Formability Assessment by Bulge Test Employing Grooved Disks (Investigation into the Optimum Geometry of the Groove)

The optimum geometry of the groove is investigated in the bulge test employing concentrically grooved disks which was earlier proposed as a press-formability test by the authors. It is recommended that a groove is formed with the circular arc profile to 0.125 t₀ in depth at the radial position of 0.4 r₂ on the disk surface, where t₀ is the initial thickness of a blank and r₂ is the radius of the die aperture. It is concluded that both deep-drawability and pure-stretchability of sheet metals can be accurately assessed by a single blank test. The deformation behavior of grooved specimens is examined also by numerical analysis.