Comparative investigation of sheet metal forming processes by the elastic-plastic finite element method with emphasis on the effect of bending

Abstract

The effect of bending is investigated through a comparison of the membrane analysis and shell analysis for stretching and deep drawing. An incremental formulation incorporating the effect of shape change and anisotropy is used for the analysis of elastic-plastic unsteady large deformation. The deformation during a step is considered using a naturally convected coordinate system. Stretching of a square blank with a hemispherical punch and deep drawing of a cylindrical cup is analyzed, and the corresponding experiments are carried out. The computational results are compared with the experiments. In stretching, the comparison has shown that both the membrane analysis and the shell analysis are in good agreement with the experiment for punch load and strain distribution. In deep drawing, the computed loads of both the membrane analysis and the shell analysis are generally in good agreement with the experiment. The computed thickness strain of the membrane analysis, however, shows a wide difference from the experiment. In the shell analysis, the thickness strain shows good agreement with the experiment. It has been shown that the membrane approach shows a limitation for the deep drawing process in which the effect of bending is not negligible and more exact information on the thickness strain distribution is required.