SUS 316 강의 온도의존성 결정입경이 크리이프 거동에 미치는 영향

오세욱,강욱,Oh, Sae-Wook,Kang, Oug 대한용접접합학회 1983 대한용접·접합학회지 Vol.1 No.2

Austenitic stainless steel has been investigated widely for creep strength of heat resistant material and effects of grain sizes due to various solution treatment time under constant temperature. It was studied that effects of grain sizes subject to solution treatment temperature 1100.deg. C, 1125.deg. C, 1175.deg. C, 1250.deg C, and 1300.deg. C respectively on the creep strength, fracture behaviour and fractography of SUS 316 stainless steel. The experimental results obtained were as follows. 1. The optimum grain size for the maximum creep strength did not vary with creep testing temperatures and stress levels. 2. Among various grain sizes due to different solution treatment temperature, the optimum grain size for the creep strength was found 0.044mm. Also the size showed the minimum initial strain regardless creep temperature. 3. Garofalo's equation of creep rupture life was applied well to SUS 316 stainless steel. 4. The fractography of optimum size was ductile intergranular fracture of dimple type and showed along with the increase of grain size intergranular fracture of w type.

第2代 會長 就任辭

吳世旭(Sae-Wook Oh) 한국해양공학회 1988 韓國海洋工學會誌 Vol.2 No.1

H₂S가스飽和 鹽酸水溶液에 의한 熔接構造用鋼의 應力腐蝕龜裂 發生擧動

吳世旭(Sae-Wook Oh),金在喆(Jae-Chul Kim),金泰亨(Tae-Hyung Kim),金廣泳(Kwang-Young Kim) 한국해양공학회 1990 韓國海洋工學會誌 Vol.4 No.1

Among the test methods to evaluate stress-corrosion cracking(SCC) on the basis of fracture mechanics, constant displacement(bolt) loading method using modified-WOL specimen is practically convenient. In this test method, compliance formula is generally required to calculate load(consequently KISCC). There are many problems in using the analytic compliance formula to calculate KISCC, so we had proposed the experimental KISCC evaluation technique in the previous report.<br/> This study has employed the slightly altered configuration of modified-WOL specimen made of weldable structural steel(BS4360-50D). With these specimens, stress-corrosion tests have been performed in H₂S gas saturated 20% HCl solution. Through the test, the problems as mentioned earlier have been discussed again, and the proposed evaluation technique has been verified.<br/> And the stress-corrosion cracks and hydrogen blisters have been investigated in the initiation step with the aids of metallurgical micrographs, SEM fractographs, and EPMA analysis.<br/> The inclusions segregated in the mid-thickness region traps hydrogen to produce the hydrogen blistering. The applied or residual stress does not contribute the occurrence of the blister. Hydrogen absorbed into the mid-thickness region is consumed to produce the blistering so that stress-corrosion crack could hardly be detected at that region.<br/> The stress-corrosion cracks initiate from the inclusions and propagate in radial pattern. And the initiation site is remote from the crack tip and is inclined from the crack plane, which is assumed to be caused by the triaxial stress and the amount of the absorbed hydrogen.

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.

計裝化衝擊試驗機에 의한 複合組織鋼의 動的破壞靭性 評價

吳世旭(Sae-Wook Oh),?在煥(Jae-Whan Yoo),李敬奉(Kyung-Bong Lee) 한국해양공학회 1989 韓國海洋工學會誌 Vol.3 No.1

In order to investigate the dynamic fracture characteristics of dual phase steel was made with a suitable heat treatment of SS41 steel, a dynamic fracture toughness was performed under an instrumented impact testing machine with the constant loading velocity at the variation of temperature.<br/> The validity of dynamic fracture toughness in the precracked V-notch charpy specimen could be confirmed through the aspect of the dynamic fracture surface.<br/> The lower self of the absorbed energy curve, the upper self of 50% brittle rupture point and the behaviour of the dynamic fracture toughness (K1d) curve were the same tendency as the factor of temperature (-80℃ RT).<br/> The value of the dynamic fracture toughness obtained by the fracture surface with shear-lip could not be assure of the application of the plane strain problem.

원자력 압력용기강(SA508-3)의 탄소성 파괴인성 평가

오세욱(Sae-Wook Oh),윤한기(Han-Ki Yoon),임만배(Man-Bae Lim) 한국해양공학회 1993 韓國海洋工學會誌 Vol.7 No.2

The elastic-plastic fracture toughness JIC of Nuclear Reactor Vessel Steel(SA 508-3) which has high toughness was discussed at temperatures RT, -20℃, 200℃ and 1/2 CT specimen was used for this study. Especially the two methods recommended in ASTM and JSME were compared. It was difficult to find JIC by ASTM R-curve method with the specimen used for this research, while JSME R-curve method yielded good result.<br/> The stretched zone width method gave slightly larger JIC values than those by the R-curve method for SA 508-3 steel.

JIC Evaluation of the Smooth and the Side-Grooved CT Specimens in the Reactor Pressure Vessel Steel(SA508-3)

Sae-Wook Oh(오세욱),Man-Bae Lim(임만배) 한국해양공학회 1994 韓國海洋工學會誌 Vol.8 No.2

원자력 압력용기강의 탄소성 파괴인성값 JIC를 CT형 시험편을 이용하여 검토하였으며, 평활 시험편 및 측면홈 시험편의 두께는 각각 BO=25.4㎜, BN=20.4㎜이다. 측면홈의 깊이는 19.7%이며, 홈의 각도는 90°로 가공하였다. 탄소성 파괴인성시험은 ASTM E813-81과 JSME S001-81의 추천방법에 따라 실시하였다. 두 추천방법으로 실험한 결과 ASTM방법에 의한 JIC값이 과대평가됨으로써 부대조건에 만족되지 못하였지만 JSME방법은 만족되었다. 측면홈 시험편은 R곡선법에 의한 ductile tearing의 결정이 평활 시험편보다 용이하였으며, 이에 따른 JIC값의 정확성을 배가 할 수 있었다. 또한 임계 스트레치존 폭(SZWC)은 측면홈에 의한 높은 3축응력이 발생되어 평활시험편보다 적게 나타났으며, 이러한 복합적인 원인에 기인하여 스트레치존법에 의한 JIC 평가는 R곡선법에 의한 평가보다 약간 과대평가됨을 알 수 있었다.

離任辭

吳世旭(Sae-Wook Oh) 한국해양공학회 1990 韓國海洋工學會誌 Vol.4 No.1

인공섬건설에 따른 해안선변형모델에 관한 연구

오세욱(Sae-Wook Oh),민병형(Byung-Hyung Min),김진후(Jin-Hoo Kim),김기철(Ki-Cheol Kim),김재중(Jae-Joong Kim) 한국해양공학회 1992 韓國海洋工學會誌 Vol.6 No.2

Beach evolution is of the most important problem is the coastal engineering. Especially, the structure construction through reclamation in the shallow water region nesar the beach will cause many severe problems around the structure. Beach evolution due to the construction of an artificial island in this study was studied using wave transform model and associated sediment transport model. Numerical simulation of the model was applied to the Kwangan beach using the data of waves and shoreline measurements of the area.<br/> The combined wave transform model and beach evolution model showed good results. The results show a breakwater will be needed to prevent severe erosion near the eastward Kwangan beach when construction an artificial island in the Suyong Bay. Good results of the study also suggest that the present model can be more widely applied to the prediction of beach evolution.

터빈 로터강의 피로크랙전파속도의 확률특성 연구(Ⅰ)

오세욱(Sae-Wook Oh),이치우(Chi-Woo Lee),장윤석(Yun-Souk Chang),정순호(Soon-Ho Chung) 한국해양공학회 1987 韓國海洋工學會誌 Vol.1 No.2

In order to estimate the running life of turbine rotors, fatigue crack propagation law, da/dN=C(ΔK)<SUP>m</SUP>, proposed by Paris et al. has been widely applied.<br/> In this study, fatigue crack propagation rates for 16 samples of 1% Cr-Mo-V rotor steel were measured and statistical characteristics of m and C values in above equation were reviewed.<br/> The results are summarized as follows.<br/> 1. C and m follow a log-normal distribution and normal distribution, respectively. And the relation of C and m shows a strong negative correlation.<br/> 2. Fatigue crack propagation equation can be expressed as da/dN=4.11×10<SUP>-4</SUP>(ΔK/153.8)<SUP>m</SUP>, introducing the relationship C=CoKo<SUP>-m</SUP>.<br/> In this case, contribution of Co distribution to the distribution of log C shows very small compared to degrees of contribution by m.