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

拉深是汽车工业生产三维零件的主要生产技术。最近的趋势是使用高强度钢。因此，拉深工具必须满足其摩擦特性和耐磨性的严格要求。在全球范围内，工具和模具制造工业过程中的摩擦和磨损导致成本高达10亿欧元。减少成形过程中的摩擦和磨损的一种有前途的方法是在拉深工具上使用特殊设计的表面结构。使用表面结构的工具的摩擦学性能的描述是没有充分探讨根据目前的最先进的。对于金属板材工件的表面结构，相互作用的固体的摩擦和磨损特性的积极影响已经显示，但它们显着不同的表面结构的工具在其塑性压扁在深冲过程中。因此，挑战在于开发对摩擦和磨损特性具有积极影响的深冲工具的耐磨表面结构。机锤喷丸与其他结构化工艺的区别在于它能产生残余压应力和应变硬化。由于易于集成到现有的制造工艺和灵活的可调过程运动学，机器锤击喷丸提供了很大的潜力，以满足低摩擦和耐磨工具结构的结构要求。本项目的目的是开发一个分析-经验和数字过程模型，以描述和解释基本的因果关系，通过机器锤击产生的表面结构的关系，旨在减少深冲压中的摩擦和磨损。第一步探讨了机锤喷丸工艺参数与表层状态之间的基本关系。在此基础上，在第二步中，结构化表面对摩擦和磨损的影响进行了描述和解释。研究的重点是理解摩擦学的作用机制，考虑到工具表面结构的机锤喷丸，润滑剂和金属板材料。所获得的基本理解允许有目的的工艺设计，以减少拉深过程中的摩擦。探索的表面结构对磨损特性的影响，相对于确定的摩擦性能如下的结论。

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.