980MPa급 초고강도 강판을 이용한 자동차 패널의 스프링백 저감에 관한 연구

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.