Comparison of the experimental and the numerically predicted mechanical damage in the sheet forming of steel

There is great economical interest in the workability prediction of a material during sheet metal forming. This type of processing involves complex sequences of stress and strain states, and the material workability cannot be evaluated through simple procedures such as tension testing. Under these circumstances, various mechanical tests have been proposed in order to analyze sheet forming. There is also an increasing interest in the description of this process through numerical approaches such as finite element analysis (FEA), which allows the evaluation of the mechanical damage of the material employing various ductile fracture criteria. The present paper presents a comparison between the mechanical damage measured experimentally during the Marciniak test of a steel sheet and the damage predicted by FEA. No clear relationship between the two approaches was found and the FEA results display a fairly high dispersion. It is concluded that the various mechanical damages calculated in the FEA are not directly connected to the experimental damage associated with pore opening and measured through metallographic techniques.