An experimental study on local thickening laws based on multi-plate extrusion

Sheet-bulk metal forming is an important manufacturing process for the production of parts with three-dimensional features on a thick plate using a typical local thickening process. The process of boss extrusion is usually applied to study the filling ability by measuring the boss height. In this paper, multi-plate extrusion process is examined as an alternative to the boss extrusion process. Based on boss extrusion, multi-plate extrusion was demonstrated using three groups of experiments in which parts on the thick plate with a much higher boss were produced from sheet metal via the multi-plate method and tested for strength. A partition of the process into three periods is proposed and demonstrated empirically, during which it is shown that the key period in boss extrusion is an efficient flowing period and that extending the flowing period can aid in boss growth. The law developed may also be applied to other local thickening processes.