Stretch flange-ability in aluminum alloy sheets for automotive body panels

Stretch flange-abilities in 5000 and 6000 series aluminum alloy sheets were investigated using the hole expansion test. The hole expansion limit (λ) of 5000 series aluminum alloy sheets was directly affected by the piercing tool clearance and the work hardening behavior of the hole edge. The effect of cut off punching on λ in 5182 and 6022 alloy sheets was also investigated. For 6022 alloy sheets, the λ-value was improved by cut off punching, however there were no effects observed for 5182. Obviously, the work hardening behavior on the 2nd punched hole edges for 6022 and 5182 alloys are different.