Forming limit of sheet metals based on mixed hardening model  

作　　者：HaiBo Wang Min Wan 

机构地区：[1] School of Mechanical Engineering and Automation, Beihang University, Beijing, 100191, China

出　　处：《Science China(Technological Sciences)》2009年第5期1202-1211,共10页中国科学（技术科学英文版）

基　　金：Supported by the National Natural Science Foundation of China (Grant No. 50475004)

摘　　要：The calculation method of forming limit of sheet metals based on M-K instability theory is proposed,and the method is applicable to different yield criterions and hardening models.The forming limit dia-grams of AA5754-O,AA6111-T4 aluminum alloy sheet and DP steel sheet under combined loading paths are obtained based on mixed hardening model with YLD2000-2D yield criterion proposed by Barlat in 2003 and L-C nonlinear kinematic hardening model proposed by Lemaitre and Chaboche.The results show that the forming limit diagram made up of limit strain(FLD-strain) is evidently influenced by the loading path.The forming limit diagram made up of limit stress(FLD-stress) is also influenced by loading path and it is not an only curve,which differs from the conventional view.The degree of the influence of loading path on FLD-stress is related with pre-strain.The larger the pre-strain is,the greater the influence of loading path on FLD-stress will be.The change of FLD-stress is small only when pre-strain is small.In addition,the hardening behavior of the material will influence the path-dependence of FLD-stress:The larger the proportion of kinematic hardening in the whole hard-ening is,namely the more obvious Bauschinger effect of the material,the greater the influence of loading path on FLD-stress will be.The calculation method of forming limit of sheet metals based on M-K instability theory is proposed, and the method is applicable to different yield criterions and hardening models. The forming limit diagrams of AA5754-O, AA6111-T4 aluminum alloy sheet and DP steel sheet under combined loading paths are obtained based on mixed hardening model with YLD2000-2D yield criterion proposed by Barlat in 2003 and L-C nonlinear kinematic hardening model proposed by Lemaitre and Chaboche. The results show that the forming limit diagram made up of limit strain (FLD-strain) is evidently influenced by the loading path. The forming limit diagram made up of limit stress (FLD-stress) is also influenced by loading path and it is not an only curve, which differs from the conventional view. The degree of the influence of loading path on FLD-stress is related with pre-strain. The larger the pre-strain is, the greater the influence of loading path on FLD-stress will be. The change of FLD-stress is small only when pre-strain is small. In addition, the hardening behavior of the material will influence the path-dependence of FLD-stress: The larger the proportion of kinematic hardening in the whole hardening is, namely the more obvious Bauschinger effect of the material, the greater the influence of loading path on FLD-stress will be.

关 键 词：PLASTIC FORMING of SHEET METALS FORMING LIMIT HARDENING model complex loading path 

分 类 号：TG301[金属学及工艺—金属压力加工]