Deformation Feature of Sheet Metals During Inclined Hole-Flanging by Two-Point Incremental Forming

Incremental hole-flanging is an applicable extension of incremental sheet forming (ISF), but the knowledge on the deformation of metallic sheets during the course is lack, especially when the axes of the flanged necks are not perpendicular to the sheet plane. The current study used Al 6061 and SUS 304 stainless steel sheets with the thickness of 1 mm and 0.3 mm to examine the inclined hole-flanging processes on the flat plates by two-point ISF processes. It was found that, although as a whole the thickness variation is thinning, the decreasing degrees within upper and lower domain are not equal, and the difference increases with the inclination angle. Crack, buckling and local deformity are typical defects found in the experiments. The maximum springback increases with tool diameter, inclination angle and feeding pitch. Due to the material properties and a thinner thickness, local deformity is easier to take place on SUS 304 sheets during forming. Utilizing the tool feeding path along the oblique plane can obtain even force and consequently, more uniform deformation. Moreover, the equations for preliminarily determining the dimension of precut holes were derived according to the radial developed length of the flanged neck.