Friction reduction in lubricated tribological contacts by micro textured surfaces

在润滑摩擦系统中，对部件表面进行改性可以改善摩擦性能，减少摩擦损失。这可以通过摩擦学层或应用于组件表面的离散微纹理来实现。对于更大的数量，这些微纹理必须通过成形工艺来实现，如微铸造，这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工艺的制造挑战，缺乏基本的知识。此外，缺乏对润滑摩擦学接触中表面微织构的影响和优化设计的深入理解。该研究项目的目的是获得关于EHL接触中表面微观结构的影响的基本科学知识，以及它们使用成形工艺的可制造性。在与工业伙伴的合作中，获得的基础知识被转移到工业应用中。通过扩展TEHL仿真模型，考虑薄层、粗糙度和固-固接触以及动态操作条件的影响，可以更真实地确定微织构对滚动-滑动接触的影响。考虑到制造限制，对于凸轮/抽杆接触的示例性，在杯子表面上导出了局部优化的微纹理。在挤压成形工艺中，采用逆织构优化方法对零件进行织构成形，使零件的织构成形更加均匀和精确。此外，与挤压工艺相比，采用了拉深、熨烫和压印的组合工艺，该工艺在压印区具有较低的物料流。目的是确定特定工艺对纹理形状的影响变量。此外，还利用磨损试验台对冲头的磨损性能进行了研究。研究的主要目的是基于数值模型和简化的台架试验，获得纹理几何的可实现精度以及工具的应用行为。从模型、组件到组合测试平台的完整测试链中，分析组件在摩擦磨损方面的应用行为有助于验证数值设计。最后，利用实验装置对所获得的合适且技术上可行的微纹理进行了不同应用案例的验证。

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.