An analytical model for straight hemming was developed based on minimum energy method to study the effect of flanging die corner radius on hemming qualities.In order to calculate plastic strain and strain energy more ...An analytical model for straight hemming was developed based on minimum energy method to study the effect of flanging die corner radius on hemming qualities.In order to calculate plastic strain and strain energy more exactly,the neutral layer of specimen corner after hemming is assumed to be a half ellipse with its major semi-axis unknown.Isotropic hardening rule is adopted to describe bending and reverse bending processes neglecting Bauschinger effect.The model takes into account the material property parameters in order to satisfy a wide application range of different materials.Specimen profile,creepage/growing(roll-in/roll-out) and maximum equivalent strain are predicted,which are greatly influenced by the flanging die corner radius.Experimental facilities were designed and hemming experiments were undertaken.The predicted results of the present analytical model were compared to experimental data as well as finite element(FE) simulation results.It was confirmed that they are in good agreement,and the model can be used to evaluate whether the material used as an outer panel for hemming is appropriate and to optimize process parameters when the material used for hemming is changed.展开更多
The purpose of this research is to explore the feasibility of roller hemming of AZ31 B magnesium alloy sheet. During the test, a special experimental setup considering the current flow and insulation was designed and ...The purpose of this research is to explore the feasibility of roller hemming of AZ31 B magnesium alloy sheet. During the test, a special experimental setup considering the current flow and insulation was designed and employed. For the sake of simplicity, the flat surface-straight edge hemming style was selected. Electrical pulses were introduced in the pre-hemming and final hemming processes. The results show that when hemming at 448 K with hemming speed of 30 mm/min, AZ31 B magnesium alloy sheet was successfully hemmed with excellent perceived quality. No recoil/warp defect, cracking or springback was observed. Electrical pulses induced dynamic recrystallized grains were observed along the grain boundaries in the severely deformed area, which is of great importance to the improvement of the ductility of the material. The hardness was slightly increased after hemming with electrical pulses, and this fact could improve the friction resistance performance of the hemmed part.展开更多
基金Project supported by the National Natural Science Foundation for Key Program of China (No. 50835002),the National Natural Science Foundation of China (No. 50975174),the National Natural Science Foundation for Innovative Research Group of China (No. 50821003)
文摘An analytical model for straight hemming was developed based on minimum energy method to study the effect of flanging die corner radius on hemming qualities.In order to calculate plastic strain and strain energy more exactly,the neutral layer of specimen corner after hemming is assumed to be a half ellipse with its major semi-axis unknown.Isotropic hardening rule is adopted to describe bending and reverse bending processes neglecting Bauschinger effect.The model takes into account the material property parameters in order to satisfy a wide application range of different materials.Specimen profile,creepage/growing(roll-in/roll-out) and maximum equivalent strain are predicted,which are greatly influenced by the flanging die corner radius.Experimental facilities were designed and hemming experiments were undertaken.The predicted results of the present analytical model were compared to experimental data as well as finite element(FE) simulation results.It was confirmed that they are in good agreement,and the model can be used to evaluate whether the material used as an outer panel for hemming is appropriate and to optimize process parameters when the material used for hemming is changed.
基金the National Natural Science Foundation of China(Nos.50975174 and 51275297)
文摘The purpose of this research is to explore the feasibility of roller hemming of AZ31 B magnesium alloy sheet. During the test, a special experimental setup considering the current flow and insulation was designed and employed. For the sake of simplicity, the flat surface-straight edge hemming style was selected. Electrical pulses were introduced in the pre-hemming and final hemming processes. The results show that when hemming at 448 K with hemming speed of 30 mm/min, AZ31 B magnesium alloy sheet was successfully hemmed with excellent perceived quality. No recoil/warp defect, cracking or springback was observed. Electrical pulses induced dynamic recrystallized grains were observed along the grain boundaries in the severely deformed area, which is of great importance to the improvement of the ductility of the material. The hardness was slightly increased after hemming with electrical pulses, and this fact could improve the friction resistance performance of the hemmed part.
