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바나듐이 添加된 AISI4140鋼의 引張性質에 미치는 Strain-Tempering의 影響
成章鉉,金營三 동아대학교 공과대학 부설 한국자원개발연구소 1980 硏究報告 Vol.4 No.2
The purpose of this study is to improve the tensile properties of AISI 4140 steel with and addition of vanadium. After quenching and initial tempering, specimens were strain-tempered under various conditions and then the tensile properties and the fratographs of fractured surface were investigated. The results obtained are as follows. 1) The tensile testing has shown that little change in tensile strength of specimens unstrained and retempered at temperatures below initial-tempering temperatures is obtained. 2) The yield strength of specimen initial-tempered at 350℃ are remarkably increased from 180㎏/㎟ to 248㎏/㎟ by straining and retempring at a temperature of 290℃. 3) In the case of retempering at temperature of 570℃ and 640℃ after 0.25% straining, the elongation of specimen initial-tempered at 350℃ is recovered to coincide with the value of unstrained specimen, whereas the recovery phenomena for tensile strength are not found. For the specimen initial-tempered at 500℃, however, unlike elongation, the tensile strength is recovered to a value equivalent to the tensile strength of unstrained specimen. 4) The fractographs of specimen 0.25%-strained have indicated that dimples appear to be larger as compared to unstrained specimen and that secondary cracks are found on various areas. These characteristics are Shown to be more remarkable for specimens initial-tempered at 500℃ than for specimens initial-tempered at 300℃.
304L 스테인레스강의 변태유기 소성에 미치는 변형온도의 영향
성장현,강창룡 동아대학교 공과대학 부설 한국자원개발연구소 1992 硏究報告 Vol.16 No.1
The effect of deformation temperature on transformation induce plasticity in 304L stainless steel with metastable austenitic phase investigaged. The result obtained from this study are summarized as follows. Tensile properties of the metastable austenitic 304L stainless steel remarkably influenced by deformation temperature and mainly controlled by transformation induced martensite. Tensile strength increased with decreasing deformation temperature and the elongation showed maximum value near 40℃ With lowering the deformation temperature, the volume fration of transformation induced martensite increased at the same strain. ε-martensite was formed at the begining stage of deformation in the low temperature region of low stability of austenite. The volume fration of ε-martensite increased with increasing strain and decreased after showing the maximum value. The maxium quantity of ε-martensite was obtained at low strain with decreasing deformation temperature.
Al 함유 13%Cr 스테인리스강의 표면 질소침투 열처리에 미치는 첨가원소 탄소의 영향 : 13%Cr 스테인리스강의 고질소 표면침투 열처리
성장현,주동원,김기돈,유대경,박진욱 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.3
This study aims to investigate the effect of carbon content on the surface nitrogen permeation of 13%Cr-1.8%Al alloyed stainless steels. The surface nitrogen permeation was performed at 1050℃-1200℃ in the 1㎏/㎠ nitrogen gas atmosphere. The nitrogen permeated surface layer of the specimen containing 0.03%C consists of AlN, martensite and retained austenite phases, while the surface layer of the specimen containing 0.14%C appears the AlFe₃C_x phase including former three phases. The specimen containing 0.14%C shows lower total case depth than that containing 0.03%C at the nitrogen permeation temperatures of 1050℃ and 1100℃, while the total case depth of the specimen containing 0.14%C is remarkably increased at the temperature of 1150℃ and 1200℃ due to the increase in the retained austenite content. Martensitic phase, AlN and AlFe₃C_x precipitate of the nitrogen permeated surface layer cause to increase the surface hardness of 550∼600Hv.
성장현,류영,성기원 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.4
This study evaluates the effects of climatic conditions and drought phase on occurrence frequency (OF) of forest fire in South Korea, and suggested a deep learning-based estimator for the occurrence frequency of fire. There was a high correlation between frequency and relative humidity (RH, R = -0.663) and wind speed (WS, R = 0.532). Using these correlations, we proposed a deep learning model that can estimate the OF. Among the three deep learning models (RH-WS-AMOF, RH-AMOF, and WS-AMOF) by combining RH and WS with average monthly OF (AMOF) during 1997 − 2019, the RH-WS-AMOF model showed the best performance. R2 and NSE were 0.838 and 0.828, respectively. The higher temperatures and drought lead to increase the potential for forest fire. Standardized precipitation evapotranspiration index was introduced for exploring the link between meteorological drought and forest fire. We confirmed that SPEI can improve the performance of the DBN based on OF estimator in spring. The framework of this study can provide a predictive model for forest fire OF combined with a weather forecast model.
성장현,정은성,김양수 한국방재학회 2014 한국방재학회 학술발표대회논문집 Vol.2014 No.-
하천수 가뭄을 평가하기 위하여 임계수준 방법을 이용한 하천수 가뭄지수 (streamflow drought index)를 소개하고 섬진강댐의 유입량을 대상으로 적용하였다. 사용한 임계수준은 고정, 월별 및 일별로써 연도별 가뭄의 1순 ~3순위 분석결과, 1984년, 1988년과 1995년이 수문학적 가뭄의 크기도 컸고 오랫동안 지속되었다. 총 물 부족량과 지속기간의 극한값을 연도별로 비교해 본 바, 1984년, 1988년, 1995년과 2001년에 발생하였던 사상이 심각한 수준이었다. 연구결과, 고정 임계수준은 계절 변동성을 반영하지 못하는 단점이 있어서 최소한 계절 이하의 임계수준 사용이 요구되었지만 월별과 일별로 정해진 임계수준은 적정하였다. 본 연구에서 제안한 방법론은 갈수예보 및 저수지 용량결정에 활용될 수 있겠다.