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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.
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.
高周波表面硬化한 SM45C 鋼에서 有效硬化層깊이가 疲勞擧動에 미치는 영향
吳世旭(Sae-Wook Oh),許正元(Chung-Weon Huh),金榮範(Young-Beum Kim),朴元祚(Won-Jo Park) 한국해양공학회 1991 韓國海洋工學會誌 Vol.5 No.1
This paper reveals the effect of the effective case depth(ECD) on the fatigue behavior of a high-frequency induction hardened SM45C in rotated bending fatigue test. In addition, the effects of fracture modes(surface origin type, inner origin type) on it are discussed.<br/> The fatigue limit of the induction hardened steel is remarkably increased compared with that of base metal. In addition, the fatigue limit is linearly increased as the effective case depth grows deep in the region of this experiment (ECD/R ; 0.23~0.49).<br/> The S-N curve and fracture mode in the induction case hardened steel are classified into two kinds, as a result : Nf<10<SUP>5</SUP> ; surface origin type fracture(at high stress), Nf>10<SUP>5</SUP> ; in ner origin type fracture(at low stress).<br/> In case of inner origin type fracture ; as the effective case depth(ECD) gets deep, the fatigue limit is increased by the reason that the fracture origin moves toward center ; in reverse, is decreased by reason that the compressive residual stress gets low. As a result, the increasing effect of the former is much bigger than the decreasing effect of the latter, and the fatigue limit is increased as the ECD gets deep.
API 5LB鋼管의 高周波電氣抵抗熔接部에 관한 破壞靱性 評價
吳世旭(Sae-Wook Oh),尹漢基(Han-Gi Yoon),安啓元(Kye-Won Ahn) 한국해양공학회 1987 韓國海洋工學會誌 Vol.1 No.1
The evaluation of the elastic-plastic fracture toughness J1C was performed on the center of weld metal (CWM), the heat affected zone (HAZ) and the base metal (BM) of API 5LB steel pipes welded by the high frequency electric resistance welding. The J1C was evaluated by the JSME R-Curve and JSME SZW methods using the smooth and side-grooved specimens.<br/> The results are as follows;<br/> (1) The J1C values by the SZW method are overestimated as compared with those by the R-curve method. because the micro-crack is formed as SZW increase with the deformation at SZ after initiation of the ductile crack.<br/> (2) The average of J1C values by the R-curve and the SZW methods in side-grooved specimens tended to decrease in comparison with smooth specimens 9.42% at CWM, 4.2% at HAZ, 23.2% at BM, respectively.<br/> (3) The boundary of the fatigue pre-crack, stretched zone, and dimple regions appeared more clearly in side-grooved specimens, for the slight change of SZW in the direction of the plate thickness, as compared with smooth specimens.
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.