Reduction of friction in EHD-contacts by microstructured surfaces of components: design, layout and manufacturing by forming

在第一个项目阶段，它已被证明，具体应用的微结构可以减少摩擦凸轮齿接触的滚动滑动接触的代表。此外，基于模拟的尺寸和设计的EHD接触的微结构的可行性可以被证明。此外，还证明了在一个工艺步骤中安全生产具有微结构表面的部件的可行性。对于微结构的设计，其几何形状和布置必须适应应用的特定载荷谱。仅通过实验来识别有利的微结构类型太耗时且效率低。事实上，微结构的效果必须通过基于模拟的方法来理解，在该方法基础上，推导出微结构表面的通用设计规则。由非牛顿润滑剂流动和饥饿润滑效应扩展的EHD接触的参数化模型允许计算各种载荷情况、微结构形状和布置。它为建立合适的元模型提供了基础。通过这个元模型，创建了优化微结构设计的能力，放弃了任何额外的详细模拟。然而，由于其精致的几何形状，理论上有利的微结构的制造达到了极限。确定了微细激光烧蚀、微细电火花加工和微细压印的工艺极限，分析了工艺参数对微结构精度的影响。在具有微结构表面的零件的大规模生产方面，采用了复合挤压成形微压印工艺。因此，研究了各个过程的相互影响和材料流的目标控制。关于微结构部件的操作，在应力持续期间改变微结构形状的磨损机制代表耐久性决定因素。在凸轮从动件试验台上对微结构构件进行摩擦学试验，可以分析在接近工作条件下由于磨损效应而引起的操作行为和微结构形状的变化。该项目的目标是开发一种经过验证的方法，以优化微观结构的形式及其在各个载荷谱中的排列，定义部件微结构表面的设计准则，并建立一个微结构表面的制造矩阵，根据微结构的尺寸、数量和排列显示适当的制造工艺。

In the first project phase it has been shown that specific applied microstructures can reduce friction in cam tappet contacts as a representative of rolling sliding contacts. Furthermore, the feasibility of a simulation-based dimensioning and design of microstructures for EHD contacts could be demonstrated. In addition, the feasibility of a process-safe production of components with microstructured surfaces in one process step has been proved. For the design of microstructures their geometry and arrangement has to be adapted to the particular load spectrum of application. An identification of advantageous microstructure types only by experiments is too time consuming and inefficient. In fact, the effect of microstructures has to be understood by a simulation-based approach upon which generalized design rules for microstructured surfaces are derived. A parameterized model of the EHD contact extended by non-Newtonian flow of lubricants and starved lubrication effects allows the calculation of various load cases, microstructure shapes and arrangements. It provides the basis for establishing a suitable meta-model. Through this meta-model the ability to optimize the design of microstructures is created, waiving any additional detailed simulations. However, manufacturing of theoretically advantageous microstructures reaches its limits due to their filigree geometries. Therefore, the process limits of micro laser ablation, micro electrical discharge machining and micro coining are determined and the influences of process parameters on accuracy of microstructures are analyzed. In terms of mass production of components with microstructured surfaces manufacturing by forming in a combined extrusion micro coining process is persued. Thereby, the mutual influence of the individual processes and the targeted control of the material flow are investigated. Concerning operation of microstructured components wear mechanisms that modify the shape of microstructures during stress duration represent the durability determining factor. Tribological testing of microstructured components on a cam follower test rig allows the analysis of the operational behavior and the change of microstructure shape due to wear effects under conditions near operation. Objectives of the project are the development of a validated methodology to optimize the form of microstructures and their arrangement for individual load spectra, the definition of design guidelines for microstructured surfaces of components and establishing of a manufacturing matrix for microstructured surfaces displaying suitable manufacturing processes depending on the size, number and arrangement of microstructures.