing demands for permanent magnet(PM) type stepping motor that greater mechanical output, smaller size. Especially, the PM type stepping motor with claw-poles is preferred solution for many small electronics position determination devices since it is small in size, low cost. But, the design of the PM type stepping motor with claw-poles is very difficult because it has a magnetic 3-D shape. This paper deals with a study of the miniaturization of the PM type stepping motor with claw-poles. We investigate the characteristic of the actual model using the equivalent magnetic circuit method and 3-D FE analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.11a
• /
• pp.121-125
• /
• 2001

We study the feasibility of synthesizing Si particles using PLA method. In the previous studies, it was possible to control the size of Si nanoparticles bythe He gas pressure. In this study, we fabricated sub-micron size Si particles with various shapes such as conical, hexagonal, and ring by controlling not only the ambient as pressure but also the laser energy density. Furthermore, we found that the conical Si particles were uniform-sized and had step shape when observed from FE-SEM and AFM. The conical Si particle has the same crystal structure as the bulk single crystalline Si by the analysis of the Raman scattering. It is shown that the relationship between the laser energy density and the He gas pressure inside the chamber affects the shape of the Si particle.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.1
• /
• pp.139-145
• /
• 2007

This paper presents the low cycle thermal fatigue of the engine exhaust manifold subject to thermomechanical cyclic loadings. The analysis includes the FE model of the exhaust system, temperature dependent material properties, and thermal loadings. The result shows that at an elevated temperature, large compressive plastic deformations are generated, and at a cold condition, tensile stresses are remained in several critical zones of the exhaust manifold. From the repetitions of thermal shock cycles, plastic strain ranges could be estimated by the stabilized stress-strain hysteresis loops. The method was applied to assess the low cycle thermal fatigue for the engine exhaust manifold. It shows a good agreement between numerical and experimental results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.28 no.5
• /
• pp.39-51
• /
• 2014

This paper deals with design of a direct-coupled, small-scaled permanent magnet generator (PMG) for wind power application. First, this paper determines rated power and speed of the PMG from measured characteristics of wind turbines. Second, we derive analytical solutions for the open-circuit field in order to determine optimum magnet thickness and pole pitch/arc ratio. Third, on the basis of open circuit field solutions, stator magnetic circuit including slot opening, teeth width and yoke thickness is designed. And then, a diameter of stator coil which agree with a required current density is calculated, and its turns are determined from the area of slot considering winding packing factor. Finally, finite element (FE) method is employed in analyzing the details of the designed PMG and, test results such as back-emf measurements are given to confirm the design.

• Journal of the Korean Society of Safety
• /
• v.23 no.5
• /
• pp.22-29
• /
• 2008

This paper provides the evaluation method for the pressure vessel with internal wall-thinning defect, which is based on ASME design criteria. Pressure vessel has wall-thinning partially and patch reinforcement has been attached for reliable operating. However, present partial wall thinning could be through wall thinning at the next inspection time with present corrosion progress speed. Therefore safety margin was calculated for various conditions from present wall-thinning condition to additive patch reinforced condition via two-dimensional and three-dimensional, geometrically linear FE analyses using elastic materials.

• Proceedings of the KIEE Conference
• /
• 2005.07b
• /
• pp.1264-1266
• /
• 2005

This paper analyzes static and transient response characteristics of a permanent magnet type stepping motor with claw poles using three-dimensional finite element method. The outer diameter of the stepping motor to be analyzed is approximately 6 mm. In this paper we analyzes only 2 poles of the stepping motor, which has 10 magnetic poles made up of NdFeB material, using periodic boundary condition. We clarify transient response and static torque charateristics using Maxwell 3D and Matlab Simulink.

• Macromolecular Research
• /
• v.17 no.8
• /
• pp.609-615
• /
• 2009

Two types of nano composite were obtained by in situ chemical method in polyaniline (PANI)/dodecyl-benzenesulfonic acid (DBSA) system depending on the use of either ammonium persulfate (APS) or ferric chloride ($FeCl_3$) as the oxidant. In order to study the difference of the two composites in the surface characteristics, thermal stability, and electric properties, the composite films were studied by transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and temperature dependent DC electrical conductivity. The results revealed a large difference in the surface morphology, thermal stability, and the microstructure properties between the two composites, and these differences were considered responsible for the molecular order and conductivity.

• Tunnel and Underground Space
• /
• v.20 no.2
• /
• pp.73-81
• /
• 2010

The paper presents the application of FE simulations of NATM tunnel using different constitutive models. The results from a series of two dimensional plane strain finite element analyses of medium-liner interaction for NATM are presented. Four types of constitutive models are considered, namely, linear elastic, elasto-plastic Mohr-Coulomb, Hardening-Soil, Soft-Soil model. The design for tunnels requires a proper estimate of surface settlement and lining forces. It is shown that the advanced constitutive model gives better predictions for both ground movement and structural forces.