Blank development and the prediction of earing in cup drawing

The article deals with the prediction of blank shapes using the method of plane strain characteristics. In one case the material is assumed to be an incompressible, non-hardening, isotropic solid, and ideal blank shapes are developed when deep drawing prismatic cups. The significance of the study is that the resulting slip line field pattern does not violate the Hencky equations. The earing behaviour when deep drawing cylindrical cups from circular disks has also been predicted based on a particular form of anisotropy which allows for four fold symmetrical earing. The technique permits the blank shape to be calculated throughout the entire drawing operation, and demonstrates how the ears develop.