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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.
김병규(B. G. Kim),정지용(J. Y. Jeong),김동진(D.-J. Kim),김교성(G.-S. Kim),금영탁(Y. T. Keum) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.10
In this study, the guideline for designing the drawbeads used in the stamping dies for advanced high strength steel (AHSS) sheets is investigated. In the drawbead drawing test, the drawbead forces for verifying the equivalent drawbead model(EDM) and the sheet strains for finding marginal strains from FLC0 are measured. In the finite element analysis (FEA), the bending allowance, R/t, is obtained. Based on the forming and bending allowances obtained, the design guideline of the drawbead for determining height and width, which depends on the restraining force and the forming allowance, is prepared by using EDM.
자동차 초고강도 강판 패널의 스프링백 저감에 관한 연구
김병규(B. G. Kim),이인석(I. S. Lee),금영탁(Y. T. Keum) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
Very big springback in advanced high strength steel(AHSS) sheets invokes undesired shape defects, which can be eliminated by the tool surface correction method or the forming process control method. Since the springback reduction by controlling the forming process is limited, in this study, the die correction method which finds die correction from the relationship between die design variable and springback is introduced to achieve springback reduction and is applied to the automotive side rail to reduce the springback of 75.8% within the assembly limit of 1mm.