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전기화학적 분석을 통해 산출된 코팅 결함율이 트라이볼로지적 특성에 미치는 영향 평가
김우중(Woo-Jung Kim),안승호(Seung-Ho Ahn),김호건(Ho-Gun Kim),김정구(Jung-Gu Kim),조정우(Chung-Woo Cho),이영제(Young-Ze Lee) 한국트라이볼로지학회 2004 한국트라이볼로지학회 학술대회 Vol.38 No.-
Recently, many of the current development in surface modification engineering are focused on multilayered coatings. Multilayered coatings have the potential to improve the tribological properties. Four different multilayered coatings were deposited on AISI D2 steel. The prepared samples are designed as WC-Ti0.6Al0.4N, WC-Ti0.6Al0.4N, WC-Ti0.53Al0.47N and WC-Ti0.43Al0.57N. The multilayered coatings were investigated with respect to coating surface and cross-sectional morphology, roughness, adhesion, hardness, porosity and tribological behavior. Especially, wear tests of four multilayered coatings were performed by using a ball-on-disc configuration with a linear sliding speed of 0.017 m/sec, 5.38 N load. The tests were carried out at room temperature in air by employing AISI 52100 steel ball (HR = 66) having a diameter of 10 ㎜. The surface morphology, and topography of the wear scars of samples and balls have been determined by using scanning electron spectroscopy (SEM). Also, wear mechanism was determined by using SEM coupled with EDS. Results have showed an improved wear resistance of the WC-Ti1-xAlxN coatings with increasing of Al concentration.
전기화학적 분석을 통해 산출된 코팅 결함율이 트라이볼로지적 특성에 미치는 영향 평가
김우중(Woo-Jung Kim),안승호(Seung-Ho Ahn),김호건(Ho-Gun Kim),김정구(Jung-Gu Kim),조정우(Chung-Woo Cho),이영제(Young-Ze Lee) 한국트라이볼로지학회 2004 한국윤활학회지(윤활학회지) Vol.20 No.6
Many of the current development in surface modification engineering are focused on multilayered coatings, which have the potential to improve the tribological properties. Four different multilayered coatings were deposited on AISI D2 steel in this study. The prepared samples are designed as WC-Ti_(0.6)Al_(0.4)N, WCTi_(0.53)Al_(0.47)N, WC-Ti_(0.5)Al_(0.5)N and WC-Ti_(0.43)Al_(0.57)N. The multilayered coatings were investigated with respect to coating surface and cross-sectional morphology, roughness, adhesion, hardness, porosity and tribological behaviors. Especially, wear tests of four multilayered coatings were performed by using a ball-on-disc configuration with a linear sliding speed of 0.017 m/sec and a normal load of 5.38 N load. The tests were carried out at room temperature in air by employing AISI 52100 steel ball (H_R = 66) having a diameter of 10 ㎜. The surface morphology, and topography of the wear scars of samples and balls have been determined by using scanning electron spectroscopy (SEM). Also, wear mechanism was determined by using SEM coupled with energy-dispersive spectroscopy (EDS). Results have showed an improved wear resistance of the WC- Ti_(1-x)AlxN coatings with increasing of Al (aluminum) concentration.
탈기된 3.5 wt.% NaCl 용액 환경에서의 스테인리스 강에 증착된 CrN 박막의 Si 첨가에 따른 영향 평가
김우중(Woo-Jung Kim),최윤석(Yoon-Seok Choi),김정구(Jung-Gu Kim),이호영(Ho-Young Lee),한전건(Jeon-Gun Han) 한국표면공학회 2005 한국표면공학회지 Vol.38 No.4
CrSiN coatings of stepwise changing Si concentration were deposited on stainless steel by closed field unbalanced magnetron sputtering (CFUBM) system. Microstructure of the films due to the Si concentration is measured by XRD. The corrosion behavior of CrSiN coatings in deaerated 3.5% NaCl solution was investigated by potentiodynamic test, electrochemical impedance spectroscopy (EIS) and surface analyses. The microstructure of CrSiN film depends on the Si concentration. When Si/(Cr+Si) was under 11.7%, preferred orientation is defined at CrN(220), CrN(311) and Cr₂N(111). The results of potentiodynamic polarization tests showed that the corrosion current density and porosity decreased with increasing Si/(Cr+Si) ratio. EIS measurements showed that the corrosion resistance of Si-bearing CrN was improved by phase transformation of the film, which leads to increase of pore resistance and charge transfer resistance. At the Si/(Cr+Si) ratio of 20, the Si-bearing CrN possesses the best corrosion resistance due to the highest pore resistance and charge transfer resistance.
김우중(Woo-Jung Kim),김재훈(Jae-Hoon Kim),장중철(Jung-Cheol Jang),김범수(Beom-Soo Kim),유근봉(Keun-Bong Yoo) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
The Heat Recovery Steam Generator(HRSG) is device that uses exhaust gas of gas turbine to increase thermal efficiency. In order to requirements global needs saving energy, reducing emission of CO2, reducing cost, many power plant appled HRSG. Generally, High Cr steels are used in steam side tube because of its high temperature strength and oxidation resistance. This paper addresses creep-rupture test of 9Cr-1Mo steel at isothermal temperature with change thermal and stress condition. the results of date are plotting to Larson-Miller parameter. Through hardness test of specimens, fluctuation of hardness values are determined to interrelation between hardness and life. Finally, The test specimen of creep rupture is observed by Transmission Electron Microscope(TEM) to analyze higt temperature material behavior of Cr steels
김우중 ( Woo Joong Kim ),김재훈 ( Jae Hoon Ki ),장중철 ( Jung Cheol Jang ),김범수 ( Beom Soo Kim ),이기천 ( Gi Chun Lee ) 한국안전학회(구 한국산업안전학회) 2013 한국안전학회지 Vol.28 No.3
The Heat Recovery Steam Generator (HRSG) is a device recycling the exhaust gas of gas turbine in combined power and chemical plants. Since service temperatures was very high, the damage of HRSG tubes intensively occurred in superheater and reheater. The aim of this paper is to determine life and hardness relationship that addresses creep-rupture test and creep-interrupt test in modified 9Cr-1Mo steel. The measured life that consists of function of hardness was found to constant tendency.
S형상 점진기능재료 나노-스케일 판의 자유진동 특성에 미치는 비국소 탄성 효과
김우중(Kim, Woo-Jung),이원홍(Lee, Won-Hong),박원태(Park Weon-Tae),한성천(Han, Sung-Cheon) 한국산학기술학회 2014 한국산학기술학회논문지 Vol.15 No.2
본 논문에서는 S형상함수를 이용한 점진기능재료 나노-스케일 판의 자유진동 특성에 미치는 비국소 탄성 이 론의 효과에 대하여 연구하였다. 비국소 탄성 이론은 미소 규모 효과를 고려할 수 있고 S형상함수는 점진기능재료의 정확한 특성변화를 고려할 수 있다. 이러한 이론을 이용하여 나노-스케일 판의 고유진동수에 미치는 비국소 이론의 효과를 제시하였고, 국소 탄성이론과의 관계를 수치해석 결과를 통하여 고찰하였다. 또한 (i) 거듭제곱 지수, (ii) 비국 소 계수, (iii) 탄성계수 비 그리고 (iv) 나노-스케일 판의 두께 및 형상 변화 등이 나노-스케일 판의 무차원 진동수에 미치는 효과에 대하여 관찰하였다. 본 연구의 결과를 검증하기 위해 참고문헌의 결과들과 비교 분석하였으며 해석결 과는 참고문헌의 결과들과 잘 일치함을 알 수 있었다. 비국소 이론에 의한 나노-스케일 판의 진동에 관한 연구는 향 후 관련연구에 비교자료로 활용될 수 있을 것이다. We study free vibration analysis of sigmoid functionally graded materials(S-FGM) nano-scale plates, using a nonlocal elasticity theory of Eringen in this paper. This theory has ability to capture the both small scale effects and sigmoid function in terms of the volume fraction of the constituents for material properties through the plate thickness. Numerical solutions of S-FGM nano-scale plate are presented using this theory to illustrate the effect of nonlocal theory on natural frequency of the S-FGM nano-scale plates. The relations between nonlocal and local theories are discussed by numerical results. Further, effects of (i) power law index (ii) nonlocal parameters, (iii) elastic modulus ratio and (iv) thickness and aspect ratios on nondimensional frequencies are investigated. In order to validate the present solutions, the reference solutions are compared and discussed. The results of S-FGM nano-scale plates using the nonlocal theory may be the benchmark test for the free vibration analysis.
김우중 ( Woo Joong Kim ),김진기 ( Jin Ki Kim ),이희정 ( Hee Jung Lee ),윤문수 ( Moon Soo Yoon ),김동현 ( Dong Hyun Kim ) 대한피부과학회 2012 대한피부과학회지 Vol.50 No.2
Turner`s syndrome (TS) is a genetic disorder caused by numeric and/or structural abnormalities of the X chromosome. It is characterized by a short stature, gonadal dysgenesis, and frequently by webbed neck, cubitus valgus, lymphedema, broad chest with wide spaced nipples, micrognathia, and brachimetacarpalia. Several cutaneous manifestations are associated with TS, including melanocytic nevi, hypertrophic scarring, and vitiligo. Rarely reported findings include hemangiomas, angiokeratomas, and halo nevi. We present a case of halo nevi and vitiligo in a 13-year-old girl with TS. To the best of our knowledge, halo nevi and vitiligo in TS has not been reported in the Korean literature. (Korean J Dermatol 2012;50(2):175~178)