Effect of Material Characteristics on Wrinkling During Dome Forming of a Beverage Can using LS-DYNA

Wrinkling of thin sheet metal products such as beverage cans continues to be experienced by can manufacturers and is observed with some aluminum material suppliers more than others. These wrinkles are caused by compressive instabilities during forming, and with small base diameter cans and light gauge material, the likelihood of this wrinkle formation increases. Manufacturing experience suggests that dome wrinkling is influenced by many factors such as mechanical properties of the aluminum sheet, tooling geometry, contact conditions including the effects of lubrication, and other process boundary conditions. It is also difficult to conduct an experimental analysis of compressive instabilities of these thin sheet metal products because the effects of all of the factors contributing to the instabilities are complex and small changes in these factors may produce widely varying results. Therefore, a numerical approach is recommended to separate the effect of each variable on wrinkle formation. This paper shows how strain-hardening and r-values influence wrinkle formation in its magnitude and frequency through dome forming of a beverage can based on a recent anisotropic yield function implemented as an LS-DYNA UMAT subroutine.