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내부 결함을 고려한 주조 제품의 피로수명 예측을 위한 결함 형상단순화 해석모델
곽시영(Si-Young Kwak),김학구(Hak-Ku Kim) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.10
내부결함은 주조제품의 강도 및 피로 수명에 있어 상당한 영향을 미치기 때문에 주조공정에서 주요 관심사 이다. 일반적으로 내부결함은 응력집중을 발생시키며 균열의 시작점이 되므로 피로 수명과 같은 기계적 거동에 있어 수축공과 같은 결함을 이해하는 것이 중요하다. 본 논문에서는 내부결함을 고려한 인장시편에 대해 피로시험을 수행하고 주조결함을 고려할 때의 특정하중피로노치 계수를 산정하였다. 실제 내부결함은 산업용 CT 장비를 통해서 확인하였으며 확인된 결함은 형상단순화법에 의해 타원체로 단순화 하고 응력해석과 피로해석을 수행하였다. 그 결과 우리가 제안한 방법이 기계적 거동에 있어 내부결함의 영향을 조사하고 피로수명 등을 예측함에 있어 유용함을 확인할 수 있었다. Internal defects are a major concern in the casting process because they have a significant influence on the strength and fatigue life of casting products. In general, they cause stress concentration and can be a starting point of cracks. Therefore, it is important to understand the effects of internal defects on mechanical properties such as fatigue life. In this study, fatigue experiments on tensile specimens with internal defects were performed. The internal defects in the casting product were scanned by an industrial CT scanner, and its shape was simplified by ellipsoidal primitives for the structural and fatigue analysis. The analysis results were compared with experimental results for casting products with internal defects. It was demonstrated that it is possible to consider internal defects of casting products in stress and fatigue analysis. The proposed method provides a tool for the prediction of the fatigue life of casting products and the investigation of the effects of internal defects on mechanical performance.
이승채,김우순,김동현 한국공작기계학회 2004 한국공작기계학회 추계학술대회논문집 Vol.2004 No.-
Rapid prototyping technologies have been widely used to reduce the development cost of new products. Manufacturing industries are nowadays characterized by the flexibility and complexity of products. This to due to the rapid development of manufacturing technology and diverse needs of customers. In this paper, the burning condition for getting casting product of resin pattern have been examined experimentally. In generally, the burning conditions have effect on the casting products. Using the direct casting. we directly producted the jewelry.
쌍롤식 박판 연속주조공정에 있어서 용탕과 냉각롤의 접촉 열저항을 고려한 전열해석
김영도,강충길,Kim, Y.D,Kim, C.G 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.1
The twin-roll type strip continuous casting process(or direct rolling process) of steel materials is characterized by two rotating water cooled rolls receiving a steady supply of molten metal which solidifies onto the rolls. A solidification analysis of molten metal considering phase transformation and thermofluid is performed using finite diffefence method with curvilinear coordinate to reduce computing time and molten region analysis with arbitrary shape. An enthalpy-specific heat method is used to determine the temperatures inthe roll and the steel. The temperature distribution of cooling roll is calculated using two dimensional finite element method, because of complex roll shape due to cooling hole in rolls and improvemnt accuracy of calculation result. The energy equaiton of cooling roll is solved simultanuously with the conservation equaiton of molten metal in order to consider heat transfer through the cooling roll. The calculated roll temperature is compared to experimental results and the heat transfer coefficient between cooling roll surface and rolling material(steel) is also determined from comparison of measured roll temperature and calculated temperature.
백성규(Sung-Kue Baek),권용남(Yong-Nam Kwon),이영선(Young-Sun Lee),이정환(Jung-Hwan Lee) 한국기계가공학회 2008 한국기계가공학회 춘추계학술대회 논문집 Vol.2008 No.-
In the present study, blow forming characteristics of commercially rolled AZ31 alloy sheets were investigated. Two different kinds of AZ31 sheets were originally fabricated by using direct casting and strip casting methods respectively. Both sheets have similar grain sizes of about 7m with a relatively equiaxed structure after rolling. A series of tensile tests were carried out to get flow behavior in terms of temperature and strain rate. Elongation increased with temperature increment as well expected. However, the differences in tensile test condition did not give much difference in elongation even at the temperature range where a large elongation would be expected with such as fine grain of 7m. Blow forming experiments showed that forming condition did not result in higher difference in dome height. However, the interesting feature from this study was that formability of this AZ31 alloy got different with stress condition. Firstly, biaxial stress condition might result in lower temperature and strain rate dependencies compared to uniaxial tension results for both DC and SC sheets. Secondly, DC showed slower grain growth in uniaxial tension than in biaxial stress state while SC has much higher grain growth rage in uniaxial tension than in bulging.