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980MPa급 초고강도 강판을 이용한 자동차 패널의 스프링백 저감에 관한 연구
김병규(B. G. Kim),안명복(M. B. An),박성진(S. J. Park),김경보(K. B. Kim) 한국소성가공학회 2014 한국소성가공학회 학술대회 논문집 Vol.2014 No.10
There are growing needs of the Advanced High Strength Steel(AHSS) sheets for improving fuel efficiency through the weight reduction of a car and secure the crashworthiness. Compare the other lightweight materials; the AHSS has two outstanding advantages. First, it brings down the cost of production. Second, it is less sensitive to manufacturing equipments. Nevertheless, it has difficulty to apply due to low formability and poor dimensional accuracy caused by excessive springback. In this study we performed comparison evaluation on dimensional change by FE-analysis and making proto-products of two different materials; 980MPa grad AHSS, 590MPa grade steel. Also, we seek the ways to reduce springback by adding the bead shape; which increased stiffness and residual stress control; on the drawing die addendum and verify the ways by FE-analysis and making proto-products. According to the comparison dimension inspection report, we can notice that excessive springback is occurred; AHSS scores 28 percent and it scores 48 percent less than 590MPa grade steel; However, we can also notice that it can be improved 16 percent by adding the bead shape on the die.
허수영(S.Y. Her),김경보(K.B. Kim),허종철(J.C. Huh) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.5
In order to clarify the characteristics of power performance and uncertainty of a wind turbine, an investigation was performed in Hangyeong wind farm, Jeju island, Korea. Data were collected for 12 months from Feb. 2, 2008 to Jan. 1, 2009. This study was conducted on the base of the International standard , and observed the methods of mesurement and evaluation form IEC 61400-12. As a result, power performance curve was calculated by measured data and compared with the sixth unit of VESTAS V90-3.0MW in Hangyeong wind farms. In consequence of this paper, uncertainty was estimated from 7% to 14% on the range of the average wind speed from 4m/s to 11m/s.
1500MPa급 핫스탬핑 강판의 연화열처리에 관한 기계적 특성 평가
심우정(W. J. Sim),전형준(H. J. Jeon),박용호(Y. H. Park),송명환(M. H. Song),김경보(K. B. Kim) 한국소성가공학회 2015 한국소성가공학회 학술대회 논문집 Vol.2015 No.5
Ultra-High strength steel is rapidly being applied in the automotive industry as safety regulation and environmental regulation have been tightened controls. So, The of Hot-Stamping steel what has two advantages has been on the rise. The First strength is that Hot-Stamping steel is obtained formability by processing at high temperature. And the second is the reducing weight due to spring-back and thickness reduction. However, Hot-Stamping steel has one drawback which is caused brittle fracture upon impact. So researchers are using a method of changing the material or the material properties locally through a partial quenching to make up for drawback. But, these two ways have problems of weld zone and schedule-cost. In this study, we use the local heat treatment process using a induction heating capable of applying the heat treatment region and reducing of processing time. The experiment was conducted as a method for output variance when the induction heating. And then the temperature and the hardness applied to the material were measured. Is this way, we studies the affect of hot-stamping steel with induction-heating.