• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2015년도 추계학술대회 논문집
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• pp.351-351
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• 2015

음극방식법은 피방식체에 외부전원을 인가하거나 보다 활성 금속을 전기적으로 연결하여 피방식체를 일정 전위까지 음극분극 되도록 하여 부식을 억제하는 방법이다. 해수 중 음극방식을 실시할 경우 생성되는 석회질 피막(Calcareous deposit)은 소요전류밀도 감소로 인한 희생양극의 수명연장 및 물리적 방호벽 역할을 한다. 그러나 일반적인 석회질 피막은 세라믹과 같은 화합물로써 밀착력이 매우 약하며, 적지 않은 피막 형성 시간이 소요된다. 따라서 본 연구에서는 해수 중 음극전류 프로세스를 응용하여 실제 강관의 해중부 및 간만대 영역까지 석회질 피막을 균일-치밀하게 형성시키기 위한 최적의 조건을 찾고자 하였다. 각 조건별로 제작된 석회질 피막은 SEM, EDS 및 XRD를 통해 막의 모폴로지, 조성원소 및 결정 구조를 분석하였으며, 이를 바탕으로 희생양극 종류(Al, Zn) 및 1, 3, $5mA/m^2$의 전류밀도 조건에서 부위-기간별 형성된 석회질 피막의 메커니즘을 해명하였다. 또한 밀착성과 내식특성을 평가하기 위해 테이핑 테스트, 침지-자연전위 거동을 분석 및 평가하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.17-22
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• 2009

Reliability analyses were performed to quantify the risk in axially loaded large-scale pile foundations in consideration of pile-soil interaction and uncertainties on various design variables. The finite difference method based on an equivalent soil spring model and a load transfer method and Monte Carlo simulation method are integrated in the framework of reliabilty analysis. The applicability and efficiency of the proposed method in the safety assessment of axially loaded pile-soil system was verified using a realistic example. Since the proposed method can explicitly consider uncertainties in various design variables, and quantify failure probability of a pile foundation, it can be used to estimate risk, to obtain basic informations for life cycle cost analysis, and to develop code requirements for a reliability-based design of pile foundations.

• 한국초전도ㆍ저온공학회논문지
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• 제4권2호
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• pp.73-77
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• 2002

In order to derive the detailed design of Thermal Shield Cryopanel. which plays a role to make the Tokamak Nuclear Fusion Equipment work at both static and efficient conditions the commercially available software package FLUENT Version 5.3, was utilized. This study investigated the effects of thermal sources and distributions on the temperatures of Lid. Body. Base. and EH-Port Cryopanel by the numerical technique whose grid generations cover the solid and 9as region of the panel. The physical model of the Thermal Shield Cryopanel is that the 10mm diameter of the pipe with 1mm thickness is soldered on the Stainless steel Panel with 4mm thickness. The heat fluxes to the panel are assumed to be by thermal radiation in the vacuum space and by conduction through the supporters. The inlet conditions of Helium gas are 20 atmospheric Pressures and 60K temperature. The panel shapes with cooling Pipes and the operational conditions to keep appropriate temperature distribution of Thermal Shield Cryopanel Have been found and suggested.

• 한국디지털건축인테리어학회논문집
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• 제12권4호
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• pp.67-75
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• 2012

The damage of greenhouse has been increasing due to frequent collapse of frame in greenhouse caused by the heavy snow and strong wind. But, greenhouses are constructed by steel tube members of pipe style and pin connection of them, so these greenhouses are very weak. Therefore, this study was carried out to find the type of member section and structural frame system in stress tolerant greenhouses. The modeling types for analysis were designed in accordance with structural frame configuration and member section in greenhouse. These types of models, which are existing type, diagrid type, symmetric and asymmetric section type of frame member in greenhouse were classified. Displacement analysis varying the vertical and horizontal loads for a series of models was carried out. As a result of this paper, it was verified that the structural frame configuration of diagrid type and asymmetric type of member section is better than existing type in the frame of greenhouses against snow loads and wind loads.

• 동력기계공학회지
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• 제18권2호
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• pp.50-56
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• 2014

Friction welding is a very useful joining process to weld metals which have axially symmetric cross section. In this paper, for the friction welding with tube-to-tube shape, the feasibility of industry application was determined using analyzing mechanical properties of weld and optimized welding variables was suggested. In order to accomplish this object, rotating speed, friction heating pressure, and friction heating time were selected as the major process variables and the experiment was performed in three levels of each parameter. Weld characteristic was investigated in terms of weld shape and metal loss, and 7mm of metal loss was regarded as the optimal metal loss. By tensile test, tensile strength and yielding strength was measured and fracture was occurred at base metal. In order to optimize the welding condition, fitness function was defined with respect to metal loss and yielding strength and the fitness values for each welding condition could be calculated in experimental range. Consequently, we set the optimal welding condition as the point which had maximum value of fitness function. As the result of this paper the optimal welding variables could be suggested as rotating speed was 1300 rpm, friction heating pressure was 15 MPa, and friction heating time was 10 sec.

• 자동차안전학회지
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• 제11권4호
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• pp.57-62
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• 2019

The seat back frame of the vehicle is subjected to load on the passenger behavior. Because of steel material, it is necessary to optimize the frame considering lightweight and safety. In this paper, finite element analysis is used for the optimal design of the seat back frame. First, a lightweight material is applied to reduce the weight of the seat back frame. Secondly, the design position of the pipe part fastened in the seat back frame was selected by considering the strength against the load generated by the occupant. Third, the shape of the side frame was derived by performing the phase optimization analysis for the AFT load condition. And we have compared the initial model with the optimal model to verify the light weighting and safety. As a result, the optimal design model of the seat back frame satisfying the weight reduction and safety has been proposed.

• Corrosion Science and Technology
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• 제11권6호
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• pp.218-224
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• 2012

Liquid droplet impingement erosion (LDIE) known to be generated in aircraft and turbine blades is recently appeared in nuclear piping. UT thickness measurements with both A-scan and B-scan UT inspection equipments were performed for a component estimated as susceptible to LDIE in feedwater heater vent system. The thickness data measured with B-Scan equipment were compared with those of A-Scan. Thermal hydraulic analysis based on ANSYS FLUENT code was performed to analyze the behavior of liquid droplets inside piping. The wall thinning rate and residual lifetime based on both existing Sanchez-Caldera equation and measuring data were also calculated to identify the applicability of the existing equation to the LDIE management of nuclear piping. Because Sanchez-Caldera equation do not consider the feature of magnetite formed inside piping, droplet size, colliding frequency, the development of new evaluation method urgently needs to manage the pipe wall thinning caused by LDIE.

• 반도체디스플레이기술학회지
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• 제15권2호
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• pp.74-80
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• 2016

This study presents a thermal device specially designed for thermal nanoimprint lithography equipments, which requires the capability of rapid heating and cooling, high temperature uniformity and the material strength to endure high stamping pressure. The proposal to meet these requirements is a planar-type hot plate extensible to a large area, in which long circular cartridge heaters and heat pipes are installed inside in parallel. The heat pipes are connected to the outside water cooling chamber. A hot plate made of stainless steel is fabricated with a dimension $240mm{\times}240mm{\times}20mm$. Laboratory experiments are conducted to examine the thermal performance of the hot plate. The results illustrate that the employment of heat pipes leads to a notable enhancement of temperature uniformity in the device and provides an efficient heat delivery from the hot plate to outside. It is verified that the suggested hot plate could be a feasible thermal tool for thermal nanoimprint lithography, satisfying the major design requirements.

• 대한조선학회논문집
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• 제47권2호
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• pp.233-241
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• 2010

Scaffolding system in the membrane LNG carrier is a steel structure composed of various pipe-shaped members connected by specific coupling devices. In this study, the automatic design program for scaffolding system in membrane LNG carrier has been developed. It enables user to arrange members easily considering design constraints and input variables such as size of tank, position of legs, level height and so on. In addition to that, it creates finite element analysis model with loading and boundary conditions automatically and carries out structural analysis. With post processor based a state-of-the-art computer graphics, users can easily check the results of structural analysis and make a report for structural safety of scaffolding system.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.899-904
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• 2009

This paper presents the analysis result of load-transfer mechanism and pile movements associated with the development of frictional resistance to understand the engineering characteristics of micropile behavior. An field load tests were performed for two different types of micropiles and they are (i) thread bar reinforcement with D=50mm and (ii) hollow steel pipe reinforcement with $D_{out}$=82.5mm and $D_{in}$=60.5mm and wrapped with woven geotextile for post-grouting. The load test results indicated that micropiling with pressured grouting provided better load-transfer characteristics than micropiling with gravity grouting under both compressive and tensile loading conditions in that unit skin frictional resistance is well distributed along installation depth. The unit weight and unconfined compressive strength of cured grout were obtained for each piling method. The strength and unit weight of micropile with pressured grouting was higher than those with gravity grouting. The fact that load bearing quality with pressured grouting is better than that of gravity grouting could be attributed to the dense mutual adhesion between surrounding ground and pile due to pressurized grouting method and better grout quality.