• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 춘계학술대회 논문집
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• pp.274-278
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• 2003

In recent, an application of high energy density beam we/ding is increasing to obtain the high quality in weldments. Laser welding, especially, has been recognized as an useful method and its beam power has also increased according to the development of relevant technology. However, welding method in the fields of power plant is conservative because their structures have required to endure high temperature and pressure. So, authors conduct the numerical simulation in order to consider the possibility of laser welding on the material of the pressure vessels ($2\frac{1}{4}Cr-1Mo$ steel). As a result of this study, we can confirm the advantages of laser welding and obtain useful information for the experiments of weldability.

• 한국표면공학회지
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• 제54권5호
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• pp.248-259
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• 2021

This study examined the influence of post weld heat treatment (PWHT) conditions on corrosion behaviors of laser-welded super duplex stainless steel tube. Due to the high cooling rate of laser welding, the phase fraction of ferrite and austenite in the weld metal became unbalanced significantly. In addition, the Cr₂N particles were precipitated adjacent to the fusion line, which can be susceptible to the localized corrosion. On the other hand, the phase fraction in the weld metal was restored at a ratio of 5:5 when exposed to temperatures above 1060 ℃ during the post weld heat treatment. Nevertheless, the high beltline speed during the PWHT, leading to the insufficient cooling rate, caused a precipitation of σ phase at the interface between ferrite/austenite in both weld metal and base metal. This resulted in the severe corrosion damages and significant decrease in critical pitting temperature (CPT), which was even lower than that measured in as-welded condition. Moreover, the fraction of σ phase in the center region of post weld heat treated steel tube was obtained to be higher than in the surface region. These results suggest that the PWHT conditions for the steel tube should be optimized to ensure the high corrosion resistance by excluding the precipitation of σ phase even in center region.

• 지능정보연구
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• 제23권1호
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• pp.47-67
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• 2017

강판 표면 결함은 강판의 품질과 가격을 결정하는 중요한 요인 중 하나로, 많은 철강 업체는 그동안 검사자의 육안으로 강판 표면 결함을 확인해왔다. 그러나 시각에 의존한 검사는 통상 30% 이상의 판단 오류가 발생함에 따라 검사 신뢰도가 낮은 문제점을 갖고 있다. 따라서 본 연구는 Simultaneous MTS (S-MTS) 알고리즘을 적용하여 보다 지능적이고 높은 정확도를 갖는 새로운 강판 표면 결함 진단 시스템을 제안하였다. S-MTS 알고리즘은 단일 클래스 분류에는 효과적이지만 다중 클래스 분류에서 정확도가 떨어지는 기존 마할라노비스 다구찌시스템 알고리즘(Mahalanobis Taguchi System; MTS)의 문제점을 해결한 새로운 알고리즘이다. 강판 표면 결함 진단은 대표적인 다중 클래스 분류 문제에 해당하므로, 강판 표면 결함 진단 시스템 구축을 위해 본 연구에서는 S-MTS 알고리즘을 채택하였다. 강판 표면 결함 진단 시스템 개발은 S-MTS 알고리즘에 따라 다음과 같이 진행하였다. 첫째, 각 강판 표면 결함 별로 개별적인 참조 그룹 마할라노비스 공간(Mahalanobis Space; MS)을 구축하였다. 둘째, 구축된 참조 그룹 MS를 기반으로 비교 그룹 마할라노비스 거리(Mahalanobis Distance; MD)를 계산한 후 최소 MD를 갖는 강판 표면 결함을 비교 그룹의 강판 표면 결함으로 판단하였다. 셋째, 강판 표면 결함을 분류하는 데 있어 결함 간의 차이점을 명확하게 해주는 예측 능력이 높은 변수를 파악하였다. 넷째, 예측 능력이 높은 변수만을 이용해 강판 표면 결함 분류를 재수행함으로써 최종적인 강판 표면 결함 진단 시스템을 구축한다. 이와 같은 과정을 통해 구축한 S-MTS 기반 강판 표면 결함 진단 시스템의 정확도는 90.79%로, 이는 기존 검사 방법에 비해 매우 높은 정확도를 갖는 유용한 방법임을 보여준다. 추후 연구에서는 본 연구를 통해 개발된 시스템을 현장 적용하여, 실제 효과성을 검증할 필요가 있다.

• 기술사
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• 제16권1호
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• pp.13-19
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• 1983

As one of staff members participated in the full course of the plant construction project of On-san Refinery to its successful completion. I had my past expierence that the plant construction project was so complicated, and a Long period required, and thus there were so money problems to be solved. Among the problem, I mainly noticed that the following listed points were solved and improved. 1. Each drawing should be in every accuracy possible. 2. Contract should be specified in every detail possible. 3. All invoiced prices of breack down list should be coped with the current market prices. 4. All execution of work should be in the most accuracy. A. Planing execution of work. B. Coordination with supervisor group. C. Economical method for execution of work. D. Safety control. 3, Calculation work field should be established seperately 6. Each staff members should be work at the best of his pride.

• 한국강구조학회 논문집
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• 제28권3호
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• pp.203-211
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• 2016

국내의 플랜트 탱크 설계를 위한 풍하중 기준은 KS B 6283 액체 저장 탱크의 내풍압 및 내진에 대한 설계 요건 등 여러기준에 제시되어 있으나, 그 내용이 서로 다르고 연관성도 없으며 실제의 풍하중을 반영하고 있는지 명확하지 않다. 국내 풍하중 기준의 정당성을 평가하고 적합한 풍하중 기준을 제안하기 위해 외국의 저장 탱크 설계를 위한 대표적 기준인 API 650, ASCE 7-10, EN 1991-1-4의 풍하중 기준 들과 비교분석하였다. 풍동 실험이 수행되어 보고된 논문에 적용된 탱크 제원을 적용하여 기본적으로 각 기준에 의한 압력계수 Cp값을 산정해 비교하고, 탱크 지붕 높이와 지름 비(f/d) 및 탱크 깊이 및 지름 비(h/d)를 변수로 한 각 기준에 의한 풍하중 좌굴해석을 수행하였다. 결과를 분석 종합하여 실제 풍하중에 의한 좌굴 거동을 반영하면서도 설계 시 쉽게 적용할 수 있는 풍하중 기준을 제안 하였다.

• 콘크리트학회논문집
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• 제29권3호
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• pp.291-298
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• 2017

이 연구에서는 강재 기둥과 접합된 하이브리드 H-보-철근 콘크리트 보(HSRC)의 반복 휨 거동을 평가하였다. 실험 변수는 HSRC 보의 연결절점에 배근되는 장부철근의 유무이다. HSRC 보의 소성힌지는 RC 보보다는 기둥 접합부 부근의 H-보에서 형성되도록 유도하였다. 모든 실험체는 하중의 급격한 감소 없이 연성적인 거동을 보였으며, 비록 예상치 못한 H-기둥과 H-보 용접 접합부의 파괴가 발생하였지만, 결과적으로 4.6 이상의 변위연성비를 나타내었다. HSRC 보 시스템에서 RC 보의 균열진전, 휨 강도 및 연성에 대한 장부철근의 영향은 매우 미미하였다. HSRC 보 시스템의 휨 강도는 단면의 완전소성으로 가정하여 산정한 H-보의 최대 휨 내력에 비해 안전 측에서 평가될 수 있었다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 가을 학술발표회 논문집
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• pp.93-100
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• 2004

In this study, a support system is developed for the design of facility structures. This system is called Expert System for Design Optimization of Industrial Plant Structures (EDIPS). Based on the strength assessment of steel-plate structures such as ships and off-shore structures, a detailed load calculation method is developed utilizing the database of various plant structures. The method, developed in support of design and for the assessment of strength, constitutes a part of EDIPS. By providing relevant and consistent design data and procedures to engineers, EDIPS is expected to be useful as an important development tool for maritime distribution system that is used to control the transportation by ships and loading unloading, and storage of cargo.

• Nuclear Engineering and Technology
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• 제54권5호
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• pp.1588-1596
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• 2022

In the nuclear power plants, stainless steel is widely used for fabrication of various components such as piping and pipe fittings. These piping components are subjected to cyclic loading due to start up and shut down of the nuclear power plants. The application of cyclic loading may lead to initiation of crack at stress raiser locations such as nozzle to piping connection, crown of piping bends etc. of the piping system. Crack initiation can also take place from the flaws which have gone unnoticed during manufacturing. Therefore, prediction of crack initiation life would help in decision making with respect to plant operational life. The primary objective of the present study is to compile various analytical models to predict the crack initiation life of the pipes with notch. Here notch simulates the stress raisers in the piping system. As a part of the study, Coffin-Manson equations have been benchmarked to predict the crack initiation life of pipe with notch. Analytical models proposed by Zheng et al. [1], Singh et al. [2], Yang Dong et al. [25], Masayuki et al. [33] and Liu et al. [3] were compiled to predict the crack initiation life of SA312 Type 304LN stainless steel pipe with notch under fatigue loading. Tensile and low cycle fatigue properties were evaluated for the same lot of SA312 Type 304LN stainless steel as that of pipe test. The predicted crack initiation lives by different models were compared with the experimental results of three pipes under different frequencies and loading conditions. It was observed that the predicted crack initiation life is in very good agreement with experimental results with maximum difference of ±10.0%.

• Environmental Engineering Research
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• 제14권3호
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• pp.195-199
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• 2009

A series of laboratory-scale corrosion experiments was carried out to observe the effect of dissolved oxygen (DO) in the presence of other water quality parameters, such as hardness, Cl-, and pH using various pipe materials. In addition, a simulated loop system was installed at a water treatment plant for pilot-scale experiment. Laboratory-scale experiment showed that corrosion rates for galvanized steel pipe (GSP), carbon steel pipe (CSP), and ductile cast iron pipe (DCIP) were decreased to 72%, 75%, and 91% by reducing DO concentration from 9${\pm}$0.5 mg/L to 2${\pm}$0.5 mg/L. From the pilot scale experiment, it was further identified that the average ionization rate of zinc in GSP decreased from 0.00533 to 0.00078 mg/$cm^2$/d by controlling the concentration of DO. The reduction of average ionization rate for copper pipe (CP) and stainless steel pipe (SSP) were 71.4% for Cu and 63.5% for Fe, respectively. From this study, it was concluded that DO could be used as a major parameter in controlling the corrosion of water pipes.

• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1669-1680
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• 2019

Seismic safety is considered to be one of the key design objectives of AP1000 nuclear power plant (NPP) in strong earthquakes. Dynamic behavior, damage development and aggravation effect are studied in this study for the three main components of AP1000 NPP, namely reinforced concrete shield building (RCSB), steel vessel containment (SVC) and reinforced concrete auxiliary building (RCAB). Characteristics including nonlinear concrete tension and compressive constitutions with plastic damage are employed to establish the numerical model, which is further validated by existing studies. The author investigates three earthquakes and eight input levels with the maximum magnitude of 2.4 g and the results show that the concrete material of both RCSB and RCAB have suffered serious damage in intense earthquakes. Considering RCAB in the whole NPP, significant damage aggravation effect can be detected, which is mainly concentrated at the upper intersection between RCSB and RCAB. SVC and reinforcing bar demonstrate excellent seismic performance with no obvious damage.