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崔載燦,趙海龍,權赫洪 부산대학교 공과대학 1991 工大論文集 Vol.42 No.-
A new helical gear forming process by cold extrusion was proposed and its numerical solution program based on the upper bound method was developed. In the analysis the involute curve was used as a shape of die and the upper bound method was used to calculate energy dissipation rate. By this method the power requirement and optimum conditions necessary for extruding helical gear were successfully calculated. These numerical solutions were in good agreement with experimental data. In the experiment, die life of a new was greatly improved compared with hat of Samanta process and 4~5 class helical gear of KS standard for automobile transmission was successfully manufactured.
崔載燦,金炳玟,崔仁根 부산대학교 공과대학 1991 工大論文集 Vol.42 No.-
At hot working temperature range, it is known that the flow stresses of nearly all metals are very much strain rate dependent. In this paper, the strain rate effects are considered in the formulation and rigid-viscoplastic finite element program is developed for axisymmetric extrusion. The influence of ram speed, temperature and friction on the flow characteristics and forming pressure are investigated. The experiments are carried out for isothermal hot extrusion with hard aluminum alloy specimens(Al7075). The theoretically predicted forming pressure showed reasonably good agreement with the experimental values.
棒材의 引拔加工에 있어서의 內部 缺陷에 관한 硏究 : 發生 機構 및 防止 對策을 中心으로
崔載燦,白南柱 부산대학교 공과대학 1983 硏究報告 Vol.26 No.-
The central burst defect in drawn product is studied. A criterion for the conditions that promote this defect has been proposed. The validity of the theory on ductile fracture proposed by S.Kobayashi et al. was examined by the experimental data found in the literature and author's experiments on multi-pass drawing. Combining the formulation of fracture criterion with the deformation mechanics based on the rigid-plastic finite-element method, the criterion for the central burst in drawing was determined and compared with experimental data. It was found that for these particular tests on multi-pass drawing, Kobayashi Criterion with tensile test results should be modified.
崔載燦,金炳玟,金炳玟 부산대학교 공과대학 1991 工大論文集 Vol.42 No.-
This study is concerned with limit analysis of metal forming problems by finite element method. New algorithm of the limit analysis is formulated by minimizing the upper bound functional in plane strain and axisymmetric forming problems with work-hardening materials, and the finite element program is developed for the drawing and extrusion. Limit loads, velocity and flow line fields are directly obtained under various process conditions and the deformation characteristics such as grid distortion, strains, strain rates and stresses are computed from the optimum velocity components by numerical calculation. Experiments are carried out for strip drawing with the aluminum alloys and for axisymmetric extrusion with the carbon steel. For the varification of this algorithm, the computations are compared with the experiments. The good agreement between theoretical and experimental results is shown that the proposed algorithm and developed programming can be effectively applied to the numerical analysis of metal forming problems.
속도의존성 재료에 대한 축대칭 전방압출의 유한요소 해석
최재찬,김병민,이종수,조남춘 대한기계학회 1991 대한기계학회논문집 Vol.15 No.2
In this study, the strain rate effects are considered in the formulation by introducing the constitutive equation of the strain rate sensitive materials and rigid-viscoplastic finite element program is developed for axisymmtric extrusion. The effect of strain rate sensitivity on the flow characteristics and forming pressure are investigated and the experiments are carried out for extrusion with pure lead specimens. The theoretically predicted forming pressure showed reasonably good agreement with the experimental values.