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Cr 첨가가 고망간강의 중성 수용액 환경 내 유동가속부식 거동에 미치는 영향
정영재 ( Yeong Jae Jeong ),박진성 ( Jin Sung Park ),방혜린 ( Hye Rin Bang ),이순기 ( Soon Gi Lee ),최종교 ( Jong Kyo Choi ),김성진 ( Sung Jin Kim ) 한국부식방식학회 2021 Corrosion Science and Technology Vol.20 No.6
The effect of Cr addition to high Mn steel on flow-accelerated corrosion (FAC) behavior in a neutral aqueous environment was evaluated. For comparison, two types of conventional ferritic steels (API X70 steel and 9% Ni steel) were used. A range of experiments (electrochemical polarization and impedance tests, weight loss measurement, and metallographic observation of corrosion scale) were conducted. This study showed that high Mn steel with 3% Cr exhibited the highest resistance to FAC presumably due to the formation of a bi-layer scale structure composed of an inner Cr enriched Fe oxide and an outer Mn substituted partially with Fe oxide on the surface. Although the high Mn steels had the lowest corrosion resistance at the initial corrosion stage due to rapid dissolution kinetics of Mn elements on their surface, the kinetics of inner scale (i.e. Cr enriched Fe oxide) formation on Cr-bearing high Mn steel was faster in dynamic flowing condition compared to stagnant condition. On the other hand, the corrosion scales formed on API X70 and 9% Ni steels did not provide sufficient anti-corrosion function during the prolonged exposure to dynamic flowing conditions.
조선·해양 기자재용 강재의 내식성에 미치는 분체도장 중 산화물 첨가의 영향
박진성 ( Jin-seong Park ),류승민 ( Seung Min Ryu ),정영재 ( Yeong Jae Jeong ),김성진 ( Sung Jin Kim ) 한국부식방식학회(구 한국부식학회) 2020 Corrosion Science and Technology Vol.19 No.2
The demand for powder-coated steel used in the marine industry is increasing owing to their superior corrosion resistance. However, the powder coatings used in commercial products can deteriorate easily by the penetration of brine. In an attempt to suppress brine penetration into the powder coating and significantly increase the corrosion resistance, three types of oxide particles were added to the coating. Electrochemical impedance spectroscopy tests in 3.5% NaCl solution were performed to evaluate the corrosion behaviors of the powder coating with oxide particles. The results showed that the addition of SiO<sub>2</sub> particles to a powder coating severely decreased the corrosion resistance due to the easy detachment of agglomerated SiO<sub>2</sub> particles with a coarse size from the coating layer. In contrast, the TiO<sub>2</sub> and SnO<sub>2</sub>-added coatings showed better corrosion resistance, and the TiO<sub>2</sub>-added coating performed best in the test conducted at room temperature. However, conflicting results were obtained from tests conducted at a higher temperature, which may be attributed to the effective suppression of brine penetration by the fine SnO<sub>2</sub> particles uniformly distributed in the coating.
이보람(Bo-Ram Lee),윤태종(Tae-Jong Yun),오원빈(Won-Bin Oh),이충우(Chung-Woo Lee),김학형(Hak Hyoung Kim),정영재(Yeong Jae Jeong),김일수(Ill-Soo Kim) 한국기계가공학회 2021 한국기계가공학회지 Vol.20 No.3
Pressure, which is a dynamic characteristic of a floodgate, is predicted using an FSI analysis method. A fluid analysis model and a hydrology analysis model were used as analysis models. As a result of the analysis, we found that a warped model has smaller acceleration than a square model. Additionally, this numerical analysis technique was applied to the actual hydrology, and the analysis results were compared with the results of the vibration tests. As a result, we confirmed that there is a small difference between the results of the vibration tests and the results of the FSI analysis. Through this analysis, the applicability and reliability of the FSI analysis method were verified. We concluded that the pressure of a floodgate can be measured through an FSI analysis method.
이보람(Bo-Ram Lee),윤태종(Tae-Jong Yun),오원빈(Won-Bin Oh),이충우(Chung-Woo Lee),김학형(Hak-Hyoung Kim),정영재(Yeong-Jae Jeong),김일수(Ill-Soo Kim) 대한기계학회 2021 大韓機械學會論文集A Vol.45 No.3
수문에 내장되어 있는 축류펌프에서 발생하는 진동은 펌프의 마모 및 소음 발생의 주요 원인이며 구조물의 수명에 영향을 줄 수 있다. 플랩게이트는 문비가 상승, 하강되는 구조로 수위가 높은 경우 방출량이 증가하여 게이트 후류에서 발생된 와류에 의한 진동이 발생한다. 와류로 발생된 일정주기의 진동은 수문을 가진시키는 가진 주파수이다. 플랩게이트의 고유 진동주파수와 고유모드를 찾기 위해 모드해석을 수행하여 6차까지의 고유진동수와 모드형상을 확인하였다. 본 연구에서는 유체-구조해석에서 발생하는 구조물 거동을 분석하고 진동해석을 통한 변형 및 응력을 최소화하여 펌프일체형수문의 수명을 연장하고, 안전성을 검증하고자 하였다. Vibrations generated by the axial flow pump in a floodgate are the main cause of wear and noise in the pump; these may affect the service life of the structure. The structure of the flap gate results in a gate ratio that increases and decreases continuously . When the water level is high, the amount of discharge increases, and vibrations are induced by the eddy currents generated in the gate wake. The constant periodic vibration generated by these vortices acts as the excitation frequency of the floodgate. Mode analyses were conducted to determine the natural vibration frequency and the natural mode of the flap gate; natural frequencies and mode shapes up to the 6th order were confirmed. This study attempted to extend the life of pump-integrated floodgates and verify their safety by analyzing their structural behaviors using fluid-structure interaction analyses and minimizing their deformation and stress through vibration analyses.
A Study on Cutting Quality Using a Mahalanobis Distance
이보람(Bo-Ram Lee),윤태종(Tae-Jong Yun),오원빈(Won-Bin Oh),이충우(Chung-Woo Lee),김학형(Hak-Hyoung Kim),정영재(Yeong-Jae Jeong),김일수(Ill-Soo Kim) Korean Society for Precision Engineering 2021 한국정밀공학회지 Vol.38 No.4
Social interest in the 4th industry, intelligent factories, and smart manufacturing is continually growing along with the core technologies like big data and artificial intelligence, which can generate meaningful information by collecting and accumulating sensor data. Demand for industrial automation equipment is increasing worldwide due to the efforts needed to modernize manufacturing facilities, reduce automation and cycle time, and improve quality. Currently, the majority of research is focused on the development of automation facilities and improving productivity. The research on the contents of real-time data considering the characteristics of the cutting machine plasma machine is insufficient. In this study, based on the current data measured according to cutting current and cutting speed, a reference value for cutting quality is presented and the optimal process parameter has been selected. A model for predicting cutting quality by introducing the Mahalanobis Distance Method is presented. An attempt has been made to derive selection and optimal cutting process variables. Based on the predictive model, threshold values were specified and used in real-time data to consider the correlations between multivariate variables and evaluate the degree of scattering around the average of specific values of each variable. Also, process parameters suitable for surface roughness were calculated.