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[論文] 方形波 펄스 加熱에 의한 BaOTiO₂,SrOTiO₂,MgOTiO₂系列의 熱物性値 測定에 관한 硏究
차경옥(K. O. Cha),장희석(H. S. Chang),이흥주(H. J. Lee) 한국자동차공학회 1991 오토저널 Vol.13 No.2
In this study, thermophysical properties of the ceramic dielectrics such as BaOTi0₂, SrOTi0₂, MgOTi0₂, were measured by a single rectangular pulse heating method.The values of thermal diffusivities, specific heats, and thermal conductivities were measured as a function of temperature range from room temperature to 1300k. The measured thermal properties of one group of ceramic material were compared with those of other group and discussed in detail in connection with the chemical composition. Thus, some criteria for thermal design with the electric-electronic ceramic material were proposed.
박승규,장희석 明知大學校 産業技術硏究所 2003 産業技術硏究所論文集 Vol.22 No.-
Abstract : The importance of forging force during the RSW(Resistance Spot Welding) process cannot be exaggerated. The sound nugget can only be guaranteed with appropriate force applied through electrode tips during the solidification cycle of RSW as well as squeeze and welding(heating and melting) cycle. The ample forging force should be applied to the solidification zone so as to prevent shrinkage voids or crack. Especially when the aluminum alloy sheets are joined by RSW process, serious voids and cracks are reported by numerous researches employing conventional air-cylinder-operated spot welder. The purpose of this research is to develop servogun system, which ha quick response capability of electrode force control for RSW process. The AC servo motor driver system and T/C(so called "timer controller" for RSW) are synchronized for RSW process control with developed 80196 based embedded servogun controller. The specially-designed 440V single phase transformer is mounted onto aluminum servogun body, which is assembled with a ball screw, L/M guide, and AC servomotor-belt-pulley-drive system. The performance of developed sevogun system is verified with a serious of experiment. The controlled force shows very quick response characteristics in comparison to the conventional air-operated spot welding system. The another promising result is the servogun can apply two-stage/multi-stage force profile during the RSW process, which means ant desired profiles of the electrode force can be programed and realized with this servogun system. Finally, actual welding experiment was done with Al 5754 sheet applying various profiles of electrode force. The serious voids and cracks were found when the conventional electrode force was applied during RSW process. The results with the two-stage force shows drastic decrease of voids and cracks. With optimal two-stage forging force no voids or cracks were found at the cross-sections of the etched weldment.
임창식,장희석 明知大學校 産業技術硏究所 2003 産業技術硏究所論文集 Vol.22 No.-
Abstract : It is designed to upgrade conventional toilet flushing unit. The new upgraded functions are automatic flushing and added safety features. By judging one's evacuation, volume of flushing water can be controlled with simple mechatronics device. Thus we can save considerable amount of water(4 liters per one operation). Futhermore, for those who are old, single, and handicapped, intelligent logic can detect emergency situation in the toilet. Thus logic triggers Home Security System and make and emergency call to prevent unexpected accidents that can happen around flushing unit.
오성원,장희석 명지대학교 대학원 1997 대학원논문집 Vol.1 No.-
Recently TIG(Tungsten Inert Gas) welding of pipe is widely used in many industrial fields. Especially. TIG welded LNG pipelines are being rapidly spread since LNG is recommended as a "clean" energy source. But it is difficult to guarantee good weld quality due to unfavorable working condition on the welding sites. Furthermore, labor cost for qualified welder is getting higher and higher. Therefore, automatic orbital TIG welding system would be good alternative. The change of surface temperature near molten pool proved to have significient effect on the back bead size. in this study, the back bead shape is estimated by ANN(Artificial Neural Net), and sampled welding process variables including surface temperature are fed into the trained neural networks to generate height and width of the back bead. The estimated back bead size shows good agreement with the actual size.
저항 점용접 품질의 실시간 모니터링 및 제어를 위한 시스템
이재범,방용우,오성원,장희석 명지대학교 대학원 1997 대학원논문집 Vol.1 No.-
Resistance spot welding has been widely used in the sheet metal joining processes because of its high productivity and convenience. In the resistance spot welding process, the size of molten nugget and tensile-shear strength are criterion to assess weld quality. However real-time monitoring of the nugget size and tensile-shear strength is a extremely difficult problem. This paper describes the design of an artificial neural networks(ANN) estimator to predict the nugget size for on-line use of weld quality monitoring. The main task of the ANN estimator is to realize the mapping characteristics from the sampled dynamic resistance signal to the actual nugget size and tensile-shear strength through training. The results are quite promising in that real-time estimation of the invisible nugget size and tensile-shear strength can be achieved by analyzing the welding process variables without any conventional destructive testing of welds.