铝合金双曲率薄壁件电磁渐进辅助拉伸成形工艺方案设计与开发

目的 针对铝合金双曲率薄壁件传统拉伸成形工艺成形均匀性差的问题，提出一种采用电磁渐进辅助拉伸成形的高精度成形工艺。方法 设计电磁渐进辅助拉伸成形工艺方案，基于有限元仿真软件LS-DYNA R13.0，建立拉伸成形和电磁成形有限元模型。通过数值仿真研究线圈移动路径和放电电压组合对成形质量的影响以及薄壁件的整体贴模成形过程和等效塑性应变。结果 与单程放电相比，双程放电能够大幅度提高板材变形均匀性。与以中间值电压连续放电以及先大电压后小电压的放电电压组合相比，在先小电压后大电压的放电电压组合下，板材的成形质量更高。选择线圈双程顺序移动路径和7 kV-10 kV放电电压组合，通过10次拉伸和9层54次放电，得到了减薄率仅为3%的贴模性良好的双曲率薄壁件。变形量基本呈现随着放电层数的增加而不断降低的趋势。电磁放电仅扩展更大的塑性应变区域，不改变已贴模区板材的塑性应变值。结论 与拉伸成形相比，电磁渐进辅助拉伸成形工艺有效提高了板材的塑性变形程度并极大控制了回弹的发生。

Design and Development of Electromagnetic Progressive Assisted Stretching Forming Process for Aluminum Alloy Double Curvature Thin-walled Parts

The work aims to propose a high-precision forming process using electromagnetic progressive assisted stretching forming to solve the poor forming uniformity in traditional stretching forming of aluminum alloy double curvature thin-walled parts. An electromagnetic progressive assisted stretching forming process scheme was designed. Based on the finite element simulation software LS-DYNA R13.0, finite element models of stretching forming and electromagnetic forming were established. The research analyzed the influence of coil movement path and discharge voltage combination on the forming quality, and the overall forming process and equivalent plastic strain of thin-walled parts by numerical simulation. Round-way discharge could greatly improve the discharge uniformity compared with single-way discharge. The sheet forming quality under the discharge combination of first small voltage and then large voltage was higher than that of the combination of continuous discharge of intermediate voltage and discharge combination of first large voltage and then small voltage. A round-way sequential movement path of the coil and a combination of 7 kV-10 kV discharge voltage were selected. A double curvature thin-walled part with a thinning rate of only 3% and good fittability was obtained through ten stretching and nine layers of 54 discharges. The deformation basically showed a decreasing trend as the number of discharge layers increased. Electromagnetic discharge only expanded the larger plastic strain area, and did not change the plastic strain value of the sheet in the molded area. Compared with stretching forming, electromagnetic progressive assisted stretching forming improves the plastic deformation of the sheet and greatly controls the occurrence of sheet rebound.