http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
최원재(W. J. Choi),김현우(H. W. Kim),백승문(S. M. Baek),강현준(H. J. Kang),이호생(H. S. Lee),정석권,윤정인(J. I,Yoon) 한국동력기계공학회 2009 한국동력기계공학회 학술대회 논문집 Vol.2009 No.6
Recently, technical trend for industrial machines is focused on enhancing of speed and accuracy. For high speed and high accuracy, a thermal deformation must minimize in industrial machines. To minimize the thermal influence, accuracy industrial machines need to be adopted a cooling system with high precision. In this study, we suggest a cooling system using PMV(Pulse Modulation Valve) control. In this system, we use a compressor which is able to be driven in condition of unloading. And a vapor refrigerant from the suction side of the compressor is injected back into the compressor suction side again using a PMV. The PMV control can be used by this method. Also, by comparing with the existing steady speed compressor method on identical operating conditions, we evaluated the efficiency and reliability of the new method. This method showed the efficiency and performance improved by lower compressor work using the vapor injection without compressor stop. And the COP of this system decreased when load capacity of compressor was decreasing. This result will be used for a basis data of comparative experiment with inverter control and manufacture of high accuracy water cooling system
금형 냉각과 압출 속도가 7075 합금 압출에 미치는 영향에 대한 현상학적 분석
성상규 ( S. G. Seong ),강현준 ( H. J. Kang ),이상용 ( S. Y. Lee ) 한국열처리공학회 2021 熱處理工學會誌 Vol.34 No.4
The extrusion experiments using the 7075 aluminum billet have been performed to investigate the effects of die cooling and ram speed on the occurrence of surface defects on the extrudate. The purpose of die cooling was to suppress overheating of the extrudate at the moment of extrusion. In the present die cooling system, liquid nitrogen has been injected in to the die and sprayed to the surface of extrudate. Ram speed was either kept or varied in the range of 1.1~1.7 mm/sec. throughout one extrusion shot to check the occurrence of surface defects. Every extrusion started at a ram speed of 1.25 mm/sec. The temperature of extrudate was measured using a laser thermometer. The 7075 billet of 180 mm in diameter and 550 mm in length was preheated at 390oC and extruded to get a single plate of 8000 mm in length, 150 mm in width and 10 mm in thickness. Each extrudate was checked by eye to find the surface defects. The microstructures were obtained in the specimen cut from each corner of the extrudate using the EBSD micrographs. (Received July 9, 2021; Revised July 16, 2021; Accepted July 22, 2021)