局所變形分布를 이용한 저 사이클 疲勞龜裂發生壽命評價

朴榮哲,吳世旭 東亞大學校 海洋資源硏究所 1990 硏究論文集 Vol.3 No.1

The parameter of local cyclic strain distribution near a crack tip, △A was applied to evaluate the fatigue crack initiation life under low cycle fatigue. The results showed that the relationship between the fatigue crack initiation life(Nc) and the parameter △A could be written as equation (1) independent of various materials. In addition, it was confirmed that the parameter Fc could be calculated, as a first approximation, by the mechanical properties of materials as shown in equation (2) Fc=△A·Nc¹/².......................(1) Fc=2.6(Jic/σY)¹/⁴..................(2)

백서에서 자가 피부이식후 항T임파구 단일클론항체 분포에 관한 면역조직화학적 연구

朴晩圭,金慶助,任昌俊,高世勳 단국대학교 치의학연구소 1991 논문집 Vol.3 No.-

This article is intended to study histopathological and immunohistochemical response after autogenous full-thickness skin graft in rat. 12 male Sprague-Dawley rats were used as the experimental animals. A 1 cm×1 cm skin (0.7mm diameter) was taken on the right inguinal area of the rat. Another full-thickness skin graft (1cm × 1cm) was taken from the left inguinal area of the rat. And it was transplanted to the right inguinal area of the rat. The left side wound was closed directly. Light microscopic observation was made at the postoperative 1, 3, 8, 16 day, after the hematoxylin-Eosin staining of the 4u-thick paraffin embedded specimens and the immunohistochemical staining of the 10u-thick frozen specimens with mouse anti-rat monoclone antibodies and ABC staining kit. The results were as follows. 1. Electromicroscopic studies revealed interstitial tissue bleeding of transplanted autogenous skin. The response was severe in the 1 day group after operation, moderate in 3 day group, mild in 8 day group, and almost resolved in the 16 days group. 2. Electromicroscopic studies also revealed a mild monocyte response in the 3 day and 8 day groups. A histiocytic infiltrate was observed. There was a mild response in the 3 day group and moderate response in the 8 day group. 3. Immunohistochemically studies revealed a few pan T cells in the 1 day group, mild appearance of pan T cells and cyototoxic T cells in the 3 day group, a moderate infiltrate of pan T cells and helper T cells in the 8 day group, and total resolution of pan T cells in the 16 day group. 4. According to these finding, a strong inflammatory response was observed around transplanted autogenous skin in the 3 & 8 day groups. In the 16 day group this response had resolved histopathologically and immunohistologically.

알루미나이징 表面處理한 構造用鋼의 彼勞强度 및 破壞擧動에 관한 硏究

吳世旭,朴春根,全泰玉,全哲昊,周原植,李圭用 東亞大學校 大學院 1978 大學院論文集 Vol.2 No.-

Aluminizing-treated structural steel is excellent in high temperature oxidation resistance, wear resistance and corrosion resistance. So, it has been widely used for the machine parts which have required such properties. However it is difficult to find out any study result of the notched influence on the aluminizing-treated materials and the second diffusion materials. In this investigation the low carbon steel plates with with V-notches were coated with aluminum and made into second diffusion. With these specimcns the bending fatigue strength and fatigue life were observed and also crack propagation of alloy layer was investigated. The results obtained are as follows: 1) On the smoothed specimens a fatigue limit of aluminizing material was lower than the one of raw material, but it was more increased than the one of heat treatment material, and the fatigue limit of second diffusion material was lowest. 2) On the V-notched specimens a fatigue limit of aluminizing material was higher with 44% increase ratio than the one of raw material and with 63% increase ratio than the one of heat treatment material, and the rate of increase became lower increase ratio in a fatigue limit comparing to aluminzing material, with no influence of notch radius. 3) According as the notch radius became smaller, the fatigue limit became. higher on the raw material, it was same on th aluminizing material and lowest on the second diffusion material. 4) Crack initiation period was 0.04% below of fatigue crack life and the full growth period of crack propagation at alloy layer was 0.1%. The crack propagation from alloy layer to matrix was 16% of the fatigue crack life. This means that the crack propagation rate at alloy layer was very fast but the crack delay at the boundary of both was so long. 5) Crack propagation grows through defects, inclusion, peeling and previous boundary.

Type Ⅳ 과지질혈증에서 나타난 다발성 건 황색종 : 1례 보고 One Case Report

천동욱,김홍태,박봉훈,변영수,홍순만,손경락,문세광 최신의학사 1992 最新醫學 Vol.35 No.10

M. E. F. 複合組織綱의 腐蝕疲勞破壞에 미치는 3.5% NaCl 水溶液 溫度變化의 影響

吳世旭,都映旼,朴洙瑩,廉永夏 東亞大學校 海洋資原硏究所 1990 硏究論文集 Vol.3 No.1

3.5% NaCl 水溶液中의 自由腐蝕條件下에서 SS41鋼과 複合組織鋼에 대한 回轉굽힘 腐蝕疲勞試驗을 행하여, 溫度影響이 腐蝕疲勞强度 및 腐蝕疲勞크랙 進展速度에 미치는 影響을 考察하였다. 溫度가 增加할수록, 腐蝕疲勞壽命은 減少하였으며 腐蝕疲勞크랙 進展速度는 加速化되었다. 303°K와 318°K의 溫度領域에서 S-N曲線과 腐蝕疲勞크랙 進展速度가 거의 一致하는 것은 陽極溶解의 制限때문이다.

계장화충격시험에 의한 복합조직강의 파괴인성에 관한 연구

오세욱,유재환,박원조,이경봉 동아대학교 공과대학 부설 한국자원개발연구소 1989 硏究報告 Vol.13 No.1

The dynamic fracture toughness (K_(Id)) is measured using the precracked standard Charpy specimen with an instrumented impact machine. The value of K_(Id) is determined as a function of yield strength and microstructure, and correlations are established between K_(Id) and both energy of initial fracture and total energy of fracture. Since the K_(Id) values of the precracted impact specimens are in accordance with their theoretical ones, this test method is sufficiently practical.

SFA55材의 機械的性質 및 비틀림疲勞特性에 미치는 熱處理溫度의 影響

吳世旭,金晋坤,朴正洙 동아대학교 공과대학 부설 한국자원개발연구소 1984 硏究報告 Vol.8 No.2

Nowadays, SFA55 has been used to train frame widely It is necessary that mechanical properties and fracture behavior of SFA55 should be evidently cleared in order to prevent fracture accident of train frame previously. For impact test specimens SFA55 have been treatted by two methods; water-quenched at 880℃, tempered at various temperatures, and for twisting fatigue test specimens; normalized at 880℃, tempered at 550℃ after quenched at 880℃. Impact test has been performed by charpy impact tester (30Kgf-m) and twisting test has been conducted by schenk type twisting tester. After tests, fracture behaviors and effects of heat treatments have been investigated with Scanning Electron Microscope. The main results obtained were as follows; 1) Impact values of SFA55 have increased, but hardnesses have decreased with the tempering-temperature increasing. That is, ductility has been increased. 2) It has been generally reported that the difference of fatigue limits between normalized materials and quenched-tempered materials was almost negligible, but it has been observed that the fatigue limit of the later was greater than that of the former. 3) In the impact test specimen, the fractured surface at vicinity of U-notch was ductile dimple style and at nearly center area was brittle cleavage fracture. 4) At the center area of the impact test specimen the dimple style has been increased with the tempering temperature. 5) The normalized materials of the twisting fatigue test specimen has smooth and clean striations but the quenched-tempered materials has discontinuous and irregular striation.

複合핀 荷重을 받는 平板에 있어서 兩圓孔 사이의 Crack에 대한 K₁解析

吳世旭,朴榮哲,趙鏞培 東亞大學校 海洋資源硏究所 1989 硏究論文集 Vol.2 No.1

The epoxy resin plate and acryl plate (Both thichness:3mm) overlapped are loaded by Pin-Joint. The stress distribution, stress intensity factors and correction factor at crack tip with various demension of the specimen are as follows; 1. When the pin is loaded, the K₁value is increased remarkable in case that length of the crack is above 6mm. 2. Correction factor(F₁) is greatly dependent on the value of a/d, but not on the value of a/w or a/r. 3. When the pin is loaded, K₁value is highly decreased with decrease in crack length because of the compression load developed between pin and specimen. 4. When the pin is loaded correction factor(F) is remakable incresed as the distance of two holes are decreased.

重疊 荷重을 받는 複合핀 주위에 發生하는 平板의 應力分布에 관한 光彈性 解析

오세욱,박영철,이성효 동아대학교 공과대학 부설 한국자원개발연구소 1989 硏究報告 Vol.13 No.1

The design, fabrication, and testing of photoelastic models of double-lap, multiple-pin connectros are discussed. Interest is in the stresses in the inner laps. These stresses are determined by constructing models with photoelastic inner laps and transparentacrylic outer laps. The connectors have two pins, in tandem, parallel to the load direction. A photoelastic-isotropic point is shown to permit the evaluation of load sharing between the two pins. A numerical scheme, utilizing the isochromatic and isoclinic-photoelastic data and a finite-difference representation of the plane-stress equilibrium equations, is used to compute the stresses around the two pins. Representative stress distributions and stress-concentration factors are shown.

X-선 회절에 의한 SS41 불림재와 M.E.F. 복합 조직강의 피로 파단면 해석에 관한 연구

허선철,박영철,박수영,김득진,오세욱 韓國非破壞檢査學會 1996 한국비파괴검사학회지 Vol.16 No.1

본 연구에서는 SS41 불림재와 M.E.F. 복합 조직강에 대해서 파괴 역학 파라미터와 X-선 피라미터 사이의 관계를 규명하였다. 피로 균열 진전 실험이 수행되었고, X-선 회절 방법이 피로 파단면에 적용되었다. 피로 파단면을 순차적으로 전해 연마하면서 깊이에 따른 X-선 파라미터(잔류응력, 반가폭)의 변화를 관찰하였다. 최대 소성역 깊이 Wy는 SS41 불림재에서는 반가폭의 분포로, M.E.F. 복합 조직강에 대해서는 잔류 응력의 분포로 결정할 수 있었다. 피로 파단면의 깊이 방향에 따른 X-선 파라미터의 분포로부터 Kmax와 Wy의 관계식이 실험 데이터로부터 얻어지고, 이 식들로부터 Kmax은 Wy의 측정에 의하여 추정되어질 수 있다. This study verified the relationship between fracture mechanics parameters and X-ray parameters for normalized SS41 steel with homogeneous crystal structure and M.E.F. dual phase steel(martensite encapsulated islands of ferrite). The fatigue crack propagation test were carried out and X-ray diffraction technique was applied to fatigue fractured surface. The change in X-ray parameters(residual stress, half-value breadth) according to the depth of fatigue fractured surface were investigated. The depth of maximum plastic zone, Wy, were determined on the basis of the distribution of the half-value breadth for normalized SS41 steel and that of the residual stress for M.E.F. dual phase steel. Kmax could be estimated by the measurement of Wy.