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【答案】应助回帖
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zoe122208: 金币+100, 翻译EPI+1, ★★★★★最佳答案 2014-02-28 10:55:08
Hot pressing technology of high strength steel plate is an effective approach to realising vehicle weight minimisation for energy conservation and waste reduction. The formability of hot pressed pieces is generally assessed by means of forming limits. However, since common hot pressing forming limits are made up of multiple isothermal forming limit lines, it is difficult to describe the formability of steel plate with varying temperatures. Moreover the exiting forming limit graphs today do not take into consideration of the impacts of phase change phenomena on the forming limits of hot pressed pieces. This project studies the advanced high strength steel B1500HS by means of Gleeble-3500 thermal simulation test facility to explore the material movement during thermal deformation for high strength steel, derive hot forming index and establish the constitutive equation considering temperature and strain rate. DIC technology is used to obtain the limit strain values for high strength steel plates above the phase transition temperature and 4-point characteristic method is used for setting up the forming limit lines of the material below phase transition temperature so that the impacts of phase transition on hot forming limits. Based on the obtained hot forming limit data, use of BP neural network and interpolation algorithm is made to construct three dimensional forming limit graphs. Hot press molds for box type pieces are designed and through process tests the three dimensional forming limit graphs are evaluated both qualitatively and quantitatively. The objectives of the project is at exploring how phase transition of high strength steel impacts the hot forming limits and establish the forming limit graphs appropriate for hot presses pieces from high strength steel plates, in order to lay the foundation for applications of home-made high strength steel to modern vehicles.
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