Characterization of High-Strength Packaging Steels: Obtaining Material Data for Precise Finite Element Process Modelling

Abstract

The steadily increasing demand for downgauging to reduce costs in packaging steel applications requires the development of high-strength packaging steel grades to meet strength requirements. At the same time, the demand for a simulative, computer-aided layout of industrial forming processes is growing to reduce costs in tool constructions for downgauging manners. As part of this work, different high-strength packaging steels were characterized for use in a finite element based process layout and validated using application-oriented experiments. Due to a low hardening rate and the occurrence of Lüders bands, high-strength packaging steels show a low amount of elongation in tensile tests, while for other stress states higher degrees of deformation are possible. Thus, common extrapolation methods fail to reproduce the flow curve of high-strength packaging steels. Therefore, a new approach to extrapolate the flow curve of high-strength packaging steels is presented using the tensile test and bulge test data together with a combined Swift–Voce hardening law. Furthermore, it is shown that the use of complex anisotropic yield locus models such as Yld2000-2d is necessary for high-strength packaging steels in order to be able to precisely simulate application-oriented loads in between plane strain and biaxial tension in validation experiments. Finally, the benefit of a material selection process for packaging steel applications guided by finite element simulations based on precisely characterized material behaviour is demonstrated.

Influence of specimen geometry and strain rate on elongation in tensile testing of packaging steel

“…As well, Sylwestrowicz et al proposed the first approach describing the velocity of the slip band front of mild steel [4]. The problems and characteristics arising in the characterization of packaging steel for finite element simulations resulting from the occurrence of slip bands in tensile tests were investigated by Knieps et al recently [5]. Due to a strong strain localization, in some cases failure occurs already before the expansion of the slip bands over the whole specimen.…”