Formability enhancement in titanium tube-flaring by manipulating the deformation path

The tube flaring process has been traditionally used to expand one end of a tube without changing its cross-sectional area. This simple process typically forms the product using a single punch. To delay failure and enhance formability, a two-step flaring process can be used. For example, if a significant elliptical flared shape is attempted in a one-step process, a necking/tearing failure would occur on the major axis of the ellipse. However, if a two-step process, starting with a mildly elliptical punch and followed by the final, sharply elliptical punch is used instead, the desired elliptical shape can be achieved. In this paper, the effects of the punch geometry of the first step on the deformation paths are numerically analyzed. By manipulating the deformation path, failure can be delayed so that higher formability is achieved. The numerical model is validated by comparison with experimental results.