Blanking with pre-bending of steel sheets-Experimental investigation and FEM Simulation

The accuracy of blanked parts can be characterized by the form errors, such as the presence of a fractured zone on the shearing surface and deflection. Conventional blanking results in an approximately one-third smooth-sheared zone and a two-third fractured zone over a full workpiece thickness and additionally usually the stamps show a curvature. In order to delay the moment of material failure and thus increase the stamp cutting surface quality, a new method of sheet blanking process is proposed. After initial bending, during the punch movement a sheet blank is flattened, which causes compressive stresses in the sheared region. In this investigation, the effect of pre-bending on both the stamp shearing surface quality and part deflection were determined experimentally. The MSC Marc 2001 package served for the FEM based simulation of the blanking process. As a result it is indicated that the pre-bending of semi-products has a beneficial effect on both the sheared surface quality and the part deflection after blanking. (author)