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김수희(Su Hee Kim),전찬후(Chan Hu Jeon),주병돈(Byeong Don Joo),김윤규(Yun Gyu Kim),문영훈(Young Hoon Moon) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5
Double layered tube is assembled with an inner tube and outer tube contacting closely and deforming simultaneously when subjected to external force. For the manufacturing of double layered tube, the hydroforming assembly technology has several advantages. Therefore in this study, hydroforming characteristics of double layered tube was investigated. The X-ray CT measurement and penetration test were performed to measure double layer tube’s gap between inner and outer tube at various hydroforming pressure. The connection force measurement was also performed to estimate the load for characterization of double layered tube.
김상윤(Sang Yun Kim),주병돈(Byeong Don Joo),전찬후(Chan Hu Jeon),문영훈(Young Hoon) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
Hydroforming is a technology that utilizes hydraulic pressure to form tube or sheet materials into desired shapes inside die cavities. Three-layered tube is assembled with inner, center and outer tube, similar in material or not and deforming simultaneously when internal pressure and axial feed were applied on the tube. Three-layered tube hydroforming is suitable to produce multiple tube joints which can be used in special applications such as automotive, aerospace, piping system and nuclear power plants. The precise control of internal pressure loading path in tube hydroforming process significantly affects on the final product quality. In this study, the effect of the loading path on forming characteristics in the tube hydroforming process is investigated. Free bulging tests were performed to study the expansion ability of the three tubes and tube hydroforming in a closed die was performed to investigate the hydroformability of the tubes. Hydroforming characteristics at various loading paths were analyzed and the loading path was optimized. The results show that final product of three-layered tube can be successfully fabricated by tube hydroforming process under optimized process parametes.
Fe-Cr계 금속 분말의 직접 레이저 용융을 통해 형성된 적층부 특성 분석
장정환 ( Jeong Hwan Jang ),주병돈 ( Byeong Don Joo ),전찬후 ( Chan Hu Jeon ),문영훈 ( Young Hoon Moon ) 대한금속재료학회 ( 구 대한금속학회 ) 2012 대한금속·재료학회지 Vol.50 No.2
Direct laser melting (DLM) is a powder-based additive manufacturing process to produce parts by layer-by-layer laser melting. As the properties of the manufactured parts depend strongly on the deposited laser-melted bead, deposited layers obtained by the DLM process were characterized in this study. This investigation used a 200 W fiber laser to produce single-line beads under a variety of different energy distributions. In order to obtain a feasible range for the two main process parameters (i.e. laser power and scan rate), bead shapes of single track deposition were intensively investigated. The effects of the processing parameters, such as powder layer thickness and scan spacing, on geometries of the deposited layers have also been analyzed. As a result, minimum energy criteria that can achieve a complete melting have been suggested at the given powder layer thickness. The surface roughnesses of the deposited beads were strongly dependent on the overlap ratio of adjacent beads and on the energy distributions of laser power. Through microstructural analysis and hardness measurement, the morphological and mechanical properties of the deposited layers at various overlapped beads have also been characterized.
링 롤링 공정에서 링 치수에 따른 블랭크 치수 최적화에 관한 연구
남윤건(Yoon-Gun Nam),김상윤(Sang-Yun Kim),전찬후(Chan-Hu Jeon),성경진(Kyung-Jin Sung),문영훈(Young-Hoon Moon) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5
The ring rolling design includes geometry design and optimization of process variables. In ring rolling, the finished ring dimensions include both the cross-sectional shape and the diameter. Therefore, the blank volume assumes would alter the final product dimensions, because the volume remains unchanged during the rolling operation. So, it is significant to design initial blank sizes. In this study, optimized dimension of blank according to target ring dimension was predicted by using FEM analysis and physical modeling experiment with lead-based was used. A commercial FEM code, Forge2008 was used to simulate the effect of various blank sizes.