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[기술논문] 폴리에틸렌 보트의 선형 디자인에 관한 연구
조석수(Seok Swoo Cho),곽원민(Won Min Kwak) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.5
Domestic boat has been manufactured by hull form of typical foreign boat. In this study, design environment for polyethylene boat is analysed to create new hul form of the boat and design elements are extracted from existing boats and consumer preferences. Key elements in our design are three words “semi-classic, urban and sporty”. Hull resistance and engine power for new developed boat can be expected by Orca 3D program. This result indicates that engine power of the boat is much less than that of commercial boat.
조석수(Seok Swoo Cho) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
This study examines thermal safety on three-way catalyst that dominates 70% among whole exhaust gas purification device in 2003. Three-way catalyst maintains high temperature in interior domain but maintains low temperature on outside surface. Therefore this device shows tensile stress on outside surface. Temperature distribution of three-way catalyst was acquired by thermal flow analysis for predicted thermal flow parameter. Thermal stress analysis for three-way catalysis was performed based on this temperature distribution. Thermal safety of three-way catalyst was estimated by strength reduction factor and failure probability.
X선 잔류응력을 이용한 냉간압연강의 피로손상 모델링에 관한 연구
조석수(Seok-Swoo Cho),주원식(Won-Sik Joo) 한국해양공학회 1999 韓國海洋工學會誌 Vol.13 No.4
Cold rolled steel has much plastic strain in the material surface produced by manufacturing process. The strain causes the variation of surface residual stress, in which influences the fatigue behavior under repeated loading. As experimental results, it was confirmed that the behavior of residual stress σr with cycle N consisted of three stages except stress amplitude near fatigue limit in SPCC steel. On the first stage compressive residual stress decreased rapidly, on the second stage gradually, and on the last stage slightly. The relation between σr and log N appeared linear behavior except the early part of cycle ratio N/Nf. The average gradient of σr with respect to log N seemed to take a constant value without initial cycle ratio. On the other hand, the Nf line was regressed by the first-order polynomial equation on σr-log Nf diagram. Therefore, this study showed that both the gradient of σr with respect to log N and the Nf line was useful in predicting the cycle ratio N/Nf
조석수(Seok Swoo Cho),함범식(Bum Sik Ham),조영철(Young Chul Cho),곽원민(Won Min Kwak) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.5-3
Boat or yacht hull has been built mainly by FRP composite materials. FRP boat hull manufacturing begins to be restricted after 2000 under international regulation on ocean environment safety. Therefore, alternatives of FRP has been proposed by many boat builders and high strength aluminium is consdiered as its standard material. But, high strength aluminium is very expensive as boat hull material. In this study, Boat hull was built by high density polyethylene and its structural strength was estimated by longitudinal strength test method in small craft. Tensile strength of polyethylene boat hull material is less than tensile strength of FRP boat hull material. But Safety factor of polyethylene boat hull is more than safety factor of FRP boat hull. This results indicate structural integrity and quality control of polyethylene boat is better than FRP boat.
조석수(Cho, Seok-Swoo) 한국산학기술학회 2013 한국산학기술학회논문지 Vol.14 No.12
가솔린 엔진 차량용 삼원촉매담체는 주로 코제라이트 세라믹으로 제작되는 다공성 부품으로 엔진의 혼합기 가 농후한 경우 삼원촉매의 열적 내구성이 급격히 떨어져 설계 내구 수명을 제대로 만족시키지 못하고 있다. 따라서 본 연구에서는 SiC 세라믹 촉매 담체의 내구성 평가에 사용할 기계적 물성치를 유한요소해석으로 구하기 위하여 등 가물성평가방법을 이용하여 SiC 세라믹 하니컴 담체의 기계적 물성치를 유한요소해석용 시험편으로 구하였다. MOR 과 탄성계수는 코제라이트 세라믹 하니컴 담체에 비하여 SiC 세라믹 하니컴 담체가 최소 2배와 9.3배 정도 크게 평 가되고 있어 SiC 세라믹 하니컴 담체는 코제라이트 세라믹 하니컴 담체에 비하여 높은 구조 강도를 가지고 있다. Automotive three-way catalyst substrate has a cordierite ceramic honeycomb structure. The substrate in the high engine speed range doesn't satisfy the design fatigue life due to the low mechanical properties of cordierite ceramic. SiC ceramic has higher mechanical properties than cordierite ceramic. If the automotive three-way catalyst substrate is made from the SiC ceramic honeycomb structure, the substrate can be prevented from premature failure. In this study, the mechanical properties of SiC ceramic honeycomb substrate were estimated by FEA. The FEA results indicated that the MOR and elastic modulus for the SiC ceramic honeycomb substrate was much higher than those for the cordierite ceramic honeycomb substrate.
조석수(Cho, Seok-Swoo) 한국산학기술학회 2013 한국산학기술학회논문지 Vol.14 No.6
2000년 이후 FRP 보트 선체 제작에 대한 국제적 법적 규제가 강화되고 있다. 본 연구에서는 보트 선체 재 료로 폴리에틸렌을 제안하였다. 폴리에틸렌은 저융점 재료로서 보트가 야외에 장기간 노출되는 경우 심각한 열피로 를 받을 수 있다. 고밀도 폴리에틸렌 보트 선체에 대한 열적 내구성을 실험적으로 평가하기 위하여 삼점굽힘하중조 건하에서 변형률 게이지를 이용하여 열응력을 측정한 뒤 열응력 데이터를 기초로 통계학적으로 열피로 손상을 분석 하였다. Material of boat hull has been used mainly with FRP composite materials until now. FRP boat hull manufacturing began to be restricted after the 2000's under international regulation on ocean environment safety. Shipyard on a small scale has manufactured polyethylene canoe and kayak hulls. Polyethylene has the melting point lower than the existing hull materials. Thermal stress occurs on outer hull surface when the polyethylene boat hull is exposed to sunlight. If it happens everyday, boat hull undergoes fatigue damage due to thermal fatigue. Therefore, this study presents the statistical fatigue life estimation on the HDPE boat hull subject to repeated thermal stress under three point bending condition.
프랙탈 차원을 이용한 Al 2024-T3 합금의 피로수명비 해석에 관한 연구
조석수(SEOK-SWOO CHO) 한국해양공학회 2000 韓國海洋工學會誌 Vol.14 No.1
Surface micro-crack grows along intergranular or transgranular region of crystal grains. But if it meets the barrier such as sessile dislocation and precipitates, it loses straightness and deflects. Investigators had many difficulties in estimating fatigue life of smooth specimen because of the random distribution, growth and coalescence of surface micro-cracks. The path of surface micro-crack has irregularity due to nonhomogeneous microstructure. Euclidian geometry can't quantify the shape of surface micro-crack but fractal geometry can. Therefore, in this paper fractal dimension is measured at various stage of cycle ratio and estimated cycle ratio in 2024-T3 aluminium alloy.