Effects of flange lubrication and blank geometry on square-shell deep drawability of hard pure aluminium sheets

The effects of lubrication, blank geometry and tool geometry on the deformation and fracture mechanisms of hard pure aluminium sheets in square-shell deep drawing were investigated. When hard aluminium square blanks were drawn using tools with a large corner radius, the reduction in friction in the corner flanges prevented localised fracture due to slip bands unique to hard aluminium sheets, and improved deep drawability. The use of blanks with an optimum geometry relieved severe deformation in the punch corners, thereby preventing localised fracture and improving deep drawability considerably. Several lines characterising the deep drawing of square shells were presented in the figures that show the relationships between corner-cut amount, drawing force and fracture force. In addition, a graphical method that uses the features of these lines for evaluating the limiting drawing ratio of optimum blanks was proposed.