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홍성석,김민호,김용환 대한기계학회 1995 대한기계학회논문집 Vol.19 No.6
A rigid visco-plastic finite element method has been developed for modeling superplastic forming processes. The optimum pressure-time relationship for a target strain rate and thickness distributions was predicted using two-node line element based on membrane approximation for plane strain and axisymmetric condition. Analysis of superplastic forming was carried out using the developed program and the numerical results were compared to the values available in the literature for plane strain problems. For description of the contact between the dies and sheet, the direct projection method was applied to the complicated problem and the validity of the scheme was tested. Experiments for the various geometries such as hemisphere and cone were performed with the developed forming machine using the calculated optimum pressure-time curves. Comparison between analysis and experiments showed good agreement.
홍성석,김진영,김홍규,박태원,백두현,심인옥,김성식 한국군사과학기술학회 2003 한국군사과학기술학회지 Vol.6 No.1
The backward extrusion process of titanium alloy with large length to diameter ratio was simulated for different punch and die shape. The process variables such as initial billet shape, interface friction, contacting time and punch velocity were investigated and compared with experimental results. To make more effectively titanium alloy cup shape forging products with vertical wall, a modified die design which can reduce forging load, prevent sticking with punch and minimize material loss was suggested.
외기온도 보상에 의한 난방시스템 에너지 절약 제어 방안 연구
홍성석(Sung-Suk Hong),송재엽(Jae-Yeob Song),안병천(Byung-Cheon Ahn) 대한설비공학회 2010 대한설비공학회 학술발표대회논문집 Vol.2010 No.11
In this study, central heating system energy saving control proposal by outdoor air temperature compensation. Various environmental variables and control variables are changed according to the analysis procedure. Predict outdoor temperature reset control and set indoor temperature point by comparing the simulation shows the performance of energy savings.
이성호,홍성석,구형회 한국군사과학기술학회 2000 한국군사과학기술학회지 Vol.3 No.2
Thermal gradient chemical vapor infiltration (TG-CVI) process, which is one of the CVI techniques to densify a porous fiber preform, requires for a heater to have uniform surface temperature distribution. Thus, it is essential to design the shape of the heater and to predict the temperature distribution when the heater has a profile which is not a simple cylinder. In this study, an analytical method has been used to design the inner profile of a conical heater showing uniform temperature distribution, if its outer shape is specified. Temperature distribution on the heater surface has been calculated with the finite difference method and compared with the experimental results. When a heater had a combined profile with a large cone and a small cylinder, temperature was higher in the cylindrical part. To reduce the temperature difference between these areas, a hole-machining method has been proposed including other possible ones. A shape design and optimization program has been made to improve the temperature uniformity of the TG-CVI heater better than that designed with the analytical method.