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Production of structure components with selective properties by means of action media based cold forming

Autoren:Behrens, B.-A.; Hagen, T.; Mielke, J.; Sidhu, K. B.
Kategorie:Zeitschriften/Aufsätze (reviewed)
Jahr:2008
Veröffentlichung:Steel Research International, Vol. 79 (2008) No. 3, pp. 233-239, Verlag Stahleisen GmbH, 2008

Abstract

Minimising a metallic component's weight can be achieved by either using lightweight alloys or by improving the component's properties. In both cases, the material formability affects the utilisability for mass production processes. Most of the high‐strength materials show a material‐restricted formability and are difficult to forge. The formability of a material is described by its maximum forming limit. Large plastic strains can lead to mechanical damage within the material. A promising approach of handling low ductile, high‐strength alloys in a forming process is deformation under superimposed hydrostatic pressure by active media. In the present study, the influence of superimposed hydrostatic pressure on the flow stress is analysed as well as the forming ability for different sample geometries at different hydrostatic pressure and temperature levels. The experimental results show that the superimposed pressure has no influence on the plastic deformation, nor does a pressure dependent near‐surface material hardening occur. Nevertheless, the formability is improved with increasing hydrostatic pressure. The relative gain at room temperature and increase in the superimposed pressure from 0 bar to 600 bar for tested materials was at least 140 % and max. 220 %. Therefore, a cold forming process under superimposed pressure is developed to produce structure components with selective properties. For example, the gain in formability will be used to enlarge local plastic strains to higher limits resulting in higher local strain hardening and hardness. This offers new design possibilities with selectively adjusted local structure or structure component properties, especially adapted to their technical application. Additionally, by applying damage models, finite‐element analysis is used in order to predict damage occurring in the cold forming process under superimposed hydrostatic pressure for various sample geometries.