板料冲压成形回弹的有限元数值模拟研究

随着对冲压件的尺寸精度要求的不断提高，精确预测给定冲压件的回弹量大小及分布显得非常重要。采用无模法模拟卸载回弹过程时，需要以加载成形后的应力为基础。本文给出了加载成形中的应力计算方法，并采用无模法建立了卸载回弹的计算模型。文中提出一种不同于传统的初始单元弹性化处理的方法，提高了回弹的计算精度。研究了卸载因子的取值规律对回弹计算的影响。利用自行开发的软件SheetForm模拟分析NUMISHEET’93标准考题中U型件深冲压的回弹情况，验证了该方法的有效性。

Study on finte element numerical simulation of springback in sheet metal stamping forming

Accurate prediction of springback is becoming more important in automotive sheet stamping operations while requirements for high accuracy in formed products has been increasing. Simulation of the unloading process is based on the stress state at the end of the loading process analysis. The stress calculation in the loading process and the springback model with tools removed and all contact nodal forces recovered were investigated. A distinct method from the traditional one dealing with the initiation of sheet elements was presented, which is proved to improve the accuracy of the springback prediction. The influence of the unloading factor on springback with the assumption of proportional loading path for stress relaxation was also discussed. Springback simulation was studied on NUMISHEET'93 2D draw bending using the proposed algorithms as well as the software SheetForm developed by authors, whose simulative results show the effectiveness of the proposed algorithm.