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슈퍼이상스테인리스강 용접열영향부의 피로균열전파거동 및 음향방출 특성
도재윤(Jae Yoon Do),김진환(Jin Hwan Kim),안석환(Seok Hwan Ahn),박인덕(In Duck Park),강창용(Chang Yong Kang),남기우(Ki Woo Nam) 대한금속재료학회 ( 구 대한금속학회 ) 2002 대한금속·재료학회지 Vol.40 No.9
Because duplex stainless steel shows the good strength and corrosion resistance properties, the necessity of duplex stainless steel, which has long life in severe environments, has been increased with industrial development. The fatigue crack propagation behavior of heat affected zone(HAZ) has been inrestigated in super duplex stainless steel. The fatigue crack propagation rate of HAZ of super duplex stainless steel was faster than that of base metal of super duplex stainless steel. We also analysed acoustic emission signals during the fatigue test with time-frequency analysis method. According to the results of time-frequency analysis, the frequency ranges of 200-400 kHz were obtained by striation and the frequency range of 500 kHz was obtained due to dimple and separate of inclusion.
수퍼 2상 스테인리스강의 피로균열진전 특성에 미치는 미세조직의 영향
이상기(SANG-KEE LEE),도재윤(JAE-YOON DO),남기우(KI-WOO NAM),강창룡(CHANG-YONG KANG),이해우(HAE-WOO LEE),안석환(SEOK-HWAN AHN) 한국해양공학회 2000 韓國海洋工學會誌 Vol.14 No.2
This study is to investigate the characteristics of fatigue crack propagation in rolled super duplex stainless steel that was changed austenite-ferrite volume fraction by heat treatment. It was used two kinds of specimen, the rolling and the transverse directions. δ-phase fraction affected sound velocity, hardness and Young's modulus. Characteristics of fatigue crack propagation was affected by anisotropy and ( δ + r) phase volume fractions.
안석환(SEOK-HWAN AHN),김진욱(JIN-WOOK KIM),도재윤(JAE-YOON DO),김현수(HYUN-SOO KIM),남기우(KI-WOO NAM) 한국해양공학회 2005 韓國海洋工學會誌 Vol.19 No.1
The study investigated the nondestructive characteristics of damage, caused by low-velocity impact, on symmetric cross-ply laminates, composed of [0o/90o]16s, 24s, 32s, 48s. The thickness of the laminates was 2, 3, 4 and 6 ㎜, respectively. The impact machine used, Model 8250 Dynatup Instron, was a drop-weight type that employed gravity. The impact velocities used in this experiment were 0.75, 0.90, 1.05, 1.20 and 1.35 m/sec, respectively. Both the load and the deformation increased when the impact velocity was increased. Further, when the load increased with the laminate thickness in the same impact velocity, the deformation still decreased. The extensional velocity was quick, as the laminate thickness increased in the same impact velocity and the impact velocity increased in the same laminate thickness. In the ultrasonic scans, the damaged area represented a dimmed zone. This is due to the fact that the wave, after the partial reflection by the deflects, does not have enough energy to touch the opposite side or to come back from it. The damaged laminate areas differed, according to the laminate thickness and the impact velocity. The extensional velocities are lower in the 0o direction and higher in the 900 direction, when the size of the defect increases. However, it was difficult to draw any conclusion for the extensional velocities in the 45o direction.
플랜트 승압펌프 재순환 배관 용접부의 용접비드에 의해 발생한 감육결함 분석 및 건전성 평가
남기우(Ki-Woo Nam),안석환(Seok-Hwan Ahn),도재윤(Jae-Yoon Do) 한국해양공학회 2010 韓國海洋工學會誌 Vol.24 No.4
The wall thinning phenomenon of pipes was simulated as metal loss due to erosion and corrosion. Such wall thinning defects in the pipes of power plants are a very important safety consideration, In this study, we analyzed wall thinning dejects thar occurred by weld bead of weld zone of boost pump recirculation. pipe. From the results of the analysis of pipe failures, numerical analysis was performed by Fluent v6.3.26 using the standard k-ε model of the weld bead shape, such as an elliptical or a spherical shape, on the inner wall of the pipe. Using the results obtained, we showed the overlap effect by cavitations corrosion and erosion-corrosion at the bottom of the wall-thinning defect.
강흥주(HEOUNG-JOO KANG),남기우(KI-WOO NAM),안석환(SEOK-HWAN AHN),강창룡(CHANG-YONG KANG),도재윤(JAE-YOON DO),박인덕(IN-DUCK PARK) 한국해양공학회 2003 韓國海洋工學會誌 Vol.17 No.2
The corrosion resistance of super duplex stainless steel on both its fibrous and dispersed phases was investigated. These structures consist of various volume fraction and distribution of austenite structure, which were obtained by changing the heat treatment temperature and cycle. The fibrous phase had higher austenite volume fraction than that of the dispersed phase at the same temperature. Corrosion resistance of super duplex stainless steel was evaluated through an immersion test and an impingement test, using 35% HCl and sea water, respectively. Super duplex stainless steel was compared with STS316L and STS304. The corrosion resistance of super duplex stainless steel was superior to STS316L and STS304. The dispersed phase of super duplex stainless steel was more stabilized than the fibrous phase in corrosion. The magnitude of corrosion rate was in order STS304, STS316L, fibrous phase of super duplex stainless steel and dispersed phase of super duplex stainless steel.
STS316L 용접부의 피로거동 및 초음파시럼에 의한 열화특성 평가
남기우,박소순,안석환,도재윤,박인덕 한국비파괴검사학회 2003 한국비파괴검사학회지 Vol.23 No.2
STS316L은 인성, 연성, 부식저항성 등 우수한 기계적 성질 때문에 에너지환경설비 등 구조물에 널리 이용되고 있다. 그러나, 용접구조물은 가혹한 환경하에서 경년열화가 심각하다. 지금까지의 연구들은 주로 용접부의 피로균열진전거동에 관하여 수행되었고, 피로균열진전속도식의 재료상수와 비파괴적 평가의 상관성에 관한 연구는 거의 없었다. 본 연구는 STS316L 용접부의 피로균열진전 거동을 조사하고, 초음파 파라미터로 열화특성을 평가하고 시간-주파수 분석으로 해석을 하였다. 본 연구 결과는 용접구조물의 사용기간 중 피로수명 등을 예측하기 위한 기초 데이터로서 사용될 수 있다. STS316L had been used as the structural material for energy environmental facilities, because austenite stainless steels like 316L have superior mechanical properties of which toughness, ductility, corrosion resistant and etc. However, those welded structures are receiving severe damage due to increasing of the aged degradation. Most studies until now have been carried out against fatigue bahaviors of weldments, and were not well studied on nondestructive evaluation methods. In this study, the fatigue crack propagation behavior of STS316L weldment usually used for vessels of the nuclear power plant was investigated. Also, the degradation characterstics of 316L stainless steel weldments were evaluated by the ultrasonic parameter such as ultrasonic velocity, attenuation factor and time-frequency analysis. The results of this study can be used as a basic data for the prediction of the fatigue crack life of weldments structures without disjointing or stopping service of structures in service.