Surface structures on deep drawing tools by machine hammer peening to reduce friction and wear

• Applicant: Professor Dr.-Ing. Fritz Klocke
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: from 2015 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 274033148

Deep drawing is a major production technology of the automotive industry for the production of three-dimensional components. Recent trends enforce the use of high strength steels. Therefore, the deep drawing tools have to fulfill stringent requirements on their friction characteristics and wear-resistance. Worldwide friction and wear in industrial processes for tool and die manufacturing cause costs up to billion euros. A promising approach to decrease friction and wear in forming processes is the use of special designed surface structures on deep drawing tools. The description of tribological performances using surface-structured tools is not sufficiently explored according to the current state of the art. For surface structures on sheet metal workpieces, positive impacts on the friction and wear characteristics of the interacting solids were already shown, but they differ significantly from surface structures on tools in their plastic flattening during deep drawing. Accordingly, the challenge is to develop wear-resistant surface structures on deep drawing tools which have a positive impact on friction and wear characteristics.The surface structures will be produced by the insufficient explored technology machine hammer peening. Machine hammer peening distinguishes itself from other structuring processes by the induction of residual compressive stresses and strain hardening. Due to an easy integration into existing manufacturing processes and the flexible adjustable process kinematics machine hammer peening offers a high potential to fulfill the requirements on the structuring of low-friction and wear-resistant tool structures.The aim of this project is the development of an analytic-empiric and numeric process models to describe and explain the fundamental cause-effect-relationships of surface structures produced by machine hammer peening intended to decrease friction and wear in deep drawing. The first step explores basic correlation between the machine hammer peening process parameters and the surface layer state. On this basis, in a second step the impact of structured surfaces on friction and wear is described und explained. The investigation is focused on the comprehension of tribological mechanism of action considering tool surfaces structured by machine hammer peening, lubricant and sheet metal material. The gained fundamental understanding allows a purposeful process design in order to decrease the friction in deep drawing processes. The exploration of the impact of the surface structure on the wear characteristics with respect to the determined friction properties follows in conclusion.

• DFG Programme: Research Grants