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3.5%NaCl 水溶液의 溫度變化가 複合組織鋼의 腐蝕疲勞破壞에 미치는 影響
吳世旭(Sae-Wook Oh),都映旼(Young-Min Do),朴洙瑩(Soo-Young Park),金在喆(Jae-Chul Kim),金廣泳(Kwang-Young Kim) 한국해양공학회 1992 韓國海洋工學會誌 Vol.6 No.1
Corrosion fatigue test was performed under rotated bending in 3.5% NaCl aqueous solution having a temperature from 278°K to 318°K in order to investigate the effects of aqueous solution temperature on the corrosion fatigue fracture of raw material steel(SS41) and dual phase steel that was produced from SS41 by a series of heat treatment.<br/> Corrosion fatigue life decreases remarkably with increase in solution temperature or with decrease in stress level.<br/> The corrosion fatigue life and the crack propagation rate at 303°K show the similar behaviors with those at 318°K, which is assumed to be caused by concentration polarization phenomena.<br/> The number and the lengths of microcracks increase with increase in solution temperature, so they lead to the decrease in corrosion fatigue life.
3.5% NaCl 水溶液의 pH變化가 複合組織鋼의 腐蝕疲勞破壞에 미치는 影響
吳世旭(Sae-Wook Oh),姜鎬珉(Ho-Min Kang),都映旼(Young-Min Do) 한국해양공학회 1987 韓國海洋工學會誌 Vol.1 No.2
Corrosion fatigue fracture of dual phase steel(SS41) and raw material steel(SS41) were investigated in 3.5% NaCl aqueous solution at pH 4, 6, 9 and 11.<br/> The fatigue limit of dual phase steel is increased approximately 1.8 times larger than that of raw material in air. The corrosion fatigue life of dual phase steel is about 5~10 times larger than that of raw material in 3.5% NaCl aqueous solution. The reduction of fatigue life is larger for the acid salt solution than for the alkali salt solution. The reduction of fatigue life of dual phase steel by the change of pH is smaller than that of raw material. The influence of stress level on the reduction ratio of corrosion fatigue life is large at pH 6~11.<br/> The reduction ratio of corrosion fatigue life of dual phase steel and raw material is nearly coincided at pH 2. While at pH4~2 the reduction ratio of corrosion fatigue life only depends on the corrosion effect. It has been found that the corrosion resistance effect of dual phase steel is smaller than that of raw material in corrosion fatigue crack propagation rate.<br/> As pH below 6 is changed, it can be clearly observed from raw material that the brittle intergranular fracture is characterized, and from the above result, the influence of corrosion of dual phase steel is small.
複合組織鋼의 腐蝕피트成長特性에 미치는 食鹽水濃度의 影響
吳世旭(Sae-Wook Oh),姜鎬珉(Ho-Min Kang),金泰萬(Tae-Man Kim),都映旼(Young-Min Do) 한국해양공학회 1988 韓國海洋工學會誌 Vol.2 No.2
In order to investigate the corrosion pit occurrence and growth characteristic of M.E.F.(martensite encapsulated islands of ferrite) dual phase steel was made with a suitable heat treatment of raw material(SS41), a corrosion fatigue test was performed under rotary bending in the salt solution having a concentration from 0.01 wt percent to 3.5 wt percent. The fatigue strength of dual phase steel was remarkably decreased with an increase in concentration of salt solution ; approximately from 63% to 80% in case of dual phase steel and from 40% to 71% in case of raw material. Corrosion pit occurred in the martensite phase and fatigue cracks from corrosion pits were selectively propagated in martensite phases. In the observation of corrosion pits at the origin of fatigue cracks, it had been found that corrosion pits were grown into hemispherical pits and a/c(the surface diameter, 2c and the depth, a of corrosion pit) was about 1.0~1.5 regardless of the variation of salt solution concentration. The difference of corrosion pit depth growth rate was increased with an increase in concentration of salt solution according to an increase in stress level.
학교체육시설물-철봉의 강도규정 및 이의 평가방법 개발에 관한 연구
강기원 ( Ki Weon Kang ),안병화 ( Byoung Hwa Ahn ),유승원 ( Sueng Won You ),도영민 ( Young Min Do ) 한국스포츠정책과학원(구 한국스포츠개발원) 2003 체육과학연구 Vol.14 No.1
학교체육시설물의 안전성 및 효율성을 향상시키기 위해서는 이의 구체적인 요건을 정하는 표준규격의 제정이 요구된다. 이러한 표준 규격은 품질규정, 형상규정 및 강도규정 등으로 세분화될 수 있으며 이 중 표준 규격의 핵심요소인 강도규정은 학교체육시설물이 보유하여야 하는 기준강도에 대한 내용을 포함하므로 이의 적합한 설정은 매우 중요하다. 또한 이와 같이 설정된 강도규정의 타당성 및 적합성을 검증하기 위해서는 강도규정에 대한 시험방법의 선정 역시 매우 중요하다. 그러나 철봉으로 대표되는 학교체육시설물은 대부분 운동장과 같은 야외에 설치·운영되고 또한 이의 운동형태가 매우 다양하므로 기존의 시험방법으로는 이에 대한 시험평가가 매우 어려운 실정이다. 따라서 본 논문에서는 대표적인 학교체육시설물인 야외용 철봉의 강도규정 및 이의 평가를 위한 시험방법을 제정하고 이들의 적합성 및 타당성 검증에 대한 연구를 수행하였다. The present study is aiming at developing the strength specification and evaluation methodology in horizontal bars intended for permanent installation for use at elementary, middle and high schools. For these purpose, the strength specification is, firstly, established through the structural analysis considering the environmental, service and loading conditions of horizontal bars. Additionally, an evaluation methodology is developed to identify the usefulness and conformity of the strength specification. And then this study ends with the tests for prototype of horizontal bars according to the strength specification and evaluation methodology through a portable universal testing machine, which is designed to be able to adjust the loading direction and operate outdoors.
SS41 강의 F. E. M. 복합조직강에서 노치변화가 부식피로파괴에 미치는 영향
도영민,이규천 한국산업안전학회 2001 한국안전학회지 Vol.16 No.2
The rotated bending fatigue test was conducted in air and in 3.5% NaCl salt solution to investigate the fatigue fracture behaviour of raw material and F.E.M dual phase steel made from raw material(SS41) by a suitable heat treatment. This study has the initial microcrack creation of material by tensile test with that by fatigue test. And the rotated bending test of cantilever type under the condition of 3.5% NaCl salt solution and air has investigated the corrosion fatigue fracture behaviour with the variation of stress concentration factor determined by each of notch shapes. The initial microcrack have been developed in fragile grainboundary with general corrosion occurring in raw material ; in the pits built up by corrosion in F.E.M. dual phase steel because pits bring out stress concentration. It is small that the degree of decrease in corrosion fatigue life for F.E.M. dual phase steel compared with raw material because the notch sensitivity of F.E.M. dual phase steel is lower than raw material in reason of characteristics with two-phase construction.
3.5% NaCl 水溶液의 溫度變化가 SS41鋼의 腐蝕疲勞破壞에 미치는 影響
吳世旭,姜鎬珉,金廣泳,都映旼 東亞大學校 海洋資源硏究所 1988 硏究論文集 Vol.1 No.1
Corrosion fatigue test was performed under rotary bending in 3.5% NaCl aqueous solution having a temperature from 278°K to 318°K in order to investigate the effects of aqueous solution temperature on the corrosion fatigue fracture of SS41 steel. Fatigue life was remarkebly decreased with an increase in aqueous solution temperature. Fatigue life reductions for high stress level were somewhat smaller than those for low stress level, but S-N curves were nearly become parallel lines. Corrosion fatigue crack propagations were accelerated with an increase in aqueous solution temperature. The corrosion fatigue result at aqueous solution temperature of 303°K was showed about the same behaviour as those at 318°K in both S-N curve and da/dN-ΔK curve, which was considered as consequence of limiting diffusion current density(??). As aqueous solution temperature was increased, corrosion was gradually activated in view of fractured surface.