Abstract: In finite element simulation,To overcome the problem of the dynamic explicit algorithm cannot obtain the exact springback value of the arc section S2 In finite element simulation and the analytical method ignores the characteristic of variable curvature in the transition section S1.To overcome these problems,a solving method of combined analytic method and Finite Element Method (FEM) simulation method was proposed to predict the springback value of the tube made by free bending technology.The simulation process of the tube forming and springback in transition section S1 was completed by explicit and standard algorithm respectively.The springback prediction model in transition section S1 was established by introduce introducing the Moving Least-Squares Methods (MLS) to fit the springback value.Meanwhile,an analytic model is was proposed by considering compressive stress caused by axial pushing force to predict the springback value of arc section S2.Results showed that the springback occurred in the transition section S1 mainly,and the springback value of transition section S1 took  a small portion of the tube.Compared with two experimental results,the error of springback angle between the proposed method and experimental  was 15.09% and 14.76%,and the error between traditional method (the curvature of transition section S1  was taken as constant) and experimental was 27.68% and 24.32%,the prediction accuracy of the springback angle was improved by 11.08%.

Key words: free bending technology, analytical method, springback prediction, finite element simulation, plastic forming

摘要： 为克服有限元模拟中圆弧段采用动力显式算法无法获得准确回弹,值及解析法忽略过渡段S1为变曲率特性的问题,提出一种结合解析法和有限元模拟分析的求解方法,以此来对基于自由弯曲技术的管材回弹数值进行预测。对于过渡段S1,分别使用显式和隐式求解器完成成形和回弹过程的仿真,基于回弹值变化特点引入移动最小二乘法(MLS)对回弹数据进行拟合,建立了过渡段S1的回弹预测模型;同时,对圆弧段S2建立了考虑轴向推力引起的压缩应力的回弹预测模型。仿真结果表明,回弹主要发生在圆弧段,过渡段S1的回弹值在整体回弹值中所占比重较小;经过两组实验结果对比分析,所提出的预测方法与实验所得回弹角误差分别为15.09%与14.76%,传统求解方式(将过渡段S1视为定曲率)与实验所得回弹角误差分别为27.68%与24.32%,回弹角综合预测精度提升了11.08%。

关键词: 自由弯曲技术, 解析法, 回弹预测, 数值模拟:塑性加工