Abstract
In the fourth report, the extrusion forces and the properties of the extruded aluminium shells were mainly described. In this, we are reporting our studies on earing behaviors of the shells. The ears of extruded aluminium shells formed due to anisotropy of the blanks are too small as compared with zinc that they will have no effects in practice, but their four developing directions are such as at 0° or 90° to the rolling direction by rolled blanks and at nearly 45° by blanks annealed at approximately 300° or more. Thes earing behaviors reverse to the case of deep drawing but the former is clarified by means of crystallographic calculations, considering the influences of flow-resistance on the actual slip systems. Special ears owing to the shape of blanks, formed at the direction of the edge of blanks, are also explained.
