Friction reduction in lubricated tribological contacts by micro textured surfaces

• Applicants: Professorin Dr.-Ing. Marion Merklein; Professor Dr.-Ing. Stephan Tremmel
• Subject Area: Engineering Design, Machine Elements, Product Development ; Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: from 2020 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 426217784

• Final Report Year: 2023

Final Report Abstract

To be able to further increase the energy efficiency of technical systems in the future, the tribological optimization of contacts is of particular importance. One effective way of reducing friction is to texture the surface of the components. Conventionally, metallic, surface-textured components are produced using ablative and additive processes, but these are limited by long process times and high costs. These incremental concepts of texturing are contrasted by processes of forming technology, which represent a promising approach especially thanks to short cycle times. However, in order to exploit the full potential, there is a lack of fundamental process understanding for combined forming processes that enable the one-step production of ready-to-use textured components. At the same time, the textures must be designed for the specific application, since unsuitable textures offer no tribological added value and, in the worst case, can lead to a deterioration in friction and wear behavior. Due to the high experimental effort required to determine the optimum texture, numerical methods can be used to design it in advance. The overall objective of the research project, which was conceived as a knowledge transfer project, was to expand the process understanding for microtextured components in a holistic approach, starting with the numerical design, through manufacturing, to product use and the experimental validation of the simulations. The aim was to further develop the methodology for the numerical design of surface microtextures developed in Priority Program 1551 and to validate it by means of practical tribological tests. Furthermore, limits of the manufacturing processes of different process classes were to be identified and extended. It was shown in the project that, in addition to the classically used high-speed steels, powdermetallurgical tool steels are also particularly suitable for microtexturing. For texturing by combined forming processes, it is essential to select those processes that allow extensive shaping of the basic body prior to the texturing step. This generally increases the precision of the process. For the numerical design of the textures, the simulation models were further developed and successfully validated. It was shown that the optimum texture patterns are strongly dependent on the contact conditions and that a locally optimized texture can indeed bring advantages. In final bench tests, it was shown that the numerically "optimal" textures exhibit significantly improved friction behavior compared to non-optimal textures. By applying an additional amorphous carbon coating, wear on the textures could also be effectively prevented.

Publications

• Transient EHL-simulation of a cam-tappet contact considering edge effects and roughness influence. 4th young tribological researcher symposium (YTRS). 8.6.2021.
  Christian Orgeldinger & Stephan Tremmel
  
• Tribologische Kontakte verstehen und optimieren: Ein numerischer Ansatz zur Berechnung hochbelasteter TEHD-Kontakte. 22. Bayreuther 3D-Konstrukteurstag 2021. 15.09.2021.
  Christian Orgeldinger & Stephan Tremmel
  
• Understanding Friction in Cam–Tappet Contacts—An Application-Oriented Time-Dependent Simulation Approach Considering Surface Asperities and Edge Effects. Lubricants, 9(11), 106.
  Orgeldinger, Christian & Tremmel, Stephan
  
• Investigation on micro-textured tappets from design and production to the application properties. Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, 237(12), 2497-2505.
  Reck, M.; Orgeldinger, C.; Tremmel, S. & Merklein, M.
  
• Investigation on tool properties for the production of components with micro textured surfaces. IOP Conference Series: Materials Science and Engineering, 1238(1), 012060.
  Reck, M. & Merklein, M.
  
• Numerical optimization of highly loaded microtextured contacts: understanding and mastering complexity. YTRS 2022 Conference. Karlsruhe.
  Christian Orgeldinger & Stephan Tremmel
  
• Reducing friction using micro-textured machine elements: An advanced simulation approach for the optimization of textured surfaces in cam-tappet contacts. NORD- TRIB 2022 Conference. 14.-17.06.2022. Alesund, Norway.
  Christian Orgeldinger & Stephan Tremmel
  
• Comparison of forming processes for micro textured cups. In: Proceedings of the 51st SME North American Manufacturing Research Conference. 2023.
  Manuel Reck & Marion Merklein
  
• Numerical optimization of highly loaded microtextured contacts: understanding and mastering complexity. Industrial Lubrication and Tribology, 75(7), 741-747.
  Orgeldinger, Christian; Rosnitscheck, Tobias & Tremmel, Stephan
  
• Wear Analysis of Micro Textured Coining Tools. In: Proceedings of the XLI. Colloquium on Metal Forming (pp. 104-109). 2023.
  Manuel Reck & Marion Merklein