Friction reduction in lubricated tribological contacts by micro textured surfaces

在润滑摩擦学系统中，对部件表面进行改性可以改善其摩擦学性能，降低摩擦损失。这可以通过摩擦学层或通过施加到部件表面的离散微纹理来实现。对于更大的数量，这些微观织构必须通过成型工艺来实现，例如微压印，这些工艺可以集成到传统的制造工艺中。到目前为止，为了了解零件生产过程中组合成形过程中的制造挑战，缺乏基本的知识。此外，对表面微结构在润滑摩擦学接触中的作用和优化设计还缺乏更深入的了解。研究项目的目的是获得关于表面微结构在弹流润滑接触中的影响以及它们在成形工艺中的可制造性的基本科学知识。在与工业伙伴的合作下，获得的基本知识被转移到工业应用中。通过对TEHL模拟模型的扩展，考虑了薄层、粗糙度、固-固接触以及动态操作条件的影响，更真实地确定了滚动-滑动接触中微观织构的影响。作为示例性的凸轮/挺柱接触，在考虑制造限制的情况下，推导出杯面上局部优化的微结构。后者被用于挤压-压延工艺，在该工艺中，通过反向织构优化在零件上获得更均匀和更精确的织构成形。此外，还比较了拉深、拉深、压延联合工艺与挤压工艺，该工艺在压铸区的物流较低。目的是确定特定工艺对织构形状的影响变量。此外，还利用磨损试验台考察了铸币冲头的磨损行为。这项研究的首要目标是获得关于纹理几何的可实现精度以及基于数值模型和简化的台架测试的工具的应用行为的知识。在从模型、部件到组合试验台的整个试验链中，从摩擦磨损角度分析部件的应用行为，以验证数值设计。最后，利用实验装置对所获得的关于合适的、同时在技术上可行的微纹理的知识在不同的应用情况下进行了验证。

The modification of component surfaces in lubricated tribological systems can improve the tribological behavior and reduce friction losses. This can be achieved by tribological layers or by discrete microtextures applied to the component surface. With regard to larger quantities, these microtextures have to be realized by forming processes such as micro coining, which can be integrated into conventional manufacturing processes. Up to now, basic knowledge is missing in order to understand the manufacturing challenges in combined forming processes during component production. In addition, a deeper understanding of the effects as well as the optimal design of surface microtextures in lubricated tribological contacts is lacking.The aim of the research project is to gain basic scientific knowledge with regard to the effect of surface microtextures in EHL contacts, as well as their manufacturability using forming processes. In cooperation with industrial partners, the obtained basic knowledge is transferred to industrial applications. A more realistic determination of the effects of microtextures in rolling-sliding contacts is achieved by the expansion of a TEHL simulation model by the influence of thin layers, roughness and solid-solid contact as well as dynamic operating conditions. Exemplary for the cam/tappet-contact, over the cup surface locally optimized microtextures are derived, taking into account the manufacturing limitations. Latter are investigated for an extrusion-coining process, in which a more homogeneous and precise texture shaping on the component by an inverse texture optimization is strived. In addition, a combined process including deep drawing, ironing and coining which has a lower material flow in the coining area is compared with the extrusion process. The objective is to identify process-specific influencing variables on the texture shape. In addition, the wear behavior of the coining punches is examined using a wear test-rig. The overriding objective of the study is to gain knowledge on the achievable accuracy of the texture geometry as well as on the application behavior of the tools based on numerical models and simplified bench tests. The analysis of the application behavior of the components in terms of friction and wear in a complete test chain from model, over component, to aggregate testing-rigs serves to validate the numerical design. Finally, the obtained knowledge about suitable and simultaneously technically feasible microtextures is validated for different application cases using experimental setups.