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Dry forming of aluminium sheet metal. Influence of different types of forming tool microstructures on the coefficient of friction

Presentation held at International Deep Drawing Research Group, IDDRG 2015; 31.Mai 2015-03.06.2015, Shanghai, China
Trockenumformen von Aluminiumblechen. Einfluss von Mikrostrukturierungen des Umformwerkzeuges auf den Reibwert
: Scholz, Peter; Börner, Richard; Härtel, Sebastian; Kühn, Ralf; Müller, Roland; Schubert, Andreas

presentation urn:nbn:de:0011-n-3434301 (1.0 MByte PDF)
MD5 Fingerprint: 30df1cb2a6e2b034b16df525146cfbd1
Created on: 11.6.2015

2015, 12 Folien
International Deep Drawing Research Group (IDDRG Conference) <34, 2015, Shanghai>
Presentation, Electronic Publication
Fraunhofer IWU ()
Trockenumformen; amorphe Kohlenstoffschicht; schmiermittelfreie Umformung; Mikrostrukturierung; Beschichtung; Reibwert; Blechumformung

In the sheet metal forming industry lubricants are applied in forming processes to expand the technological boundaries by reducing friction and wear. The friction between tool and sheet metal is crucial to the deep drawing process. Due to economic and ecological reasons the aim of the manufacturers is to reduce or even avoid the use of lubricants. Consequently, this approach enables both a shortening of the process chains and an essential saving of resources. The advantages of structured forming tools in lubricated processes concerning the reduction of the coefficient of friction by the appearance of lubricating micro pockets are well-known. However, without using lubricant this effect does not work. In this case the true contact surface is reduced by structuring the forming tool which affects the tribological system.
In this paper the influence of microstructures with different geometries and surface treatments (uncoated / a-C:H:Si-coating) on the coefficient of friction in dry forming is compared to the frictional behavior of unstructured forming tools using lubricant as reference. Machining of the forming tool functional surface before coating is done by milling to generate tribologically effective microstructures. With the use of a strip drawing plant the effects of different surface structures and materials on the coefficient of friction are investigated. Beyond that, a numerical simulation based on FE analysis is used to predefine the surface structure. This requires a consideration of the normal pressure dependency on the coefficient of friction in the FE-model. Additionally, the strip drawing plant is used to evaluate the wear behaviour of the different microstructures and materials.