Effect of plastic anisotropy on ironing formability of 3104 aluminum alloy hard sheets

3104 aluminum alloy hard sheet is used for aluminum beverage can body, and it is having high ironing formability. This alloy has large anisotropy of r and n-value, but the effect of such anisotropy on ironing formability is not clear. In this study, cup forming and DI forming were performed using 3104 aluminum alloy cold rolled hard sheets having different anisotropy of r and n-values. Magnitude of the anisotropy changes by drawing and ironing. Ironing fracture tests revealed that fracture occurs at angles between 10 and 20 ° in the can circumferential direction. From the strain distribution measurement of the can wall, it was found that the axial strain of can wall at fracture angle is larger. Theoretical analysis method of ironing stress considering r and n-value anisotropy, based on Hill's anisotropic plasticity theory (quadratic yield function) was devised. From this analysis, it was found that when the anisotropy of r-value in the can wall are small, (1) the fracture occurs less, (2) margin of stress (calculated from ratio of can axial tensile stress to fracture stress) is larger. © 2020 Japan Institute of Light Metals. All rights reserved.