Response of ductile metal sheet parameters to the cone angle of indenting conical tool and fracture toughness evaluation

The indentation and perforation of ductile metal sheet with a conical tool is accompanied by elastoplastic bending, stretching, plastic flow, and crack initiation and propagation. This ultimately results in material fracture in the form of petals. It has been observed that the perforation process is dependent upon the angle of the conical tool. Fracture toughness, crack initiation, work input before and after crack initiation, number of petals, and sheet and petal bending angles all depend on the tool angle. Crack initiation has resulted at minimum tool displacement for a tool angle α=45°, while minimum work input before and after the crack initiation is observed when the tool has an angle α=35°. The optimum range of tool angles for the indentation process is α=22.5 to 50°. In this range, the aluminum sheets showed minimum fracture toughness as well as minimum work input to overcome the offered resistance.