板料局部成形成形极限的数值研究

The Numerical Analysis for Local Forming Limit of Sheet Metal

通常在板料冲压成形中,通过成形极限图来预测板料成形时的缩颈、破裂现象。而采用增量成形技术成形板料时,板料的成形极限高于传统冲压成形。这一现象导致了从成形机理上研究板料增量成形极限为什么会高于传统冲压成形极限成为当前的研究热点。假定厚度方向的几何缺陷来表示局部弱化区,通过在板料厚度方向引入工具作用来研究局部材料的稳定性的影响。分别采用BAMMAN_DAMAGE模型和假定几何缺陷的方法来研究横向模具作用对板料成形均匀化的影响。通过数值模拟的方法研究了增量成形能提高成形极限的原因及机理,并考察在这个过程中板料应力和板料应变的变化情况。

Generally,the forming limit diagram is used to predict the sheet neck and fracture in the conventional forming process. The phenomenon that for forming the parts via Incremental sheet forming（ ISF）,the forming limit is much higher than that via conventional sheet forming has aroused a research interest in forming mechanism of local forming process in recent years. In this paper,the geometrical imperfection in the thickness was considered to represent local weakening zone and by using the BAMMAN_ DAMAGE material model and assuming geometric imperfection method separately to study the effect of the non-homogenization on the sheet forming limit. The cause and mechanism for improving of forming limit during the incremental forming process was studied by the numerical simulation method. And the variations of stress and strain during the forming process were also studied.