• 대한조선학회논문집
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• 제51권3호
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• pp.212-219
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• 2014

As subsea production has been revived up, the demand of subsea equipment has also been increased. Among the equipment, subsea tree plays a major role in safety. The tubing hanger is one of the most important components in subsea tree. In this study structural reliability analysis on dual bore tubing hanger of subsea tree is performed. The target reliability which is introduced in ISO regulation is used for judging whether tubing hanger is safe or not. The considered loads are working pressure, working temperature and suspended tubing weight. Thermal-stress analysis on tubing hanger is performed and kriging model is created based on the results of FEM analysis. According to von Mises criterion, limit state equation can be estimated. Reliability analysis is performed by using level 2 method and the result is verified by that of Monte Carlo Simulation. For finding most probable failure point, enhanced HL-RF method is adopted. Because the reliability of model doesn't reach target reliability, an improvement measure should be considered. Thus, it is suggested to change the material of tubing hanger main body to AISI 4140.

• 한국산학기술학회논문지
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• 제15권3호
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• pp.1707-1710
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• 2014

본 논문은 실리콘 원료의 용융과 방향성 응고에 의해 결정성이 양호한 방향성 응고에 대한 연구이다. 방사화 분석 결과 총 10가지 금속 불순물이 검출 되었지만, 농도 분포는 같은 위치에서 위와 아래의 차이는 크게 나지 않고, 어떤 특정한 위치에서 한쪽으로 집중되거나 어떤 경향성 없이 전체의 샘플의 모든 부분에서 농도가 거의 일정하게 분포를 나타냈다. 열 해석 시뮬레이션에 의한 결과, 용융은 유지 시간이 80분일 때 실리콘이 전체적으로 고르게 용융 온도에 도달하였고 냉각은 상부 냉각 온도가 $1,400^{\circ}C$와 60분 냉각 시 가장 좋은 결과 값을 나타내었다. 제작된 웨이퍼가 기존의 상용 웨이퍼보다 결정립계에서의 에칭이 훨씬 적게 이루어졌다.

• 한국융합학회논문지
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• 제11권5호
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• pp.139-144
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• 2020

본 연구에서는 드럼자체와 브레이크에 대한 시뮬레이션 해석을 하였으며 열해석 결과와 구조 해석을 통한 내구성을 고찰하여 그 해석 결과를 얻었다. 브레이크 실린더로 인하여 힘을 받는 라이닝,라이닝의 확장으로 인하여 힘을 받는 드럼 내부, 축의 회전으로 인하여 힘을 받는 드럼에 대한 열응력 및 구조 해석을 통하여 어느 부분에 등가응력과 변형량이 큰지를 확인하였다. 본 연구 결과를 종합하여 브레이크 디스크설계에 응용한다면 열변형 방지 및 그 내구성을 증대시키는데 활용성이 클 것으로 사료된다. 본 연구 결과는 실제적으로 드럼 브레이크에서의 열응력에 견딜 수 있는 내구성 있는 설계에 유용하게 적용할 수 있다. 계절별 기차선로 이음새에서의 내구성 해석을 적용함으로서 본 연구 결과가 미적인 설계에 응용되는 융합 연구에 유리하다고 보여진다.

• 제어로봇시스템학회논문지
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• 제6권9호
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• pp.831-835
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• 2000

The uniformity of themperature on a wafer is a wafer is one the most important parameters to conterol the RTF(Rapid Thermal Process) with proper input signals. It is impossible to achieve the uniformity of temperature without the exact estimation of temperature ar all points on the wafer. There fore, it is difficult to understand the internal dynamics as well as the structural complexities of the RTP, which is aprimary obstacle to measure the distributed temperatures on the wafer accurately. Furthermore, it is also hard to accomplish desirable estimation because only a few pyrometers are available in the general equipments. In the paper, a thermal model based on the chamber grometry of the AST SHS200 RTP system is developed to effectively control the thermal uniformity on the wafer. First of all, the estimation method of one-point measurement is developed, which is properly extended to the case of multi-point measurements. This thermal model is validated through simulation and experiments. The proposed work can be utilized to building a run-by -run or a real-time control of the RTP.

• 융복합기술연구소 논문집
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• 제10권1호
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• pp.37-40
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• 2020

Automotive battery system consists of various components such as battery cells, mechanical structures, cooling system, and control system. Recently, various computational technologies are required to develop an automotive battery system. Physics-based cell modeling is used for designing a new battery cell by conducting optimization of material selection and composition in electrodes. Structural analysis plays an important role in designing a protective system of battery system from mechanical shock and vibration. Thermal modeling is used in development of thermal management system to maintain the temperature of battery cells in safe range. Finally, vehicle simulation is conducted to validate the performance of electric vehicle with the developed battery system.

• Structural Monitoring and Maintenance
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• 제3권4호
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• pp.335-347
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• 2016

One of major errors in flow rate measurement for two-phase flow using an Electrical Capacitance Sensor (ECS) concerns sensor sensitivity under temperature raise. The thermal effect on electrical capacitance sensor (ECS) system for air-water two-phase flow monitoring include sensor sensitivity, capacitance measurements, capacitance change and node potential distribution is reported in this paper. The rules of 12-electrode sensor parameters such as capacitance, capacitance change, and change rate of capacitance and sensitivity map the basis of Air-water two-phase flow permittivity distribution and temperature raise are discussed by ANSYS and MATLAB, which are combined to simulate sensor characteristic. The cross-sectional void fraction as a function of temperature is determined from the scripting capabilities in ANSYS simulation. The results show that the temperature raise had a detrimental effect on the electrodes sensitivity and sensitive domain of electrodes. The FE results are in excellent agreement with an experimental result available in the literature, thus validating the accuracy and reliability of the proposed flow rate measurement system.

• Nuclear Engineering and Technology
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• 제53권2호
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• pp.466-473
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• 2021

Fire protection is one of important issues to ensure safety and reduce risks of nuclear power plants (NPPs). While robust programs to shut down commercial reactors in any fires have been successfully maintained, the concept and associated regulatory requirements are constantly changing or strengthening by lessons learned from operating experiences and information all over the world. As part of this context, it is necessary not only to establish specific fire hazard assessment methods reflecting the characteristics of research reactors and educational reactors but also to make decisions based on advancement encompassing numerical analyses and experiments. The objectives of this study are to address fire simulation in the control room of an educational reactor and to discuss integrity of digital console in charge of main operation as well as analysis results through comparison. Three electrical fire scenarios were postulated and twenty-four thermal analyses were carried out taking into account two turbulence models, two cable materials and two ventilation conditions. Twelve supplementary thermal analyses and six subsequent structural analyses were also conducted for further examination on the temperature and heat flux of cable and von Mises stress of digital console, respectively. As consequences, effects of each parameter were quantified in detail and future applicability was briefly discussed. On the whole, higher profiles were obtained when Deardorff turbulence model was employed or polyvinyl chloride material and larger ventilation condition were considered. All the maximum values considered in this study met the allowable criteria so that safety action seems available by sustained integrity of the cable linked to digital console within operators' reaction time of 300 s.

• Structural Engineering and Mechanics
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• 제42권6호
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• pp.815-829
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• 2012

This paper proposes a nonlinear computational modeling approach for the behaviors of structural systems subjected to fire. The proposed modeling approach consists of fire dynamics analysis, nonlinear transient-heat transfer analysis for predicting thermal distributions, and thermomechanical analysis for structural behaviors. For concretes, transient heat formulations are written considering temperature dependent heat conduction and specific heat capacity and included within the thermomechanical analyses. Also, temperature dependent stress-strain behaviors including compression hardening and tension softening effects are implemented within the analyses. The proposed modeling technique for transient heat and thermomechanical analyses is first validated with experimental data of reinforced concrete (RC) beams subjected to high temperatures, and then applied to a bridge model. The bridge model is generated to simulate the fire incident occurred by a gas truck on April 29, 2007 in Oakland California, USA. From the simulation, not only temperature distributions and deformations of the bridge can be found, but critical locations and time frame where collapse occurs can be predicted. The analytical results from the simulation are qualitatively compared with the real incident and show good agreements.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 춘계학술대회 논문집
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• pp.116-123
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• 1999

A case of the axle gear box which was one of tile power transmission components of high speed train was supported by the bearings installed in axle and the reaction arm connected in bogie frame. Structural analyses of this case were executed for investigation the application of aluminum for weight reduction. The evaluations of the material strength, the thermal strength and deformation, and the stability of natural vibration were carried out according to computer simulation. It was found out that the steel case was safe from the structural failure. For the aluminum case, there was no worry about the vibration resonance and the static failure, but some efforts to reduce tile deformation of the bearing mounting part.

• Structural Engineering and Mechanics
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• 제47권1호
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• pp.1-25
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• 2013

A combined thermal and mechanical action in roller compacted concrete (RCC) dam analysis is carried out using a three-dimensional finite element method. In this work a numerical procedure for the simulation of construction process and service life of RCC dams is presented. It takes into account the more relevant features of the behavior of concrete such as hydration, ageing and creep. A viscoelastic model, including ageing effects and thermal dependent properties is adopted for the concrete. The different isothermal temperature influence on creep and elastic modulus is taken into account by the maturity concept, and the influence of the change of temperature on creep is considered by introducing a transient thermal creep term. Crack index is used to assess the risk of occurrence of crack either at short or long term. This study demonstrates that, the increase of the elastic modulus has been accelerated due to the high temperature of hydration at the initial stage, and consequently stresses are increased.