• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.12
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• pp.540-545
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• 2005

The transformer tank is pressurized by atmosphere at the time of vacuum oiling and, plastic deformation occurs at the section of stress concentration on transformer tank at this time. It is important to predict where the sections of stress are in order to prevent deformation and to add reinforcement. This paper presents prediction results where the sections of stress are occurred and whether plastic deformation occur or not, using structure analysis program(ANSYS-design program).

• Steel and Composite Structures
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• v.37 no.4
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• pp.419-429
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• 2020

Composite structures are generally pressurized at both sides when repaired by the scarf repair method. But single-face vacuum bag curing (SVC) may be used in some practical scarf repair of penetration damage due to the low accessibility of composite structures, which can decrease bonding quality and may reduce structural mechanical properties. In this paper, experimental investigations were conducted on tensile and compressive properties of scarf-repaired composite laminates using SVC and double-face vacuum bag curing (DVC) in four hygrothermal environments. Finite element models of composite scarf joints with voids were established to further explore the failure mechanism of scarf-repaired laminates. Results show that the curing condition hardly affects tensile and compressive properties of the repaired laminates though it significantly affects the bonding quality with adhesive inner voids. Failure loads of scarf joints almost keep unchanged with adhesive voids increasing.

• Journal of Energy Engineering
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• v.24 no.4
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• pp.175-182
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• 2015

A methodology to determine the most conservative initial condition based on random sampling of operation parameters is established, in which a best-estimate computer code is adopted to minimize the conservatism in code models. To validate the applicability of the suggested method, safety evaluation for a transient of loss of condenser vacuum in a pressurized water reactor is performed. One-hundred different initial conditions are generated by MOSAIQUE program automatically and the peak pressure for the most conservative case is determined from transient analyses. The safety margin obtained with the new approach is almost equivalent to the values determined with the existing methodologies. It is found that the time and human resources required for the safety evaluation could be reduced with the suggested approach.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.975-980
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• 2001

Like composite material. the coil winding pack of the KSTAR (Korea Superconducting Tokamak Advanced Research) consist of multiphase element such as metallic jacket material for protecting superconducting cable, vacuum pressurized imprepregnated (VPI) insulation, and corner roving filler. For jacket material, four CS (Central Solenoid) Coils, $5^{th}$ PF (Poloidal Field) Coil, and TF (Toroidal Field Coil) use Incoloy 908 and $6-7^{th}$ PF coil, Cold worked 316LN. In order to analyze the global behavior of large coil support structure with coil winding pack, it is required to replace the winding pack to monolithic matter with the equivalent mechanical properties, i.e. Young's moduli, shear moduli due to constraint of total nodes number and element numbers. In this study, Equivalent Young's moduli, shear moduli, Poisson's ratio, and thermal expansion coefficient were calculated for all coil winding pack using Finite Element Method.

• The KSFM Journal of Fluid Machinery
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• v.19 no.4
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• pp.39-42
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• 2016

A PFA lined ball valve, which is machined with fluorinated resin PFA to its inner part for improving corrosion resistance, non-stickness, heat-resistance, has been widely used to the chemical/pharmaceutical industries, the semiconductor/LCD manufacturing processes, etc. with the high purity chemicals as working fluid. EPA stated that 60% of all fugitive emissions come from the valve stem packing in a typical petroleum or chemical processing plant. They monitor regulated components for leaks and maintain seal performance at acceptable levels. Korean industrial standards only deals with the bubble test for in-line leakage of valves, which has the detectable leak rate of $10^{-4}$ [$mbar{\cdot}L{\cdot}s^{-1}$], therefore, it is not sufficient to check fugitive emissions. In this study, we conducted Helium leak detection from a PFA lined ball valve and evaluated fugitive emissions according to ISO 15848-1, which has the detectable leak rate of $10^{-9}$ [$mbar{\cdot}L{\cdot}s^{-1}$], for manufacturing the high-reliable PFA lined ball valves against fugitive emissions.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.7
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• pp.1-7
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• 2021

Restrictions on the emissions of nitrogen oxides, sulfur oxides, carbon dioxide, and particulate matter from marine engines are being tightened. Each of these emissions requires different reduction technologies, which are costly and require many pieces of equipment to meet the requirements. Liquefied natural gas (LNG) fuel has a great advantage in reducing harmful emissions emitted from ships. Therefore, the marine engine application of LNG fuel is significantly increasing in new ship buildings. Accordingly, this study analyzed the internal support structure, insulation type, and fuel supply piping system of a 35 m3 International Maritime Organization C type pressurized storage tank of an LNG-fueled ship. Analysis of the heat transfer characteristics revealed that A304L stainless steel has a lower heat flux than A553 nickel steel, but the effect is not significant. The heat flux of pearlite insulation is much lower than that of vacuum insulation. Moreover, the analysis results of the constraint method of the support ring showed no significant difference. A553 steel containing 9% nickel has a higher strength and lower coefficient of thermal expansion than A304L, making it a suitable material for cryogenic containers.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.310-313
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• 2009

Several high nitrogen stainless steel ingots(100kg) were fabricated with changing Ni and $[N]_2$ contents by Pressurized Vacuum Induction Melting(P_VIM). After free forging process, chemical compositions, microstructure and mechanical properties were estimated. Hardness was increased with the increase of $[N]_2$ content. Furthermore, microstructure including a lot of tempering twins was observed with optical microscope. Mechanical properties were estimated as function of solution treatment temperature and cooling method(air/water) under duration time of 1 hr on sample that were fabricated with Ni content under the atmospheric $[N]_2$ pressure. At solution treatment range of $1050{\sim}1100^{\circ}C$, hardness was decreased with the increase of solution temperature and there were little discrepancy of microstructure and hardness with cooling method. Computer simulation was carried out in order to inspect pass schedule in cold rolling process. When the condition of simulation was roll speed of 2.5mpm, rolling rate $15{\sim}17%$ per pass, it was ascertained that the formation such as deformation by sticking and lamellar sliver etc. was restricted from a simulation.