On the thinning variations in hydrostatic forming of sheet metal

Abstract

In sheet metal forming, thinning phenomenon is one of the most concerned topics to ameliorate the final quality of the manufactured parts. The thinning variations depend on many input parameters, such as technological parameters, geometric shape of die, workpiece’s materials, and forming methods. Hydrostatic forming technology is particularly suitable for forming thin-shell products with complex shapes. However, due to the forming characteristics, the thinning variations in this technology are much more intense than in other forming methods. Therefore, in this paper, an empirical study is developed to determine the thinning variations in hydrostatic forming for cylindrical cup. Measurement of thickness at various locations of deformed products are conducted to investigate the thickness distribution and determine the dependence of the largest thinning ratio on the input parameters (including the blank holder pressure, the relative depth of the die and the relative thickness of the workpiece). The results are expressed in charts and equation which allow determining the effect of each input parameter on the largest thinning ratio.