• Journal of the Korean Society of Safety
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• v.21 no.1 s.73
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• pp.28-34
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• 2006

A procedure of estimating failure probability is demonstrated for a pressurized pipe of CrMo steel used at $538^{\circ}C$. Probabilistic fracture mechanics were employed considering variations of pressure loading, material properties and geometry. Probability density functions of major material variables were determined by statistical analyses of implemented data obtained by previous experiments. Distributions of the major variables were reflected in Monte Carlo simulation and failure probability as a function of operating time was determined. The creep crack growth life assessed by conventional deterministic approach was shown to be conservative compared with those obtained by probabilistic one. Sensitivity analysis for each input variable was also conducted to understand the most influencing variables to the residual life analysis. Internal pressure, creep crack growth coefficient and creep coefficient were more sensitive to failure probability than other variables.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.4
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• pp.416-424
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• 2016

A robust design of head gasket is pursued by using FEA model of engine assembly. Engine assembly model consists of cylinder head, block, gasket, and head bolt is constructed to understand a complex behavior of this engine compound. Thermal loading is performed on the assembled engine cylinder and block to obtain temperature field. Firing load is added to the results of heat transfer analysis to simulate the engine operation condition. Temperature filed results from heat transfer analysis are mapped into the structural mesh. Contact pressure distribution along the bead has been monitored for the engine operation condition. Based on the results obtained from the analysis, Taguchi method has been adopted for a robust design process of head gasket. Among the control factors, bolt size affects most robustness of head gasket sealing.

• Bulletin of the Korean Chemical Society
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• v.24 no.1
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• pp.19-22
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• 2003

For CHNO explosives, two new correlations of the form $P_{CJ}\;=\;8.7({\alpha}T_c')^{1/2}{\rho}_0^2-5\;and\;P_{CJ}\'=\'9.5({\alpha}T_c')^1/2{\rho}_0^2-9$ have been demonstrated, which relate detonation pressure, $P_{CJ}$; combustion temperature of the explosive in gas phase, $T_c$; combustion temperature of the explosive in crystalline state, $T_c'$; and the number of moles of gaseous products per unit weight of explosive, α; at initial density of the explosive, ${\rho}_0$. Experimental and semi-empirical PM3 procedures were used for the computation of $T_c$. Detonation pressures derived in this manner have a simple form without need to use computer code.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2186-2188
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• 2000

A fiberoptic sensor using an SLD as a light source has been studied. The sensor system employs an intrinsic fiber Fabry-Perot interferometer as a sensing tip and a fiber Mach-Zehnder interferometer as a processing one. A free loading test for temperature application shows that the fiberoptic sensor has a wide-dynamic range as well as high resolution. Due to the inherent property of the optical fiber itself and the intrinsic Fabry-Perot interferometer. the fiberoptic sensor gives obvious benefits when it is applied to harsh environments to monitor some physical parameters such as temperature, strain, pressure and vibration.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.1
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• pp.128-134
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• 2012

This paper gives an overview of the requirements for electrical equipment in potentially explosive atmospheres and describes how these are applied to electrical machines and drives in hazardous areas. The method by which equipment can be shown to be safe in a whole range of gases, by testing in a single test gas, is covered. It is shown how the more recently introduced methods of protection for hazardous areas, increased safety and nonsparking, are ideally suited to AC machines and drives. A novel method of measuring the fullload temperature rise of electrical machines for hazardous, and other areas, without the need to connect a mechanical load to the machine's drive shaft is explained.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.99-106
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• 2002

This paper presents an analytical investigation on the behavior of simple span integral abutment bridge. An integral abutment bridge is a simple span or multiple span continuous deck type bridge having the deck integral with the abutment wall. Although the temperature variation and earth pressure are the major attributor to the total stress in integral abutment bridge, the superstructure has been designed by modeling it as a simple or continuous beam In order to investigate the effect of temperature change and earth pressure on the superstructure of integral bridge, the simple span integral bridge is modeled as a plane frame element. Performing frame analysis, the variations of bending moment and axial force of superstructure due to the various loading combination are investigated with respect to the flexural rigidity of piles, and the bending moment and axial force obtained by frame analysis are compared with the maximum bending moment obtained by conventional design method and initial prestressing force respectively.

• Proceedings of the Korean Reliability Society Conference
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• 2006.05a
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• pp.158-164
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• 2006

The creep behavior of newly developed composite geogrids which consists of PET yarns sheathed in PP were evaluated using SIM. For the SIM procedure, three test parameters, the applied loads, temperature steps and number of ribs were investigated, The study confirmed that temperature steps of 10 and 14$^{\circ}C$ up to 80$^{\circ}C$ are applicable for composite geogrids due to the different transition temperatures between two materials. At applied loads of 40 and 50%, only primary creep state was measured, while secondary creep state appeared at the applied loads of 60%, The lifetimes of composite geogrids were estimated at each of loading level using statistical reliability analysis technique. The results show that the lifetimes longer than 100 years can be predicted within 16 hours. Therefore, SIM is very effective and economical accelerated creep test methods, especially for lifetime prediction. This gives guidelines for users to select the appropriate factor of safety against creep considering the field condition within shorter test times.

• International Journal of Railway
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• v.3 no.4
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• pp.126-133
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• 2010

The thermal buckling analysis of curved continuous welded rail (CWR) is studied for the lateral buckling prevention. This study includes a thermal buckling theory which accounts for both thermal and vehicle loading effects in the evaluation of track stability. The parameters include rail size, track lateral resistance, track longitudinal and torsional stiffnesses, initial misalignment amplitude and wavelength, track curvature, tie-ballast friction coefficient and truck center spacing. Parametric studies are performed to evaluate the effects of the individual parameters on the upper and lower critical buckling temperatures. The results show that the upper critical buckling temperature is highly affected by the uplift due to vehicle loads. This study provides a guideline for the improvement of stability for dynamic buckling in curved CWR track.

• Proceedings of the KAIS Fall Conference
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• 2001.05a
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• pp.287-289
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• 2001

The morphology of silica supported MoO$_3$ catalysts, which was prepared by impregnation of ammonium heptamolybdate with various weight loadings up to 35 wt%, was studied using x-ray diffraction. In addition to the orthorhombic phase, the behavior of the rarely studied hexagonal phase was characterized. For high loading catalysts, excess ammonium ions present in the monoclinic and triclinic precursors are capable of occupying interstitial sites of microcrystalline MoO$_3$ during moderate temperature calcinations and in doing so enhance the MoO$_3$-SiO$_2$ interaction. This results in a "well dispersed" morphology at high loadings. Sintering at high temperature is due to loss of ammonium from the oxide framework. Ammonia reimpregnation, which leads back to the well dispersed hexagonal phase, may offer a simple regeneration process for spent Mo containing catalysts.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.1
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• pp.203-208
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• 2004

To make practical applications of Al-Zn-Mg ternary aluminum alloy effectively in various field, a series of static creep tests under the 16 temperature-stress combination conditions had been performed. The creep tester with constant stress loading was designed and made by the authors and used in this study. The higher the creep temperature rose, the less the stress exponents became. The bigger the applied stresses became, the less values the creep strain activation energy showed. The life prediction constant of Larson-Miller parameter was calculated as about 2.3. In the fractography, the ductile fracture with dimples by intergranular breakage was primarily observed. We can make practical use of these test data in the design, the life prediction and the prevention of the accidents of the thermal facilities, etc.