Multi-materialdesigns for complex lightweight applications become more and more important inthe context of reducing fossil fuel consumption and subsequent exhaustemissions. Electromagnetic forming (EMF) can be used to plastically deform lessductile materials (e.g. Mg and Al compared to steel), reduce spring back, and/orcreate a solid-state weld between dissimilar materials. Thus, there are variousniche applications in the automotive, aerospace, and biomedical industries forthis technology.

Electromagneticforming theory involves multidisciplinary content such as electricity, electromagnetism, and electrodynamics. Due to the complexity of electricity, electromagnetism,electrodynamics and the imperfection of plasticity itself, especially theinteraction between the discharge process and the high-speed deformationprocess of the blank during electromagnetic forming, the theoretical study ofelectromagnetic forming is very complicated and difficult. At present, thereare still many problems in the field of electromagnetic forming that need to befurther studied and solved.

In1958, the United States General Electric Company exhibited the world's first electromagneticforming machine at the second International Peace Atomic Energy Conference inGeneva. In 1962, Brower and Harrey of the United States inventedelectromagnetic forming machines for industrial production. Since then,electromagnetic forming has attracted extensive attention and high attentionfrom various industrial countries. The research on electromagnetic formingtechnology has achieved many application results, among which the United Statesand the former Soviet Union are in a leading position in this field. In theearly 1970s, the former Soviet Union experts studied the influence of blankdeformation on the discharge loop parameters of the machining coil and blanksystem during the discharge process, and pointed out that the RLC circuit can onlybe approximated when it is small deformation; In 1979, the magnetic fielddistribution of the flat coil was studied, and the unevenness of the distribution(the weak center and the strongest 1/2 radius of the coil) was the main reasonfor the insufficient stamping at the center of the blank. In the mid-1960s,electromagnetic forming machines with energy storage of 50kJ, 200kJ and 400kJappeared. More than 400 electromagnetic forming machines were used in variousproduction lines in the mid-1970s. In the mid-1980s, electromagnetic formingwas widely used in the United States, the former Soviet Union, Japan and othercountries. In 1994, Makoto Marata studied the method of electromagnetic bulgingof tube material by direct contact of electrodes. Through the experimentalanalysis, the influence of working conditions on current and tube deformationwas studied. The elastoplastic analysis of its bulging process was carried outby finite element method.

Theresearch on electromagnetic forming technology in China began in the 1960s andwas interrupted during the Cultural Revolution. In the late 1970s, HarbinInstitute of Technology began to study the basic theory and process ofelectromagnetic forming, and on the basis of experimental devices, successfullydeveloped the first electromagnetic forming machine for production in China in1986. At present, many universities and research institutes in China havecarried out research on electromagnetic forming technology and applied it toactual production.

1.1研究背景

在节能减排，降低能耗的社会大背景下，汽车、航空航天等制造业结构轻量化成为如今的发展趋势，高强度低成形性材料（如钛、铝、镁合金等）应用日益增加。而电磁成形是一种利用瞬态高强度磁场对金属工件进行成形的方法，它的成形速率极高，能够提高金属的成形性能，从而改善应变分布，减少工件的起皱与回弹。因此可以克服这些材料的成形困难，促进其在轻量化结构中的应用，且电磁成形技术具有加工能量易于精确控制、工装简单、成形精度高、环保、效率高等特点。综上所述，电磁成形技术在板材成形方面具有独有的优势，因此在轻合金平板件成形中将有着光明的应用前景。

电磁成形理论涉及到电学、电磁学、电动力学等多学科内容。由于电学、电磁学、电动力学的复杂性和塑性动力学本身的不完善性，特别是电磁成形过程中放电过程与毛坯高速变形过程的交互影响，使电磁成形的理论研究非常复杂和困难。目前，电磁成形领域仍有很多问题有待于进一步研究解决。

1.2国内研究现状

中科院电工研究所在60年代做过电磁成形方面的研究，并取得一些成果,但文革时期中断^[1]。70年代末期，哈尔滨工业大学开始研究电磁成形的基本理论及工艺，并于1986年成功研制了我国首台生产用电磁成形机^[2]。

1997年，王立峰等用ADINA非线性有限元件对强脉冲磁场作用下的平板毛坯自由胀形过程进行了模拟分析，得出了电磁成形中平面工作线圈的磁场强度分布规律及描述其分布特征的一系列曲线，通过有限元分析获得了动态变形的速度场、加速度场和位移场，同时研究了电参数对成形过程的影响规律，直接揭示了板坯电磁成形的变形过程，并用相关实验对模拟结果进行了验证，误差较小^[3]。吴莉花在此基础上考虑了板坯与线圈之间的互感，建立了电—力学耦合过程的载荷计算模型，并对各工艺参数进行了优化^[4]。