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로프각도와 강판두께를 고려한 패드아이 용접부 강도설계에 관한 연구
정호승,김정렬,Jeong, Ho-Seung,Kim, Jung-Ryul 한국마린엔지니어링학회 2007 한국마린엔지니어링학회지 Vol.31 No.4
Pad-eye is connected to crane with sling. When block is lift, pad-eye have a various applied force. Applied force on pad-eye is related to sling angle. Sling angle is decided by various parameters, including pad-eye location, sling length and crane location. Welded joint on pad-eye requires strength design because sling angle changes force on pad-eye. Strength design for welded joint of pad-eye will calculate with general mechanical design and FE analysis. FE analysis would become a useful tool in the analysis of welded joint. A commercial software(ANSYS 10.0) was used in the structural strength analysis for welded joint of pad-eye.
미세조직 변화를 고려한 대형 배기밸브 스핀들 제조공정 해석
정호승,조종래,박희천,Jeong Ho-Seung,Cho Jong-Rae,Park Hee-Cheon 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.8
The microstructure evolution in hot forging process is composed of dynamic recrystallization during deformation as well as grain growth during dwell time. Therefore, the control of forging parameters such as strain, strain rate. temperature and holding time is important because the microstructure change in hot working affects the mechanical properties. Modeling equations are developed to represent the flow curve. grain size. recrystallized volume fraction and grain growth phenomena by various tests. The developed modeling equations were combined with thermo-viscoplastic finite element modeling to predict the microstructure change evolution during hot forging process. The large exhaust valve spindle (head diameter of 512mm) was simulated by closed die forging with hydraulic press and cooled in air after forging. The preform was heated to each 1080 and 1150$^{\circ}C$. Numerical calculation was performed by DEFORM-2D. a commercial finite element code. Heat transfer can be coupled with the deformation analysis in a non-isothermal deformation analysis. In order to obtain the fine and homogeneous microstructure and good mechanical properties in forging. the FEM would become a useful tool in the simulation of the microstructure development. In forging, appropriate temperature, strain and strain rate and rapid cooling are required to obtain the fine grain microstructure The optimal forging temperature and effective strain range of Nimonic 80A for large exhaust valve spindle are about 1080$\∼$l120$^{\circ}C$ and 150$\∼$200$\%$.
열점소성 유한요소법을 이용한 대형 배기밸브 스핀들 마찰용접 공정개발
정호승(Ho-Seung Jeong),박희천(Hee-Cheon Park),오중석(Jung-Seok Oh),한명섭(Myoung-Seoup Han),조종래(Jong-Rae Cho) 한국마린엔지니어링학회 2006 한국마린엔지니어링학회 학술대회 논문집 Vol.2006 No.-
Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint face, and energy required for welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy, amount of upset, working time, and residual stresses in the joint. Inertia welding was conducted to make the large exhaust valve spindle for low speed marine diesel engine, superalloy Nimonic 80A for valve head of 540㎜ and high alloy SNCrW for valve stem of 115㎜. Due to different material characteristics, such as, thermal conductivity and flow stress, on the two sides of the weld interface, modeling is crucial in determining the optimal weld geometry and parameters. FE simulation was performed by the commercial code DEFORM-2D. A good agreement between the predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters, especially for welds for which are very expensive materials or large shaft.