Multi-step simulation approach of sheet metal forming processes based on flow theory

DOI：10.7511/dllgxb201801004

 作者 单位 张向奎,刘伟杰,胡平

为克服一步逆成形法忽略变形历史而导致最终零件应力估计不准的问题，提出了通过引入构造的若干中间构型以反映变形历史的多步成形模拟方法，实现了对最终零件的应力精确评估．该方法通过求解二次规划模型，并筛选接触节点的方式构造一般三维的中间构型滑移约束曲面，之后采用滑移曲面合适位置物质点映射的方法生成中间构型的初始解，并结合基于流动理论的局部积分和滑移曲面运动约束更新应力使得中间构型趋于平衡状态．对汽车弹簧盒支座零件的数值模拟分析表明，通过引入的中间构型，该多步成形模拟方法借助拟最小面积法和接触节点集合选择改善滑移曲面侧壁，可以显著地提高对成形零件的应力评估精度．

In order to overcome the defects of poor stress estimations of the final part obtained from the one-step inverse forming approach, the multi-step forming simulation approach, which introduces several constructed middle configurations representing the deformation histories to improve the stress estimations, is developed. In this approach, the general three dimensional sliding constraint surface with middle configuration is efficiently constructed by solving a quadratic programming model and extracting the contact nodal set, the initial solution of the middle configuration is generated by mapping the material points on the sliding surface with proper positions, and the middle configurations are updated during the equilibrium iteration with the constraint of movement on the sliding surface as well as the local integration based on the flow theory. Numerical analysis of the spring box shaped holder part of automobile shows that the sloping wall of the middle configuration is improved with the help of the pseudo minimum area method and the selections of contact node, and the stress estimation accuracy of the final pre-designed part is clearly improved.