法向应力对板料成形极限影响的研究进展

在板料成形过程中应力状态对板料(板材和管材)的成形极限有很大影响,通过对板料施加法向应力可以提高板料的成形极限。文章综述并分析了法向应力对板料成形极限影响的理论模型、有限元模型以及实验研究方面的进展。理论模型方面的主要进展,是根据经典塑性失稳理论和M-K理论,建立了考虑法向应力影响的成形极限理论模型,可以准确地预测法向应力对板料成形极限的影响;有限元分析的主要进展,是在韧性断裂准则的基础上,利用体单元建立了考虑法向应力影响的数值模型;有关实验研究方面只是初步的探索,还有待进行深入的研究;对影响法向应力提高板料成形极限的因素进行了总结分析。

Progress on effects of through-thickness normal stress on sheet metal forming limit

The stress state imposed on the sheet metal(blank and tube) has a great influence on the forming limit in sheet metal forming process.The forming limit of the sheet increases when the through-thickness normal stress is applied on the sheet.In this paper,research progress on effects of through-thickness normal stress on sheet metal forming limit is reviewed and analyzed from theoretical model,finite element model and experimental study.The main progress in theoretical model is that forming limit theory model including through-thickness normal stress effect has been established based on the classical plastic instability theory and M-K theory,and can accurately predict the influence of normal stress on the sheet metal forming limit.The main progress in finite element analysis is that numerical model with consideration of through-thickness normal stress has been established using solid element based on the ductile fracture criterion.Some preliminary exploration has been conducted on the experimental study and further studies are needed.Finally,some factors that influence the dependence of sheet metal formability on through-thickness normal stress are summarized and analyzed.