基于表面层的微细薄板弯曲回弹预测建模与实验研究

An analytical and experimental study on springback behavior of sheet metals subjected to micro/meso scale bending based on the surface layer model

基于微／介观材料尺度效应表面层模型，对薄板表面层材料和内部材料分层处理，在纯弯矩弯曲模型基础上，考虑受到表面层晶粒影响的材料本构尺度效应并引入薄板回弹计算，分别对表面层和内部材料进行分析求得弯曲弯矩，从而建立了考虑尺度效应的微细薄板弯曲回弹预测模型。为了讨论模型的准确性，对不同晶粒、不同介观尺度的纯铜薄板开展了弯曲回弹的实验研究，实验结果表明，对于同一厚度的试样，薄板弯曲回弹角随着试样晶粒尺寸的增大而减小，对于不同厚度而晶粒尺寸相近的试样，回弹角随着试样厚度的增大而减小。分别利用传统回弹模型和考虑尺度效应的预测模型计算了弯曲回弹角，与实验结果对比发现，本文建立的模型能更准确地预测介观条件下微细薄板弯曲回弹现象。

Based on surface layer model dealing with the size effect of material in the micro/meso scale forming scenario, the surface lay- er and inner layer were dealt respectively. Based on bending model of material constructive scale effect influenced by grain in surface layer was considered and introduced in the calculation of sheet springback. The surface and internal layers were discussed respectively to obtain the grain and geometry dimensions dependent bending moment, an analytical model was established to predict the springback behavior of sheet metals subjected to bending process at micro/meso level. To discuss the accuracy of this model, meso scale bending experiments of copper sheet metals with different dimensions and grain sizes were conducted to explore the size effect of springback behavior. The results show that the sheet springback angles decrease with increasing grain size for sample of the same thickness, and the sheet springback angles decrease with increasing thickness for sample of the same grain size. The springback angles were calculated based on both traditional spri- ngback prediction model and the model established in the present study with the consideration of size effect. By comparing to the experimen- tal observations, the present model was revealed to be able to estimate the springback behavior at micro/meso scale with better accuracy.