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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.
BLDC 모터에서 전류시간에 의한 토크맥동에 관한 연구
김철주(C.J.Kim),강병희(B.H.Kang),목형수(H.S.Mok),김덕근(D.K.Kim),김병규(B.K.Kim) 전력전자학회 2000 전력전자학술대회 논문집 Vol.2000 No.11
Torque pulsation generated in every commutation period is the main drawback of BLOC motor, which deteriorates the precision of BLOC motor. Many methods to solve this problem have been proposed. In this paper, a new torque model considered with decaying phase back EMF is introduced and from it the cause of torque pulsation in commutation period is analyzed. From this analysis, new algorithms to reduce the torque pulsation by commutation time are proposed and with simulation, the validity is verified.