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남중희(J. H. Nam),정성환(S. H. Jung),정택우(T. W. Jung),이영선(Y. S. Lee) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.5
Gear is used for various purpose and one component of a wide range machines, many researchers have been done to study manufacture method using cold forging technology(by Cold forging and Extrusion) due to high productivity and material utilization. But forging technology of helical gear is very difficult because of helix angle, tool life and deformation control of material. So this work was focused method to forge without rotation of die-set. Multi-stage forming process to produce helical gear was designed total 4 processes that 1-3 processes are hot forging and 4 process is cold forming process. Tooth shape forming process of helical gear investigated that forming method by bottom pressurization was optimum process in the results using finite element simulations. It was found that simulation results to predict forming load were slightly different from experiment results, but material flow and burr generation were in good agreement with experiment results.
NiCuZn ferrite의 특성에 미치는 조성의 영향
남중희(J. H. Nam),정현학(H. H. Jung),신재영(J. Y. Shin),오재희(J. H. Oh) 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.3
NiCuZn ferrites were prepared by a solid-state reaction and sintered at 900℃ for 5 hours. Its properties were investigated by controlling the ferrite composition and processing. NiCuZn ferrite with a composition of (Ni_(0.2)Cu_(0.2)Zn_(0.6)O)_(1.02)(Fe₂O₃)_(0.98) was found to have the maximum initial permeability as a result of the variation of Cu content and the (Ni+Cu) / Zn ratio. Curie temperature(Tc) of NiCuZn ferrite was decreased with the larger Cu content and increased with the larger Ni content. NiCuZn ferrites of (Ni_(0.2)Cu_(0.2)Zn_(0.6)O)_(1-w)(Fe₂O₃)_(1+w) composition milled for 20~80 hours had the maximum initial permeability at w=-0.015 and Curie temperature(Tc) was decreased with the increasing of Fe₂O₃ deficiency(w).
권주리(J. R. Kwon),남중희(J. H. Nam),이영선(Y. S. Lee),강창원(C. W. Kang),이진길(J. G. Lee),손재환(J. H. Son),최원식(W. S. Choi) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.10
In this study, we will simulate the hydrodynamic load capacity and equivalent roughness for textured surface in oil lubrication for well understanding of friction properties by hydrodynamic lubrication theory. In the dimple pattern, dimple depth is 2μm and dimple size is 40μm, 70μm, and 100μm. Calculated Rrms<SUP>*</SUP> is 47nm from measured value of Rrms,1 and Rrms,2. Viscosity was 3.125Pa · s for paraffin oil. It can be seen that hydrodynamic load capacity WHL increased with the decreasing of minimum oil film thickness hmin. And if we compare the maximum WHL at hmin=Rrms<SUP>*</SUP>,100μm diameter dimples showed largest of all as 9.2N. Maximum WHL at hmin=Rrms<SUP>*</SUP> is 7.5N and 6.2N for 70μm, 40μm diameter dimples, repectively. WHL of the flat slider shows almost of zero. It was shown the hydrodynamic lubrication in dimple patterning and could be seen that an increase in durability.