Shape Imperfection in Cylindrical Cups Formed by Processes of Deep- and Stretch-Drawing with Ironing. (Three-Dimensional Radius Distribution of Cup Wall).

Abstract

In order to pave the way for development of a new field of cup-forming (i.e. 'precision cup-forming'), shape quality of formed cups is investigated in detail, for no such data have been reported thus far. Cups are formed by the processes of deep-drawing and stretch-drawing with or without ironing action. The shape quality is evaluated by the radius distribution of the cup wall, which is displayed as three-dimensional colored maps, representing clearly the distortion pattern of the cup. The materials tested are four kinds of metal, including pure titanium. Spring-back occurs very irregularly in three dimensions, whose magnitude differs from material to material depending on the process type. Initial planar anisotropy cannot explain the distortion pattern, which suggests that its strain-history dependency plays a significant role. The cup wall radius becomes larger than the die cavity radius over some region around the cup lip and smaller over other regions. Generally, the cup shape is better for greater ratio of ironing, but notable exceptions may exist for some materials.